h.w. veltkamp - improvement of the glas-fep teflon-glass bond

Internship Mesoscale Chemical Systems

Improvement of the

Glass-FEP Teflon-Glass bond

for the µDNP-HR-1HNMR valve system

Different approaches

Henk-Willem Veltkamp

Student number: 2417203

Improvement of the Glass-FEP Teflon-Glass bond

for the µDNP-HR-1HNMR valve system

Different approaches

Internship report

Institution:

University of Twente (Enschede, NL)

Faculty TNW

MESA+ Institute for nanotechnology

Mesoscale Chemical Systems research group

By:


Student number: 2417203

[email protected]

[email protected]

Period:

30th

of August 2010 – 28th

of January 2011

Education:

Bachelor Chemistry (HBO, University of Applied Science)

Class/Year:

DCH4

Ultimate responsibility:

Prof. Dr. J. G. E. (Han) Gardeniers (MCS/TNW/UT, Enschede, NL)

[email protected]

Internship trainer:

P. (Piotr) Kurek MSc ( MCS/TNW/ UT, Enschede, NL)

[email protected]

Responsible teacher:

T.L.G.P. (Taco) Graafsma (Saxion University of Applied Science, Deventer, NL)

[email protected]

IVENTAS VITAM JUVAT EXCOLUISSE PER ARTES Literal translation: Inventions enhance life which is beautified through art

From:

Aeneid, the 6th song, vers 663

Vergilius (October 15, 70 BCE – September 21, 19 BCE)

Preface t is obligatory to do an internship for the Bachelor Chemistry at the Saxion University of Applied

Science. This is an internship of 5 months and I did it from September 2010 to January 2011.

Because I want to do a Master after my bachelor I have chosen for an internship at the University.

After some research I have found a project at MESA+ Institute for Nanotechnology at the University

of Twente that was called “NMR on a chip”. Because I am interested in lab-on-a-chip devices, I have

sent an e-mail to that University. They replied that I should contact the group of prof. Gardeniers (see

annex 1 for more information about MESA+ and the research group). After sending an e-mail to the

secretary of that group I got an answer with the contact information of the professor. After contacting

him I arranged a meeting to discuss a research proposal for the internship.

The subject of that proposal was to improve the bonding of Fluorinated Ethylene Propylene Teflon

(FEP-Teflon) to glass chips by chemical surface modification, using “Click Chemistry” as a basic

guideline. The bonding procedure will be used for a microfluidic valve system. With this valve it is

possible to design a shuttling system for transporting small liquid plugs between microwave (MW)

resonance cavity and a nuclear magnetic resonance probe. The proposal was designed by prof. dr. Han

Gardeniers and my internship trainer Piotr Kurek MSc

The goal of this research is directly quoted from the proposal:

__________________________________________________________________________________

The goal of this project is to develop chemical processes to manufacture these valves from FEP-foil.

The valves should be able to operate inside large static magnetic field, therefore it is of great

importance that no parts should be used that disturb magnetic field homogeneity or generate

unwanted NMR background signals. This means that the materials should be proton free. The valves

should also be chemically inert and should at least have a lifetime of 10 days in harsh chemicals.

A promising route is the use of Teflon foil as a material for the valves. Previously FEP-Teflon and AF-

Teflon was already used as a bonding layer between glass plates, for example, glass devices were

made by a room temperature FEP-bonding technique using EDC-NHS chemistry. The major

challenge is the pressure the devices can withstand. To handle sample plugs with high speed, a new

bonding technique, based on Teflon-like foils, should be developed which allows higher mechanical

stability.

__________________________________________________________________________________

After I had received approval from Saxion for the research proposal I started on Monday the 30th of

August 2010 and I finished on the 28th of January 2011.

The results of this research can be found in this report.

27-01-2011 HENK-WILLEM VELTKAMP

PIOTR KUREK MSC PROF. DR. HAN GARDENIERS

I

Summary This report describes an investigation of bonding techniques between glass and FEP-Teflon. The

former developed bond is based on EDC-NHS chemistry. The disadvantage of this bonding technique

is the relative large quantity of side-products, so another technique is investigated.

Two different methods are developed. One is based on the reaction between an azide and an alkyne

(Click Chemistry) and the other is based on the reaction between an amine and an epoxy. Only the

first method is tested experimentally, due to some starting problems.

An azide functionality must be put on the glass substrates and an alkyne functionality must be put on

the FEP-Teflon in order to perform this click reaction. The first step is done very often, so there is

enough information available about this method. First a bromo-terminated monolayer is placed on the

glass substrate. This is done with 11-bromoundecyltrichlorosilane. This bromine group is substituted

for an azide group. This is done in a sodium azide solution. The second step was harder to find, due to

the great chemically inertness of FEP-Teflon. First the foil is treated with FluoroEtch®. This etching

material will strip the fluorine atoms from the carbon backbone. This only occurs at a few Ångströms

depth, so the rest of the co-polymer remains unaffected. The free carbon radicals get protonated and

oxidized as soon as they get in contact with air, carboxylic acid groups are formed. This functionality

undergoes an esterification with propargyl alcohol in order to get a terminal alkyne group. This step is

never done on a surface before. The bonding reaction is done under pressure.

Other functionalities are needed to perform the amine-epoxy bonding. First an APTES monolayer is

formed on the glass substrate. This is a very common step and it gives an amine functionality. The step

to make an epoxy functionality on FEP-Teflon was hard to find. First of all a hydroxylated FEP-

Teflon surface is needed. Almost every article describes a RFGD plasma deposition technique with a

H2/MeOH plasma. This is not possible at the University of Twente. An article that describes a wet

chemical hydroxylation technique is found after a long search. In this article they use a sodium

naphthalene solution (main component of FluoroEtch®) and a borane solution. A GPTMS monolayer

is put on the hydroxylated FEP-Teflon surface. After this step the surface are bond together with

pressure.

There was only time to perform the Click Chemistry bonding technique. The glass and FEP-Teflon

foil were bond together after applying the pressure. The bond is tested with a maximum pressure test.

The channels can withstand the pressures that are shown in table 1. The difference in age is caused by

a vacation.

__________________________________________________________________________________ Table 1. Average of the maximum pressure tests.

Age of chips Activation of FEP Amount of chips Average Standard deviation

2.5 weeks No 8 2.6 0.56

3 days No 3 7.9 6.48

3 days, without outlier No 2 4.2 0.19

3 days Yes 3 3.3 0.82

__________________________________________________________________________________

The outlier had a maximum pressure of 15 bar. The surfaces are analyzed with contact angle

measurements and FT-ATR-IR. There are also other analysis methods discussed in this report, but

there was not enough time to perform them.

The following conclusion can be made by looking at the results: the bonding technique works, but is

not as strong as the previous EDC-NHS bond.

Keywords: Chemical surface modification, Click Chemistry, Microfluidic chip/valve, amine-epoxy

bonding.


10 Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Table of contents Preface .................................................................................................................................................... 7

Summary ................................................................................................................................................ 9

List of abbreviations and glossary ..................................................................................................... 12

Chapter 1. General introduction ........................................................................................................ 15

1.1 Introduction ........................................................................................................................... 16

1.1.1 General introduction .............................................................................................................................16

1.1.2 Research topic ......................................................................................................................................16

1.2 Different bonding techniques ...................................................................................................... 17

1.3 About the former developed bond ............................................................................................... 18

1.3 Fluorinated ethylene propylene ................................................................................................... 19

1.4 Measuring techniques .................................................................................................................. 20

1.4.1. Surface analysis ...................................................................................................................................20

1.4.1.1. Contact angle measurement ........................................................................................................ 20

1.4.1.2. Fourier-transformation attenuated total reflectance infra red spectroscopy ................................ 23

1.4.1.3. Scanning electron microscopy .................................................................................................... 24

1.4.1.4. X-ray photoelectron spectroscopy ............................................................................................... 25

1.4.2. Mechanical tests ..................................................................................................................................25

1.4.2.1. Tensile strength test .................................................................................................................... 25

1.4.2.2. Maximum pressure test ............................................................................................................... 25

1.4.2.3. Chemical compatibility tests ....................................................................................................... 29

1.5 References ................................................................................................................................... 30

Chapter 2. The Click Chemistry approach ....................................................................................... 33

2.1 About Click Chemistry ................................................................................................................ 34

2.2 Developed bonding technique ..................................................................................................... 35

2.3 Results ......................................................................................................................................... 38

2.3.1 Step 1, the glass treatment ....................................................................................................................38

2.3.2 Step 2, the FEP-foil treatment, part 1 ...................................................................................................39

2.3.3 Step 3, the FEP-foil treatment, part 2, esterification ............................................................................41

2.3.4 Step 4, the bonding reaction .................................................................................................................42

2.3.5 Testing of the bond ...............................................................................................................................42

2.3.5.1 Maximum pressure test ................................................................................................................ 42

2.4 Conclusion and discussion .......................................................................................................... 43

2.5 References ................................................................................................................................... 45

Chapter 3. The amine-epoxy bond approach.................................................................................... 47

3.1 About the amine-epoxy bond ...................................................................................................... 48

3.2 Developed bonding technique ..................................................................................................... 48



3.3 Results ......................................................................................................................................... 50

3.5 References ................................................................................................................................... 51

Chapter 4. Summarized conclusion and discussion, and future perspectives .............................. 53

4.1 Summarized conclusion and discussion ...................................................................................... 54

4.2 Future perspectives ...................................................................................................................... 54

Nederlandse samenvatting .................................................................................................................. 56

Dankwoord ........................................................................................................................................... 57

Annexes. .................................................................................................................................................. I

Annex 1. The institute ......................................................................................................................... II

About MESA+ ................................................................................................................................................ II

About the Mesoscale Chemical Systems research group ............................................................................. IV

References ...................................................................................................................................................... V

Annex 2. Click Chemistry ................................................................................................................. VI

References .................................................................................................................................................... VI

Annex 3. Detailed process for the Click Chemistry bonding technique .......................................... VII

Annex 4. Detailed process for the amine-epoxide bonding technique .............................................. IX

Annex 5. Used chemicals with safety information ............................................................................ XI

Annex 6. Results .............................................................................................................................. XV

Contact angle measurements, ARCA mode ................................................................................................ XV

Contact angle measurements, static mode ............................................................................................... XVIII

FT-ATR-IR spectra ................................................................................................................................... XIX



List of abbreviations and glossary General:

µCP microcontact printing

A form of soft lithography

µL micro litre

µPAT microfluidic process analytical technology

Analytical devices for limited sized samples

°C degrees centigrade

CC Click Chemistry

A philosophy about organic reactions

cm-1

reciprocal centimeters

cm2 square centimeters

CMOS complementary metal oxide semiconductor

A technology for constructing integrated circuits

CPM Catalytic Processes and Materials

Research group from MESA+

EDC-NHS chemistry an reaction that involves EDC and NHS, see EDC and NHS.

ETCS European Credit Transfer System

A system for study points

Faculty TNW faculty Science and Technology

h hour

L litre

LoC lab-on-a-chip

miniaturized laboratory equipment for limited sized samples

MCS Mesoscale Chemical Systems

Research group from MESA+

MEMS micro electromechanical systems

Chip based electromechanical systems

min minutes

mL millilitre

MPa mega Pascal

MST microsystem technology

Collective noun for chip based systems

Pa Pascal

RFDG radio frequency glow discharge

A method for changing the functional groups on a surface

RT room temperature

s seconds

SAM self-assembled monolayer

A layer of one molecule thickness on a surface

SNR signal-to-noise ratio

The resolution of a device

Analysis techniques:

µDNP- HR-1HNMR micro dynamic nuclear polarization high resolution proton nuclear

magnetic resonance

A combination between two analysis methods to identify molecular

structures.

µNMR micro nuclear magnetic resonance

The same as NMR, but for limited sized samples

ARCA advancing and reducing contact angle

A measurement technique for contact angle measurements.

DNP dynamic nuclear polarization



A method that transfers the enhanced polarization of the electrons too

the nuclei.

FT -ATR-IR Fourier transformation attenuated total reflectance infra red

spectroscopy

A method to characterize bounds in a molecule, based on vibrations of

the bounds

HR-1HNMR high resolution proton nuclear magnetic resonance

A method to identify molecular structures based on the spin of the

nuclei.

MS mass-spectrometer

A method to identify samples based on their molecular weight

NMR Nuclear Magnetic Resonance

A method to identify molecules based on the spin of the nuclei.

SEM scanning electron microscopy

A microscopy method

XPS X-ray photoelectron spectroscopy

A method to determine the composition of a surface.

Chemicals:

APTES (3-aminopropyl)triethoxysilane

DCM dichloromethane

DI-water de-ionised water

DMAP (4-dimethylamino)pyridine

DMF N,N-dimethylformamide

EDC 1-ethyl-3-[3-dimethylaminopropyl]-carbodiimide hydrochloride

ETFE ethylene tetrafluoroethylene

FEP-Teflon fluorinated ethylene propylene

GPTMS (3-glycidoxypropyl)trimethoxysilane

H2 hydrogen

H2O2 hydrogen peroxide

H2SO4 sulfuric acid

HCl hydrochloric acid

HF hydrofluoric acid

IPA isopropyl alcohol (a.k.a. isopropanol or 2-propanol)

MeOH methanol

NaOH sodium hydroxide

NHS N-hydroxy succinimide

O2 oxygen

PDMS polydimethylsiloxane

PFA perfluoroalkoxy

PTFE polytetrafluoroethylene



Chapter 1.

General introduction



1.1 Introduction

The following topics are discussed in this introduction: general information about this research,

different kind of bonding techniques, the previous developed bonding technique and the used

measuring techniques.

1.1.1 General introduction

Nuclear magnetic resonance (NMR) spectroscopy is a very often used technique in chemistry, biology,

pharmacy, and material sciences. It is a technique that can be used for getting information about the

molecular physics, quality, and (three-)dimensional structure of the molecules. It can be used for

liquids as well as solids.

Normally a NMR device is a big bottle filled with liquid helium. In the helium there is a coil that

becomes superconductive, due to the very low temperature. This means that applied electrical current

stays in the coil and with this electrical current it is possible to apply a magnetic field. With this

magnet the protons of a molecule gets polarised. For this big device a sample of millilitre size is

needed. The growth interest in mass-limited samples increased because some liquids are not available

in this size, for example blood and human cerebrospinal fluid. A µNMR for limited sized samples was

developed in the PhD research of Jacob Bart [1]

.

The Achilles heel of this µNMR device is the low signal-to-noise ratio (SNR). This means that the

experiment must be repeated many times in order to obtain a strong signal. It is possible to enhance

this SNR by means of hyper-polarizing the nuclear spin system. This can be done by connecting MW

resonance cavity to the µNMR probe. The electrons gets polarised in MW cavity. Here dynamic

nuclear polarization (DNP) using free radical containing paramagnetic species is one of the most

promising generic methods, due to the Nuclear Overhauser Effect. A big advantage with this method

is that a broad range of applications. Both liquids and solids can be analysed. They all require the

presence of paramagnetic species. This is not possible with other polarizing methods.

In DNP, the much larger electron spin polarization can be transferred to nuclear spins through a partial

saturation of electron polarization. A theoretical SNR enhancement of 600 times the normal signal can

be achieved if the enhanced polarisation of the electrons is transferred to the protons during the NMR

measurement (hyper-polarizing the protons) [2]

.

A combination of DNP and µNMR is called a micro dynamic nuclear polarization high resolution

proton nuclear magnetic resonance device (µDNP- HR-1HNMR)

The main issue of the existing µDNP setup is the lack of spectral resolution, which is needed for

biological samples. This can be enhanced by separating the NMR detection system from the MW

resonance cavity because NMR is done with radiofrequency waves and MW resonance is done with

microwaves. There is a difference between the kind of waves that are applied because the electrons are

much lighter and therefore they have a much higher spin than the protons.

It is required to transport the samples (as small liquid plugs) very fast in order not to lose the

polarization of the electrons during the transport from the µDNP to the µNMR. This must be done

within 100 milliseconds. To achieve this, the sample will be “shuttled” through a glass capillary. A

microfluidic system with fast valves is required to drive the shuttling. The bond between glass and

fluorinated ethylene propylene Teflon (FEP-Teflon) is developed in this research and can probably be

used for the valve system.

1.1.2 Research topic

In this research a bond is developed between glass and FEP-Teflon foil. This bond can probably be

used for the valve system. In the glass there are microfluidic channels, so it can also be used for

microfluidic systems (Lab-on-a-Chip, LoC) and micro electromechanical systems (MEMS) devices.



To achieve this goal, the bond needs some requirements:

1. It should resists a volume pressure of at least 3 bars;

2. It should be chemically inert;

3. It should at least have a lifetime of 10 days in harsh chemicals;

4. It should be mechanically stabile;

5. It would be nice if there should be a “resistance” against Piranha solution* for a small period

of time. Because this gives it the possibility to chemically activate the microfluidic channels if

the device is used in a LoC or MEMS device.

6. And finally, it is desirable that the bond can operate in a large magnetic field. Therefore no

parts can be used that disturb that field. This means that the use of a large amount of metals

(like metallic coatings) and other bulky materials is prohibited and the bond must contain a

minimal amount of protons;

Point 6 is unreachable because everything disturbs the magnetic field and the glass substrates already

contain a certain amount of protons. Therefore this point has a lower priority.

The main question of this research is how a strong bond between can be developed that can be used

for the shuttle system.

1.2 Different bonding techniques

In the past many different bonding techniques are developed for glass (or silicon) wafers. The most

frequently used wafer bonding techniques are “direct bonding”, “anodic bonding”, and “intermediate

layer bonding”.

To obtain a strong hermetic bond by direct bonding high annealing temperatures are required, usually

between 450-650°C for glass and over 1000°C for silicon. At these temperatures there is a chemical

reaction between the hydroxyl-groups that are present at the surfaces. It is possible to form a covalent

bond between the wafers at low-to-intermediate temperatures, but for this there is a nitride or oxide

surface modification needed. The bonds formed at lower temperatures are not as robust as the fusion

bonds. Another disadvantage of this bonding technique is the clean and ultra flat surfaces that are

necessary [3]

. To achieve this level of cleanliness and ultra flatness there are some rigorous, diligent

and laborious cleaning procedures required [3-7]

. The direct bonding technique can be improved by the

activation of the surfaces before bonding. This can be done e.g. by wet chemistry [6-7]

, UV/Ozone

exposure [8]

, plasma treatments [4, 9-12]

or a combination of these techniques.

The second frequently used way of bonding is the anodic bonding (or field-assisted bonding) method.

To create a robust and leak-free bond, this must be done at moderate temperatures (150-200°C) and

with a large electric potential (200-1500 V) [13]

. Due to this large electric potential, this bonding

technique has less stringent requirements for the surface quality of the substrates and particle

contamination compared with the other bonding techniques. This bonding technique is not compatible

with integrated complementary metal oxide semiconductor (CMOS) processes, due to its large electric

potential and it is also detrimental for wafers that contain temperature-sensitive components such as

metal thin-films, organic compounds, and waveguides.

Intermediate layer bonding (or adhesive bonding) was developed to avoid the above mentioned issues.

It also puts lower demands on the surface roughness and cleanliness (micron-sized particles are

tolerated to some extent). The intermediate layer between the wafers makes it possible to assemble

different kinds of wafers to each other. The bonding is usually done with a polymer as an intermediate

layer and a curing temperature below 300°C is required [14-17]

. To make intermediate layer bonds at

room temperature, an UV curable epoxy resin must be used instead of the polymer [18-20]

. But with

resins there is a risk for voids, gaps, and bubbles. There is also a chance that the microfluidic channels

get contaminated. This contamination with resin can be avoided by selective coating of one of the

* Piranha solution: 3:1 v/v mixture of 96% sulfuric acid and 31% aqueous hydrogen peroxide.



substrates using a “stick-and-stamp” method [18-19]

. But with this method a leakage-free bond between

the substrate and the intermediate layer is not reliable and the long-term stability of these adhesive

bonds is limited due to moisture uptake and chemical reactivity of the used resins [16-17, 20]

.

To avoid all these problems there is a new promising bonding technique. It was recently reported as

“bonding of unstructured wafers via chemical gluing”. This method is based on the anchoring of

chemical functionalities on surfaces via monolayers of several nanometers in thickness (a kind of

intermediate nano layer bonding technique), for example hydroxylated and aminosylated glass wafers

were strongly bonded via formation of C-C covalent bonds by a Diels-Alder cycloaddition reaction at

200°C [22]

. Due to this very small intermediate layer there is great reduction of the risk of clogging of

the micron-sized fluidic channels and structures on the device.

In a previous research done by J. Bart a glass/ Teflon/glass bond was developed by using this chemical

gluing technique. In this research EDC-NHS chemistry* is used

[23]. One of the recommendations of

this research is to develop an intermediate layer bond based on the principle of “Click Chemistry”

(CC). This way of bonding will be analysed in this research.

1.3 About the former developed bond

The bond that is developed in the PhD research of J. Bart is based on EDC-NHS chemistry [1, 23]

.

Silicon or glass is used as a substrate ((a) in figure 1) and the Teflon co-polymer fluorinated ethylene

propylene (FEP-Teflon) is used as an intermediate layer (d). First some microfluidic channels are

etched in the substrate (b) and then the substrate is treated with a 3-aminopropyl-triethoxysilane

(APTES) solution to create an amino-terminated monolayer, since APTES forms a self-assembled

monolayer (SAM) on silicon-terminated monolayers [24-26]

. The FEP- Teflon foil (d) is threatened with

FluoroEtch®†

to strip the fluorine atoms from the carbon backbone, with sodium naphthalene as a

residue left on the foil to protect the carbon radicals. This stripping of fluorine atoms only occurs at a

depth less than a nanometer. After removal of the residue the free site is exposed to air to protonate

and oxidize the carbon radicals. This results in a surface which is rich in carboxyl groups (e). After

this surface modification the modified FEP-Teflon foil is treated with an EDC solution and a sulfo-

NHS solution to obtain a semi-stable amine-reactive NHS-ester (f). This ester reacts with the amino-

terminated monolayer on the substrate to create a covalent amide bond.

Figure 1. Schematic overview of the EDC-NHS bonding technique. Starting with the substrate (a). On this substrate a microfluidic channel is etched (b) and covered with an amino-terminated

monolayer (c). A FEP-foil is used as an intermediate layer (d), of which the fluor-atoms are stripped (e). After protonation

and oxidation the carboxyl-groups are modified to an amine-reactive NHS-ester. Picture is taken with permission from [1].

* A reaction that involves 1-ethyl-3-[3-dimethylaminopropyl]-carbodiimide hydrochloride (EDC) and N-hydroxy

succinimide (NHS) † For detailed product information see: http://www.actontech.com/fluor1.htm and

http://www.actontech.com/fluor5.htm (last viewed on 16-sep-2010)



After the surface modifications the substrates were bond together with a load of 0.4 metric tons per

cm2 for 4 h at 75°C (or 15 h at RT). After this bonding time there is a FEP-(C=O)-NH-glass bond (see

inlet figure 2) created between the APTES layer and the amine-reactive NHS-ester layer.

This bond has a tensile strength of 5.2 ± 0.6 MPa and it can resist a fluidic pressure of ± 10 bar (with a

maximum of 23.2 bar). See figure 2 for a schematic overview of the bond and a cross-sectional SEM

image of the bond.

Figure 2. At the left is the schematic overview of the bond and at the right is the cross-sectional SEM image of

the bond. The inlet shows the amide bond with the FEP-foil intermediate layer (1) and the glass substrate (2). Picture is taken with permission from [1].

1.3 Fluorinated ethylene propylene

In this research the intermediate layer is the same as in the previous research done by J. Bart [1, 23]

,

namely the FEP co-polymer foil. It is also know under the name poly(tetrafluoroethylene-co-

hexafluoropropylene)*.

This co-polymer was invented by the DuPont Corporation and sold with the brand name Teflon-FEP®.

It consists of the two monomers tetrafluoroethylene and hexafluoropropylene. See figure 3 for the

structural and molecular formula of FEP.

Figure 3. Structural and molecular formula of FEP. It has an “n” amount of hexafluoropropylene and an “m”

amount of tetrafluoroethylene.

This intermediate layer is used because of its flexibility. This flexibility will be used for the pneumatic

controlled valve. The development of the valve is not a part of this research; this will be done by my

internship trainer. It is also chosen because of the great chemically-inertness and of the thermal-

stability. It has these properties because the polymer is comprised entirely of carbon and fluorine

atoms. The maximum operating temperature is 204°C and the melting point of FEP is 264°C. It is also

sunlight resistant and it is softer than other fluoropolymers, for example PTFE and PFA. It also has a

smoother surface and the sheets have a smaller thickness than PTFE and PFA. Besides all these facts it

* In the figures the FEP-foil is colored green. The real FEP-foil is transparent. The glass is colored red, but is also

transparent.



is also highly transparent, so it is very useful for microfluidic devices (the channels beneath it can be

seen) [27-28]

.

As mentioned before, FEP-Teflon is “soft”. This is a great advantage for the fabrication of

microfluidic devices. It is hard to make a leakage free wafer to wafer bond because the wafers are not

always flat. Sometimes they are concave or convex. Because of the softness of the FEP foil the wafers

are being pushed inside the FEP-foil, to create a hermetic sealed bond [29]

.

FEP-Teflon foil has a great chemical inertness, although it is still possible to etch (or strip) the fluorine

atoms from the carbon backbone. This method is very useful for a surface modification of FEP-Teflon.

After the stripping of the fluorine atoms from the carbon backbone, the free radicals get protonated

and oxidized as soon as there is contact with air. This ensures carboxyl and hydroxyl groups

(carboxylic acids are formed). With these functional groups a lot of reactions are possible [30]

.

This can be done with the use of FluoroEtch®. The main component of FluoroEtch

® is sodium

naphthalene. The sodium, which is a reactive metal, is responsible for the etching. The sodium

undergoes a chemical reaction with the fluorine in the FEP co-polymer (it can also be used for PTFE,

PFA, and ETFE). The etching only occurs at an area with a depth of a few Ångströms. This means that

the bulk of the polymer remains unaffected, so the polymer keeps its properties [1, 23]

.

1.4 Measuring techniques

In this paragraph the used measurement techniques are discussed. There is no theoretical background

information about the different techniques given. There are various good books about these techniques

written and it is impossible to explain the background of each technique in a short way and that is also

not the focus of this research. Only the information that is useful for this research is given: the

reference values, sample preparation, and used equipment.

Contact angle measurements and Fourier-transformation attenuated total reflectance infra red

spectroscopy (FT-ATR-IR) will be used to verify the steps during the development stage. This is done

because every step relies on the previous one. When the complete bond is obtained, the microfluidic

channels will be checked with scanning electron microscopy (SEM).

After the creation of a reliable bonding technique x-ray photoelectron spectroscopy (XPS) is used to

verify each surface. These results are used for an article.

The used measuring techniques will be discussed in separate paragraphs.

1.4.1. Surface analysis

During this research different kinds of surface analysis are used, namely contact angle measurements,

FT-ATR-IR, and XPS. These methods will be discussed in the following paragraphs.

1.4.1.1. Contact angle measurement

This method is used to verify the changes of the surface. With every step the

hydrophilicity/hydrofobicity of the surface got modified and therefore the contact angle of the surface

with water changes.

This measurement is done on 2 different ways, the static analysis and the Advancing and Reducing

Contact Angle (ARCA mode). A droplet of 4 µL DI-water is used for the first technique. The angles

of these droplets are calculated with the software and a picture of the droplet is taken. Than the ARCA

mode is started. In this mode the device will add 20 µL, in steps of 2 µL/s to the droplet. Than the

device will suck up the 20 µL, also in steps of 2 µL/s. This is repeated 5 times. The device continuous



measure the contact angle and afterwards he will calculate the average and the standard deviation of

the dataset.

See table 2 for the reference values for the different surfaces.

__________________________________________________________________________________ Table 2. Contact angle measurement reference values.

Surface Structural formula

Reference value

Glass

50° [31]

Piranha cleaned glass

< 3° [23, 32]

Bromoundecylsilane

on glass

84° [32]

Azido terminated

SAM

77-84° [32]

FEP-Teflon foil

108-117° [33-34]

Fluorine stripped and

60-90 s Piranha

cleaned FEP

3.8-4.4° [23]

Alkyne terminated

PTFE*

> 115° [32]

APTES

functionalized glass

57° [23]

Hydroxyl

functionalized FEP

59° [33]

GPTMS

functionalized

PDMS**

30.9° [34]



* This reference value is not exactly the one that is needed in this research. A reference value for the

following structural formula that is needed:

Figure 4. Alkyne terminated FEP-Teflon surface.

This one is slightly different from. An extra ketone group is present in this research. So the surface

functionality is more hydrophilic, and therefore the contact angle will be lower.

** This reference is based on GPTMS functionalized PDMS. As far as the author knows there are no

references for GPTMS functionalized FEP. The structure that is fabricated is shown in figure 6.

Figure 5. GPTMS terminated FEP-Teflon surface.

Both are GPTMS terminated, so the contact angle values will be comparable.

__________________________________________________________________________________

This measurement is done between each step. Before measuring the substrate must be cleaned with

DI-water and dried with a stream of nitrogen.

Device specifications:

Brand name: DataPhysics system

Parameters: fresh DI-water, sessile drop mode

This measurement is done at the University of Twente, Enschede (NL).

Figure 6. The contact angle measurement device.



1.4.1.2. Fourier-transformation attenuated total reflectance infra red spectroscopy

FT-ATR-IR is used to confirm the functional group modification on the different surfaces. ATR is

used because this research is focussed on substrates. The surface of the substrate can be put on top of

the ATR device and the infra red beam only measures the top of the substrate.

There are some reference values available for the determination of the different functional groups. See

table 3 for these reference values.

__________________________________________________________________________________ Table 3. FT-IR reference wavenumbers of the functional groups

[37].

Functional group Wavenumber (cm-1

)/type of peak

Terminal bromine

1250-1200/s, 650-800/s

Terminal azide

2100-2000, 1300-1250*

FEP-Teflon foil

1350-1150/s, 750/s

Carboxylic acid

3400-2600/m, 1800/m, 1450/m, 1350-1200/s, 1000-900/m

Terminal alkyne

3200/s, 2300/w, 1350-1250/w, 700/s

Terminal amine

3400/m/w, 1600/m, 1200-1100/m, 800/s/br

Terminal hydroxyl

3700-3400/s

Terminal epoxy

1210/m, 900-810/m

Explanation of used letters:

s = strong

m = medium

w = weak

br = broad

* The wavenumbers of an azido-group were found in another publication [38]

.

__________________________________________________________________________________



Prior to this measurement the substrate must be cleaned with DI-water and dried with a stream of

nitrogen. Besides this cleaning step there is no further sample preparation necessary.

The specifications of the used FT-ATR-IR:

Brand name: Bruker

Type: Vector 22 FT-IR with Golden Gate Diamond ATR

Range: 4000 cm-1

to 800 cm-1

Frequency: 32 scans per sample

Resolution: 4 cm-1

This measurement is done at Saxion University of Applied Science, Deventer (NL).

Figure 7. Bruker Vector 22 FT-ATR-IR.

1.4.1.3. Scanning electron microscopy

This technique is only used at the end of the complete bonding procedure. After the bonding of the

substrates, the sample is diced through half and a SEM picture of the cross section is taken. See figure

8 for an example of the dicing.

Figure 8. The chip is cutted through the dotted line.

This is done just to look if the microfluidic channels are fine.

This measurement is done at the University of Twente, Enschede (NL).



1.4.1.4. X-ray photoelectron spectroscopy

This technique is used to determine the composition of the surface of the substrate. This composition

is given in atom percentages.

XPS is often used for the determination of functional groups on polymer surfaces and the

identification of other surfaces and it is used for identification of surface contamination [39]

. Therefore

it is ideal for the verification of the formed monolayers.

The samples must be clean, because the XPS also measures the contamination on the surface of the

substrate. To achieve this, the sample must be cleaned with DI-water and dried with a stream of

nitrogen.

These measurements are carried out with the following device.

Brand name: Physical Electronics

Type: Quantera system

This measurement is done at the University of Twente, Enschede (NL). It is not sure if this analysis

will be used because it is expensive, around € 200.00 per hour. It is so expensive because of the ultra

high vacuum that is required.

1.4.2. Mechanical tests

After the bonding procedure the specifications of the bond are be determined. This is done with

several mechanical tests. The used techniques are discussed in the following paragraphs.

1.4.2.1. Tensile strength test

The wafers are diced in samples of 1 x 1 cm for this test. These “chips” are bond together. The bonded

samples are glued against the sample holders of the commercial available tensile strength tester [23]

.

Highly adhesive 2-component epoxy glue is used. This glue has a relative long drying time of 12 h.

Glue specifications:

Manufacturer: UHU GmbH, Germany

Type: UHU plus endfest 300

The tensile strength tester specifications:

Brand name: Zwick/Roell, Germany

Type: Z020

1.4.2.2. Maximum pressure test

This is done on the same way as described in the article of J. Bart et al. [23]

. The chip is mounted in a

home-made Teflon chip holder and the fluidic connections between the chip and the pump are made

with flexible fused silica capillary tubing (Polymicro Technologies, USA) and Upchurch Nanoport

assembly parts.

A short capillary with a wide diameter is used as an inlet (length 20 cm, O.D. 360 µm, I.D. 250 µm)

and is put between the pump and the inlet on the chip. The outlet of the chip is connected with a

thinner capillary (length 70 cm, O.D. 360 µm, I.D. 100 µm). This long outlet capillary will ensure a

constant pressure in the chip, since its hydraulic resistance is significantly larger than the hydraulic

resistances of the short inlet capillary and the microfluidic channel of the chip.

Normal DI-water with a few drops of red ink (this is used for visualization purposes) is used. This

flow is increased until leakage is observed.



Pump details:

Brand name: Harvard

Type: PHD 2000

Syringe: 5 mL Hamilton Gastight #1005

Ink: Trodat color 7011

The pressure can be calculated with the observed flow rate. An equation based on the Ohm‟s Law is

necessary. Ohm‟s Law:

(1.1)

In this equation:

is the resistance in ohm‟s (Ω)

is the potential difference or voltage between two points in volts (V)

is the electric current in amperes (A)

The following equation can be used for calculating the pressure drop in a microfluidic channel [40]

:

(1.2)

In this equation:

is the pressure drop in Newton/square meter (Nm-2

or Pascal: Pa)

is the hydraulic resistance in Pascalseconds/cubic meter (Pasm-3

or Nsm-5

)

(sometimes referred as ) is the flow rate in cubic meters/second (m3s

-1).

The flow rate can be found on the pump

Equation 1.2 corresponds with the following version of Ohm‟s Law:

(1.3)

The channels in the used chips are etched with hydrofluoric acid (HF), so it is not possible to calculate

precise. This is not possible due to the isotropic etching of HF: the channels are more ellipsoid of

shape than rectangular because the HF is etching in all directions. See figure 9 for the etching effect.

Figure 9. The isotropic etching of HF.



The can be estimated with the following equation [41]

:

(1.4)

In this equation:

(sometimes referred as ) is the dynamic viscosity in Pascalseconds (Pas or Nsm-2

)

is the channel length in meters (m)

is the half of the channel width in m

is the channel depth in meters m

The combined equations give the final equation:

(1.5)

This is a kind of Hage-Poiseuille equation for ellipsoid channels.

The specifications of the used channels are as follow:

= 8.0*10-2

m

= 175*10-6

m

= 50*10-6

m

= 0.01002 poise [42]

= 1.002*10-3

Nsm-2

These values give the following equation:

(1.6)

This leads to:

(1.7)

The in the outlet capillary is also necessary for calculating the . Equation 1.2 can be

used for calculating the , but the equation for the is different [41]

.

(1.8)

In this equation:

is the radius of the inside of the capillary in m.

Combining equation 1.2 and 1.8 gives the following equation.

(1.9)

The specifications of the used channels are as follow:

= 70*10-2

m

= 50*10-6

m



This leads to the following equation.

(1.10)

Solving this lead to:

(1.11)

There is also a gravity correction because of the fact that the outlet capillary is pointing down. This

correction can be calculated. First of all the internal volume of the capillary must be calculated.

(1.12)

In this equation:

is the volume of the capillary in m3

is the length of the capillary = 70*10-2

m

is the radius of the capillary = 50*10-6

m

The total internal volume in m3 is:

(1.13)

The solution of this equation is 5.498*10

-9 m

3. This volume has a weight of 5.498*10

-7 kg because the

density of water is 1 kg L-1

.

The following equation can be used to calculate the pressure.

(1.14)

In this equation:

is the pressure caused by the gravity in Pa

is the weight of the water inside the capillary in kg (calculated in equation 1.3)

is the standard gravity constant: 9.807 N

is the radius of the inside of the capillary in m

This will lead to:

(1.15)

The solution is 686.52 Pa. This is 0.0069 bar because 1 bar equals 100,000 Pa.

Now all the equations can be combined:

(1.16)

After this is calculated in bars (1 bar equals 100,000 Pa).

This test is done with an “n” amount of chips. The average and standard deviation will be determined

after calculating the maximum pressure in bar for each chip. See figure 10 for the used equipment.



1.4.2.3. Chemical compatibility tests

Another way to determine the strength of the bond is a chemical compatibility tests. In these tests

the chemical resistance of the FEP-based bond against several solvents is tested, namely water,

ethanol, IPA, acetone, toluene, and chloroform. These solvents are pumped through the channels with

a continuous pressure for 1 h. The pressure will be determined after the tests described in the previous

paragraph. After the “normal” solvents this test is also done with Piranha solution. The tests are done

with 3 chips except the test with Piranha solution. For this last “chemical” only 1 chip is used because

Piranha solution does not only affect the bond, but the complete glass and FEP-Teflon surface [23]

.

Figure 10. Harvard pump connected to chip. In the actual set up the chip was positioned at the edge of the table and the outlet capillary was pointing down.



1.5 References

1. J.Bart, Stripline-based microfluidic devices for high-resolution NMR spectroscopy, PhD

thesis, 2009, ISBN-13: 978-90-365-2898-6, pp 125-140 (digitally available on:

http://doc.utwente.nl/67414/1/thesis_J_Bart.pdf, last viewed on 16-09-2010)

2. Information given by Piotr Kurek MSc on 28-January-2011

3. M.J. Madou, Fundementals of microfabrication, CRC Press, Boca Raton (FL), USA, 2002

4. W. Bower, M.S. Ismail, B.E. Roberts, Low temperature Si3N4 direct bonding, Appl. Phys.

Lett., 62, 1993, pp 3485-3487

5. N. Chiem, et al., Room temperature bonding of micromachined glass devices for capillary

electrophoresis, Sens. Actuators, B, 63, 2000, pp 147-152

6. Q.-Y. Tong, et al., Fluorine-enhanced low-temperature wafer bonding of native-oxide covered

Si wafers, Appl. Phys. Lett., 85, 2004, pp 3731-3733

7. Q.-Y. Tong, G. Fountain, P. Enquist, Room temperature SiO2/SiO2 covalent bonding, Appl.

Phys. Lett., 89, 2006, pp 042110/1-042110/3

8. Z. Lin, et al., UV surface exposure for low temperature hydrophilic silicon direct bonding,

Microsyst. Technol., 15, 2009, pp 317-321

9. H. Takagi, et al., Low-temperature direct bonding of silicon and silicon dioxide by the surface

activation method, Sens. Actuators, A, 70, 1998, pp 164-170

10. P. Amirfeiz, et al., Formation of Silicon Structures by Plasma-Activated Wafer Bonding, J.

Electrochem. Soc., 147, 2000, pp 2693-2698

11. M.M.R. Howlader, S. Suehara, T. Suga, Room temperature wafer level glass/glass bonding,

Sens. Actuators, A, 127, 2006, pp 31-36

12. M. Eichler, et al., Atmospheric-pressure plasma pre- treatment for direct bonding

of silicon wafers at low temperatures, Surf. Coat. Technol., 203, 2008, pp 826-829

13. G. Wallis, D. I. Pomerantz, Field assisted glass-metal sealing, J. Appl. Phys., 40, 1969, pp

3946-3649

14. H. Wu, B. Huang, R.N. Zare, Construction of microfluidic chips using polydimethylsiloxane

for adhesive bonding, Lab Chip, 5, 2005, pp 1393-1398

15. B. Ilic, et al., Low Temperature Nafion Bonding of Silicon Wafers, Electrochem. Solid-State

Lett., 2, 1999, pp 86-87

16. F. Niklaus, et al., Low-temperature full wafer adhesive bonding, J. Micromech. Microeng., 11,

2001, pp 100-107.

17. X. Zhou, S. Virasawmy, C. Quan, Wafer-level BCB bonding using a thermal press for

microfluidics, Microsyst. Technol., 15, 2009, pp 573-580.

18. S. Schlautmann, et al., Fabrication of a microfluidic chip by UV bonding at room temperature

for integration of temperature-sensitive layers, J. Micromech. Microeng., 13, 2003, pp S81-

S84

19. S. Carroll, et al., Room temperature UV adhesive bonding of CE devices, Lab Chip, 8, 2008,

pp 1564-1569

20. Z. Huang, et al., A method for UV-bonding in the fabrication of glass electrophoretic

microchips, Electrophoresis, 22, 2001, pp 3924-3929

21. C.-T. Pan, et al., A low-temperature wafer bonding technique using patternable materials, J.

Micromech. Microeng., 12, 2002, pp 611-615.

22. M. Zhang, J. Zhao, L. Gao, Glass wafers bonding via Diels–Alder reaction at mild

temperature, Sens. Actuators, A, 141, 2008, pp 213-216

23. J. Bart, et al., Room-temperature intermediate bonding for microfluidic devices, Lab Chip, 9,

2009, pp 3481-3488

24. S. Liu, et al., Evaporation-induced self-assembly of gold nanoparticles into a highly organized

two-dimensional array, Phys. Chem. Chem. Phys., 4, 2002, pp 6059-6062

25. Y.-T. Li, et al., Gold nanoparticles for microfluidics-based biosensing of PCR products by

hybridization-induced fluorescence quenching , Electrophoresis, 26, 2005, pp 4743-4750

26. N. Crampton, et al., Formation of Aminosilane-Functionalized Mica for Atomic Force

Microscopy Imaging of DNA, Langmuir, 21, 2005, pp 7884-7891



27. FEP-Teflon information page:

http://www2.dupont.com/Teflon_Industrial/en_US/products/product_by_name/teflon_fep/inde

x.html (last viewed on 16-sep-2010)

28. Fluor polymers specifications: http://www.boedeker.com/feppfa_p.htm (last viewed on 16-

sep-2010)

29. Conversation on the 8th of September, 2010 with dr. ir. R.M. Tiggelaar, post-doctoral

researcher at the MCS research group of the MESA+ Institute for Nanotechnology and co-

author of reference [22]

30. FluoroEtch® information page: http://www.actontech.com/fluor1.htm (last viewed on 16-sep-

2010)

31. A. Sklodowska, M. Woźniak, R. Matlakowska, The method of contact angle measurements

and estimation of work of adhesion in bioleaching of metals, Biol. Proc. Online, 1, 1999, pp

114-121

32. S. Prakash, et al., “Click” Modification of Silica Surfaces and Glass Microfluidic Channels,

Anal. Chem., 79, 2007, pp 1661-1667

33. R.C. Bening, T.J. McCarthy, Surface Modification of Poly(tetrafluoro-co-

hexafluoropropylene). Introduction of Alcohol Functionality, Macromolecules, 23, 1990, pp

2648-2655

34. N.Y. Lee, B.H. Chung, Novel Poly(dimethylsiloxane) Bonding Strategy via Room

Temperature “Chemical Gluing”, Langmuir, 25, 2009, pp 3861-3866

35. D.W. Dwight, W.M. Riggs, Fluoropolymer Surface Studies, J. Colloid Interf. Sci., 47, 1974,

pp 650-660

36. B. Coupe, et al., Surface Modification of Poly(tetrafluoroethylene-co-hexafluoropropylene) by

Adsorption of Functional Polymers, Langmuir, 17, 2001, pp 1956-1960

37. R.M. Silverstein, F.X. Webster, D. Kiemle, Spectrometric Identification of Organic

Compounds, 7th edition, John Wiley & Sons, October 2005, ISBN 978-0-471-39362-7, pp

120-124

38. E. Lieber, et al., Infrared Spectra of Organic Azides, Analytical Chemistry, 29, 1957, pp 916-

918

39. The XPS available at the UT:

http://www.utwente.nl/mesaplus/nanolab/equipment/materials%20characterization/152.%20X

PS%20-%20PHI%20Quantera/ (last viewed on 05-oct-2010)

40. Wikibooks about Microfluidics/Hydraulic resistance and capacity:

http://en.wikibooks.org/wiki/Microfluidics/Hydraulic_resistance_and_capacity (last viewed

on 06-01-2011)

41. R.E. Oosterbroek, Modeling, Design, and Realization of Microfluidic components, PhD

thesis, 1999, ISBN: 90-36513464, pp 31-85 (digitally available:

http://doc.utwente.nl/13884/1/t0000019.pdf, last viewed on 06-01-2011)

42. R.C. Weast, M.J. Astle, Handbook of Chemistry and Physics, 59th edition, CRC Press,

1978/1979, ISBN: 0-8493-0549-8, table F-49



Chapter 2.

The Click Chemistry approach



2.1 About Click Chemistry

One of the approaches is CC. This is a relatively new philosophy. See annex 5 for a short introduction

into CC. Click reactions usually have the following criteria [43-44]

:

1. High chemical yield;

2. Application in a wide scope;

3. No generation of side-products, or at least no offensive side-products;

4. It is stereospecific;

5. Simple/mild reaction conditions;

6. No difficult purification of the end product;

7. No harmful solvents are involved;

8. Large thermodynamic driving force (over 84 kJ mol-1

). Due to this fact, a single reaction

product is favoured.

Due to this criteria click reactions are very important in a great amount of different disciplines, for

example biochemistry, drug discovery, materials science, macromolecular science, and surface

chemistry/modification.

In this research the most frequently used “click” reaction will be used, namely the Huisgen 1,3-dipolar

cycloaddition of alkynes and azides to form 1,4-disubstituted-1,2,3-triazoles. This reaction, with the

use of a copper catalyst is often called the “perfect click reaction” or simply referred as “the click

reaction” [45]

. In some cases, ruthenium complexes are used as a catalyst. With this catalyst the

reaction is 1,5-regioisomer favoured [46-48]

. See figure 11 for the reaction mechanism. Other click

reactions are cycloadditions (like Diels-Alder reaction) and addition reactions to carbon-carbon double

bonds [49]

.

Figure 11. Reaction mechanism of the “perfect click reaction”.

The click reaction that is used in this research is the same as in figure 11 but without the copper

catalyst [49]

. The copper catalyst is not necessary for microcontact printing (µCP) [49]

, but this is never

tried for bonding surfaces together. The reason why the catalyst is not used is contamination. A metal

contamination between the surfaces of a chip that needs to operate in a large magnetic field is not

preferred.

As can been seen in figure 11 there are no side-products. This fact makes it attractive for the

construction of MEMS and LoC devices. And this is also reason why there is chosen for this bonding

technique.



2.2 Developed bonding technique

There was no useful bonding description found in the literature. The author developed a technique by

combining different articles.

As can been read in the previous chapter, a terminal alkyne and an azido-group are necessary for the

Huisgen 1,3-dipolar cycloaddition. With this fact there are two possibilities, namely the azido-group

on the glass substrate and the terminal alkyne on the FEP-foil intermediate or the terminal alkyne on

the glass substrate and the azido-group on the FEP-foil intermediate.

The first possibility is chosen because the second way needs a copper catalyst [50]

. And the use of

catalysts is not preferred as this will lead to contamination between the layers.

To achieve this click reaction, an azido-group must be mounted as a SAM on a glass substrate. This is

done in several steps which are explained below.

The first step is to clean and activate the glass substrate [1, 23]

. This is done with a Piranha solution

(96% H2SO4 / 31% H2O2 3:1 v/v mixture) followed by a quick dump rinsing in DI-water. The Piranha

solution is used to remove all the organic compounds on the surface of the glass substrate, and it will

also hydroxylate the surface (activation of the surface). This hydroxylation is necessary for the next

step. The hydroxylated surface is shown as surface 1 in figure 12.

After the cleaning and hydroxylation of the glass substrate, a durable 11-bromoundecylsiloxane SAM

is formed [51]

. This is done with an 11-bromoundecyltrichlorosilane solution in toluene. In this solution

11-bromoundecyltrichlorosilane splits in an 11-bromoundecylsiloxane ion and three chloride ions.

This trichlorosilane-functional initiator was chosen for the formation of the SAM, since these kinds of

molecules reacts relatively fast with the silanol groups on the glass substrate to form a durable SAM

with a cross-linked siloxane network [52-54]

. See substrate 2 in figure 5 for the glass substrate with the

11-bromoundecylsiloxane SAM.

Figure 12. The formation of the 11-bromoundecylsilane SAM with a cross-linked siloxane network.

Besides the used 11-bromoundecyltrichlorosilane there is also the possibility to perform the monolayer

formation with 3-bromopropyltrichlorosilane. This shorter one is not chosen because 11-

bromoundecyltrichlorosilane gives a stronger SAM, due to the greater amount of the Van der Waals-

force between the longer carbon chains [55]

. So 11-bromoundecyltrichlorosilane is more used than the

shorter version and therefore there is more information available about the formation about the 11-

bromoundecylsilane SAM‟s than about 3-bromopropylsilane SAM‟s.



Figure 13. The substitution of the bromide with an azido-group.

The third step of the glass surface modification is the substitution of the bromo-group with an azido-

group (see figure 13) [56]

. This is done by putting substrate 2 in a saturated solution of sodium azide in

DMF. The reaction is a SN2 nucleophilic substitution with sodium bromide as a side product [57]

, see

figure 14. There is chosen for the bromine terminated version of the alkyl because these have a higher

reactivity (better leaving group) than the chloride version. There is one other, more reactive

nucleophile, namely iodide, but this one is too reactive [58]

.

Figure 14. Nucleophilic substitution (SN2) of bromine with sodium azide.

The glass substrate is finished and ready for the click reaction. The next step is the modification of the

FEP-foil.

The first step of the FEP-foil modification is the stripping of the fluorine atoms from the carbon

backbone [1, 23]

. As mentioned in the previous chapters, this is done with FluoroEtch®. During this

procedure a brownish layer of sodium naphthalene is formed on the surface. After cleaning with

Piranha solution the carbon backbone gets protonated and oxidized to carboxyl groups and hydroxyl

groups (carboxylic acids).

Figure 15. The FEP-foil treatment, fluorine-stripping and protonation and oxidation.

The second step is to add a terminal alkyne on surface 5. This is done through an esterification with

propargyl alcohol [59]

.



This is done with the use of EDC and DMAP in DCM. The DMAP is a base catalyst used to make the

reaction more efficient. The EDC is used to consume the liberated water that is formed during the

reaction. Therefore this reaction must be performed under an inert and dry nitrogen atmosphere and

the DCM must be water free. This can be achieved with a 4Å molecular sieve.

Figure 16. Esterification of FEP-foil surface 5.

This esterification is the last step before the click reaction. This kind of click reactions is as far as the

author knows, never done with two complete surfaces, only with µCP [51]

.

The mechanism of the click reaction is shown in figure 11. The author thinks that the click reaction

that is performed in this research is 1,4-regioisomer selective, because of the great steric hindrance of

the SAM. The azido-group is on top of the SAM and the terminal alkyne is on top of the FEP-foil,

therefore it is not thinkable that the 1,5-regioisomer will be formed.

The click reaction is done by laying the modified FEP-foil on top of a modified glass substrate with a

fluidic channel and on top of the FEP-foil another modified glass substrate, but without a microfluidic

channel. These layers are pressed together for 5-6 h with a load of ± 0.27 metric tons per cm2.

After the reaction is finished the bond will look like the schematic view in figure 17.

Figure 17. Schematic view of the theoretical formed bond.

After the reaction the FEP-foil will be cut on the right size and the bond will be tested for its strength.

After each step the surface will be analyzed with contact angle measurements and FT-ATR-IR. At the

end a SEM image will be recorded of the cross-sectional view of the microfluidic channels, to look if

the channel is still fine. It is also possible to analyse the surfaces with XPS, but this method is very

expensive (around € 200.00 per hour). For detailed information about the steps, see annex 2.



2.3 Results

This method is done 3 times. After every time there were some remarks to improve the method.

During the experiment some interesting results are found. These results are given per step. For detailed

information about the steps, see annex 2.

2.3.1 Step 1, the glass treatment

This step was done 3 times. The first time it was done in a beaker containing 60 mL Piranha. A bigger

volume could not be used because the wet benches for Piranha cleaning in the new clean room were

not operational. See figure 18 for the used equipment. The Piranha was removed by dipping the holder

with chips in 4 baths of DI-water and subsequently dried in the oven (20 min at 120°C).

Figure 18. First Piranha cleaning.

The second and third time it was done in the clean room with a container containing 2 L of Piranha

and the Piranha was removed by quick dump rinsing and afterwards they were spin-dried.

There was a big difference between the two methods because bigger holders were used in the

container. The holders that were used in the beaker covered a part of the glass chips. This covered part

of the glass did not have enough contact with the Piranha. This was visible during the drying. The

covered area did not dry very well.

A contact angle measurement is done after this step. The contact angle for normal glass was 47.2°

(only a static analysis was done) and the contact angles for Piranha cleaned glass were 23.3° in the

static mode and19.5° with a standard deviation of 5.60 in the ARCA mode. This value is not as low as

the found reference value [23, 32]

because the measurement was done a few days after cleaning. In this

period the glass got deactivated.

Figure 19. The home-made nitrogen reaction chamber.



The bromine and azide functionalized SAM formation were carried out in a Petri dish that was put into

a home-made nitrogen chamber. See figure 19 for a photograph of this home-made reaction chamber.

It was made with an exsiccator and a plastic garbage bag. The plastic bag is for protection of the

samples against PDMS waste. The exsiccator was mostly used for PDMS curing.

After these 2 steps there were also some contact angle measurements done. The contact angles for the

bromo terminated glass were 82.8° in the static mode and 79.1° with a standard deviation of 10.40 in

the ARCA mode. The ARCA mode measurements are shown in figure 20.

Figure 20. The ARCA mode contact angle measurement of the bromo-terminated glass.

The contact angles of the azide functionalized glass were 82.0° in the static mode and 81.8° with a

standard deviation of 8.22 in the ARCA mode. The ARCA mode measurements are shown in annex 6.

There were also FT-ATR-IR measurements done after these steps. These spectra showed the results

that are showed in table 4.

__________________________________________________________________________________ Table 4. Explanation of the found peaks.

Glass functionality Peak in cm-1

Explanation

Bromo 975-800 Alkyl bromides

Azide 992-800 Alkyl bromides

1375 Azide

__________________________________________________________________________________

See annex 6 for all the ARCA scatter plots, photographs of the droplets of the contact angle

measurements and the FT-ATR-IR spectra.

2.3.2 Step 2, the FEP-foil treatment, part 1

The FluoroEtch® was heated up to 60°C on a hotplate prior to the treatment. After that the

FluoroEtch® was put into a glass box with a heating device, thermometer, and argon degassing system.

The box is shown in figure 21.

0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000

Co

nta

ct a

ngl

e

Number of measurements



Figure 21. The FluoroEtch® set up.

The pressure of the argon flow was maintained at 0.7 bar. The total amount of sheets that where

prepared was 3.

The sheets were put into home-made holders. See figure 22 for an example before treatment. The rings

have a diameter of 15 cm.

It is necessary to move the sheet around in the FluoroEtch® during the exposure. This was done by

moving the sheet up and down, from left to the right, and from the front to the back. During this

movement the whole sheet of FEP-Teflon comes in good contact with the FluoroEtch®.

Figure 22. The holding device with FEP-foil before and after the FluoroEtch® treatment.

Picture is taken with permission from [23].

After the washing of the sheets they were covered with a nice brownish sodium naphthalene residue

layer, as described in previous research [22]

. It was not possible to fully dry the sheets after washing in

IPA, 70°C DI-water, and RT DI-water. It was not possible to dry the sheets completely. A few

droplets stayed behind.

A beaker was used during the first Piranha cleaning of the FEP-Teflon (the same as with the glass

cleaning). After this cleaning treatment there was still a brownish residue layer on the sheet. The

second and third foil were cleaned in the same container as the glass, the one with 2 L of Piranha.



After this treatment the residue was almost completely removed. The reason for this is the diffusion

rate of the waste in the Piranha solution. With a greater amount of Piranha there is also a greater

amount of “useable” Piranha and the waste is more diluted in the big volume, in other words: the

reactive volume is higher.

The contact angle measurements for a piece of FEP-Teflon without any treatment showed a contact

angle of 85.3° in the static mode and 83.7° with a standard deviation of 4.88 in the ARCA mode. The

contact angle for FluoroEtch® treated FEP-Teflon in the static mode was 62.9° and in the ARCA mode

it was 46.9° with a standard deviation of 13.66. The contact angles decreased to 9.9° in the static mode

and 10.5° with a standard deviation of 4.57 in the ARCA mode after Piranha cleaning of the

FluoroEtch® treated FEP-Teflon. The last sample was taken after the third cleaning.

There were also FT-ATR-IR measurements done after these steps, but these spectra were all the same.

They showed 2 sharp peaks, one around 1200 cm-1

and one around 1150 cm-1

. These correspondents

with the FEP-Teflon peaks that were found in the reference (see table 3). More literature study learned

that FT-ATR-IR with a Golden Gate ATR is not suitable for the FEP-Teflon because the penetration

depth of the light is too deep, namely between 0.1 µm and 1 µm deep [60]

and the surface modifications

only occur at a depth of a few Ånströms [1, 23]

.

2.3.3 Step 3, the FEP-foil treatment, part 2, esterification

The first time this step was done in a Petri dish and on a closable stirring plate. In this chamber there

was a continuous flow of nitrogen. This gave problems with stirring because the Petri dish was not

high enough. During the second and third time a large flat beaker with a Petri dish were used. See

figure 23 for a photograph of the used equipment.

The reaction was started at the beginning of the afternoon and the FEP-Teflon foil was turned at the

end of the afternoon and it stayed in the solution overnight.

Figure 23. The stirring plate with flat beaker and a Petri dish on top. The tube is the nitrogen inlet.

The contact angles of the surface after the esterification were 39.6° in the static mode and 31.5° with a

standard deviation of 9.72 in the ARCA mode.

FT-ATR-IR analysis showed the same results as during the previous step.



See annex 6 for all the ARCA scatter plots, photographs of the droplets of the contact angle

measurements and the FT-ATR-IR spectra.

A part of the FEP-Teflon foil was also activated in a solution of 1 mM Cu2SO4•5H2O and 10 mM

sodium ascorbate (ascorbic acid) in 50 mL H2O for 1 h. Followed by washing with DI-water and

drying with nitrogen stream. This activation was recommended by Carlo Nicosia from the Molecular

Nanofabrication (MNF) research group.

2.3.4 Step 4, the bonding reaction

A Carver Model 3851 CE Hydraulic plate with

electrically heated platens/controls is used for the

bonding. See figure 24 for a picture of the used

press.

It is very important that the chips are of the same

height. Two different chips were used during the

first time. The thickest chips were completely

pulverized at the moment the pressure was

applied because that pressure was calculated for

the area of all chips together. The thickest chips

were around a quarter of the total area. The

thinner ones broke after they thickest chips were

pulverized because they got also too much

pressure.

The pressure that is used was 0.4 metric tons per

cm2.

During the second and third run a lower pressure

was applied, namely 0.27 ± 0.03 metric tons per

cm2.

2.3.5 Testing of the bond

The bond was tested with the maximum pressure test. There was not enough time to do the pull tests,

the SEM analysis and the chemical compatibility test.

2.3.5.1 Maximum pressure test

The chips were mounted in the home-made Teflon chip holder. See figure 25 for a photograph of a

mounted chip.

Figure 25. A chip mounted in the home-made chip holder.

Figure 24. The used Carver 3851 CE Hydraulic plate.



The maximum pressure tests give the results shown in table 5. Equation 1.7, 1.11 and 1.16 are used for

the calculation of the pressure drop ( ).

__________________________________________________________________________________ Table 5. Results maximum pressure tests.

Chip Age of chips Max

in µl/min

in bar

in bar

1.1 without activation 2.5 weeks 55 0.351 2.620 2.978








1 without activation 3 days 80 0.511 3.811 4.329



1 with activation 3 days 45 0.288 2.144 2.439



__________________________________________________________________________________

2.4 Conclusion and discussion

After all the experiments the following conclusion can be made.

The developed bond is not strong in comparison with the previous developed EDC-NHS bond. The

major cause is the FEP-Teflon foil treatment. The Piranha cleaning step is very sensitive and the 90 s

described in previous research is not always long enough for making the foil transparent. There was a

big difference between the second and third foil. The third foil was more transparent and therefore the

maximum pressure was higher. This is visible in table 6. The chips with an age of 3 days are made out

of the third cleaned foil.

It is also not sure if the esterification occurred. The contact angle measurements showed an increased

value between the Piranha cleaned FEP-Teflon foil and the esterificated FEP-Teflon foil. So there

occurred a change between the functionality of the surface, but it was not possible to confirm the

alkyne terminated surface.

There occurred some kind of bonding reaction, although it was not possible to say if it was the click

reaction. The average inside the channels is shown in table 6 and figure 26. The black error bars

indicate the standard deviation. The outlier of 15.406 bar is excluded in the purple bar.

__________________________________________________________________________________ Table 6. Average of the maximum pressure tests.

Age of chips Activation of FEP Amount of chips Average Standard deviation

2.5 weeks No 8 2.6 0.56

3 days No 3 7.9 6.48

3 days, without outlier No 2 4.2 0.19

3 days Yes 3 3.3 0.82



Figure 26. Comparison of the fluidic bond strength. The bars show the standard deviation of the data.

__________________________________________________________________________________

There was also no difference between activated FEP-Teflon foil and not activated FEP-Teflon foil.

Besides this conclusion there are also some remarks on the method.

First of all FT-ATR-IR with Golden Gate ATR is not suitable for the FEP-Teflon foil because the

penetration depth is too deep. The foil gets activated in a few Ångströms depth [1, 23]

and the

penetration depth of FT-ATR-IR with Golden Gate ATR is between the 0.1 µm and 1.0 µm [60]

. It can

be useful to redo this method and analyse the surfaces with another kind of IR spectroscopy method

with a lower penetration depth or with XPS.

A relative big volume of Piranha must be used for the cleaning of the glass and FEP-Teflon foil. A

container with 2 L of Piranha is good. The diffusion of the used Piranha and the waste is bigger than in

a beaker containing 60 mL of Piranha. There is also more reactive Piranha available.

0

2

4

6

8

10

12

14

16Fl

uid

ic P

ress

ure

(b

ar)

2.5 weeks old chips, no activation of FEP

3 days old, no activation of FEP

3 days old, no activation of FEP (without outlier)

3 days old, activation of FEP



2.5 References

43. H.C. Kolb, M.G. Finn, K.B. Sharpless, Click chemistry: diverse chemical function from a few

good reactions, Angew. Chem. Int. Ed., 40, 2001, pp 2004-2021

44. R.A. Evans, The Rise of Azide–Alkyne 1,3-Dipolar „Click‟ Cycloaddition and its Application

to Polymer Science and Surface Modification, Aust. J. Chem., 60, 2007, pp 384-395

45. T. Lummerstorfer, H. Hoffman, Click Chemistry on Surfaces: 1,3-Dipolar Cycloaddition

Reactions of Azide-Terminated Monolayers on Silica, J. Phys. Chem. B., 108, 2004, pp 3963-

3966

46. Binder W. H., Sachsenhofer R., „Click‟ Chemistry in Polymer and Materials science,

Macromol. Rapid comm., 28, 2007, p 41

47. L. Zhang, et al., Ruthenium-Catalyzed Cycloaddition of Alkynes and Organic Azides, J. Am.

Chem. Soc., 127, 2005, pp 15998-15999

48. B.C. Boren, et al., Ruthenium-Catalyzed Azide-Alkyne Cycloaddition: Scope and

Mechanism, J. Am. Chem. Soc., 130, 2008, pp 8923-8930

49. M. Zhang, J. Zhao, L. Gao, Glass wafers bonding via Diels-Alder reaction at mild

temperature, Sensor Actuat. A., 141, 2008, pp 213-216

50. W.H. Binder, R. Sachsenhofer, ‘Click‟ Chemistry in Polymer and Materials science,

Macromol. Rapid comm., 28, 2007, pp 15-54

51. D.I. Rozkiewicz, et al., “Click” Chemistry by Microcontact Printing, Angew. Chem. Int. Ed.,

45, 2006, pp 5292-5296

52. S. Edmondson, W.T.S. Huck, Controlled growth and subsequent chemical modification of

poly(glycidyl methacrylate) brushes on silicon wafers, J. Mater. Chem., 14, 2004, pp 730-734

53. A.Y. Fadeev, T.J. McCarthy, Self-Assembly Is Not the Only Reaction Possible between

Alkyltrichlorosilanes and Surfaces: Monomolecular and Oligomeric Covalently Attached

Layers of Dichloro- and Trichloroalkylsilanes on Silicon, Langmuir, 16, 2000, pp 7268-7274

54. A. Ulman, Formation and Structure of Self-Assembled Monolayers, Chem. Rev., 96, 1996, pp

1533-1554

55. MESA+ meeting 14-September-2010, Seminar: Designing, Measuring, and Controlling

Molecular and Supramolecular Devices by prof. Paul Weiss, University of California, Los

Angeles, USA.

56. G.A. Holmes, E. Feresenbet, D. Raghavan, Using self-assembled monolayer technology to

probe the mechanical response of the fiber interphase-matrix interphase interface, Compos.

Interface., 10, 2003, pp 515-546

57. Solution manual for: Burrows, et al., Chemistry, Oxford University Press:

http://www.oup.com/uk/orc/bin/9780199277896/01student/solutions/ch20student.pdf (last

viewed on 03-jan-2011)

58. Information powerpoint sheets about nucleophilic substitution and competing elimination:

http://chemconnections.org/organic/chem226/Presentations/Chap08-Sn2-08/Chapter08-Sn2-

08.pdf (last viewed on 05-oct-2010)

59. R. Ranjan, W.J. Brittain, Combination of Living Radical Polymerization and Click chemistry

for surface modification, Macromolecules, 40, 2007, pp 6217-6223 60. A. Tuchbreiter, et al., High-Throughput Evaluation of Olefin Copolymer Composition by

Means of Attenuated Total Reflection Fourier Transform Infrared Spectroscopy, J. Comb.

Chem., 3, 2001, pp 598-603



Chapter 3.

The amine-epoxy bond approach



3.1 About the amine-epoxy bond

Recently a new bonding technique was introduced for bonding 2 pieces of PDMS [34]

. Because PDMS

is transparent, this technique can be used to manufacture microfluidic devices. This “chemical gluing”

technique that is reported is based on the reaction between the functional amine and epoxy groups in

aminosilane and epoxysilane. These aminosilane and epoxysilane are anchored on the PDMS surface

and then hold together at RT for 1 h to form a strong amine-epoxy bond. After the reaction the bond

was very robust and it could withstand an intense introduction of liquid whose per-minute injection

was almost 2000 times larger than the internal volume of the used microfluidic channels. This

technique of amine-epoxy bonding is used in this research with glass substrates and FEP-Teflon

intermediate layers instead of PDMS. This technique is never used for the bonding of glass and FEP.

The author invented a bonding technique that is composed from different references. It is not

completely sure if it will work.

Epoxides are cyclic ethers with only three ring atoms. Because there are only three ring atoms, the

structural formula of an epoxide is like an equilateral triangle with angles of 60°. Due to this small

cyclic structure there is a great force on its ring. Therefore epoxides are more reactive than normal

ethers [61]

.

3.2 Developed bonding technique

The major challenge with this technique is the replacement of PDMS with FEP and glass. In this

research the microfluidic valve is made of a piece of FEP-foil between two pieces of glass. The

APTES modification of the glass is not the problem. This is a very common technique and this

technique is very often done [23, 62-63]

. But methods for the creation of a hydroxylic surface on FEP-foil

were very hard to find. There are a lot of research groups that describe a Radio Frequency Glow

Discharge (RFGD) plasma deposition technique with a plasma that consists of a gas/liquid mixture, in

this case H2/MeOH [64-70]

. This technique was not possible at the UT because it needs a modified

RFGD plasma deposition apparatus to introduce the H2/MeOH mixture inside the plasma chamber and

this was not available at the UT. But there was an alternative method found by the author and this is

described further on.

First the glass substrate is modified. This is done via a regular method [23]

. First the glass is cleaned

and activated in a Piranha solution in order to obtain a hydroxylated glass surface. After the activation

the substrate is put into an APTES solution in ethanol in order to obtain an aminosilaneted monolayer.

Figure 27. APTES monolayer formation on Piranha activated glass.

The treatment of the FEP-Teflon is the biggest problem because there is no RFGD plasma deposition

device at the UT. Another way to create a hydroxylated surface on FEP-Teflon was found [33]

. This

article describes a fluorine stripping technique with a homemade sodium naphthalene solution. But in

this research FluoroEtch® is used because sodium naphthalene is the reactive component of

FluoroEtch®.



The FEP-Teflon is treated with FluoroEtch® like it is done in chapter 2.2, but now the brown residue is

left on the surface in order to protect the carbon backbone from protonation and oxidation.

Figure 28. FluoroEtch® treatment.

After this treatment the FEP-Teflon with brownish sodium naphthalene residue is put in a solution of

borane in THF.

Figure 29. Creation of a hydroxyl surface (FEP-OH).

After 18 hours the FEP-Teflon is washed with THF and an aqueous peroxide solution is added. After 3

hours at 0°C the FEP-foil is washed with diluted NaOH, diluted HCl, water, and THF and afterwards

dried at a reduced pressure.

This borane treatment is used instead of the O2 plasma treatment that was used in the research

described in the used article [34]

.

The dried FEP-foil is put in a solution of GPTMS in water or hexane. After 20 minutes the FEP-foil is

washed with DI-water and ultrasonically cleaned with hexane and methanol and dried with nitrogen.

Figure 30. Creation of an epoxy functionalized FEP-foil surface.

Now both parts are ready for the bonding reaction. This is done by simply putting the modified FEP-

foil on the modified glass substrate and after 1 h at RT with ± 0.3 metric tons per cm2 the reaction is

finished.



Figure 31. Amine-epoxide reaction mechanism.

And the final bond that is formed is shown in figure 32.

Figure 32. Schematic view of the theoretical formed bond.

3.3 Results

This method is not tested, due to some problems with the wet benches in the new Nanolab clean room.



3.5 References

61. http://chemistry2.csudh.edu/rpendarvis/EtherSH.html

62. M. Qin, et al., Two methods for glass surface modification and their application in protein

immobilization, colloid surface B, 60, 2007, pp 243-249

63. S. Flink, F.C.J.M. van Veggel, D.N. Reinhoudt, Functionalization of self-assembled

monolayers on glass and oxidized silicon wafers by surface reactions, J. Phys. Org. Chem., 14,

2001, pp 407-415

64. D.J. Tarnowski, E.J. Bekos, C. Korzeniewski, Oxygen Transport Characteristics of

Refunctionalized Fluoropolymeric membranes and Their Application in the Design of

Biosensors Based upon the Clark-Type Oxygen Probe, Anal. Chem., 67, 1995, pp 1546-1552

65. T.G. Vargo, et al., Monolayer Chemical Lithography and Characterization of Fluoropolymer

Films, Langmuir 8, 1992, pp 130-134

66. L. Sigurdson, et al., A comparative study of primary and immortalized cell adhesion

characteristics to modified polymer surfaces: Toward the goal of effective re-epithelialization,

J. Biomed. Mater. Res., 59, 2002, pp 357-365

67. U.S. Patent 4,946,903 Oxyfluoropolymers Having Chemically Reactive Surface Functionality

And Increased Surface Energies

68. U.S. Patent 5,266,309 Refunctionalized Oxyfluoropolymers

69. U.S. Patent 5,627,079 Refunctionalized Oxyfluorinated Surfaces

70. D.J. Hook, et al., Silanization of Radio Frequency Glow Discharge Modified Expanded

Poly(tetrafluoroethylene) Using (Aminopropyl)triethoxysilane, Langmuir, 7, 1991, pp 142-

151



Chapter 4.

Summarized conclusion and discussion,

and future perspectives



4.1 Summarized conclusion and discussion

Two different bonding techniques are developed during this research. One of these bonds is tested

experimentally, namely the CC bonding technique.

Maximum pressure tests showed that the bond is not stronger than the EDC-NHS bond that was

developed by Jacob Bart [1, 23]

.

The following points are given as recommendations:

- Redo the CC bonding technique, but with adequate surface analysis methods. Contact angle

measurements and FT-ATR-IR are used in this research. The first method only tells you

something about the hydrophilicity/hydrophobicity of the surface, but it does not tell you

anything about the composition. The second method is performed with a Golden Gate ATR,

but this is not suitable for this kind of chemistry. The penetration depth is too big. The

modifications are performed on a nanometer scale, but the penetration of the light is between

0.1 µm and 1.0 µm [60]

.

- The Piranha cleaning of the FEP-Teflon foil is very sensitive. The foil must be completely

transparent. The esterification can‟t occur if it is not transparent enough. The 90 s described in

the article of Jacob Bart [23]

is not always long enough. It is recommended to watch the foil

and take it out of the Piranha when it is transparent. It would be of interest to look for other

surface modifications of FEP-Teflon foil, for example plasma treatment.

- Perform the amine/epoxy bonding technique.

- Maybe it is also possible to perform a bonding reaction based on a Diels-Alder reaction.

4.2 Future perspectives

This kind of bonding can be very useful for pneumatic controlled microfluidic valves. See figure 33

for an example.

These valves consist of a fluidic chip and a pneumatic chip with a piece of FEP-Teflon between. The

channel will be closed if pressure is applied in the pneumatic chip. And the channel in the chip is open

when there is a vacuum applied in the air chamber of the pneumatic chip.

Figure 33. The cross-section view of a microfluidic valve.

These microfluidic valves can be used as a sample shuttling system in the µDNP-HR-1HNMR system.

The sample can be transferred as a small liquid plug in the chemically inert fluorinert solvent. See

figure 34 for a design developed by P. Kurek MSc.



Figure 34. The design for a sample shuttling system.

It can be used for many more application because of the great transparency and chemical inertness of

the FEP-Teflon.



Nederlandse samenvatting In dit onderzoek is er gekeken naar een binding tussen glas en FEP-Teflon folie. Een eerder

ontwikkelde manier ging uit van EDC-NHS chemie. Deze methode had als nadeel dat er relatief

gezien veel bijproducten waren. Er is dus gekeken naar een alternatieve methode.

In dit onderzoek zijn twee verschillende methodes gevonden, eentje gebaseerd op de reactie tussen een

alkyn en een azide (Click Chemie) en de andere op de reactie tussen een amine en een epoxy groep.

Deze eerste methode is experimenteel getest.

Voor deze Click Chemie binding moest een azidegroep op het glassubstraat gezet worden en een

alkyngroep op het FEP-Teflon. Deze eerste is relatief vaak uitgevoerd in andere onderzoeken. Deze

azide groep wordt bereikt door eerst een laag van 11-broomundecyltrichloorsilaan op het glas te zetten

en daarna de broomgroep voor een azidegroep te vervangen. Dit gebeurt met natrium azide. De tweede

stap is echter een stuk moeilijker, mede dankzij de chemische inertheid van het FEP-Teflon. Deze is

uiteindelijk uitgevoerd door de folie eerst met FluoroEtch® te behandelen. Dit haalt tot een paar

Ångströms diepte de fluoratomen van de folie. De vrij liggende koolstof reageert vervolgens met de

lucht tot carboxylzuurgroepen. Deze groep kan vervolgens een esterificatie met propargyl alcohol aan

gaan, om zo een alkyngroep te krijgen. Deze esterificatie is nooit eerder op een oppervlakte

uitgevoerd. Na deze stap kunnen de oppervlaktes aan elkaar gezet worden door middel van een druk.

Om de amine/epoxy binding te kunnen doen moet eerste een APTES laag op het glas gezet worden.

Deze stap is wereldwijd in veel onderzoeken gebruikt en levert een amine functionaliteit op het glas

op. Een manier om een epoxy groep aan de folie te krijgen was wat moeilijker. Om dit voor elkaar te

krijgen kan GPTMS gebruikt worden, maar hiervoor moet eerst een oppervlakte met hydroxylgroepen

gemaakt worden. Veel van de gevonden artikelen beschrijven een manier die op de Universiteit

Twente niet uit te voeren is, namelijk een RFGD plasma depositie methode met een H2/MeOH

mengsel als plasma. Er is uiteindelijk een manier gevonden om na de FluoroEtch® behandeling de

vrije koolstofatomen te hydroxyleren. Na deze stap kan GPTMS op het oppervlak gezet worden,

waarna de oppervlaktes tegen elkaar gedrukt kunnen worden.

Gedurende dit onderzoek was er alleen tijd om de Click Chemie binding te proberen. Na het

aanbrengen van de druk zaten het glas en de folie aan elkaar. Na het testen van de sterkte bleken de

kanaaltjes de drukken die weergegeven zijn in tabel 7 aan te kunnen. Het verschil in leeftijd komt door

een vakantie.

__________________________________________________________________________________ Tabel 7. Gemiddelde van de maximale druk testen.

Leeftijd van de chips Activatie van FEP Aantal Gemiddelde Standaard deviatie

2.5 weken Nee 8 2.6 0.56

3 dagen Nee 3 7.9 6.48

3 dagen, zonder uitschieter Nee 2 4.2 0.19

3 dagen Ja 3 3.3 0.82

__________________________________________________________________________________

De uitschieter had een maximum druk van iets meer dan 15 bar. De oppervlakten zijn telkens met

contacthoek metingen en FT-ATR-IR geanalyseerd.

In dit verslag worden ook nog andere analyse methodes besproken, maar deze zijn net als de amine-

epoxy binding niet uitgevoerd wegens opstartproblemen in de nieuwe clean room.

Uit de resultaten kan de conclusie getrokken worden dat deze bindingsmethode niet sterker is dan de

vorige EDC-NHS bindingsmethode.

Sleutelwoorden: Chemical surface modification, Click Chemistry, Microfluidic chip/valve, amine-

epoxy bonding.



Dankwoord Dit onderzoek is tot stand gekomen dankzij een aantal mensen. Deze wil ik dan ook graag wil

bedanken.

Allereerst wil ik professor Han Gardeniers bedanken voor deze stageplek. Met hem werd ik in contact

gebracht toen ik aangaf dat ik graag een stage richting de microfluidics/lab-on-a-chip wilde doen.

The man who I need to thank the most is Piotr Kurek. He was my internship trainer. I learned a lot

from him and he always tried to answer my questions. Sometimes he could not give me an answer,

because his background was electrical engineering. But then he pushed me in the proper direction. I

wish him the best with his promotion!

Een andere man wie ik veel dank verschuldigd ben is Roald Tiggelaar. Toen ik er net begon was hij

bezig met zijn laatste maand als postdoctoraal onderzoeker. Hij was de laatste nog aanwezige die met

Jacob Bart heeft samengewerkt aan de EDC-NHS bonding techniek. In deze laatste maand heeft hij

me veel (praktische) tips gegeven. Toen hij eenmaal weg was kon ik hem ook nog altijd blijven

mailen. Hiervan heb ik dan ook dankbaar gebruik gemaakt.

Ik noemde hem net al, maar ook Jacob Bart wil ik graag bedanken. Hij heeft tijdens zijn PhD traject

een bonding techniek ontwikkeld die berust op EDC-NHS chemie. Hierin maakte hij de aanbeveling

om ook eens naar Click Chemistry te kijken. Dit heb ik dus gedaan. Hij stond altijd klaar om mijn

mails te beantwoorden. Ook wil ik hem bedanken voor het toestemming verlenen voor het gebruik van

zijn afbeeldingen.

Iemand anders wie ik graag wil bedanken is Brigitte Bruijns. Zij heeft zowel mijn verslag als

presentatie doorgelezen en van de nodige nuttige tips voorzien. Heel erg bedankt!

I also need to thank Carlo Nicosia MSc for his advice for the Click Chemistry technique. He is a PhD

student in the Molecular Nanofabrication (MNF) research group.

There is another person who I would like to thank. His name is Burak Eral and he introduced the

contact angle measurement device to me. Without his help I was not enable to operate the device.

Thank you very much for your time!

There is a group of people that I would like to thank for the great lunches we had. And after the lunch

we always took a cup of coffee or tea (in my case strong espresso). I am not going to name everybody

because I am afraid that I am going to forget somebody. So I say to everybody: Thank you very much!

It is impossible to mention every person that I have spoken with. So everybody that is not listed here

and contributed in what kind of way whatsoever thank you very much!


I Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Annexes.


II Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Annex 1. The institute

For the internship part of the bachelor Chemistry I have chosen for an assignment at the Mesoscale

Chemical Systems (MCS) research group. This research group is a part of MESA+ Institute for

nanotechnology, which is a part of the Faculty Science and Technology (TNW, “Technische

Natuurwetenschappen”).

About MESA+

As mentioned before MESA+ is a part of the Faculty TNW at the University of Twente. It is one of the

largest micro- and nano-technology research institutes in the world and created a perfect place for

start-ups in the micro- and nano-industry to establish their company and to develop [1]

. It started in the

year 2000 and currently it has the organizational structure that is displayed in figure 35.

Figure 35. Organizational structure of MESA

+ [5]

.

The institute falls under the responsibility of

the University Executive Board. The MESA+

Scientific Advisory Board assists MESA+

management in matters concerning research

done at the institute and gives feedback on

the scientific results of that research. The

MESA+ Governing Board advises MESA

+

management in organizational matters. The

Scientific Director accepts responsibility for

the institute and the scientific output. The

current Scientific Director is prof. dr. ing.

Dave. H. A. Blank and the Technical

Commercial Director is ir. Miriam Luizink. The Managing Director is

responsible for commercialization, central laboratories, finance, communications and the internal

organization. The participating research groups and the Strategic Research Orientations program

directors form the MESA+ advisory board

[5].

The institute employs a multidisciplinary team of 500 people of which 275 are PhD‟s or postdoc

researchers. Thanks to this unique structure of researchers from different scientific disciplines they

support and facilitate the researchers and stimulate (inter)national cooperation actively [1]

.

Figure 36. prof. dr. ing

Dave. H. A. Blank [5]

.

Figure 37. Ir. Miriam

Luizink [5]

.


III Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

MESA+ combines a great amount of disciplines. For example: nanotechnology, electromagnetism,

optics, acoustics, solid-state physics, materials science and technology, microelectronics,

biophysics/clinical physics, electrical engineering, and mathematics [1, 4]

. These researchers are divided

in a great amount of multidisciplinary research groups [2, 3]

:

Biomolecular electronic structure;

Biomolecular nanotechnology;

Biosensors, the Lab-on-a-chip group;

Catalytic processes and materials;

Complex photonic systems;

Computational materials science;

Constructive technology assessment;

Inorganic materials science;

Integrated optical microsystems;

Interfaces and correlated electron systems;

Laser physics and nonlinear optics;

Low temperature division;

Materials science and technology of polymers;

Membrane technology group;

Mesoscale chemical systems;

Molecular nanofabrication;

Nanobiophysics;

Nanoelectronics;

Nanoionics;

Optical science;

Physical aspects of nanoelectronics;

Physics of complex fluids;

Physics of fluids;

Semiconductor components;

Solid state physics;

Supramolecular chemistry and technology;

Transducers science and technology.

For more about a research group, please see:

http://www.utwente.nl/mesaplus/participating_research_groups/

In these research groups internationally appealing research is achieved through this multidisciplinary

way of working. To date, MESA+ already made more than 40 high-tech start-ups. To achieve this

amount of start-ups, they have a targeted program for setting up small and medium-sized enterprises.

These start-ups and MESA+ work together to promote the transfer of knowledge and to form a bridge

between research and industrial application [1]

.

Besides the different research group laboratories MESA+ has its brand new NanoLab facilities. These

facilities contain about 1000 m2 of clean room space and state of the art research equipment. The build

of this building was ended in 2010 and it will be fully operational at the end of 2010 [5]

.


IV Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Figure 38. Impression of the new MESA

+ NanoLab

[5].

Here the red part with the chimneys is the laboratory/clean room part and the trapezium part with all the windows is the

office part. This is an animated view. The real building only has three chimneys.

MESA+ has an integral turnover of 45 million euro per year of which 60% is acquired in competition

from external sources [1]

.

About the Mesoscale Chemical Systems research group

As mentioned in the last paragraph MCS is a part of MESA+ and it is the research group where this

intern is done.

The aim of this research group is to study the behaviour and control of fluids and can be summarized

in three main themes [3]

:

I. “Exciting” chemistry in microreactors, focusing on microfluidic systems to which electronically

controlled stimuli are applied in order to control the course of chemical reactions.

II. Microfluidic process analytical technology (µPAT), focusing on integrated chromatography-

based separation methods, like MS, and integrated spectroscopic techniques, like NMR. This is

done with a longstanding collaboration with the Vrije Universiteit van Brussel and Radboud

Universiteit Nijmegen, respectively.

III. Catalytic microdevices and nanostructures, focusing on high precision sustainable chemical

conversion.

There is a lot of collaboration

with the catalytic processes

and materials (CPM) research

group. The interaction

between these two groups is

showed in figure 39.

The name Mesoscale comes

from the mesoscopic scale.

This is the length scale at

which one can reasonably

discuss material properties or

phenomena without having to

discuss individual atom

behaviour.

Figure 39. Cooperation between the MCS and CPM research groups.

[3]


V Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

The applied research in this research group covered by the

fields of micro- and nano-technology, this includes

microsystem technology (MST), micro electromechanical

systems (MEMS), and microreaction technology.

The program director of MCS is prof. dr. Han Gardeniers.

See figure 40.

References

1. http://www.utwente.nl/mesaplus/about_mesa/

2. http://www.utwente.nl/mesaplus/participating_research_groups/

3. http://www.utwente.nl/tnw/mcs/research/

4. http://www.onderzoekinformatie.nl/en/oi/nod/organisatie/ORG1237363/

5. Annual year report MESA+ 2008

Figure 40. Prof. dr. ing. Han Gardeniers.

Program director of MCS [1e]

.


VI Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Annex 2. Click Chemistry

A relative new philosophy in the chemistry is “Click Chemistry” (CC). This new view on chemical

reactions was first introduced in 2001 by Nobel Laureate in Chemistry Karl Barry Sharpless of the

Scripps Research Institute [1]

. K.B. Sharpless was born on the 28th April 1941 in Philadelphia,

Pennsylvania (USA). He graduated from Friends‟ Central school and continued his studies at

Dartmouth College. He earned his PhD from Stanford University and continued working as a post-

doctoral researcher at Stanford University and Harvard University. He is an American chemist, with a

specialisation in stereoselective reactions. For this specialisation he earned the Nobel Prize in

Chemistry (half-shared). Examples of his research are: Sharpless epoxidation, Sharpless asymmetric

dihydroxylation, and the Sharpless oxyamination. Currently he is working at the Scripps Research

Institute, where he holds the W.M. Keck professorship [2-3]

.

As mentioned above, CC was first introduces in 2001 and in 2007 there where over 900 publications

written that are related to click reactions [4]

.

References

1. Zie 40

2. The Notable Names Database, 2008: http://www.nndb.com/people/854/000100554/ (last viewed

on 05-oct-2010)

3. The Sharpless Lab: http://www.scripps.edu/chem/sharpless/cv.html (last viewed on 05-oct-2010)

4. http://www.scripps.edu/chem/sharpless/click.html (last viewed on 05-oct-2010)


VII Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Annex 3. Detailed process for the Click Chemistry bonding technique

PRIOR TO USE, ALL GLASSWARE WILL BE CLEANED FOR AT LEAST 1 HOUR IN CA.

2% V/V HELMANEX SOLUTION IN WATER, FOLLOWED BY RINSING WITH WATER

AND FLUSHIG WITH HIGH-PURITY WATER (MILLIQ, 18.2 MΩ CM) AND DRYING.

ALSO CLEAN TWEEZERS ARE NECESSARY FOR SURFACE CHEMISTRY!

Step 1. Preparation of the glass samples References:

First 2 steps: J. Bart, et al., Room-temperature intermediate layer bonding for microfluidic devices, Lab

Chip, 9, 2009, pp 3481-3488

Other steps: D.I. Rozkiewicz, et al., “Click” Chemistry by microcontact printing, Angew. Chem. Int. Ed.,

45, 2006, pp 5292 – 5296

Also cited in: W. H. Binder, R. Sachsenhofer, „Click‟ Chemistry in Polymer and Materials science,

Macromol. Rapid comm., 28, 2007, pp 15 – 54

Clean room work:

- Clean and activate the glass sample in a Piranha solution (96 % H2SO4/31% H2O2 3:1 v/v

mixture) at 81±3°C for 45 min. Caution: Piranha solution is a very strong oxidant and

reacts violently with many organic compounds.

- Follow with quick dump rinsing in DI-water and spin-drying.

MCS chemical lab work:

- Make a SAM of 11-bromoundecyltrichlorosilane on SiO2 in an 11-

bromoundecyltrichlorosilane in dry toluene (25 µl/25 mL) for 1 h at 20°C under nitrogen gas.

- Rinse the substrate 3 times with toluene to remove the unbound silane.

- Substitute the Br-group with an azido-group by putting the sample in a saturated solution of

NaN3 in DMF (about 1.5 mg NaN3/100 mL) at RT for 24 h.

- Rinse the substrate with MilliQ 18.2 MΩ cm water and ethanol and dry with a stream of

nitrogen.

Step 2. Preparation of the FEP-foil, part 1 Reference: J. Bart, et al., Room-temperature intermediate layer bonding for microfluidic devices, Lab

Chip, 9, 2009, pp 3481-3488

Clean room work:

- Strip the fluorine from the carbon backbone with FluoroEtch®, exposure time 60 s and

temperature 60°C.

- Immerse in RT IPA for 20 s, in 70°C DI-water for 30 s, store at least 15 min in RT DI-water

and dry with nitrogen stream.

- Remove the brownish sodium naphthalene in 81±3°C piranha solution for 90 s.

- Extremely flush the sheet with DI-water and dry with nitrogen stream.

- Protonate and oxidize the carbon backbone in the air.

Step 3. Preparation of the FEP-foil, part 2 Reference: R. Ranjan, W.J. Brittain, Combination of Living Radical Polymerization and Click chemistry

for surface modification, Macromolecules, 40, 2007, pp 6217-6223


- In a flat beaker add about 25 mL DCM and 10.25 mmol EDC and 10.25 mmol DMAP.

- Add the FEP-foil and stir for a few minutes under an inert (nitrogen) atmosphere.

- Add 1.0 mL propargyl alcohol.

- Start this reaction at the beginning of the afternoon and turn the sheet at the end of the

afternoon and stir overnight at RT.


VIII Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

- Wash the product with acidic water (1-5% HCl solution), water, brine (saturated NaCl

solution), and DI-water several times and dry under reduced pressure.

Note: The DMAP is a base catalyst and EDC consumes the liberated water from the condensation

(mail contact with prof. Brittain).

Step 4. The click reaction Reference: W. H. Binder, R. Sachsenhofer, „Click‟ Chemistry in Polymer and Materials science,

Macromol. Rapid comm., 28, 2007, p 41


- Apply the alkynated FEP-foil directly to the azido-modified SAM with a load of 0.27 metric

tons/cm2 at RT for 5-6 h.

After the reaction this bond is formed:

If the reaction don‟t occur, then try to activate the FEP-foil in a solution of 1 mM Cu2SO4•5H2O and

10 mM sodium ascorbate (ascorbic acid) in 50 mL H2O for 1 h. Followed by washing with DI-water

and drying with nitrogen stream.


IX Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Annex 4. Detailed process for the amine-epoxide bonding technique

PRIOR TO USE, ALL GLASSWARE WILL BE CLEANED FOR AT LEAST 1 HOUR IN CA.

2% V/V HELMANEX SOLUTION IN WATER, FOLLOWED BY RINSING WITH WATER

AND FLUSHIG WITH HIGH-PURITY WATER (MILLIQ, 18,2 MΩ CM) AND DRYING.

ALSO CLEAN TWEEZERS ARE NECESSARY FOR SURFACE CHEMISTRY!

Step 1. Preparation of the glass samples References:

First part: J. Bart, et al., Room-temperature intermediate layer bonding for microfluidic devices, Lab

Chip, 9, 2009, pp 3481-3488

Second part: M. Zhang, J. Zhao, L. Gao, Glass wafers bonding via Diels-Alder reaction at mild temperature,

Sensor. Actuat. A., 141, 2008, pp 213-216

Clean room work:

- Clean and activate the SiO2 sample in a piranha solution (96 % H2SO4/31% H2O2 3:1 v/v

mixture) for 15 min. Caution: Piranha solution is a very strong oxidant and reacts

violently with many organic compounds.

- Follow with quick dump rinsing in DI-water and spin-drying.


- Place for 2 h the glass substrates horizontally in a solution of 3% v/v 3-aminopropyl-

triethoxysilane (APTES) and ethanol.

- Clean the substrates ultrasonically in fresh ethanol for 5 min.

- Rinse the substrates with ethanol and IPA and dry with a stream of nitrogen.

Step 2. Preparation of the FEP-foil, part 1 Reference:

First part: J. Bart, et al., Room-temperature intermediate layer bonding for microfluidic devices, Lab

Chip, 9, 2009, pp 3481-3488

Second part: R.C. Bening, T.J. McCarthy, Surface Modification of Poly(tetrafluoroethylene-co-

hexafluoropropylene). Introduction of Alcohol Functionality, Macromolecules, 23, 1990, pp

2648-2655

Clean room work:

- Strip the fluorine from the carbon backbone with FluoroEtch®, exposure time 60 s;

- Immerse in RT IPA for 20 s, in 70°C DI-water for 30 s, store at least 15 min in RT DI water

and dry with nitrogen stream.

- Do not remove the brownish layer!


- Put a substrate (about 1.5 x 4 cm) in a Schlenk tube, containing borane in THF (10 mL, 0.5

M).

- Keep it for 18 h on RT under N2 atmosphere.

- Remove the solution.

- Wash the substrate with THF (3 x 20 mL)

- Add a basic aqueous peroxide solution at 0°C (1.2 g NaOH, 20 mL H2O, and 10 mL of 30%

H2O2).

- Keep for 3 h on 0°C.

- Remove the solution.

- Wash the substrate with dilute aqueous NaOH (5 x 20 mL), dilute aqueous HCl (5 x 20 mL),

water (5 x 20 mL), and THF (5 x 20 mL).

- Dry at reduced pressure.


X Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Step 3. Preparation of the FEP-foil, part 2 Reference: N.Y. Lee, B.H. Chung, Novel Poly(dimethylsiloxane) Bonding Strategy via Room



- Put the FEP-OH substrate in a 1% v/v aqueous solution of (3-

glycidoxypropyl)trimethoxysilane (GPTMS) and let it react for 20 min.

- Or a 1% v/v GPTMS solution in hexane, like the APTES solution for the Diels-Alder?

- Wash the surfaces with DI-water.

- Clean ultrasonically in hexane and methanol (1 min each) and dry with nitrogen.

Step 4. Bonding reaction Reference: N.Y. Lee, B.H. Chung, Novel Poly(dimethylsiloxane) Bonding Strategy via Room



- Put the glass and FEP-foil substrates together with a load of 0.27 metric tons/cm2, at r.t. for 5-

6 h

After the reaction this bond is formed:


XI Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Annex 5. Used chemicals with safety information

The chemicals used for this research are bought by different chemical suppliers. All chemicals that are

used where not further purified. Chemicals that are used for this research are:

Name: Hellmanex II cleaning solution

CAS#: mixture of chemicals

tripotassium orthophosphate CAS#: 7778-53-2

trisodium nitrilotriacetate CAS#: 5064-31-3

Purity: n/a

Supplier: Hellma Analytics GmbH & Co. KG

R-phrases: 22, 36/38

S-phrases: 24/25, 26, 35, 37

Symbols: Xi, Xn

Safety precautions: lab coat, glasses, gloves

Spill response: flood with water

Extinguishing media: water spray, powder, carbon dioxide

Name: sulphuric acid

CAS#: 7664-93-9

Purity: 95-97%, puriss., p.a.

Supplier: Sigma-Aldrich

R-phrases: 35

S-phrases: 26, 30, 45

Symbols: C

Safety precautions: lab coat, glasses, thick gloves, fume hood

Spill response: use absorbent material and transfer to a suitable container or disposal

Extinguishing media: water spray, foam, carbon dioxide, dry chemical

Name: hydrogen peroxide

CAS#: 7722-84-1

Purity: 30%, puriss., stabilized

Supplier: Riedel-de Haën

R-phrases: 22, 41

S-phrases: 26, 39

Symbols: Xn

Safety precautions: lab coat, glasses, gloves, fume hood

Spill response: contain spillage, and then collect with an electrically protected vacuum cleaner

or by wet-brushing and place in container for disposal


Name: 11-bromoundecyltrichlorosilane

CAS#: 79769-48-5

Purity: 95%

Supplier: ABCR

R-phrases: 34-36/37/38

S-phrases: 25, 35/37/39, 45

Symbols: C


Spill response: use absorbent material and transfer to a suitable container or disposal



XII Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Name: Toluene

CAS#: 108-88-3

Purity: anhydrous, 99.8%


R-phrases: 11, 38, 48/20, 63, 65, 67

S-phrases: 36/37, 46, 62

Symbols: F, Xn


Spill response: eliminate ignition sources, use absorbent material and transfer to a suitable

container of disposal, consider evacuation

Extinguishing media: foam

Name: N,N-dimethylformamide

CAS#: 68-12-2

Purity: anhydrous, 99.8%


R-phrases: 20/21, 36, 61

S-phrases: 45, 53

Symbols: T


Spill response: water spray, do NOT fight fire with BCF extinguisher

Extinguishing media: eliminate ignition sources, absorbent material and transfer to a suitable


Name: sodium azide

CAS#: 26628-22-8

Purity: ReagentPlus, ≥99.5%


R-phrases: 28, 32, 50/53

S-phrases: 28, 45, 60, 61

Symbols: T+, N


Spill response: avoid dust, sweep/shovel to a suitable container

Extinguishing media: water spray

Name: FluoroEtch®

CAS#: mixture of components

2-methoxyethyl ether CAS#: 111-96-6

sodium naphthalene CAS#: 7440-23-5 & 91-20-3

Purity: n/a

Supplier: Acton Technologies

R-phrases: 19, 22, 36/37/38, 51/53, 60, 61

S-phrases: 16, 26, 36/37/39, 45, 53

Symbols: n/a

Safety precautions: lab coat with extra apron, glasses, thick gloves, fume hood

Spill response: flood with water, neutralize with acetic or hydrochloric acid, then absorb with

absorbent material and transfer to a suitable container



XIII Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Name: Isopropanol

CAS#: 67-63-0

Purity: handelskwaliteit

Supplier: Boom

R-phrases: 11, 36, 67

S-phrases: 7, 16, 24/25, 26

Symbols: F, Xi

Safety precautions: lab coat, glasses, gloves

Spill response: use absorbent material and transfer to a suitable container of disposal

Extinguishing media: foam, carbon dioxide, dry chemical

Name: 4-(dimethylamino)pyridine

CAS#: 1122-58-3

Purity: puriss., ≥99%

Supplier: Fluka

R-phrases: 25, 27, 36/37/38

S-phrases: 26, 28, 36/37/39, 45

Symbols: T+


Spill response: eliminate ignition sources, use absorbent material and transfer to a suitable

container of disposal, consider evacuation, take off contaminated clothing, and

clean all contaminated material with water

Extinguishing media: water spray, foam

Name: 1-ethyl-3-[3-dimethylaminopropyl]-carbodiimide hydrochloride

CAS#: 25952-53-8

Purity: purum, ≥98%

Supplier: Fluka

R-phrases: 37/38, 41

S-phrases: 26, 36/37/39

Symbols: Xi


Spill response: avoid dust, sweep/shovel to a suitable container


Name: dichloromethane

CAS#: 75-09-2

Purity: puriss., ACS reagent, ≥99.9% (GC)

Supplier: Fluka

R-phrases: 40

S-phrases: 23, 24/25, 36/37

Symbols: Xn


Spill response: small quantities will evaporate quick, use absorbent material and transfer to a

suitable container of disposal

Extinguishing media: water spray


XIV Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Name: propargyl alcohol

CAS#: 107-19-7

Purity: 99%

Supplier: Aldrich

R-phrases: 10, 23/24/25, 34, 51/53

S-phrases: 26, 28, 36, 45, 61

Symbols: T, N


Spill response: eliminate ignition sources, absorbent material and transfer to a suitable


Extinguishing media: water spray, foam

Name: hydrochloric acid

CAS#: 7647-01-0

Purity: 37%, reagent grade


R-phrases: 34, 37

S-phrases: 26, 45

Symbols: C

Safety precautions: lab coat, glasses, thick gloves, fume hood

Spill response: use absorbent material and dispose as hazardous waste

Extinguishing media: use media that are appropriate to local circumstances and the surrounding

environment

Name: sodium chloride solution

CAS#: 7647-14-5

Purity: 26% in water


R-phrases: none

S-phrases: none

Symbols: none

Safety precautions: wash hands afterwards

Spill response: clean with water


For more detailed safety information, please contact the MSDS.

Used glass: Borosilicate glass (Borofloat 33, 100 mm diameter, thickness 1.1 mm, Schott Technical

Glasses, Germany)

Used TEF-Teflon: FEP sheet 10 m x 152 mm (FEP type 100A, thickness 25 µm, DuPont, USA)


XV Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Annex 6. Results

Contact angle measurements, ARCA mode

Piranha cleaned glass:

Glass with bromo terminated SAM:

0

5

10

15

20

25

30

35

0 200 400 600 800 1000

Co

nta

ct a

ngl

e


0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000

Co

nta

ct a

ngl

e



XVI Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Glass with azide terminated SAM:

Bare FEP-Teflon foil:

FluoroEtch® treated FEP-Teflon foil:

0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000

Co

nta

ct a

ngl

e


0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500

Co

nta

ct a

ngl

e


0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600

Co

nta

ct a

ngl

e



XVII Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Piranha cleaned FEP-Teflon foil:

Alkyne terminated FEP-Teflon foil:

0

2

4

6

8

10

12

14

16

18

20

0 100 200 300 400 500 600 700 800

Co

nta

ct a

ngl

e


0

10

20

30

40

50

60

0 200 400 600 800 1000

Co

nta

ct a

ngl

e



XVIII Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Contact angle measurements, static mode

Surface Photograph of the droplet Contact angle

Glass

47.2°

Piranha cleaned glass

23.5°

Bromo-terminated glass

82.8°

Azide-terminated glass

82.0°

Bare FEP-Teflon foil

85.3°

FluoroEtch® treated

FEP-Teflon foil

62.9°

Piranha cleaned

FEP-Teflon foil

9.9°

Alkyne terminated

FEP-Teflon foil

39.6°


XIX Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

FT-ATR-IR spectra

Bromo-terminated glass:

Azide-terminated glass:


XX Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

FEP-Teflon foil:

FluoroEtch® treated FEP-Teflon foil:


XXI Internship at MESA+ Institute for Nanotechnology, Mesoscale Chemical Systems research group

Piranha cleaned FEP-Teflon foil:

Alkyne terminated FEP-Teflon foil:

h.w. veltkamp - improvement of the glas-fep teflon-glass bond

Documents

glassfep teflonglass

glass devices

group of

research proposal

glass chips

glass plates

glass substrates

azide group