Chemical Microsystems Applications

Fundamentals of MicromachiningDr. Bruce Gale

With Special Thanks to Dr. Ron Besser

Outline• Microfluidic Component Examples• Chemical Microsystems for Analysis• Chemical Microsystems for Synthesis

Microchannels, Fluidic Vias KOH Etch vs. DRIE

KOH Etched (100 µm channels) DRIE Etched (5 µm channels)

Microchannels Microchannel Reaction Zone

100 µm Channels 5 µm Channels

Reactor Cross Section

Inside Channel

Urea AmmoniaProduct

“First generation” PDMS Microreactors

5 cm 7.5 cm 10 cm

150 µµµµmScale = 1 mm

Scale = 100 µµµµm

PDMS MicroReactor

Flow characteristics of transverse mixing featuresFeatures

•Flow depicted by contrasting dark lines/light green areas

•Fluid mixing to bring soluble reactant into contact with catalyst surface

Scale Comparison

Nanoreactor or Micelle Macroscale, Industrial Scale

C.M. for Analysis• Definition• Lab-on-chip• Example: micro gas-analysis device• Example: Caliper oligonucleotide

separation• Example: Nanogen biochips

Lab-On-Chip

Micro-Gas-Analyzer Micro-Gas Analyzer Result

Applications of Microreactors1. Distributed Processing2. Toxic or Hazardous Chemicals3. Chemical Prototyping4. High-Value, Low-Volume Chemicals5. Bulk Production of Commodity Chemicals6. Special Environments7. Laboratory Systems8. Combinatorial Chemistry

C.M. for Synthesis• Definition• Conversion• Selectivity• Example: IfM Microreactor

IfM Microreactor for Synthesis Device Design

Inlet Via Outlet Via

Silicon Chip

Catalyst

Inlet ChannelPyrex Cover

Microchannels5µm or 100 µm

Manifold

Device Fabrication

Final 1 x 3 cm2 device

100 mm Si wafer, 18 reactors

topside via

inlet/outlet

bottom via

channels

anodic bond

starting wafer mask layer

[KOH or DRIE Etching]

Temperature Effect

0.00.10.20.30.40.50.60.70.80.91.0

0 50 100 150 200 250

Temperature (°C)

Cyclohexane Benzene

0.00.10.2

0.30.4

0.5

0.60.70.8

0.91.0

0 50 100 150 200

Temperature (ºC)

100 µm channels

Temperature holds1

2 3 4 5 67 8

109

Degradation of Conversion

hydrogenation dehydrogenation

Selectivity Reversal at T>150°C

Conversion near 100%

Activity at Troom

Both products at Troom

Benzene Space Time Yield-Effect of Composition

Benzene Space Time Yield (200ºC)

0.0E+00

5.0E-04

1.0E-03

1.5E-03

2.0E-03

2.5E-03

3.0E-03

3.5E-03

0 100 200 300 400 500 600

PH2 (torr)

STY A

(g/c

m^2

/min

)

0.3 sccm Ar (E) 0.6 sccm Ar (E) 1.0 sccm Ar (E)0.3 sccm Ar (F) 0.6 sccm Ar (F) 1.0 sccm Ar (F)

Space Time Yield =yield X flow rate / catalyst area

Increasing H2suppresses dehydrogenation

Increasing C6H10 favors dehydrogenation

Benzene Space Time Yield (200ºC)

0.0E+00

5.0E-04

1.0E-03

1.5E-03

2.0E-03

2.5E-03

3.0E-03

3.5E-03

0 20 40 60 80 100

PC6H10 (torr)

STY

A (g

/cm

^2/m

in)

0.3 sccm Ar (E) 0.6 sccm Ar (E) 1.0 sccm Ar (E) 0.3 sccm Ar (H)0.6 sccm Ar (H) 1.0 sccm Ar (H) 0.3 sccm H2 (D)

Features•6 channels•50 channel length•transverse mixing features in each straight section

Microreactor 2 Design

Observations•4-6 samples averaged for each data point

•critical influence of residence time evident

•microreactoroperated 48 hours with no substantial loss in enzyme activity

Flow rate (mL/min-channel)

Ure

a C

onve

rsio

n (X

)

Continous Microreactor Results50 cm channel with transverse features

Averaged data

Packaged Microreactor

Systems

Distributed Processing• Nature’s Model• Example: Oil Processing• An Analogy of Distributed vs. Centralized

Processing

Distributed Processing: the Cell

Mitochondrion: chemical factory in every cell

Distributed Processing: Petroleum Petroleum Processing

centralized

distributed

Analogy: Centralized vs. Distributed

1965 2000

Toxic or Hazardous Chemicals• Toxic = • Hazardous = • Motivation: Operation in “explosive

regime”• Motivation: transport, storage, monitoring• Example: ion-implantation of As+

Explosive Regime Example• H2 + ½ O2 → H2O• 500°C, water produced without explosion

MIT Microreactor Fabrication

Mass Transfer Characteristics: MIT Example: Ion-Implantation Source

Silicon wafer

“Doped” n-type region

0.1 to 1 µm

[As+]≈ 1e18 cm-3

Ion-Implanter Schematic

AsH3 tank

Scale-Up

Benchtop

PilotPlant Iteration 1 Plant Iteration 2

MicroreactorPrototype

Plant

Scale-Up Example

High-Value, Low-Volume Chemicals• Examples

– Pharmaceuticals– NO

• Motivation– Short shelf lives– Toxicity– New therapies– Implantation

Bulk Production of Commodity Chemicals

• Definitions: No distinction by “brand”– Oil– Polymers

• Motivation– Higher yields– Less pollution– Modularity (repairs)

• Likely impact– Slow adoption

Special Environments: Space

Combinatorial Screening for Discovery of New Materials

• Applications– Pharmaceuticals– Luminescent Materials– Superconductors– Magnetic Materials– Heterogeneous

Catalysts

• Method– Batch Processing– Systematic Variation

of Composition or Substitutional Groups

– High Sample Count– Rapid Evaluation

Systematic Variation of Component Compositions

Substrate

Pure B

Pure A

Pure

C

Rapid Evaluation

Rapidly Probe Each Unit Sample for Desired Activity

Amount of B →

←A

mount of A

Act

ivity

Pure B

Pure A

Pure

C

UCLA SystemArray Microreactor System: A: Feed gas preheater; B: Catalyst pellets; C: Reactant gas inlet; D:

Flow distribution baffles; E: Bottom aluminum heating block; F: Reactor channels; G: Signal detection microelectrodes;

Combinatorial Array for Screening Catalysts

75 Microreactor Array

Systematic variation of catalyst by sputter deposition

Evaluation of conversion and selectivity by Mass Spectrometry