sensors, energy, and automation laboratory (seal), university of washington, seattle 1 autonomous...

Sensors, Energy, and Automation Laboratory (SEAL), University of Washington, Seattle

1

Autonomous Microsensors for Chemical Analysis

PI: Alexander Mamishev

Department of Electrical Engineering

University of Washington, [email protected]

http://www.ee.washington.edu/research/seal

Sensors

, Ene

rgy,

and Automation Laboratory

SE A L


2

Outline

Motivation Theoretical background System overview

Smart tubing External sensors Internal sensors In-line sensors

Cost considerations Conclusions


3

Motivation

Continuous process monitoring and control for microreactorsBefore, during, and after reactionFeedforward and feedback controlAuto-calibration of sensors through

multi-point measurements Miniaturization of sensor arrays Cost-reduction of sensing systems


4

Physics of Dielectrics

The figure depicts an idealized view of dielectric phenomena. A variety of physical mechanisms contribute to the polarization of the material. Each mechanism has a characteristic frequency above which its contribution vanishes. Therefore dielectric spectra will generally appear as decreasing functions of frequency.

Innerelectrons

Outer electrons

Freeelectrons

Boundions

Freeions

Multipoles

Response Resonance Resonance Relaxation Relaxation Relaxation Relaxation

Type Atomic polarizatio

n

Atomic polarization

Space charge polarization

Orientation polarization

Space charge polarization

Orientation polarization

Resonance Frequency

~1019 Hz ~1014 Hz ~10-1 Hz ~108 Hz ~10-1 Hz ~108 Hz

The table shows the different physical mechanisms and their typical characteristic frequencies.


5

Multipoles

The concept of multipoles is used to describe the distribution of charges (and, consequently, distribution of space potential) in complex molecules. Multiple color peaks in the figure on the right indicate equivalent multiple charge concentrations with the associated radii larger then those of outer electrons. Naturally, such structures have slower response to alternating electric field excitation.Practical example: Organic materials contain long molecular chains that have specific relaxation times. Detection of associated peaks may allow identification of molecular structure (in a limited subset of suspect materials).

This color map show the distribution of space potential in n-pentane (alkaline).


6

Nature of dielectric signatures

• Dielectric signatures are characterized by smooth variation rather than narrowband features.

• Best selectivity will be obtained by measuring with relatively few data points over a large a frequency range.

• Measurements below about 1 Hz are impractical for a real time system because measurement time becomes too long (proportional to period).

• For selectivity, the method should be combined with other techniques.


7

Dielectrometry

M easurecapacitancesand conductances

C alib ra tion-basedsensing

D iffe ren tia lsensing

C om puted istribu tionof d ie lectricproperties

C om puted istribu tionof physica lp roperties

Im aging

Faster S low er

* , tan

th icknesssurface texturetem pera turedegree o f curem oistureporositydensityconcentrationpercolationstructura l in tegrityaging sta tuscontam ination .......


8

Sensor Embodiments

Micro-

reactor

Smart tubing

External sensor

Internal sensor In-line

sensor


9

Smart tubing: spectroscopy and imaging

• Concentration• Composition• Reaction stage• Micro-particle size• Viscosity


10

Smart tubing: differential measurements

• Flow uniformity• Auto-calibration• Residual

contamination


11

Macroworld example of “smart tubing”

Metal pipe section replaced with custom made plastic pipe fitted with an dielectric spectroscopy sensor


12

External sensors

• Non-destructive, one-sided access• Non-uniform field energy distribution• Non-uniform measurement sensitivity – allows

correction for barrier effects

Flexib le substra te

B ackp lane

1l2l

3l

E lectrodes


13

The Ideal Internal Sensor

Wireless Self-powered Non-invasive Can withstand harsh environments Explosion proof Inexpensive


14

WISP system

RFIDReader

power

WISP

ID

ComputingPower

Harvesting

ID

Sensing

sensor Data

No battery!


15

PCB version of the WISP

Completed fully function WISP

Ready for applications Still working on range

and antenna design

Generations of Power Harvesters and WISPs


16

In-line sensor on NeSSI Platform

Initial tests will be focused on detection of water in oil, and mixtures of alcohols

Allows for high material feed rates due to non-contact sensor design

Offers non-destructive, inline testing of material

Uses data acquisition hardware previously developed in SEAL

Integration of a microfabricated sensor with a NeSSI block for fluid measurement


17

Test Wafers Back form Fab


18

Reaction Monitoring Example


19

Cost considerations “Headquarter” labs routinely install analytical

instrumentation in the price range of $50K to $200K High-end dielectric spectroscopy equipment falls in

this range (Agilent, Solartron, Novocontrol) Small plants and micro-reactors cannot support

this level of investment Dielectric spectroscopy equipment in the range $5K -

$10K would be adequate Commerciallization of system developed in SEAL is

currently supported by the NSF STTR grant in partnership with Kraft (we could use additional partners)


20

mini-DiSPEC

Small, low-cost, portable, dielectric spectroscopy system


21

LabView Screenshot


22

Conclusions: Sensor Miniaturization

Dielectric spectroscopy sensors are positioned for installation throughout the micro-reactor platform

Measurements range from sophisticated dielectric spectroscopy (instrumentation cost about $15K per channel) to simple single frequency units (instrumentation cost below $1K per channel) Inexpensive and mature technology available for

mass fabrication at MEMS level Small and disposable


23

Acknowledgements

Presented research work includes results from projects sponsored by:

National Science Foundation Center for Processing Analytical Chemistry Kraft

Key contributing graduate students: Xiaobei Li, Kishore Sundara-Rajan, Gabriel

Rowe, Abhinav Mathur

sensors, energy, and automation laboratory (seal), university of washington, seattle 1 autonomous...

Documents