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Electrokinetic Properties of Microfluidic Substrates
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Funding: DOE, Lockheed Martin, Cornell, ACS-PRF
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Among the unique properties of microfluidic
devices is the ability to move liquids via
electroosmosis.
When the solid-liquid interface acquires a
surface charge, an electrical double layer
is formed as ions
in the electrolyte solution align preferentially
based on their charge. When this occurs, an electric
field applied parallel to the wall will induce fluid flow.
Modeling and predicting the electrokinetic
properties of microfluidic substrates that lead
to electroosmosis is inherently difficult.
The surface charges are a function of chemical
reactions and adsorption/desorption processes, many of which
are not fully understood. Further, the
electrical double layer is often nanometers
thick, and bulk
fluid properties typically do not apply
close to the wall, where the highest charge density (and
therefore most of the action) resides.
Our work on the electrokinetic properties of
microfluidic substrates includes (1) experimental
characterization
of interface properties, (2) chemical
modification of interface properties,
and (3) analytical and numerical modeling
of double layer phenomena.
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Publications and Presentations on Electrokinetic Properties of Microfluidic Substrates
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Kirby BJ
"Micro- and Nanoscale Fluid Mechanics for Engineers,"
textbook in preparation for publication in 2009.
click here for html version|
Cambridge University Press
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Tandon V,
Bhagavatula SK,
Nelson WC,
Kirby BJ
"Zeta potential and electroosmotic mobility in microfluidic devices
fabricated from hydrophobic polymers: 1. The origins of charge",
Electrophoresis 29(5):1092-1101, 2008.
doi
pdf
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Tandon V,
Kirby BJ
"Zeta potential and electroosmotic mobility in microfluidic devices
fabricated from hydrophobic polymers: 2. Slip and interfacial water structure",
Electrophoresis 29(5):1102-1114, 2008.
doi
pdf
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Mela P, van den Berg A, Fintschenko Y,
Cummings EB, Simmons BA,
Kirby BJ
"The zeta potential of cyclo-olefin polymer microchannels and its effects on insulative (electrodeless)
dielectrophoresis particle trapping devices,"
Electrophoresis 26:1792-1799 (2005).
doi
pdf
text
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Kirby BJ,
Hasselbrink, Jr. EF
"The Zeta
Potential of Microfluidic Substrates. 1. Theory, experimental
techniques, and effects on separations,"
Electrophoresis, 25:187-202
(2004).
doi
pdf
text
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Kirby BJ,
Hasselbrink, Jr. EF
"The Zeta
Potential of Microfluidic Substrates. 2. Data for polymers,"
Electrophoresis, 25:203-213 (2004).
doi
pdf
text
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Reichmuth DS,
Kirby BJ
"Effects of
Ammonioalkyl sulfonate internal salts on electrokinetic
micropump performance and Reversed-Phase HPLC separations,"
Journal of Chromatography A, 1013:93-101
(2003).
doi
pdf
text
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Reichmuth DS, Chirica GS,
Kirby BJ
"Increasing the Performance of High-Pressure,
High-Efficiency Electrokinetic Micropumps Using Zwitterionic
Solute Additives," Sensors and Actuators B-Chemical, 92:37-43 (2003).
doi
pdf
text
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Kirby BJ,
Wheeler AR, Zare RN, Fruetel JA,
Shepodd TJ
"Programmable Modification of Cell Adhesion
and Zeta Potential in Silica Microchips,"Lab On a Chip
3:5-10 (2003).
doi
pdf
text
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We use laser-microfabrication to make microscale polymer elements within
etched microchannels, for use for
microfluidic control
or
dialysis.
A frequency-tripled Nd:YAG laser is used to photopolymerize a liquid-phase solution
of monomers, solvents, and photoinitiators. The structural, tribological, and chemical
properties of the resulting solid polymer structure are controlled by the material
precursors.
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