Research Projects
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Electrokinetic Instabilities
The fluid flow in microfluidic and nanofluidic devices are often stable and strongly damped by viscous forces (with Reynolds numbers of order unity or smaller). However, heterogeneous ionic conductivity fields in the presence of applied electric fields can, under certainconditions, generate an unstable flow field owing to electrokinetic instabilities (EKI). Conductivity gradients are prevalent in …
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Electroosmotic Pumps
We are developing high performance electroosmotic pumps for variety of applications including IC chip cooling, drug delivery, high performance liquid chromatography, and water management in hydrogen PEM fuel cells. Electroosmotic (EO) pumps use ion drag in micro- and nano-scale flow channels to pump electrolytes. EO flow is the motion of an electrolyte caused by the …
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Hydrodynamic Particle Separation
We are investigating a hydrodynamic particle separation technique that employs pinching of particles to a narrow microchannel. The particles are subject to a sudden expansion which results in a size-based particle separation transverse to the flow direction. The separation resolution and particle dispersion are measured using epifluorescence microscopy. The resolution and dispersion are predicted using …
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Nanofluidics
We have fabricated silicon nanoscale pores and examined their electrokinetic transport behaviors.13, 26 We have shown that nanoscale pores in series with microchannels can exhibit asymmetric concentration polarization that can be leveraged for DNA sequencing, biomolecule separation, and desalination, for example. We have also functionalized the pore with antibodies in the goal of developing nanofluidic …
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Three-Dimensional Velocimetry
A diagnostic platform for measuring three dimensional velocity fields in whole microscopic volumes is presented. The imaging system is based on Nipkow spinning disk confocal microscopy. The confocal system provides optical sectioning using pinhole spatial filtering which rejects light originating from out of focus objects. Volumetric scanning is obtained by rapid translation of the high …
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Nano-bio Interface
This work is to understand the mechanisms and conditions under which engineered nanomaterials can cause disruption of, and passive transport through, simplified model of artificial cell membranes, namely lipid bilayers. We believe that under some conditions engineered, ENMs, can passively translocate across, and cause nanoscale defects in lipid membranes, which plays a role in cellular …
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PEM Fuel Cells
We are developing polymer electrolyte membrane fuel cells (PEMFCs) as high power density alternatives to portable power batteries and automobile internal combustion engines. Recent reports from automobile manufacturers (Gasteiger et al. Applied Catalysis B-Environmental, 2005) and the DOE suggest a five-fold reduction of the specific Pt-catalyst loadings (to 0.2 g/kW) must be made for large …
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High Speed Velocimetry of Unsteady Microscale Flows
In µPIV, ensemble averaging is often used to reduce errors due to noise from out-of-focus particles. However, unsteady non-periodic flows require two-frame correlations which can be difficult to achieve with acceptable accuracy using µPIV. The confocal microscope uses pinhole spatial filtering to remove much of the light originating from outside the focal plane, reducing light …
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Electrokinetic Phenomena in Non-dilute Suspensions
Many lab-on-a-chip applications use samples with non-dilute suspensions of biomolecules and cells. Electrokinetic manipulation is one of favored transport mechanisms for pumping, mixing, injecting, concentrating, and separating analytes in micro and nanofluidic devices. We are interested in the behavior of non-dilute colloidal suspensions in these confined geometries. We are interested in two main phenomena 1) …
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Catalytic Nanomotors
Bi-metallic rod-shaped nanoparticles, 2 microns in length and 200 nanometers in diameter, are known for their ability to “swim,” or move autonomously, in aqueous hydrogen peroxide solutions. These so-called “nanomotors” were first introduced in a 2004 paper by Sen and Mallouk’s groups at Pennsylvania State University. Since then, several different mechanisms (interfacial tension gradient, viscous …
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Microfluidic Fuel Cells
Microfluidic fuel cell uses controlled flow patterns to separate liquid fuel and oxidizer instead of a physical membrane. In our group we are developing unique cell architectures that provide increased power density, fuel flexibility, and an increase in fuel utilization.
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