Archived Research
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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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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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