Levich Institute Seminar Announcement, 11/13/2012
Tuesday, 11/13/2012
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Aditya Khair
Carnegie-Mellon University
Department of Chemical Engineering

"Novel Phoretic Particle Transport "


Electric fields, temperature gradients, and solute fluxes can be employed to transport colloidal particles in microscale environments, including microfluidic devices and porous media. Such "phoretic" particle motion arises due to the imposed (electrical, thermal, or concentration) field driving the nano-scale interfacial, or screening, layer that envelopes a colloid out of equilibrium. Morrison (1970) proved that the phoretic velocity of a colloid with a thin surrounding interfacial layer is independent of the particle size or shape, and even the colloid concentration. This remarkable result has been observed for concentrated charged dispersions and is the reason that DNA strands of different length (but uniform charge) move at equal electrophoretic velocities in free solution, requiring a gel matrix, for example, to affect separation. Here, we present three instances of phoretic transport that "break" Morrison's result. First, we demonstrate that non-Newtonian fluid rheology leads to size- and shape-dependent electrophoretic motion of charged colloids. Second, we show that the transient phoretic dynamics of an ion-permselective particle persist on a time scale orders of magnitude larger than that of a dielectric (inert) colloid. Third, we predict that solute or temperature advection causes relative diffusion-phoretic or thermo-phoretic drift, respectively, between colloidal particles.


Aditya Khair studied as an undergraduate at Imperial College London, where he received a degree in Chemical Engineering in 2001. Next, he attended the University of Cambridge and obtained a Certificate of Advanced Study in Mathematics. In 2002 he began a Ph.D. in Chemical Engineering at the California Institute of Technology under the supervision of John Brady. After completing his Ph.D. in 2007, he embarked on a postdoctoral scholarship in Chemical Engineering at the University of California at Santa Barbara, working in the research group of Todd Squires. In 2010 Dr. Khair joined the Chemical Engineering Department at Carnegie Mellon University as an Assistant Professor.


Fluid mechanics, electrokinetics, electrochemical systems, colloidal hydrodynamics, and rheology

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