Physics Colloquium - Thursday, June 11th, 2009, 3:00 P.M.

>>> Note special time and place!!! <<<

Dr. Mihail Popescu
Ian Wark Research Institute
University of South Australia, Adelaide

For applications in, e.g., drug-delivery systems or micromechanics, one of the most challenging problems at this stage is to develop ways to enable small-scale objects to perform autonomous, controlled motion. One such possibility is the phoretic transport via actively generated composition gradients [1]. As a benchmark model for such systems we consider the case of a prolate-shaped particle which is suspended in an unbounded solvent and has a point-source of solute particles on one of its poles, reflecting a chemical reaction, which is active only on certain parts of the surface (see also [1-3]), of the solvent. We account for the (correct) phoretic hydrodynamical flow (similarly to Refs. [3,4] and in contrast to Refs. [1, 2]) and derive analytically the quasi-steady state velocity of the resulting diffusio-phoretic motion. This allows us to study the motion as a function of the shape of the particle, including the limiting cases of a cylindrical rod [1-3] (here approximated by a prolate with a large aspect ratio) and of a spherical object [3], respectively, which are frequently encountered in experimental studies.

[1] W.F.Paxton et al, J. Am. Chem. Soc., 126, 13424 (2004).
[2] N. Bala Saidulu and K.L. Sebastian, J. Chem. Phys. 128, 074708 (2008).
[3] R. Golestanian, T.B. Liverpool, and A. Ajdari, New J. Phys. 9, 126 (2007).
[4] J.L. Anderson, Annu. Rev. Fluid Mech. 21, 61 (1989).