Using artificial microswimmers for particle separation

Microscopic self-propelled swimmers capable of autonomous navigation through complex environments provide appealing opportunities for localization, pick-up and delivery of micro-and nanoscopic objects. Inspired by motile cells and bacteria, man-made microswimmers have been created, and their motion was studied experimentally in patterned surroundings [1]. We propose to use artificial microswimmers -- Janus spheres [2] illuminated by light -- as ``driving agents'' that move through a binary mixture of colloidal particles. We demonstrated [3] that binary mixtures can be effectively separated in this way. We analyzed the main features of the particle separation and explained mechanisms of different regimes including the one with a velocity inversion. Our finding can be readily verified in experiments with colloidal binary mixtures and could be of use for various biological and medical applications. \\[4pt] [1] G.~Volpe et al., Soft Matter {\bf 7}, 8810 (2011).\\[0pt] [2] Q.~Chen et al., Science {\bf 331}, 199 (2011).\\[0pt] [3] W.~Yang, V.R.~Misko, K.~Nelissen, M.~Kong, and F.M.~Peeters, arXiv:1109.5099 (2011).