Swimming at the micrometer scale is a fascinating and hot topic in condensed matter physics. The constraint of low Reynolds numbers, where inertial effects are absent requires completely new strategies to move objects. In biologic systems asymmetric organelles push or pull freely moving bacteria. In artificial systems, this is either mimicked or alternative propulsion mechanisms are sought based on thermo-phoresis, electro-phoresis or diffusio-phoresis (R. Kapral, J. Chem. Phys.138, 020901 (2013); A. Sen, M. Ibele, Y. Honga, D. Velegol, Faraday Discuss.143, 15–27 (2009)). Most experiments with artificial micro-swimmers are performed using individual swimming objects, some more recent are concerned with their collective behaviour. A very recent review highlights several approaches taken in this rapidly evolving and expanding field (Sen, Nano Today8, 531-554 (2013)).
Our approach differs from these main stream approaches by addressing modular micro-swimmers, composed of different parts taking different functionalities. The underlying mechanism is of electro-osmotic nature and has already been exploited to assemble autonomous micro-swimmers of different complexity as well as stationary aggregates (A. Reinmüller, H. J. Schöpe, T. Palberg, Langmuir29, 1738-1742 (2013); A. Reinmüller, E. Oguz, R. Messina, H. Löwen, H. J. Schöpe and T. Palberg, J. Chem. Phys.136, 164505 (2012)).
We are interested in the interplay between fuel reservoir particles (RP), substrate surface charges generating the driving flow, additional particles acting as gearing or steering, and cargo particles to be collected and released. To illustrate the flexibility of our modular approach, we show some examples and highlights below and some videos here.
Within the SPP 1726 we persue a project aiming at optimized performance based on a thorough characterization and mechanistic understanding. There we will utilize a recently developed optical cell (A. Reinmüller, H. J. Schöpe, T. Palberg, Rev. Sci. Instrum.84, 063907 (2013)) and our long standing expertise on electro-kinetic phenomena (T. Palberg, T. Köller, B. Sieber, H. Schweinfurth, H. Reiber, and G. Nägele. J. Phys.: Condens. Matter24, 464109 (19p) (2012)). In 2014 we will further submit applications for two subprojects within the local SFB on “Molecularly controlled Non-Equilibrium”. Several Master and Batchelor thesis topics are waiting for interested students. One Post-doc and three PhD-positions are available within these projects, the MAINZ graduate school and the MPGC.