Hydrodynamic ratchet: Controlled motion of a polymer in an alternating microchannel flow

¹ Department of Chemical Physics, University of Science and Technology of China - Hefei, Anhui, 230026, China
² Institut für Theoretische Physik, Technische Universtität Berlin - Hardenbergstrasse 36, D-10623 Berlin, Germany
³ Abteilung Physikalische Chemie, Fritz-Haber-Institut der Max-Plank-Gesellschaft - Faradayweg 4-6, 14195 Berlin, Germany

Received: 2 September 2013
Accepted: 2 October 2013

Abstract

Using ratchets, periodic or irregular oscillations can be transformed into steady translational or rotational motions. Here, we consider a model system that operates as a hydrodynamic ratchet. A polymer is placed inside a narrow channel where an oscillating Poiseuille flow is externally created. The ratchet mechanism is implemented by introducing a feedback control for the lateral position of the polymer through which its mobility becomes effectively dependent on the direction of its motion along the channel. We employ the semi-flexible elastic chain modeling for the polymer and use the method of multi-particle collision dynamics to simulate the fluid. We indeed observe directed motion of the polymer and determine the dependence of the propagation velocity on the model parameters.