Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 25: Focus: Active Fluids

CPP 25.4: Talk

Wednesday, March 24, 2010, 11:00–11:15, H39

Efficiency of phoretic micromotors — •Benedikt Sabass and Udo Seifert — II. Institut für Theoretische Physik, Universität Stuttgart

Small objects, propelled through phoretic surface processes, could be employed for active transport or even as micromotors. A common characteristic of these processes is the generation of a surface flow around the motor by different mechanisms. Here we investigate the thermodynamic properties of phoretic effects. We derive a general expression for the efficiency of motors and show that it is bounded by its hydrodynamic contribution. A general argument is proposed according to which the hydrodynamic efficiency of propulsion mechanisms relying on surface effects scales as L/R where L is the thickness of the interface layer and R is the lengthscale of the object. This finding supports the notion that this class of processes is very often quite inefficient. We also illustrate our findings with concrete examples.