Pulling and pushing a cargo with a catalytically active carrier

¹ Ian Wark Research Institute, University of South Australia - 5095 Adelaide, South Australia, Australia
² Max-Planck-Institut für Metallforschung - Heisenbergstr. 3, 70569 Stuttgart, Germany, EU
³ Institut für Theoretische und Angewandte Physik, Universität Stuttgart - Pfaffenwaldring 57, 70569 Stuttgart, Germany, EU

^a Mihail.Popescu@unisa.edu.au
^b miko@mf.mpg.de
^c dietrich@mf.mpg.de

Received: 21 March 2011
Accepted: 30 May 2011

Abstract

Catalytically active particles suspended in a liquid can move due to self-phoresis by generating solute gradients via chemical reactions of the solvent occurring at parts of their surface. Such particles can be used as carriers at the micro-scale. As a simple model for a carrier-cargo system we consider a catalytically active particle connected by a thin rigid rod to a catalytically inert cargo particle. We show that the velocity of the composite strongly depends on the relative orientation of the carrier-cargo link. Accordingly, there is an optimal configuration for the linkage. The subtlety of such carriers is underscored by the observation that a spherical particle completely covered by catalyst, which is motionless when isolated, acts as a carrier once attached to a cargo.