(474g) Osmotic Motor: Influence of Hydrodynamic Interaction for a Releasing Particle

The analysis of self-propelling particles is one of the challenges in modern science with a huge number of potential applications in biology, medicine, and chemistry. Construction of a catalytic motor, which converts the chemical energy into a directional motion, is one of the perspective ways in this field. We consider so-called osmotic motor, i.e. a Janus catalytic particle moving through a suspension of product particles. The simplest case, when the motor releases the product particles from its surface, is analyzed. Hydrodynamic interactions are taken into account.

The first case under consideration is an absence of product particles far from the motor. In this case the motor velocity increases as the production rate grows; for a slow chemical reaction the growth is linear, for a fast one the squared velocity of self-propulsion is proportional to the production rate.

If the motor moves through a suspension of particles identical to product ones, an additional hindrance appears. The concentration of particles can be decomposed into two fields: the first one is generated by a chemical reaction only, the second one is the same as studied within the active microrheology concept (Squires & Brady, Phys. Fluids, 2005). The first contribution makes the particle moving, whereas the second one produces an additional hindrance. This hindrance becomes prevailing over the Stokes drag as the background concentration increases.