Boundaries can steer active Janus spheres

TLDR

Autonomous self‑propulsion has spurred research into colloidal machines, but steering such devices remains limited due to Brownian rotation randomizing particle orientations. This study reports directed motion of catalytic Janus motors when they move close to solid surfaces. Steering is achieved by actively quenching Brownian rotation within a rotational well created by hydrodynamic effects. The authors demonstrate that combining these geometric constraints allows the motors to be steered along arbitrary trajectories.

Abstract

Abstract The advent of autonomous self-propulsion has instigated research towards making colloidal machines that can deliver mechanical work in the form of transport, and other functions such as sensing and cleaning. While much progress has been made in the last 10 years on various mechanisms to generate self-propulsion, the ability to steer self-propelled colloidal devices has so far been much more limited. A critical barrier in increasing the impact of such motors is in directing their motion against the Brownian rotation, which randomizes particle orientations. In this context, here we report directed motion of a specific class of catalytic motors when moving in close proximity to solid surfaces. This is achieved through active quenching of their Brownian rotation by constraining it in a rotational well, caused not by equilibrium, but by hydrodynamic effects. We demonstrate how combining these geometric constraints can be utilized to steer these active colloids along arbitrary trajectories.