Steering Active Colloids

Active colloids can generate autonomous motion in liquids, however due to their small size, their paths are rapidly randomised by Brownian diffusion. Consequently a long held aim is to develop methods to harness this motion more effectively in order to steer the colloids towards particular targets. A wide range of methods to achieve this goal for catalytic Janus colloids will be surveyed. These approaches exploit a range of phenomena including the colloids interaction with magnetic fields, gravity, and nearby surfaces; mediated by phoretic and hydrodynamic effects. The ability to directly observe these hydrodynamic interactions will also be demonstrated. A particular focus will be placed on recent advances which exploit the ability of catalytic active colloids in confined volumes to self-generate well defined fluid flows. We have recently found that the interaction of these self-induced flows with ellipsoidal Janus colloids provides a new method to access cross-flow migration behaviour, steering the colloids path in relation to the macroscopic containers geometry. Additionally we will report the potential for responsive active colloids to statistically migrate towards a chemically defined target based on their ability to change size and modulate their motion.