The importance of being a cube: Active cubes in a microchannel

Abstract

Cubic shaped micrometer and nanometer sized colloids have become a popular research subject in experimental and theoretical soft matter physics. However, they are underrepresented in the field of active matter where the most investigated colloidal shapes are spheres or rods, for which hydrodynamic interactions vary from cube ones due to distinct body shape anisotropies. In this article, we are building on this knowledge by performing simulations to elucidate how active cubes in microchannels interact hydrodynamically with planar and curved boundaries through the flow field generated by an active force. We find that cubes tend to not show the same oscillatory behaviour previously found for other particle shapes, but move along a straight line near the channel centre for a range of initial conditions and parameters that can be accounted for in simulations. This effect arises through the cubes unique shape anisotropy interacting with the flow field and demonstrates that a cube constitutes an interesting hydrodynamic shape that deserves more attention in colloidal active matter research, in order to fully utilise its potential as an enrichment to commonly used particle shapes. © 2022 The Authors