Light-switchable propulsion of active particles with reversible interactions

Hanumantha Rao Vutukuri, Maciej Lisicki, Eric Lauga Lauga, Jan Vermant, Apollo-University Of Cambridge Repository, Apollo-University Of Cambridge Repository
Active systems such as microorganisms and self-propelled particles show a plethora of collective phenomena, including swarming, clustering, and phase separation. Control over the propulsion direction and switchability of the interactions between the individual selfpropelled units may open new avenues in designing of materials from within. Here, we present a self-propelled particle system, consisting of half-gold-coated titania (TiO 2 ) particles, in which we can quickly and on-demand reverse
more » ... propulsion direction, by exploiting the different photocatalytic activities on both sides. We demonstrate that the reversal in propulsion direction changes the nature of the hydrodynamic interaction from attractive to repulsive and can drive the particle assemblies to undergo both fusion and fission transitions. Moreover, we show these active colloids can act as nucleation sites, and switch rapidly the interactions between active and passive particles, leading to reconfigurable assembly and disassembly. Our experiments are qualitatively described by a minimal hydrodynamic model.
doi:10.17863/cam.54449 fatcat:fpjk7yc2w5ftpchiuntbbpa6gq