Passive Janus Particles Are Self-propelled in Active Nematics

Abstract

While active systems possess notable potential to form the foundation of new classes of autonomous materials [1], designing systems that can extract functional work from active surroundings has proven challenging. In this work, we extend these efforts to the realm of designed active liquid crystal/colloidal composites. We propose suspending colloidal particles with Janus anchoring conditions in an active nematic medium. These passive Janus particles become effectively selfpropelled once immersed into an active nematic bath. The self-propulsion of passive Janus particles arises from the effective +1/2 topological charge their surface enforces on the surrounding active fluid. We analytically study their dynamics and the orientational dependence on the position of a companion −1/2 defect. We predict that at sufficiently small activity, the colloid and companion defect remain bound to each other, with the defect strongly orienting the colloid to propel either parallel or perpendicular to the nematic. At sufficiently high activity, we predict an unbinding of the colloid/defect pair. This work demonstrates how suspending engineered colloids in active liquid crystals may present a path to extracting activity to drive functionality.

Network topology of interlocked chiral particles

“…This will possibly be a powerful tool in understanding the emergent topological structures [49][50][51]. Recent years have also seen an increased interest in non-equilibrium systems, where the individual particles consume energy from their surrounding to propel themselves [52][53][54][55]. It has been shown, that in these systems, the orientational defects have dynamical properties, which in turn depend on the respective topological charges [56][57][58].…”

Topological fine structure of smectic grain boundaries and tetratic disclination lines within three-dimensional smectic liquid crystals

“…The most prominent type of ordering, which is typically found in liquid crystals, is orientational (nematic) ordering, where the characteristically shaped subunits, i.e, molecules or colloidal particles in close proximity, show a tendency to align. If this preferred order gets frustrated, e.g., by confinement to a finite container [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49], constraining on a surface [50][51][52][53][54][55][56][57] or insertion of obstacles [58][59][60][61][62][63][64][65][66][67], topological defects emerge, which are discontinuities in the ordered structures that can display particlelike properties themselves [6,16,[68][69][70]. * Rene.Wittmann@hhu.de FIG.…”