Abstract
We study the dynamics of quasi-two-dimensional concentrated suspensions of colloidal particles in active gels by computer simulations. Remarkably, we find that activity induces a dynamic clustering of colloids even in the absence of any preferential anchoring of the active nematic director at the particle surface. When such an anchoring is present, active stresses instead compete with elastic forces and re-disperse the aggregates observed in passive colloid-liquid crystal composites. Our quasi-two-dimensional "inverse" dispersions of passive particles in active fluids (as opposed to the more common "direct" suspensions of active particles in passive fluids) provide a promising route towards the self-assembly of new soft materials.
Highlights
Active fluids are an intriguing example of far-from-equilibrium matter, with various instances present in the living world
The movie shows that the chaotic character of spontaneous flow is similar to that observed in active nematics without colloids, It demonstrates the dynamic clustering induced by the flow, which we describe in the text, and holds for no or weak anchoring
In the weak anchoring regime (w - 0) colloidal particles do not perturb the nematic order in the static limit; the spontaneous flow patterns resemble those found with j = 0,7–9 and at large |z| they feature vortices associated with splay-bend distortions in the orientational order (Fig. 1(d), Movie S1, Electronic supplementary information (ESI)†)
Summary
Active fluids are an intriguing example of far-from-equilibrium matter, with various instances present in the living world. The non-thermal forces that active particles exert on their environment can be modelled, in the simplest approximation, as force dipoles.[1,6] The interplay between the dynamics of the nematic order parameter describing the orientation of such dipoles and the Navier–Stokes equation, which models the flow of the underlying solvent in the presence of the active forcing, a Laboratoire de Physique Theorique et Modeles Statistiques, Universite Paris-Sud, UMR 8626, 91405 Orsay, France b Univ. CNRS, LOMA, UMR 5798, F-33405 Talence, France c EPCC, School of Physics and Astronomy, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK d DAMTP, Centre for Mathematical Sciences, University of Cambridge, Cambridge CB3 0WA, UK e SUPA, School of Physics and Astronomy, University of Edinburgh, James Clerk
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