Rastko Sknepnek

Rastko Sknepnek, University of Dundee
Active matter and Curvature

Active motion and curvature are an integral part of fundamental biological processes such as gastrulation or intestinal crypt fission; their interplay creates a previously unexplored avenue for pattern formation. Here we use simple particle-based models to study the interplay between activity and curvature in dense systems. Using detailed numerical simulations and simple physical arguments, we show that the presence of curvature results in a number of steady-state configurations that have no analogues in flat geometries. These states are particularly interesting if topological constraints require the presence of defects in the ground states in the passive limit. We focus on polar and nematic active systems confined to move on the surface of a sphere and show that activity can lead to the formation of moving band and multidefect states. We extend our models to active polymers confined to a plane or the surface of a sphere and undergoing treadmill-like motion. We show that the activity leads to an effective softening of the polymer chain. As a result of this softening, with the increase in activity, the system transitions between a jammed polymer-melt state, an active turbulent state characterised by a proliferation of hair-pin defects, to a region dominated by phase segregation (MIPS) finally followed by the onset of a homogenous state characterised by spiral motion of individual polymers.

(In collaboration with: Silke Henkes (University of Aberdeen) and Prathyusha K R (University of Dundee)