Self-organization and shape change by active polarization in nematic droplets

TL;DR

This paper presents a hydrodynamic model explaining how active forces within nematic droplets of cytoskeletal filaments can lead to self-organization, shape change, and division, aligning with recent experimental observations.

Contribution

It introduces a minimal hydrodynamic model combining motor-filament kinetics with nematic phase separation to explain droplet self-organization and division.

Findings

Motors organize into polarized aster defects within droplets.

High motor activity can deform or divide droplets.

The phase diagram matches experimental shapes.

Abstract

Active forces occurring within cells can drive crucial biological processes that involve spontaneous organization and shape change, such as cell division. Motivated by recent in vitro experiments of nematic droplets of cytoskeletal filaments and motors that self-organize and divide, we present a minimal hydrodynamic model that combines the nonequilibrium kinetics of motor-filament interactions with equilibrium nematic phase separation. The motors organize within droplets and structure filaments into polarized aster defects. At large motor activity, they can even deform or divide the droplet, or form multi-aster chains of droplets. Our predicted phase diagram recapitulates these experimentally observed shapes.