Active Particles with Soft and Curved Walls: Equation of State, Ratchets, and Instabilities

N. Nikola , A.P. Solon , Y. Kafri , M. Kardar , J. Tailleur , R. Voituriez

Bibtex , URL
Published 22 Aug. 2016
DOI: 10.1103/PhysRevLett.117.098001
ISSN: 0031-9007


We study, from first principles, the pressure exerted by an active fluid of spherical particles on general boundaries in two dimensions. We show that, despite the nonuniform pressure along curved walls, an equation of state is recovered upon a proper spatial averaging. This holds even in the presence of pairwise interactions between particles or when asymmetric walls induce ratchet currents, which are accompanied by spontaneous shear stresses on the walls. For flexible obstacles, the pressure inhomogeneities lead to a modulational instability as well as to the spontaneous motion of short semiflexible filaments. Finally, we relate the force exerted on objects immersed in active baths to the particle flux they generate around them.

This publication is related to:

Stochastic dynamics of reactive and living systems