Active Particles with Soft and Curved Walls: Equation of State, Ratchets, and Instabilities.
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.
Department of Physics, Technion, Haifa 32000, Israel.
Nikolai
N
Nikola
Université Paris Diderot, Sorbonne Paris Cité, MSC, UMR 7057 CNRS, 75205 Paris, France.|Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Alexandre P
AP
Solon
Department of Physics, Technion, Haifa 32000, Israel.
Yariv
Y
Kafri
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Mehran
M
Kardar
Université Paris Diderot, Sorbonne Paris Cité, MSC, UMR 7057 CNRS, 75205 Paris, France.
Julien
J
Tailleur
Laboratoire de Physique Théorique de la Matière Condensée, UMR 7600 CNRS /UPMC, 4 Place Jussieu, 75255 Paris Cedex, France.|Laboratoire Jean Perrin, UMR 8237 CNRS /UPMC, 4 Place Jussieu, 75255 Paris Cedex, France.
Raphaël
R
Voituriez