Interface-mediated interactions: Entropic forces of curved membranes

TL;DR

This paper investigates how thermal fluctuations and membrane curvature influence forces between particles on fluid membranes, revealing entropic effects that can cause repulsion contrary to typical Casimir attraction.

Contribution

It demonstrates that entropic forces mediated by membrane fluctuations can enhance curvature-induced repulsion between particles, contrasting with traditional Casimir forces.

Findings

Entropic effects increase repulsion between particles on curved membranes.

Thermal fluctuations modify surface tension of flat membranes.

Large-distance behavior aligns with renormalized surface tension.

Abstract

Particles embedded in a fluctuating interface experience forces and torques mediated by the deformations and by the thermal fluctuations of the medium. Considering a system of two cylinders bound to a fluid membrane we show that the entropic contribution enhances the curvature-mediated repulsion between the two cylinders. This is contrary to the usual attractive Casimir force in the absence of curvature-mediated interactions. For a large distance between the cylinders, we retrieve the renormalization of the surface tension of a flat membrane due to thermal fluctuations.