Depletion forces between two spheres in a rod solution

TL;DR

This paper investigates the depletion interaction between spherical particles in a rod solution, providing exact numerical results that challenge existing approximations and shed light on colloidal phase behavior.

Contribution

It offers the first exact numerical computation of depletion forces between spheres in a rod solution for any size ratio R/L, improving understanding of colloidal interactions.

Findings

Depletion well depth is smaller than Derjaguin approximation predicts.

Results are exact for any rod length to sphere radius ratio.

Insights into the absence of phase separation in sphere-rod colloids.

Abstract

We study the depletion interaction between spherical particles of radius R immersed in a dilute solution of rigid rods of length L. The computed interaction potential is, within numerical accuracy, exact for any value of L/R. In particular we find that for L of order R, the depth of the depletion well is smaller than the prediction of the Derjaguin approximation. Our results bring new light into the discussion on the lack of phase separation in colloidal mixtures of spheres and rods.