Determining depletion interactions by contracting forces

TL;DR

This paper presents a new physical method to determine effective interactions in concentrated colloidal systems by contracting forces, demonstrated through depletion force measurements in 2D mixtures, enabling analysis near metastable or non-equilibrium states.

Contribution

It introduces a general formulation for deriving effective interactions from bare forces applicable at high concentrations and out-of-equilibrium conditions.

Findings

Validated method on 2D colloidal mixtures with up to 70% packing fraction.

Allows determination of effective interactions at finite concentration.

Potential to study systems near metastable or out-of-equilibrium states.

Abstract

We introduce a general physical formulation that allows one to obtain uniquely the effectiveinteractions by contracting the bare forces, even in highly concentrated systems. We tested it bystudying depletion forces in two-dimensional binary and ternary colloidal mixtures with a totalpacking fraction up to 70%. Our result opens up the possibility of finding an efficient route todetermine effective interactions at finite concentration and even at thermodynamic conditions nearto meta-stable or out of equilibrium states.