Three- and four-body interactions in colloidal systems

TL;DR

This study directly measures three- and four-body interactions among charged colloidal particles, revealing attractive three-body and repulsive four-body interactions, with results aligning qualitatively with nonlinear Poisson-Boltzmann calculations.

Contribution

The paper provides the first direct experimental measurements of three- and four-body interactions in colloidal systems, confirming theoretical predictions.

Findings

Attractive three-body interactions observed.

Repulsive four-body interactions observed.

Experimental results agree qualitatively with nonlinear Poisson-Boltzmann calculations.

Abstract

Three-body and four-body interactions have been directly measured in a colloidal system comprised of three (or four) charged colloidal particles. Two of the particles have been confined by means of a scanned laser tweezers to a line-shaped optical trap where they diffused due to thermal fluctuations. By means of an additional focused optical trap a third particle has been approached and attractive three-body interactions have been observed. These observations are in qualitative agreement with additionally performed nonlinear Poissson-Boltzmann calculations. Two configurations of four particles have been studied experimentally as well and in both cases a repulsive four-body interaction term has been observed.