Many-Body Electrostatic Forces Between Colloidal Particles at Vanishing Ionic Strength

TL;DR

This study measures electrostatic forces between colloidal particles at very low ionic strength, revealing non-pairwise additive interactions that are well described by the linearized Poisson-Boltzmann equation, impacting understanding of colloidal stability.

Contribution

It demonstrates non-pairwise electrostatic interactions at large screening lengths and confirms the applicability of the linearized Poisson-Boltzmann model with constant potential boundary conditions.

Findings

Forces are non-pairwise additive at large screening lengths.

Both pair and multi-particle forces fit the linearized Poisson-Boltzmann model.

Results are relevant for understanding colloidal stability in various systems.

Abstract

Electrostatic forces between small groups of colloidal particles are measured using blinking optical tweezers. When the electrostatic screening length is significantly larger than the particle radius, forces are found to be non-pairwise additive. Both pair and multi-particle forces are well described by the linearized Poisson-Boltzmann equation with constant potential boundary conditions. These findings may play an important role in understanding the structure and stability of a wide variety of systems, from micron-sized particles in oil to aqueous nanocolloids.