Chiral motion in colloidal electrophoresis

TL;DR

This paper introduces a computational method to predict complex translational and rotational motions, including chiral twisting, of asymmetrically charged colloidal particles under electric fields, accounting for electrostatic and hydrodynamic interactions.

Contribution

It presents a novel approach to calculate body tensors for nonspherical colloids, enabling accurate prediction of their electrophoretic behavior and chiral motions.

Findings

Method accurately predicts electrophoretic mobility within a few percent.

Demonstrates strong chiral twisting motions in symmetric colloidal shapes.

Applicable to active colloidal swimmers beyond static particles.

Abstract

Asymmetrically charged, nonspherical colloidal particles in general perform complex rotations and oblique motions under an electric field. The interplay of electrostatic and hydrodynamic forces complicate the prediction of these motions. We demonstrate a method of calculating the body tensors that dictate translational and rotational velocity vectors arising from an external electric field. We treat insulating, rigid bodies in the linear-response regime, with indefinitely small electrostatic screening length. The method represents the body as an assembly of point sources of both hydrodynamic drag and surface electric field. We demonstrate agreement with predicted electrophoretic mobility to within a few percent for several shapes with uniform and nonuniform charge. We demonstrate strong chiral twisting motions for colloidal bodies of symmetrical realistic shapes. The method applies more generally to active colloidal swimmers.