DC-conductivity of a suspension of insulating particles with internal rotation

TL;DR

This paper investigates how Quincke rotation of insulating particles in a suspension affects its DC conductivity, showing that rotation can enhance ion migration and increase overall conductivity.

Contribution

The study provides a theoretical framework and experimental validation for the impact of Quincke rotation on suspension conductivity, highlighting a novel mechanism for conductivity modulation.

Findings

Below critical field, particles decrease conductivity by blocking ion flow.

Above critical field, particle rotation increases conductivity by facilitating ion migration.

Experimental results confirm the theoretical predictions.

Abstract

We analyse the consequences of Quincke rotation on the conductivity of a suspension. Quincke rotation refers to the spontaneous rotation of insulating particles dispersed in a slightly conducting liquid and subject to a high DC electric field: above a critical field, each particle rotates continuously around itself with an axis pointing in any direction perpendicular to the DC field. When the suspension is subject to an electric field lower than the threshold one, the presence of insulating particles in the host liquid decreases the bulk conductivity since the particles form obstacles to ion migration. But for electric fields higher than the critical one, the particles rotate and facilitate ion migration: the effective conductivity of the suspension is increased. We provide a theoretical analysis of the impact of Quincke rotation on the apparent conductivity of a suspension and we present experimental results obtained with a suspension of PMMA particles dispersed in weakly conducting liquids.