Phase-separation in ion-containing mixtures in electric fields

TL;DR

Applying external electric fields to ion-containing liquid mixtures can induce a robust phase separation at low voltages, with potential applications in microfluidics such as creating nanometer-scale lubrication layers.

Contribution

This paper reveals that electric field-induced ionic screening can trigger phase separation in homogeneous mixtures, a novel mechanism with broad electrode geometry applicability and low voltage requirements.

Findings

Phase separation occurs in any electrode geometry.

Voltage needed for phase separation is typically around 1 V or less.

Potential applications include nanometer-scale lubrication layers in microfluidics.

Abstract

When a liquid mixture is subjected to external electric fields, ionic screening leads to field gradients. We point out that if the mixture is initially in the homogeneous phase, this screening can bring about a robust phase-separation transition with two main features: (i) the phase separation is expected to occur in any electrode geometry, and (ii) the voltage required is typically of the order of 1 V and even less. We discuss several applications of the effect relevant to the field of microfluidics, focusing on the creation of a nanometer-scale lubrication layer in the phase-separation process.