Electric Field Induced Macroscopic Cellular Phase of Nanoparticles

TL;DR

This paper investigates how applying AC and DC voltages induces a macroscopic cellular phase in nanoparticle suspensions, revealing the underlying electrohydrodynamic mechanisms and potential for reversible nanoscale material assembly.

Contribution

It provides a mechanistic understanding of cellular phase formation in nanoparticle suspensions and introduces a reversible assembly method for microscale structures.

Findings

Cellular phase forms under combined AC and DC voltages.

Electrophoretic assembly and spinodal decomposition drive phase transition.

Reversible assembly enables new material fabrication approaches.

Abstract

A suspension of nanoparticles with very low volume fraction is found to assemble into a macroscopic cellular phase under the collective influence of AC and DC voltages. Systematic study of this phase transition shows that it was the result of electrophoretic assembly into a two-dimensional configuration followed by spinodal decomposition into particle-rich walls and particle-poor cells mediated principally by electrohydrodynamic flow. This mechanistic understanding reveals two characteristics needed for a cellular phase to form, namely 1) a system that is considered two dimensional and 2) short-range attractive, long-range repulsive interparticle interactions. In addition to determining the mechanism underpinning the formation of the cellular phase, this work presents a method to reversibly assemble microscale continuous structures out of nanoscale particles in a manner that may enable the creation of materials that impact diverse fields including energy storage and filtration.