Liquid crystal-enabled electroosmosis through spatial charge separation in distorted regions as a novel mechanism of electrokinetics

TL;DR

This paper introduces a novel electrokinetic mechanism in liquid crystals where anisotropic conductivity and spatial charge separation enable efficient electro-osmosis, with potential applications in microfluidics and sensing.

Contribution

The study reveals that anisotropic conductivity in liquid crystals facilitates a new electro-osmosis mechanism based on charge separation in distorted regions, expanding electrokinetics applications.

Findings

Electro-osmosis velocities scale with the square of the electric field.

AC fields can drive steady flows, reducing electrode damage.

Liquid crystals can be used for versatile electrokinetic applications.

Abstract

Electrically-controlled dynamics of fluids and particles at microscales is a fascinating area of research with applications ranging from microfluidics and sensing to sorting of biomolecules. The driving mechanisms are electric forces acting on spatially separated charges in an isotropic medium such as water. Here we demonstrate that anisotropic conductivity of liquid crystals enables new mechanism of highly efficient electro-osmosis rooted in space charging of regions with distorted orientation. The electric field acts on these distortion-separated charges to induce liquid crystal-enabled electro-osmosis (LCEO). LCEO velocities grow with the square of the field, which allows one to use an AC field to drive steady flows and to avoid electrode damage. Ionic currents in liquid crystals that have been traditionally considered as an undesirable feature in displays, offer a broad platform for versatile applications such as liquid crystal enabled electrokinetics, micropumping and mixing.