Walk ferroelectric liquid droplets with light

TL;DR

This study demonstrates that light irradiation can control the movement of ferroelectric liquid droplets on a lithium niobate substrate, enabling long-distance manipulation through polarization coupling.

Contribution

It introduces a novel method to manipulate ferroelectric liquid droplets using light-induced polarization effects on a ferroelectric substrate.

Findings

Droplets are attracted or repelled depending on light exposure side.

Moving the light beam causes droplets to walk across the substrate.

Effect is absent in non-ferroelectric nematic phase.

Abstract

We show that the motion of ferroelectric liquid sessile droplets deposited on a ferroelectric lithium niobate substrate can be controlled by a light beam of moderate intensity irradiating the substrate at a distance of several droplet diameters from the droplet itself. The ferroelectric liquid is a nematic liquid crystal in which almost complete polar ordering of the molecular dipoles generates an internal macroscopic polarization locally collinear to the mean molecular long axis. Upon entering the ferroelectric phase droplets are either attracted toward the center of the beam or repelled, depending on the side of the lithium niobate exposed to light irradiation. Moreover, moving the beam results in walking the ferroelectric droplet over long distances on the substrate. We understand this behavior as due to the coupling between the polarization of the ferroelectric droplet and the polarization photoinduced in the irradiated region of the lithium niobate substrate. Indeed, the effect is not observed in the conventional nematic phase, suggesting the crucial role of the ferroelectric liquid crystal polarization.