Optical manifestation of thermal expansion of a nematic liquid crystal

Abstract

A unique feature of liquid crystals (LCs) is orientational order of molecules that can be controlled by electromagnetic fields, surface modifications and pressure gradients. We describe a new effect in which the orientation of LC molecules is altered by thermal expansion. Thermal expansion (or contraction) causes the LC to flow; the flow imposes an orienting torque on the LC molecules and the optical axis. The optical and mechanical responses activated by a simple temperature changes can be used in sensing, photonics, microfluidic, optofluidic and lab-on-a-chip applications as they do not require externally imposed gradients of temperature, pressure nor electromagnetic fields.