The limits of flexoelectricity in liquid crystals

TL;DR

This paper investigates the fundamental limits of flexoelectricity in nematic liquid crystals, establishing upper bounds on flexoelectric coefficients based on continuum theory, which impacts their potential use in energy conversion devices.

Contribution

It derives theoretical upper bounds on flexoelectric coefficients in liquid crystals, highlighting fundamental limits for their application in energy conversion and device design.

Findings

Flexoelectric coefficients are limited to a few tens of pC/m for typical material parameters.

Upper bounds are derived based on elastic and dielectric properties.

Implications for device design and energetics of liquid crystal structures are discussed.

Abstract

The flexoelectric conversion of mechanical to electrical energy in nematic liquid crystals is investigated using continuum theory. Since the electrical energy produced cannot exceed the mechanical energy supplied, and vice-versa, upper bounds are imposed on the magnitudes of the flexoelectric coefficients in terms of the elastic and dielectric coefficients. For conventional values of the elastic and dielectric coefficients, it is shown that the flexoelectric coefficients may not be larger than a few tens of pC/m. This has important consequences for the future use of such flexoelectric materials in devices and the related energetics of distorted equilibrium structures.