What is "flexoelectricity"

n. (context physics English) The mechanoelectrical production of electricity by bending a material (especially some types of liquid crystal)

Flexoelectricity is a property of a dielectric material whereby it exhibits a spontaneous electrical polarization induced by a strain gradient. Flexoelectricity is not the same as Ferroelasticity.

The electric polarization due to mechanical stress in a dielectric is given by

$$P_i=d_{ijk}\sigma_{jk}+\mu_{ijkl}\frac{\partial\epsilon_{jk}}{\partial x_l}$$

where the first term corresponds to the direct piezoelectric effect and the second term corresponds to the flexoelectric polarization induced by the strain gradient.

Here, the flexoelectric coefficient, μ, is a fourth-rank polar tensor and d is the coefficient corresponding to the direct piezoelectric effect.