Novel Measurement Method for Flexoelectric Coefficients of Nematic Liquid Crystals

Abstract

A new measurement method for the flexoelectric coefficients e 11 and e 33 (corresponding to the splay and bend strain, respectively) of nematic liquid crystals (LCs) is proposed. The values of e 11 + e 33 and e 11 - e 33 can be determined by fitting experimental electrooptical characteristics of hybrid aligned nematic (HAN) cells with numerical simulations. For the measurement of e 11 + e 33 and e 11 - e 33 , a dc electric field is applied along the cell normal and along the cell surface, respectively. The measurements were carried out for two nematics, N -(4-methoxybenzylidene)-4 ′ - n -butylaniline (MBBA) and ZLI-4792. As a result, e 11 + e 33 =(-5.4 ±1.0) ×10 -11 C/m and e 11 - e 33 =(1.4 ±0.1) ×10 -11 C/m for MBBA, | e 11 + e 33 | ≤1.0 ×10 -11 C/m and e 11 - e 33 =(-1.5 ±0.1) ×10 -11 C/m for ZLI-4792 were obtained.