Strong deformations induced by a DC electric field in homeotropic flexo-electric nematic layers

Abstract

Elastic deformations of homeotropic nematic liquid crystal layers subjected to a DC electric field were studied numerically in order to determine their development under increasing voltage. Both signs of the dielectric anisotropy, Δϵ, and of the sum of flexo-electric coefficients, e ₁₁ + e ₃₃, were considered, as were also low, moderate and high ion concentrations. The electrical properties of the layer are described in terms of a weak electrolyte model. Quasi-blocking electrode contacts and a finite surface anchoring strength were adopted. Director orientation, the electric potential and the ion concentrations were each calculated as a function of the coordinate normal to the layer. The director distributions turned out to depend not only on the sign of Δϵ but also on the sign of e ₁₁ + e ₃₃, due to the difference in the mobility of anions and cations. The importance of ion content was also confirmed.

Keywords:

• nematic
• flexo-electricity
• director deformations
• homeotropic layers

Acknowledgements

Mariola Buczkowska holds a scholarship under the project: “Innovative teaching without limitations – integrated development of Technical University of Łódź – management of the university, modern educational offer and strengthening of employment capability, also for disabled persons”. This is financed by the European Union as part of the European Social Fund.