Measurement of Azimuthal Backflow in a Dual-Frequency Chiral HAN Cell

Abstract

An optical characterization technique has been used to determine the response of a chiral dual-frequency hybrid aligned nematic liquid crystal cell to a multiple frequency pulse. The cell goes from homeotropic to twisted homogeneous alignment when the frequency of an applied voltage is switched from below to above the cross-over frequency of the material. Analysis of the response of the director reveals a new form of backflow which arises due to a coupling between the rotation and flow of the liquid crystal. The results show good agreement with modelled profiles generated using the Leslie-Ericksen-Parodi nematodynamics theory.

Keywords:

• backflow
• cholesteric
• dual-frequency
• hybrid aligned

Acknowledgments

The authors would like to thank Dr. C. V. Brown of Nottingham Trent University, UK for the dielectric anisotropy and elastic constant measurements. This project forms part of a COMIT Faraday partnership funded by the Engineering and Physical Sciences Research Council and the DTI.