Experimental study of the growth of cholesteric fingers subjected to an AC electric field and a temperature gradient

Abstract

We study the behaviour of cholesteric fingers of the first and second types (CF1 and CF2, respectively) which form in cholesteric samples treated for homeotropic anchoring when they are subjected to the combined action of an AC electric field and a temperature gradient. We investigate under which conditions each type of finger can drift and form a spiral. We then show that the ends of the growing CF1 follow circular trajectories, the curvatures of which depend linearly on the temperature gradient. This observation opens the possibility of measuring the thermal Lehmann coefficient in any cholesteric liquid crystal at all temperatures.

Keywords:

• liquid crystals
• cholesteric fingers
• spiral
• circular growth
• Lehmann effect