Formation of self-assembled periodic grooves via thermal drawing lithography for alignment layers in liquid crystal devices

Abstract

In this paper, we present a fascinating soft lithography—thermal drawing lithography (TDL)—to fabricate self-assembled periodic grooves. The pre-patterned silicon mold with protruding grating is placed on a bottom substrate spin-casted with a polymer film. According to the image charge-induced electrohydrodynamic-instability (ICE) model, the attractive electrostatic force between upper and lower substrates would cause a heat-induced melting polymer film to rise and form a positive replica grating pattern similar to the upper mold. In our work, we confirm that thermal drawing lithography could be achieved without an external electric field and fit the ICE model with experimental results. We have utilized these self-assembled grooves to align liquid crystal molecules for both reflective and transmissive liquid crystal (LC) cells. As well as for LC displays, this straightforward approach could be utilized for fabricating submicrostructures and possibly nanostructures.