Fabrication of Micro-Grating Structures by Direct Laser Writing Based on Two Photon Process and Their Liquid Crystal Alignment Abilities

Abstract

The authors have demonstrated the local alignment of nematic liquid crystal with local micro-grating structure fabricated by the curing of an ultraviolet curable material via a three dimensional micro-fabrication technique known as two photon excitation direct laser writing [1]. The molecular alignment of the nematic liquid crystals on the fabricated micro-grating structures was firstly investigated by the observations of a local twisted nematic region in a liquid crystal cell made of a substrate with locally fabricated micro-grating structure and a counter substrate with rubbed polyimide. The optical polarizing microscope observation of the micro-grating structures indicated that liquid crystals molecules have aligned parallel to the grooves of the micro-grating structure and that local alignment was successfully achieved. The alignment characteristics of the liquid crystals on these micro-gratings was also investigated and discussed quantitatively in details through the measurement of anchoring energy by the conventional torque balance method and the Berreman method. The azimuthal anchoring energy for the micro-grating was found to be in the order of 10-6J/m2 and inversely proportional to the grating period.kn-abstract=