Three-Dimensional Planar Alignment of Nematic Liquid Crystal by Direct Laser Writing of Nanogratings

We demonstrate a new method of aligning liquid crystals along polymer surfaces that are printed vertical to the focal plane using direct laser writing. The method is based on nanogrooves that are imprinted into surfaces of polymer structures and provide robust, reliable, repeatable, and well-controlled alignment patterns. Our results demonstrate that the anchoring strength of a liquid crystal on printed nanogratings is comparable to that of conventional polyimide layers. The advantages are at least 2-fold. First, we can print large vertical areas of well-defined patterns of nanogrooves with uniform anchoring strength, and, second, we can control the azimuthal anchoring strength by adjusting the amplitude and the periodicity of nanogrooves. Printing of alignment nanogrooves on tilted, curved and surfaces of arbitrary shape could be realized using printing protocols based on the principle shown here with potential applications in emerging microphotonic devices based on liquid crystals.