Oriented Yttrium Strontium Tin Oxide Micro/Nanostructures Induced by Brush Coating for Low-Voltage Liquid Crystal Systems

We present a convenient liquid crystal (LC) alignment method using brush hairs. An yttrium strontium tin oxide (YSrSnO) solution was prepared using a sol-gel process, and the one-step brush-coating process integrated film deposition and alignment. X-ray photoelectron spectroscopy confirmed a well-formed YSrSnO film via thermal oxidation. Atomic force microscopy showed oriented micro/nanostructures of the brush-coated film, attributed to shearing stress from brush-hair movements on the coating surface; the directionality was identical to that of the brushed coating, which caused physical surface anisotropy and uniform LC alignment on the YSrSnO layer. Uniform and homogeneous LC alignment was confirmed by polarized optical microscopy and pretilt angle measurements. Thermal stability tests of the LCs showed a suitable thermal budget, and the YSrSnO film showed fine optical transparency. Excellent electro-optical properties were observed in twisted-nematic LC system with remarkable low operating voltage. Thus, we expect brush coating to be a viable next-generation technology for LC systems.