Homeotropic liquid crystal device employing vertically aligned carbon nanotube arrays as the alignment agent

Vertically aligned carbon nanotube (VA-CNT) arrays were grown on several chromium (Cr)-coated glass substrates using a plasma-enhanced chemical vapor deposition system. The CNTs were 2μm long and had a site density of 2×10^{9}cm^{-2} on the substrates. Two VA-CNT slides on Cr glass substrates were put together to design a homeotropic electro-optic liquid crystal (LC) device. A negative dielectric anisotropic LC was used in the device. The π-π stacking interaction between the LC and the VA-CNTs allows the LC material to align homeotropically in the cell. When an external electric field was applied using the transparent conducting Cr layers, the LC achieves a planar orientation above a threshold field. These results successfully demonstrate the optical, electro-optical operations, and the field-induced dynamic response of a homeotropic LC device employing the VA-CNT arrays as the homeotropic-alignment agent. This study significantly advances the range and understanding of nanostructured surfaces that provide vertical alignment of LCs.