Electrooptical Responses of Carbon Nanotube-Doped Liquid Crystal Devices

Abstract

The electrooptical characteristics of carbon nanotube-doped liquid crystal (LC) devices were investigated. Two complementary operation modes of the liquid crystal cells were fabricated. The measured results reveal that anisotropic carbon nanosolids modify the dielectric anisotropy and the viscosity of the liquid crystal carbon nanotube mixture, hence significantly modifying the threshold voltage and the switching behavior of a liquid crystal device. Doping a small amount of carbon nanotubes into the liquid crystal mixture is effective in improving the electrooptical characteristics of an LC device when the employed LC mixture is viscous.

Carbon Nanotubes in Liquid Crystals

“…a display. Reported effects include reduced effective ion content 16,18,20,21 , increased dielectric anisotropy 16,17,19 , suppressed backflow effects 16,17 , faster 10 electrooptic response due to reduced rotational viscosity 14 and lower switching threshold 16,17,19 . The CNT concentration was in all these works kept extremely low, yet substantial effects were reported.…”

On the effect of carbon nanotubes on properties of liquid crystals

“…Reports include a CNT-induced decrease of the Frederiks threshold (the threshold for switching the director orientation between the surface-induced OFF state and the field-induced ON state) [23][24][25][26][27][28], suppression of ionic field screening [24,27,[29][30][31] and increased switching speed [23,26,28]. The situation is however confused by data showing the opposite behaviour: unaffected or even clearly increased switching threshold [25,26,[28][29][30][31], clear signs of increased ion content [26,31] and slower switching [25,26,28]. While it is difficult to understand the origin of the discrepancy between the different reported results, due to lack of information on CNT quality, preparation procedure or crucial aspects of the experimental conditions, there are indications that the CNT concentration plays an important role [26] but also dispersion quality.…”

Techniques of aligning carbon nanotubes

“…Nanotubes are mixed with a solution of a liquid crystal substance, which can also be used for CNT dispersion [89]. Alignment is achieved in solution, usually by applying electric [90,91] or magnetic [89,92,93] fields, but also with light or mechanical force [94]. The enormous advantage of wrapping CNTs with liquid-crystal molecules is that much lower fields (orders of magnitude) are sufficient for alignment as compared to CNT alignment without the liquid crystal molecules.…”