Takashi Kato’s research while affiliated with The University of Tokyo and other places

Based on the continuum theory of nematic liquid crystals, the authors analyzed the electrorheological effect. Regarding one-dimensional shear flow between infinite parallel flat boards, based on the parallel anchoring model and uniform director model which put forth differing assumptions regarding directors, we determined an equation which describes changes in apparent viscosity because of electric fields. We compared the theoretical and actual values for 4-pentyl-4′-cyanobiphenyl (5 CB) and after verifying the adequacy of this analysis, with analysis using the physical property values of 5 CB, the authors quantitatively clarified (1) the thinner the film and lower the shear rate and electric field strength, the more likely the influence of surface anchoring will appear, and (2) when flat board movement speed is kept fixed, the thinner the film, the lower the voltage at which one can get a fixed electrorheological effect.

Experiments are described in which friction coefficients under boundary lubrication regime are measured with a nematic liquid crystal as the lubricant. Using steel-to-steel contacts, with one of the mating surfaces coated with a thin insulating film, electric fields are applied across the liquid crystal film. A substantial decrease in the friction coefficient is observed with both d.c. and low-frequency a.c. voltages, suggesting the possibility of controlling friction by external fields.