Viscosity Measurement of Ferroelectric Liquid Crystal Using Shear Horizontal Wave Propagation in a Trilayer Structure

Propagation characteristics of a shear horizontal (SH) wave in a trilayer structure, having a viscous liquid layer between a piezoelectric ceramic plate and a glass plate, are described on the basis of numerical and experimental investigations. Viscosity dependences of mechanical displacement distributions and relationships between the fractional velocity change and the square root of viscosity are discussed. The viscosity is related to the acoustic phase delay, accompanied by the SH wave propagation, between two interdigital transducers on the SH wave device. The measured temperature dependence of viscosity of silicon oil is in good agreement with the numerical analysis result of the SH wave propagation. An electrorheology effect and the temperature dependence of the viscosity in a ferroelectric liquid crystal (FLC: CS1014) are also measured by this technique.