A system for measuring the sound velocity in a liquid is described, which uses an interdigital transducer (IDT) for a leaky surface acoustic wave. The IDT on a piezoelectric substrate effectively operates as a radiator and a detector of the bulk wave at a liquid-solid interface. The measurement is accomplished by a frequency sweeping method under the condition of the fixed sound path length. The output curve is obtained as a function of the frequency at the IDT in the form of the interference between the input and the output signal reflected from the reflector. The measurement resolution of the present system is within 0.1%.

An interaction between an elastic wave and a liquid crystal is investigated from the view point of evaluation of the elastic properties of the liquid crystal. A periodical stripe domain pattern is induced by an interaction between the elastic wave and the nematic liquid crystal, the pattern is observed by a polarizing microscope. In the numerical analysis of elastic wave propagation in a nematic liquid crystal cell, the 0th mode depends on the liquid crystal properties, on the other hand the 1st mode is influenced predominantly by the properties of two sheets of glasses composing the cell. The 0th and 1st mode phase velocities are estimated from the periodic length of the stripe domain pattern. The 0th mode phase velocity in the nematic liquid crystal cell strongly depends on the cell layer thickness. The phase velocity obtained from the observed result is in good agreement with the numerical analysis result.

Measurement of Sound Velocity in Liquid Using Frequency Sweeping-Interdigital Transducer

Citations

Evaluation of elastic properties in nematic liquid crystal using elastic wave propagation

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