Fabrication of poly(vinylidene fluoride-trifluoroethylene) ultrasound focusing transducers and measurements of elastic constants of thin plates

This paper investigates a modified method for fabricating focusing ultrasound transducers based on spin-coated poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer films. The ferroelectric hysteresis loops of the spin-coated P(VDF-TrFE) films are measured to establish the best fabrication parameters. The fabricated transducers are used for high-frequency wave velocity measurements and for non-destructive determination of elastic constants of thin isotropic plates. Both through-thickness longitudinal wave velocities and Rayleigh surface wave velocities of thin-plate samples with thicknesses ranging from 125 to 250 μm are measured, and hence their elastic constants can be determined in a straightforward and accurate way. The obtained results are in good agreement with the data reported by the manufacturers. Limitation of the proposed fabrication method and conventional method is compared and discussed in terms of signal intensity and frequency characteristics.