Design of piezoelectric piston-like piezoelectric transducers based on a phononic crystal

Many clinical surveys have evaluated the use of ultrasound in physiotherapy treatments, the question of its effectiveness still being under discussion possibly because of the randomized energy density applied, which depends on the acoustic pressure beam of the transducers. In this work, a phononic crystal made of holes in solid materials is the basis for the design of a transducer with a piston-like vibration pattern where the radial modes are stopped, thus favoring the thickness vibration and resulting in a better mechanical vibration amplitude and acoustic efficiency. Finite element simulations have been made of the standard transducer and the proposed design; then demonstrator devices have been manufactured and tested so experimental results could be compared to the calculated ones. The transducers with this phononic structure show an efficient piston-like emission. The electrical impedance, the emitting surface vibration pattern and the acoustic diffraction field have been calculated and experimentally measured.