Capacitance devices for the controlled generation of ultrasonic fields in liquids

Capacitance devices capable of efficiently radiating ultrasonic waves into liquids and air are described. Several designs have been characterized by examining the amplitude variations of the emerging beams, in both the near-field and far-field regions, and by determining their pulse responses using an interferometer. Although many aspects of their construction affect their bandwidth and beam profiles, the most influential appears to be the sizes and distribution of the air pockets trapped within the metallic backplate surface features. Techniques based upon conventional IC manufacturing could allow careful control over these backplate characteristics and hint at a new generation of water and air coupled standard ultrasonic transducers