Capacitance transducers for generating ultrasonic fields in liquids and gases

The Si/Kapton transducers presented have a whole host of desirable properties and are capable of making numerous and unique practical measurements. They are non-contact transducers which are wideband, reversible and well damped, and appear to be linear over the range of incident amplitudes studied to date. They are capable of non-contact detection of surface breaking waves, Lamb waves and Rayleigh waves propagating in solid media, while retaining the ability to alternatively generate these waves. They are even sensitive enough to detect thermoelastic generation in solids by pulsed lasers, not to mention the onset of ablation. They appear to be simple capacitors electrically, which makes their coupling to generating and receiving circuitry a well defined problem. In gaseous media they are available for sensitive work in through transmission and pulse-echo modes with the potential to easily detect small objects at distances close to the transducer aperture