SILICON MICROMACHINED ULTRASONIC IMMERSION TRANSDUCERS

Broadband transmission ultrasound in water using capacitive, micromach ined transduces is reported. Transmission experiments using the same p air of devices at 4, 6, and 8 MHz with a signal-to-noise ratio greater than 48 dB are presented. Transmission is observed from 1 to 20 MHz. Better receiving electronics are necessary to demonstrate operation be yond this range. Furthermore, the same pair of transducers is operated at resonance to demonstrate ultrasound transmission in air at 6 MHz. The versatile transducers are made using silicon surface micromachinin g techniques. Computer simulations confirm the experimental results an d are used to show that this technology promises to yield immersion tr ansducers that are competitive with piezoelectric devices in terms of performance, enabling systems with 130 dB dynamic range. The advantage of the micromachine. transducers is that they can be operated in high -temperature environments and that arrays can be fabricated at lower c ost. (C) 1996 American Institute of Physics.