Lamb wave devices based on capacitive micromachined ultrasonic transducers

This paper describes the theory, design, and realization of a new type of Ultrasonic Lamb Wave Transducer. The excitation mechanism of this device is unlike any other as it relies on the Capacitive Micromachined Ultrasonic Transducer (CMUT). Built using fundamental integrated circuit techniques, this device has an insertion loss of 20 dB at an operating frequency of 2.1 MHz. The dominant propagating mode in the device is that of the lowest order antisymmetric flexural wave (A₀). The substrate upon which the device rests is 18 μm thick and is almost entirely made up of crystalline silicon. When configured as a delay line oscillator, the transducer functions well as a sensor to changes in environmental conditions.