Inverse biasing capability of a dual deflectable membrane MEMS ultrasonic transducer for medical applications

A novel dual deflectable membrane capacitive micromachined ultrasonic transducer was fabricated for imaging applications. This transducer benefits from an additional flexible membrane suspended between the transducer upper membrane and the fixed bottom electrode. The presence of this vibrating middle membrane enables the transducer to operate in inverse bias condition where the driving voltage is sandwiched between two grounded electrodes. Electrical and optical measurements were conducted and the results show no significant change or reduction in the transducer vibrating mode and resonant frequency when operating in an inverse bias condition. Due to the isolated biased membrane configuration of the dual membrane transducer, this device can be potentially employed in medical fields where safety is a concern.