Design and Fabrication of 1D CMUT Arrays for Dual-Mode Acoustic Angiography Applications - Preliminary Results

When microbubble contrast agents are excited at low frequencies (less than 5 MHz), they resonate and produce higher order harmonics due to their non-linear behavior. We propose a novel scheme with a capacitive micromachined ultrasonic transducer (CMUT) array to receive high-frequency microbubble harmonics in collapse mode and to transmit a low-frequency high-pressure pulse by releasing the CMUT plate from collapse and pull it back to collapse again in the same transmit-receive cycle. By patterning and etching the substrate to create glass spacers in the device cavity we can operate the CMUT in collapse mode and receive high-frequency signals. Finite element model simulation results show that the fabricated devices can transmit at low frequency (< 5 MHz) and receive echoes at high frequency (> 15 MHz), which are verified by experimental results.