Transparent capacitive micromachined ultrasound transducer linear arrays for combined realtime optical and ultrasonic
Abstract:
Transparent ultrasound transducers could enable many novel applications involving both ultrasonics and optics. Recently, we reported transparent capacitive micromachined ultrasound transducers (CMUTs) and demonstrated through-illumination photoacoustic imaging. This work presents the feasibility of transparent CMUTs for combined ultrasound imaging and through-array white-light imaging with a miniature camera placed behind the array. Transparent CMUT devices are fabricated with an adhesive wafer bonding technique and provide high transparency up to 90% in visible wavelengths. Fabricated linear arrays have a central operating frequency of 9 MHz with 128 active elements. Realtime plane-wave imaging is performed for ultrasound imaging, and lateral and axial resolutions of, respectively, 234 and 338 µm are achieved. Transparent CMUT has demonstrated a high transmit sensitivity of 1.4 kPa/V per channel with a 100 VDC bias voltage. The signal-to-noise ratio for a beamformed image of wire targets is determined to be 28.4 dB. To the best of our knowledge, this is the first report of combined realtime optical and ultrasonic imaging with transparent arrays. This technology may enable one to visually see what is being scanned and scan what one sees without co-registration errors. Future applications could include multi-modality probes for interventional and surgical procedures.
