Stanford
Khuri-Yakub Group

Khuri-Yakub Group Research

Research

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STANDARD CMUT CELL CROSS SECTION
FIG. 1: STANDARD CMUT CELL CROSS SECTION

Capacitive micromachined ultrasound transducers (CMUTs) have recently emerged as an alternative to piezoelectric transducers, offering advantages such as wide bandwidth, ease of fabricating large arrays, and integration with supporting electronic circuits. CMUT technology can produce the type of integrated catheter arrays and external probes enabling advanced 3-D imaging. A CMUT is simply a device with two plate-like electrodes biased with a DC voltage and driven with an additional AC signal to harmonically move one of the plates. The main components are the cavity, the membrane, and the electrode. Using common integrated circuit (IC) fabrication processes, a capacitor cell appears as a metallized membrane (top electrode) suspended above a heavily doped silicon substrate (bottom electrode), as shown in Fig. 1. An insulating layer is included to prevent the two electrodes from shorting in case of contact. A single transducer element uses many small capacitor cells connected in parallel. By organizing transducer elements in different geometries, any array shape is possible.

64 element CMUT Ring array on a flexible PCB for an intra-cardiac catheter assembly.
64 element CMUT Ring array on a flexible PCB for an intra-cardiac catheter assembly.
Real-time volumetric imaging of a metal spring phantom using a ring CMUT array
Real-time volumetric imaging of a metal spring phantom using a ring CMUT array and GPU-based imaging software.
2D CMUT array hydrophone
2D CMUT array hydrophone measuring single element piezoelectric reference source compared to mechanically scanned commercial needle hydrophone and theory.
Methane detection
The CMUT can be used as a chemical sensor by coating it with a chemical-sensitive interface layer. When the chemical of interest bonds to the interface layer, the mass of the CMUT membrane increases, decreasing the resonant frequency. This plot shows the
A novel CMUT called post-CMUT (PCMUT)
A novel CMUT called post-CMUT (PCMUT) can highly improve the transducer performance over the classical CMUT architecture by increasing the average volume displacement as well as fill factor.
Pressure Field of a focused 2-D CMUT array
Simulated pressure XZ-field of the focused 2-D CMUT array, 20-mm focal depth.
3-D diagram of the CMUT half-size cell
3-D diagram of the CMUT half-size cell (used for the Thick-BOX process).
Large airborne devices on a 4-inch wafer.
Large airborne devices on a 4-inch wafer. We used direct wafer bonding processes to fabricate large airborne devices with cell radius ~ 2 mm with a target frequency ~ 100 kHz.
A CMUT cell in permanent contact mode.
A CMUT cell in permanent contact mode. A permanent contact operational mode was proposed for airborne applications with varying ambient pressure from 1 to 20 atm, such as flare gas flow metering.
A CMUT cell in permanent contact mode.
A CMUT cell in permanent contact mode. A permanent contact operational mode was proposed for airborne applications with varying ambient pressure from 1 to 20 atm, such as flare gas flow metering.
Pitch catch signal
Pitch-catch signal from a pair of wideband airborne CMUTs with 170 kHz center frequency and 21% 3-dB fractional bandwidth.
A 32x32 Integrated CMUT Array for Volumetric Ultrasound Imaging.
A 32x32 Integrated CMUT Array for Volumetric Ultrasound Imaging. Two approaches used for integration. Use of an interposer board allows for tiling of CMUT Arrays (left) and possibly arrays with large apertures. Direct flip-chip bonding allows for more com