Piezoelectric Micromachined Ultrasonic Transducers With Pinned Boundary Structure

Bimorph Pinned Piezoelectric Micromachined Ultrasonic Transducers for Space Imaging Applications

“…Here, we demonstrate a bimorph, dual-electrode PMUT with a quasi-pinned boundary, which combines the previous works on the bimorph dual-electrode PMUTs [3] and PMUTs with pinned boundary [4]. The design concept, fabrication and equivalent circuit model of the bimorph pinned dual-electrode PMUT are investigated with a demonstration example on 2D space imaging tests.…”

“…The piezoelectrically-induced strain gradient in the top and bottom active layers causes the diaphragm to deform out of plane and move in the flexural mode, which launches acoustic waves into the medium. When a differential voltage is applied on the middle electrodes, the PMUT deflects into the quasi-pinned mode [4]. The bimorph pinned dual-electrode design allows for a larger deformation amplitude comparing to that of the conventional clamped boundary design, which leads to a higher elastic strain energy in the diaphragm.…”

“…In Figure 2a, the electrically induced stress of a conventional unimorph, clamped single-electrode PMUT only exists in the top active layer within the inner electrode. Figure 2b shows a unimorph, pinned PMUT, which has 2.8 times higher induced stress due to a relaxed quasi-pinned boundary [4]. Figure 2c shows the induced stress of a unimorph, clamped dual-electrode design.…”

An Improved Lumped Element Model for Circular-Shape pMUTs

“…There are two transduction mechanisms in MUTs: the capacitive [13] and piezoelectric scheme [14]. Performance enhancement studies can be summarized in two approaches; (1) optimal geometric designs such as collapse mode [15] in capacitive MUTs (cMUTs) or curved [16], ring [17], free [18] and pinned [19] boundary, bimorph [20] structures in piezoelectric MUTs (pMUTs); and (2) thin film materials with high piezoelectric properties such as PZT [21] and AlN [22]. In this study, pMUTs are investigated since they have shown prominent features in air applications such as no need for a bias voltage and the large displacement under the flexural vibration mode.…”

Beam-Membrane Coupled Piezoelectric Micromachined Ultrasonic Transducers with Enhanced Transmitting Sensitivity

“…Combining the advantages of residual stress localization and piston-like mode shape, the output sound pressure of the proposed PMUT could be improved by around 23 dB. Liang et al utilized the pinning boundary to increasing the vibration amplitude of PMUT [ 16 ], and the output sound pressure of the prototyped devices was 3.5 times higher than that of the traditional PMUTs with a clamped boundary. The above studies provide some effective methods for transmitting sensitivity optimization of PMUTs, but the transmitting sensitivity can be further improved since only part of the vibrating diaphragm is utilized.…”