Dual-frequency piezoelectric micromachined ultrasonic transducers

Abstract

A piezoelectric micromachined ultrasonic transducer (pMUT) operating at dual frequencies (3.75 MHz and 18 MHz) was designed to achieve an ultrasound-on-a-chip solution for next-generation biomedical applications. Optimal electrode configurations for the dual-frequency pMUT were analyzed using finite element methods. It was found that a configuration with two ring electrodes enabled dual-frequency actuations of the diaphragm of the pMUT. Simulations showed that the first two resonances of the diaphragm can be tuned independently, especially with regard to amplitude, by optimizing electrode parameters (e.g., position and dimension) and applied voltage. It was also found that optimized distribution of the R and Z components of the displacement field contributes to near ideal mode superposition in a single diaphragm. Simulations for dual-actuations with both inner and outer ring electrodes showed that the two resonant modes are superimposed without significant vibrational crosstalk and result in high-quality dual-frequency acoustic radiation in water. Unlike transducers using two or more single-frequency ultrasonic resonators to generate dual-frequency ultrasound, every element of dual-frequency pMUTs exhibits dual-resonant response simultaneously.

Visualizing tactile feedback: an overview of current technologies with a focus on ultrasound elastography

“…PMUT have been developed to achieve both superficial, high-resolution imaging and deep, low-resolution imaging ( 61 , 62 ). Especially in diagnostic imaging, the resolution and depth of the image determine the sonographer’s ability to detect irregularities in tissue and vasculature.…”

“…To expand the operating frequency of these transducers, beam-coupled PMUTs (BM-PMUTs) combine both low- and high-frequency elements into a single array. This design allows for 2 resonant frequencies, maintaining high sensitivity in both low- and high-frequency modes (3.5 and 18 MHz) so that deep and shallow regions can be visualized with a single hand-held probe ( 61 , 62 ).…”

“…In essence, a CMUT is a parallel plate capacitor, with a flexible top plate (membrane) and a fixed bottom plate (substrate) ( Figure 3B ) ( 59 ). CMUTs function by applying an AC voltage and a DC bias voltage simultaneously between the membrane and the substrate, which causes the membrane to move due to Coulomb forces, known as electrostatic actuation ( 64 ). The movement, as well as the vibration from the AC voltage excitation, generates ultrasonic waves ( 65 ).…”

On-chip photoacoustic transducer based on monolithic integration of piezoelectric micromachined ultrasonic transducers and metasurface lenses

“…The lateral resolution improves with OR-PAM imaging, whereas the axial resolution remains restricted by the transducer bandwidth. Super-harmonic imaging was the original application of dual-frequency PMUT 3 . Recently, applications including intravascular ultrasound (IVUS) and photoacoustic imaging were thought to benefit from the dual-frequency PMUT or PMUT array.…”

A Nonlinear Pulse Shaping Method Using Resonant Piezoelectric MEMS Devices

“…Recent work on PMUTs focuses on improving their performance. This includes overcoming the limitations due to process variation during fabrication [14], providing methods on how to tune the resonant frequency of the PMUTs [6], augmenting the acoustic pressure generated by the PMUTs [2], [15] and creating dual frequency responses [16]. While these works generally use commercially available MEMS fabrication processes on silicon wafers [6], [14], [15], [17], others develop customs fabrication processes to improve the integration of PMUTs.…”