PMUT and CMUT Devices for Biomedical Applications: A Review

Abstract

Piezoelectric Micromachined Ultrasonic Transducers (PMUT) and Capacitive Micromachined Ultrasonic Transducers (CMUT) have seen great developments in recent years, both in terms of performance and scope of applications within the biomedical ultrasound domain. This paper presents a review of the state-of-the-art of PMUT and CMUT technologies, focusing on their principle of operation, microfabrication techniques and use in different biomedical imaging and therapeutic applications. The advantages and drawbacks of PMUT and CMUT technologies in comparison with conventional bulk transducers are highlighted, the trade-offs among PMUTs and CMUTs are discussed, and their relevance in the current landscape of medical diagnostics and therapeutic uses is outlined, thus providing a clear overview of these promising technologies for the present and the next generation biomedical ultrasound applications.

Fully Integrated Pitch-Matched AlScN PMUT-on-CMOS Array for High- Resolution Ultrasound Images

“…2 It gives the acoustic output pressure from 1 mm 2 PMUT area at 1.5 mm from its surface when 1 V is applied. 3 The area is computed taking into account the number of elements, 60 µm diameter and 75 µm of pitch. 4 Extracted pressure from Fig.…”

“…The fast development of Micro-Electro-Mechanical Systems (MEMS) technology has aroused significant interest for this catheter-based ultrasound imaging systems. While ultrasoundbased medical diagnosis has proven invaluable in detecting and evaluating various diseases, the advancement of MEMS technology holds particular promise in enhancing their capabilities, specifically providing robust fabrication processes for phased-array solid-state catheter based probes [2,3].…”

“…In respect MEMS-based solutions, two different types of micromachined ultrasound transducers (MUTs) have been reported for catheter-based ultrasound imaging probes [3]: Capacitive Micromachined Ultrasonic Transducers (CMUTs) [14][15][16][17][18][19][20] and Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) [21][22][23]. Both are MEMS devices based on flexural membranes capable to produce and sense the ultrasound acoustic field by electrostatic actuation (CMUTs) or using a piezoelectrical layer as part of the membrane's layers (PMUTs).…”

“…CMUTs, despite their requirement for high polarization voltages, demonstrate promise due to their small dimensions, compatibility with CMOS processes, and potential for high-density array fabrication. PMUTs, on the other hand, offer further advantages by eliminating the need for DC polarization voltages, simplifying the fabrication process (same element to transmit and receive) while maintaining the integration capabilities with CMOS circuitry [3,24]. Some examples from the literature using CMUTs or PMUTs for phased-array systems, are described here.…”