“…In [48], fabrication of flexible PMUTs using flexMEMS technology is described, where the PMUTs were developed on flexible polyimide substrates instead of the conventional rigid silicon substrate. In [49], the bendable structure is made out of several silicon islands containing a PMUT PZT array and are connected to each other by silicon springs, resulting in a fully conformal silicon based structure without the necessity of thinning down the wafer.…”
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.
“…In [48], fabrication of flexible PMUTs using flexMEMS technology is described, where the PMUTs were developed on flexible polyimide substrates instead of the conventional rigid silicon substrate. In [49], the bendable structure is made out of several silicon islands containing a PMUT PZT array and are connected to each other by silicon springs, resulting in a fully conformal silicon based structure without the necessity of thinning down the wafer.…”
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.
“…Since the transducer structure does not require the support layer, expensive SOI silicon wafers are also not needed in fabrication. In addition, no additional SiO 2 18 or AlN 19 film is needed as the support layer, simplifying the laminated structure and reducing the fabrication complexity. Fig.…”
Eye blinking is closely related to human physiology and psychology. It is an effective method of communication among people and can be used in human–machine interactions. Existing blink monitoring methods include video-oculography, electro-oculograms and infrared oculography. However, these methods suffer from uncomfortable use, safety risks, limited reliability in strong light or dark environments, and infringed informational security. In this paper, we propose an ultrasound-based portable approach for eye-blinking activity monitoring. Low-power pulse-echo ultrasound featuring biosafety is transmitted and received by microelectromechanical system (MEMS) ultrasonic transducers seamlessly integrated on glasses. The size, weight and power consumption of the transducers are 2.5 mm by 2.5 mm, 23.3 mg and 71 μW, respectively, which provides better portability than conventional methods using wearable devices. Eye-blinking activities were characterized by open and closed eye states and validated by experiments on different volunteers. Finally, real-time eye-blinking monitoring was successfully demonstrated with a response time less than 1 ms. The proposed solution paves the way for ultrasound-based wearable eye-blinking monitoring and offers miniaturization, light weight, low power consumption, high informational security and biosafety.
“…making stretchable interconnects for rigid chips, piezoelectric thin-film transfer to flexible substrates, and direct synthesis of piezoelectric material (including flexible piezoelectric materials like PVDF) on flexible substrates with lowtemperature processes. As shown in figure 13(a), a fabrication method is presented to achieve a bendable pMUT array by making stretchable interconnects [272]. The bendable structure consists of several rigid chip islands (each with a 3 × 3 pMUT array) connected together with silicon springs, which are fabricated using the deep reactive ion etching process.…”
Section: Development and Application Trends Of Piezoelectric Mems In ...mentioning
The rapid development of the fifth-generation mobile networks (5G) and Internet of Things (IoT) is inseparable from a large number of miniature, low-cost, and low-power sensors and actuators. Piezoelectric micro-electromechanical system (MEMS) devices, fabricated by micromachining technologies, provide a versatile platform for various high-performance sensors, actuators, energy harvesters, filters and oscillators (main building blocks in radio frequency (RF) front-ends for wireless communication). In this paper, we provide a comprehensive review of the working mechanism, structural design, and diversified applications of piezoelectric MEMS devices. Firstly, various piezoelectric MEMS sensors are introduced, including contact and non-contact types, aiming for the applications in physical, chemical and biological sensing. This is followed by a presentation of the advances in piezoelectric MEMS actuators for different application scenarios. Meanwhile, piezoelectric MEMS energy harvesters, with the ability to power other MEMS devices, are orderly enumerated. Furthermore, as a representative of piezoelectric resonators, Lamb wave resonators are exhibited with manifold performance improvements. Finally, the development trends of wearable and implantable piezoelectric MEMS devices are discussed.
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