Piezoelectric MEMS—evolution from sensing technology to diversified applications in the 5G/Internet of Things (IoT) era

Abstract

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.

Machine Learning-Assisted Multifunctional Environmental Sensing Based on a Piezoelectric Cantilever

“…The development of micro-electromechanical systems (MEMS) technology promotes the miniaturization of environmental sensors, and many environmental sensors have been developed based on different principles such as optical sensors, chemiresistors, electrochemical sensors, and field-effect transistors (FETs). − Among them, a piezoelectric cantilever is one of the most promising environmental sensing platforms because of its advantages of small size, large sensing range, high compatibility with CMOS processes, and easy interfacing with digital circuits. , The piezoelectric cantilever-based environmental sensors usually consist of a cantilever with a sensing layer, whose properties, such as mass, viscoelasticity, and electrical conductivity, will be changed after its exposure to various environments. − However, the metallic top electrode of the conventional piezoelectric cantilever, which is normally covered by the sensing layer, as shown in Figure S1, usually has excellent electrical conductivity, which eliminates the effects of conductivity changes of the sensing film on the output signal of the sensor. Currently, most environmental sensors based on the piezoelectric cantilevers only detect their resonant frequency shifts after exposure to various environments, which are mainly due to the mass changes of the sensing film .…”

Reconfigurable terahertz metamaterials: From fundamental principles to advanced 6G applications

“…Microelectromechanical system (MEMS) technology enables micro/nanoscale mechanical manipulation, which is suitable for meta-atom construction in the THz region, bringing various applications in THz functional devices. The reconfigurable MEMS metamaterials can be further classified by their actuator mechanisms, such as piezoelectric ( Willatzen and Christensen, 2014 ; Amirkhan et al., 2020 ; Le et al., 2022 ), electrothermal ( Lee and Wu, 2005 ; Lee and Yeh, 2005 ; Lee, 2005 ; Lee, 2006 ; Lee, 2007 ; Pitchappa et al., 2017 ), and electrostatic ( Pitchappa et al., 2015a , 2015b , 2015c , 2016a , 2016c ; Shih et al., 2017 ) ( Pitchappa et al., 2021a , 2021b ), and so on ( Lee et al., 2005 ; Lee, 2005 ; Yeh et al., 2006 ). Combining with metamaterial resonator designs, the deformed structures can effectively modify the electromagnetic field distribution inside the resonators.…”

“…Microelectromechanical system (MEMS) technology enables micro/nanoscale mechanical manipulation, which is suitable for meta-atom construction in the THz region, bringing various applications in THz functional devices. The reconfigurable MEMS metamaterials can be further classified by their actuator mechanisms, such as piezoelectric (Willatzen and Christensen, 2014;Amirkhan et al, 2020;Le et al, 2022), electrothermal Lee, 2005;Lee, 2006;Lee, 2007;Pitchappa et al, 2017), and electrostatic (Pitchappa et al, 2015a(Pitchappa et al, , 2015b(Pitchappa et al, , 2015c(Pitchappa et al, , 2016a(Pitchappa et al, , 2016cShih et al, 2017)…”

Noncontact Human–Machine Interface Using Complementary Information Fusion Based on MEMS and Triboelectric Sensors

“…In the past few decades, by leveraging the wafer‐level and low‐cost micromachining processes, microelectromechanical system (MEMS) sensors such as inertial and pressure sensors have achieved a huge commercial success. [ 7 , 8 , 9 , 10 , 11 , 12 ] These MEMS sensors are able to be integrated into various wearable equipment or with other wearable sensors, exhibiting good integration compatibility, low power consumption, and negligible effect on the flexible and stretchable properties of wearable HMIs. [ 13 , 14 , 15 ] On the other hand, wearable HMIs can be directly fabricated from intrinsically flexible or stretchable materials, e.g., electronic skin, [ 16 , 17 , 18 , 19 ] electronic‐textile, [ 20 , 21 , 22 , 23 , 24 , 25 ] wearable patch, [ 26 , 27 , 28 ] etc.…”