With the fast development of the fifth-generation cellular network technology (5G), the future sensors and microelectromechanical systems (MEMS)/nanoelectromechanical systems (NEMS) are presenting a more and more critical role to provide information in our daily life. This review paper introduces the development trends and perspectives of the future sensors and MEMS/NEMS. Starting from the issues of the MEMS fabrication, we introduced typical MEMS sensors for their applications in the Internet of Things (IoTs), such as MEMS physical sensor, MEMS acoustic sensor, and MEMS gas sensor. Toward the trends in intelligence and less power consumption, MEMS components including MEMS/NEMS switch, piezoelectric micromachined ultrasonic transducer (PMUT), and MEMS energy harvesting were investigated to assist the future sensors, such as event-based or almost zero-power. Furthermore, MEMS rigid substrate toward NEMS flexible-based for flexibility and interface was discussed as another important development trend for next-generation wearable or multi-functional sensors. Around the issues about the big data and human-machine realization for human beings’ manipulation, artificial intelligence (AI) and virtual reality (VR) technologies were finally realized using sensor nodes and its wave identification as future trends for various scenarios.

Development Trends and Perspectives of Future Sensors and MEMS/NEMS.

Highly selective detection of sulfur hexafluoride decomposition components H2S and SOF2 employing sensors based on tin oxide modified reduced graphene oxide

Power utilities are struggling to reduce power failure incidents in substations and their components to operate more reliably and economically [1]. Many power failures are produced directly or indirectly because of the insulation system of utility components [2], [3]. The selection of the insulation should ensure power plant operational continuity along with completely resolving or significantly limiting the actual power system's failures [4]. Gas insulated substations (GIS) have the best insulation performance which ensures achieving minimum failure incidents, although at high installation cost. The most common insulating gas used in GIS is Sulfur hexafluoride (SF 6 ) gas, which is widely used as an effective electrical insulation as well as an arc-quenching medium [5]. Basic GIS and gas insulated transmission lines (GITL or GIL) consist of a conductor supported by solid insulators inside an enclosure filled with SF 6 gas or its mixture [6].

Partial discharge detection and diagnosis in gas insulated switchgear: State of the art

The detection of partial discharge and analysis of the composition and content of sulfur hexafluoride SF6 gas components are important to evaluate the operating state and insulation level of gas-insulated switchgear (GIS) equipment. This paper reported a novel sensing material made of pure ZnO and NiO-decorated ZnO nanoflowers which were synthesized by a facile and environment friendly hydrothermal process for the detection of SF6 decomposition byproducts. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the structural and morphological properties of the prepared gas-sensitive materials. Planar-type chemical gas sensors were fabricated and their gas sensing performances toward the SF6 decomposition byproducts SO2, SO2F2, and SOF2 were systemically investigated. Interestingly, the sensing behaviors of the fabricated ZnO nanoflowers-based sensor to SO2, SO2F2, and SOF2 gases can be obviously enhanced in terms of lower optimal operating temperature, higher gas response and shorter response-recovery time by introducing NiO. Finally, a possible gas sensing mechanism for the formation of the p–n junctions between NiO and ZnO is proposed to explain the enhanced gas response. All results demonstrate a promising approach to fabricate high-performance gas sensors to detect SF6 decomposition byproducts.

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Synthesis, Characterization and Enhanced Sensing Properties of a NiO/ZnO p–n Junctions Sensor for the SF6 Decomposition Byproducts SO2, SO2F2, and SOF2

Transfer printing that enables heterogeneous integration of materials in desired layouts offers unprecedented opportunities for developing high-performance unconventional electronic systems. However, large-area integration of ultrathin and delicate functional micro-objects with high yields in a programmable fashion still remains as a great challenge. Here, we present a simple, cost-effective, yet robust transfer printing technique via a shape-conformal stamp with actively actuated surface microstructures for programmable and scalable transfer printing with high reliability and efficiency. The shape-conformal stamp features the polymeric backing and commercially available adhesive layer with embedded expandable microspheres. Upon external thermal stimuli, the embedded microspheres expand to form surface microstructures and yield weak adhesion for reliable release. Systematic experimental and computational studies reveal the fundamental aspects of the extraordinary adhesion switchability of stamp. Demonstrations of this protocol in deterministic assemblies of diverse challenging inorganic micro-objects illustrate its extraordinary capabilities in transfer printing for developing high-performance flexible inorganic electronics.

Programmable and scalable transfer printing with high reliability and efficiency for flexible inorganic electronics

A novel temperature monitoring system for gas-insulated switchgears (GISs) based on surface-acoustic-wave (SAW) sensing is proposed in this paper. Compared with the existing systems, this system has several unique advantages, such as being wireless, passive, and at a proper cost with continuous monitoring. First, an accurate SAW temperature sensor is designed for the GIS conductor, where epoxy encapsulating and loop antennas are adopted in the SAW sensor to prohibit the potential partial discharge of the sensor itself. After that, a multifunctional reader antenna is developed, which can measure the conductor temperature and partial discharge by the time-division multiplexing technique. Experiments are carried out to examine the accuracy and response speed of the SAW sensors, and the results indicate that the uncertainty of the contact temperature measurement is smaller than 10 $^{\circ}$ C. Moreover, the insulation level and anti-interference ability are demonstrated based on experiments carried out on a 126-kV GIS. At last, temperature monitoring performance of the developed system is investigated by changing the current in the 126-kV GIS conductor. The experiment results prove that the developed system can meet the requirement of temperature monitoring in GIS.

A Wireless and Passive Online Temperature Monitoring System for GIS Based on Surface-Acoustic-Wave Sensor

Most work about the measurement of very fast transient overvoltage (VFTO) was carried out in the laboratory and test base. Because of the different GIS arrangement and power capacity, the time and frequency characteristics of VFTO in ultra high voltage (UHV) substation could be different with that obtained in the laboratory and test base. A series of VFTO measurements were carried out in two 1100 kV GIS substations to investigate the characteristics of on-site VFTO. The port-hole sensor based on surface-mounted device was chosen to measure the VFTO for its reliability and wide band-width. The whole measurement system was introduced and the schematic layout of each experiment was given. Measurement results of different switch conditions and measure points were presented for comprehensive understanding of the VFTO characteristics on site. The results indicated that the striking number during one operation was 16 (closing) and 14 (opening), similar to that obtained from test base result. Besides, single strike with front time 5.3 ns and voltage steepness 186.1 kV/ns was recorded, and the steepness was relatively higher than that gained in the test base. Moreover, the spectral analysis based on S transform was investigated to get the duration of different frequency components of VFTO waveform. Compared with the data obtained from the test base, the high frequency components of VFTO were reduced, while the lower frequency components lasted longer. The results provided references for the investigation of the electromagnetic interfere, the insulation coordination, and VFTO mitigation methods.

Xiong Li

Papers

A Wireless and Passive Online Temperature Monitoring System for GIS Based on Surface-Acoustic-Wave Sensor

Time and frequency characteristics of very fast transient overvoltage in ultra high voltage substation