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This paper reports a MEMS capacitive pressure sensor (CPS) based on the operating principle of touch mode. The CPS was designed and fabricated using wafer-level self-packaged MEMS processes. The variable capacitance sensing structure was vacuum-sealed in a cavity using the Si–glass anodic bonding technique, and the embedded Al feedthrough lines at the Si–glass interface were used to realize the electrical connections between the parallel plate electrodes and the electrode pads through Al vias. The optimal design of the CPS structure was performed to trade-off the performance and reliability using finite element simulation. The CPS based on a circular-shaped diaphragm with a radius of 2000 µm and a thickness of 40 µm exhibits good comprehensive performance with a sensitivity of 52.3 pF/MPa and a nonlinearity of 2.7%FS in the pressure range of 100–500 kPa when the ambient temperature is less than 50 °C. [ABSTRACT FROM AUTHOR]

The weak photon absorption and high recombination rate of electron-hole pairs in disordered zinc oxide nanowires (ZNWs) limit its application in UV photodetection. This limitation can be overcome by introducing graphene sheets to the ZNWs. Herein we report a high-performance photodetector based on one-dimensional (1D) wide band-gap semiconductor disordered ZNWs composited with reduced graphene oxide (RGO) for ultraviolet (UV) photoresponse enhancement. The RGO/ZNWs composites have been successfully synthetized through UV-assisted photochemical reduction of GO in ZNWs suspension. The material characterizations in morphology, Raman scattering, and Ultraviolet-visible light absorption verified the formation of graphene sheets attached in ZNWs network and the enhancement of UV absorption due to the introduction of graphene. In comparison with photodetectors based on pure ZNWs, the photodetectors based on RGO/ZNWs composite exhibit enhanced photoresponse with photocurrent density of 5.87 mA•cm-2, on/off current ratio of 3.01 x 104, and responsivity of 1.83 A•W-1 when a UV irradiation of 3.26 mW•cm-2 and 1.0 V bias were used. Theory analysis is also presented to get insight into the inherent mechanisms of separation and transportation of photo-excited carriers in RGO/ZNWs composite. [ABSTRACT FROM AUTHOR]

High frequency surface acoustic wave (SAW) technology offers many opportunities for aerospace applications in passive wireless sensing and communication. This paper presents the design, simulation, fabrication, and test of an L-band SAW resonator based on 128° Y-X LiNbO3 substrate. The design parameters of SAW resonator were optimized by the finite element (FEM) method and the coupling-of-mode (COM) theory. Electron-beam lithography (EBL) technology was used to fabricate the submicron-scale of interdigital transducers (IDTs) and grating reflectors. The effects of some key EBL processes (e.g., the use of electron beam resist, the choice of metal deposition methods, the charge-accumulation effect, and the proximity-effect) on the fabrication precision of SAW devices were discussed. Experimentally, the LiNbO3-based SAW resonators fabricated using improved EBL technology exhibits a Rayleigh wave resonance peaks at 1.55 GHz with return loss about −12 dB, and quality factor Q is 517. Based on this SAW resonator, the temperature and strain sensing tests were performed, respectively. The experimental results exhibit a well linear dependence of temperature/strain on frequency-shift, with a temperature sensitivity of 125.4 kHz/°C and a strain sensitivity of −831 Hz/με, respectively. [ABSTRACT FROM AUTHOR]

High frequency surface acoustic wave (SAW) technology offers many opportunities for aerospace applications in passive wireless sensing and communication. This paper presents the design, simulation, fabrication, and test of an L -band SAW resonator based on 128° Y-X LiNbO 3 substrate. The design parameters of SAW resonator were optimized by the finite element (FEM) method and the coupling-of-mode (COM) theory. Electron-beam lithography (EBL) technology was used to fabricate the submicron-scale of interdigital transducers (IDTs) and grating reflectors. The effects of some key EBL processes (e.g., the use of electron beam resist, the choice of metal deposition methods, the charge-accumulation effect, and the proximity-effect) on the fabrication precision of SAW devices were discussed. Experimentally, the LiNbO 3 -based SAW resonators fabricated using improved EBL technology exhibits a Rayleigh wave resonance peaks at 1.55 GHz with return loss about -12dB, and quality factor Q is 517. Based on this SAW resonator, the temperature and strain sensing tests were performed, respectively. The experimental results exhibit a well linear dependence of temperature/strain on frequency-shift, with a temperature sensitivity of 125.4 kHz/C and a strain sensitivity of -831 Hz/με, respectively., Competing Interests: The authors declare no conflict of interest.

Designs and simulations of silicon-based micro-electromechanical systems (MEMS) infrared (IR) thermal emitters for gas sensing application are presented. The IR thermal emitter is designed as a bridge-style hotplate (BSH) structure suspended on a silicon frame for realizing a good thermal isolation between hotplate and frame. For investigating the reliability of BSH structure, three kinds of fillet structures were designed in the contact corner between hotplate and frame. A 3-dimensional finite element method (3D-FEM) is used to investigate the electro-thermal, thermal-mechanical, and thermal-optical properties of BSH IR emitter using software COMSOL TM (COMSOL 4.3b, COMSOL Inc., Stockholm, Sweden). The simulation results show that the BSH with oval fillet has the lowest stress distribution and smoothest flows of stress streamlines, while the BSH with square fillet has the highest temperature and stress distribution. The thermal-optical and thermal-response simulations further indicate that the BSH with oval fillet is the optimal design for a reliable IR thermal emitter in spite of having slight inadequacies in emission intensity and modulation bandwidth in comparison with other two structures.