In this article, an electromagnetic vibrational energy harvester (EVEH) device has been designed and fabricated based on the hybrid microelectromechanical system and flexible circuit technology. The designed EVEH is composed of a disc magnet suspended by four microfabricated silicon springs above a stack of high-density flexible planar coils. At a sinusoidal acceleration with a peak-to-peak amplitude of 1 g, an output peak-to-peak voltage of 208.3 mV, and an output power of 10.5 μW are measured at the resonant frequency of 143 Hz. At an elevated acceleration of 7 g, a maximum output peak-to-peak voltage of 333.1 mV is realized with an increased magnet-coil distance of 0.65 mm.

Polymers are ever more widely and more prominently used in microelectromechanical systemsdevices. They provide significant added value to the existing silicon-based technologies, such as flexibility, low stiffness, easy fabrication, and low cost. Nevertheless, the intrinsic properties of polymer materials also bring new challenges and issues to their applications as structural materials in MEMS devices, such as fabrication failures, electrical drift/failures (induced by charging, leakage, or breakdown), as well as mechanical drift/failures (induced by residual stress, environmental conditions, or viscoelasticity). This paper presents a review on the origin, impact, underlying physics, and mitigation methods to those challenges for polymer devices (especially SU-8). [2017-0191]

The existing temperature sensors using carbon nanotubes (CNTs) are limited by low sensitivity, complicated processes, or dependence on microscopy to observe the experimental results. Here we report the fabrication and successful testing of an ionization temperature sensor featuring non-self-sustaining discharge. The sharp tips of nanotubes generate high electric fields at relatively low voltages, lowering the work function of electrons emitted by CNTs, and thereby enabling the safe operation of such sensors. Due to the temperature effect on the electron emission of CNTs, the collecting current exhibited an exponential increase with temperature rising from 20 °C to 100 °C. Additionally, a higher temperature coefficient of 0.04 K⁻¹ was obtained at 24 V voltage applied on the extracting electrode, higher than the values of other reported CNT-based temperature sensors. The triple-electrode ionization temperature sensor is easy to fabricate and converts the temperature change directly into an electrical signal. It shows a high temperature coefficient and good application potential.

The bottleneck of the miniaturized electromagnetic vibration energy harvester (EVEH) device is the limited output voltage and power. Commonly reported mV-level AC output of the EVEHs cannot be rectified and used. In this work, we report a cost-effective EVEH device based on batch-fabricated flexible springs and coils. At an acceleration of ±1 g peak-to-peak amplitude (±9.8 m s ⁻² ), a maximum output peak-to-peak voltage of 1.57 V and an output power of 91.8 μ W are measured, at a frequency of 66 Hz. The output voltage of the EVEH is successfully rectified, amplified (passively) and used to charge a supercapacitor.

On-line detection of fault characteristic gases released by the insulation oil of transformers is developed as a scientific basis for estimating explosion accidents. However, the performance of most gas sensors, such as H ₂ and C ₂ H ₂ sensors, is usually affected by temperature, and there exists large detection error when the temperature of transformer oil changes in operation. And the existing temperature compensation methods suffer from problems such as low integration, large volume, and high costs. Herein, a sensor array based on three triple-electrode sensors with carbon nanotubes was fabricated. Each of the three sensors has three vertically stacked electrodes with various interelectrode distances. The first and second sensors were used to detect H ₂ and C ₂ H ₂ , respectively, and the third sensor was used to measure temperature. All the detection mechanisms are based on the dependence of discharge current on gas concentration and temperature. The sensor array could detect H ₂ /C ₂ H ₂ mixture and temperature due to the exponential function between the output currents and electrode separations. The proposed sensor exhibited low relative and repeatability error values less than 5.1% and 4.9%, respectively, and displayed humidity compensation potential like temperature. High integration makes the sensor array superior among the other mechanism sensors.