Used for thermal energy harvesting, thermoelectric generator (TEG) can convert heat into electricity directly. Structurally, the main part of TEG is the thermopile, which consists of thermocouples connected in series electrically and in parallel thermally. Benefiting from massive progress achieved in a microelectromechanical systems technology, micro TEG (μ-TEG) with advantages of small volume and high output voltage has obtained attention in recent 20 years. The review gives a comprehensive survey of the development and current status of μ-TEG. First, the principle of operation is introduced and some key parameters used for characterizing the performance of μ-TEG are highlighted. Next, μ-TEGs are classified from the perspectives of structure, material, and fabrication technology. Then, almost all the relevant works are summarized for the convenience of comparison and reference. Summarized information includes the structure, material property, fabrication technology, output performance, and so on. This will provide readers with an overall evaluation of different studies and guide them in choosing the suitable μ-TEGs for their applications. In addition, the existing and potential applications of μ-TEG are shown, especially the applications in the Internet of things. Finally, we summarize the challenges encountered in improving the output power of μ-TEG and predicted that more researchers would focus their efforts on the flexible structure μ-TEG, and combination of μ-TEG and other energy harvestings. With the emergence of more low-power devices and the gradual improvement of ZT value of the thermoelectric material, μ-TEG is promising for applications in various fields. [2017-0610]

This letter presents a novel MEMS-based thermoelectric-photoelectric power generator, which integrates a micro-scale thermoelectric generator (μ-TEG) and a solar cell on a single silicon chip by MEMS technology for the first time. To optimize the heat flux path of μ-TEG, one side of the thermocouple square array is on the interdigitated electrode of the solar cell and the other side is on the thick oxide passivation layer to realize thermal isolation. Moreover, the hot side and the cold side are insulated by a thick polyimide thermal insulating layer above the thermopile, and a series of square holes is created to enhance the thermal coupling between the thermopile and surrounding environment. Several common measures, like the back-surface field and oxide passivation layer with limited contact openings, are adopted for the design of the solar cell. All the measuring electrodes are on the same side of the device for the convenience of bonding wire and package. When a sputtered Al membrane covers the front side of the device, the maximum output voltage factor and the power factor of the μ-TEG are 0.149 V·cm⁻²,K⁻¹ and 3.03x 10⁻³ μ W·cm⁻²,·K⁻², respectively. When the front and back sides of device receive light, the measured photoelectric conversion efficiencies are 4.45% and 0.682%, respectively. [2018-0214]

A novel multi-source micro power generator for harvesting thermal and optical energy is proposed for the first time. The fabrication of the power generator is compatible with complementary metal-oxide-semiconductor transistor technology. The device consists of a micro thermoelectric generator (μ-TEG) and a solar cell on a single chip. In order to optimize the heat flux path of the device, the two ends of the thermopile are insulated by the polyimide thermal insulating layer and oxide passivation layer. To improve the performance of the solar cell, the oxide passivation layer is perforated with limited metal contact openings and interdigitated poly-Si electrodes are adopted. The measured results show that if the liquid metal thermal grease covers the top side of the device, the maximum output voltage factor and power factor of the μ-TEG are 0.316 Vcm ^-2 K ^-1 and 6.34×10 ^-3 μWcm ^-2 K ^-2 , respectively. When the top and bottom sides of the device are chosen as the light-receiving surfaces, the measured efficiencies of the solar cell are 4.11% and 0.5%, respectively. In practical use, measuring electrodes on the same side and vertical injected/ejected heat flux path allow for convenient package.

This study presents a Ka‐band radio frequency (RF) micro electro mechanical systems (MEMS) capacitive switch with low loss, high isolation, long‐term reliability and high power handling based on GaAs microwave monolithic integrated circuit (MMIC) technology. In this design, a T‐matching structure is employed to realise impendence matching at ‘up‐state’ by modifying the dimensions of centre signal line. Thus, the reflection loss and insertion loss are improved effectively. Measurement results show that in ‘up‐state’ position, the input reflection coefficient ( S ₁₁ ) is less than −20.4 dB with the forward transmission coefficient ( S ₂₁ ) of better than −0.27 dB at Ka‐band (27–40 GHz). At ‘down‐state’, the switch is designed in a state of self‐resonance to obtain high isolation. The measured isolation is better than 20 dB over Ka‐band and can reach 35 dB at its self‐resonant frequency of 35 GHz. The measured actuation voltage is about 36 V. The measured lifetime is at least 5.76 × 10 ⁷ cycles. The measured power handling capability can reach up to 39 dBm. The proposed compact RF MEMS capacitive switch possesses excellent performances in terms of low insertion loss, high isolation, long lifetime and high power handling capability.

This letter reports a microwave power sensor with improved dynamic range based on MEMS cantilever beam. The proposed power sensor is manufactured using GaAs microwave monolithic integrated circuit (MMIC) technology. In this design, a cantilever by-pass coupling structure is adopted for high power detection, while the terminating thermoelectric sensor is utilized for low power detection. The novelty of the proposed device is that the concatenation of a cantilever beam and the thermoelectric sensor allows the ultra-high dynamic range power detection. Measurement results show that the sensitivities are 0.0315, 0.0261, and 0.0237 mV/mW at 1, 2, and 3 GHz for input power from 0.1 to 100 mW, respectively. For input power from 100 mW to 1W, the sensitivities are 2.398, 3.753, and 5.416 μV/mW at 1, 2, and 3 GHz, respectively. This compact power sensor has the potential prospect for dynamic range application.