Microsupercapacitors (MSCs) are integrated into microdevices or chip‐based systems to store energy and power the chip efficiently, as they present excellent performance capabilities including high power density, fast charge/discharge rate, and long cycle time. Providing sufficient surface area and high electric conductivity are effective ways to enhance ion diffusion and charge transportation in electrodes, which in turn leads to high performance behavior. Herein, the novel progress of on‐chip MSCs in the past few years ranging from active materials synthesis to high‐resolution fabrication techniques is summarized, and the strategies to enhance the performance of MSCs are focused upon. From conventional materials to nanocomposite hybrid structures, the main active materials for MSC electrodes and the related fabrication techniques are reviewed in detail according to their different electrochemical performance. It is concluded that hierarchical porous‐structured materials and high‐resolution fabrication processes are of great importance in constructing high‐performance devices, which also demonstrates the future developing direction of on‐chip energy devices. The new developments of fabrication technologies such as microfabrication, laser direct writing, and inkjet printing are also discussed to show their advantages in forming high‐performance electrodes.
An integrated microoxygen sensor based on the nanostructured TiO 2 thin film is presented. A pair of interdigitated electrodes was designed with the microheater around them on the same layer, which was aimed at simplifying the structure and avoiding fracture of the embedded heater. To fabricate the sensor chips, an optimisation process consisting of 14 steps was designed. The adiabatic cavity was formed by releasing the Si substrate from backside to a certain thickness at first, then a TiO 2 film was prepared by the sol-gel process and patterned by the wet etching process, after that electrodes and the heater were patterned and finally the remaining silicon was thinned further. Response properties to different gases were tested, and the sensor shows a good sensitivity of 0.093 and high selectivity of 0.258 to O 2 than H 2 , response time of 51 s and hysteresis of 2.93%. The integrated microoxygen sensor has potential applications on the occasions of miniaturised, integrated, low power and mass production.
A serpentine-shaped semi-packed micro gas chromatography (GC) column with mesoporous inner surface and ionic liquid (IL) coating was developed for the separation of various typical volatile organic compounds (VOCs) in exhaled air. The mesoporous surface was prepared by coating silica nanoparticles on the inner surface of the micro GC column through static method and used as stationary phase support to improve the separation performance by its high surface area. The micro GC columns provide efficient separations for analytes including nonpolar (alkanes), weak polar (benzene series) and polar compounds (alcohols), as well as various typical markers of non-alcoholic fatty liver disease (NAFLD). The test results show that the resolution of most analytes is higher than 1.5, the elution peaks are symmetrical. Moreover, due to the chemical stability of IL, the micro GC had good repeatability, thermal stability and oxygen robustness. The maximum relative standard deviation of retention time was 0.44% in four weeks. During the programmed heating, a stable baseline was achieved and the baseline drift value was less than 4.8 mV when the operating temperature increased from 50℃ to 140℃. The oxygen robustness was verified by a decrease of 7.2% in the peak capacity after exposure to dry air at 140 ℃ for 48 h. These characteristics showed the micro GC column is suitable for a portable breath analyzer.
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