Nanomaterials are widely utilized as sensing materials in semiconductor gas sensors. As sensor sizes continue to shrink, it becomes increasingly challenging to construct micro-scale sensing materials on a micro-sensor with good uniformity and stability. Therefore, in-situ growth with a desired pattern in the tiny sensing area of a microsensor is highly demanded. In this work, we combine area-selective seed layer formation and hydrothermal growth for the in-situ growth of ZnO nanowires (NWs) on Micro-electromechanical Systems (MEMS)-based micro-hotplate gas sensors. The results show that the ZnO NWs are densely grown in the sensing area. With Pd nano-particles’ modification of the ZnO NWs, the sensor is used for hydrogen (H₂) detection. The sensors with Pd-ZnO NWs show good repeatability as well as a reversible and uniform response to 2.5 ppm–200 ppm H₂. Our approach offers a technical route for designing various kinds of gas sensors.

In a chamber-based digital PCR (dPCR) chip fabricated with polydimethylsiloxane (PDMS), bubble generation in the chambers at high temperatures is a critical issue. Here, we found that the main reason for bubble formation in PDMS chips is the too-high saturated vapor pressure of water at an elevated temperature. The bubbles should be completely prevented by reducing the initial pressure of the system to under 13.6 kPa to eliminate the effects of increased-pressure water vapor. Then, a cavity was designed and fabricated above the PCR reaction layer, and Parylene C was used as a shell covering the chip. The cavity was used for the negative generator in sample loading, PDMS degassing, PCR solution degassing in the digitization process and water storage in the thermal reaction process. The analysis was confirmed and finally achieved a desirable bubble-free, fast-digitization, valve-free and no-tubing connection dPCR.

Transmission electron microscopy (TEM) is a highly effective method for scientific research, providing comprehensive analysis and characterization. However, traditional TEM is limited to observing static material structures at room temperature within a high-vacuum environment. To address this limitation, a microchip was developed for in situ TEM characterization, enabling the real-time study of material structure evolution and chemical process mechanisms. This microchip, based on microelectromechanical System (MEMS) technology, is capable of introducing multi-physics stimulation and can be used in conjunction with TEM to investigate the dynamic changes of matter in gas and high-temperature environments. The microchip design ensures a high-temperature uniformity in the sample observation area, and a system of tests was established to verify its performance. Results show that the temperature uniformity of 10 real-time observation windows with a total area of up to 1130 μm² exceeded 95%, and the spatial resolution reached the lattice level, even in a flowing atmosphere of 1 bar.

The selective detection of propane gas molecules using semiconductor gas sensors has always been a challenge within research. In this study, we successfully synthesized a γ-Fe₂O₃ nanomaterial with a selective catalytic effect on propane and loaded it onto a ZnO sensing material to construct a double-layer microsensor, which showed good sensing response characteristics in the detection of the refrigerant R290 (which is mainly propane). In addition, we also prepared a series of iron oxides, including nanomaterials such as α-Fe₂O₃, Fe₃O₄, and FeO, as well as γ-Fe₂O₃ materials with different specific surface areas obtained at various processing temperatures, and we carried out gas sensing research on R290. The results show that the γ-Fe₂O₃ material has a better sensitivity to R290, and the γ-Fe₂O₃ material calcined at 200 °C shows the best performance. Our results can provide a theoretical basis for the design and optimization of semiconductor gas sensors for alkane detection.

Acetylene detection plays an important role in fault diagnosis of power transformers. However, the available dissolved gas analysis (DGA) techniques have always relied on bulky instruments and are time-consuming. Herein, a high-performance acetylene sensor was fabricated on a microhotplate chip using In₂O₃ as the sensing material. To achieve high sensing response to acetylene, Pd–Ag core-shell nanoparticles were synthesized and used as catalysts. The transmission electron microscopy (TEM) image clearly shows that the Ag shell is deposited on one face of the cubic Pd nanoseeds. By loading the Pd–Ag bimetallic catalyst onto the surface of In₂O₃ sensing material, the acetylene sensor has been fabricated for acetylene detection. Due to the high catalytic performance of Pd–Ag bimetallic nanoparticles, the microhotplate sensor has a high response to acetylene gas, with a limit of detection (LOD) of 10 ppb. In addition to high sensitivity, the fabricated microhotplate sensor exhibits satisfactory selectivity, good repeatability, and fast response to acetylene. The high performance of the microhotplate sensor for acetylene gas indicates the application potential of trace acetylene detection in power transformer fault diagnosis.