Intelligent MEMS Sensor Based on an Oxidized Medium-Entropy Alloy (FeCoNi) for H2 and CO Recognition.

In this paper, we present the design and evaluation of an intelligent MEMS sensor employing the oxidized medium-entropy alloy (O-MEA) of FeCoNi as the gas-sensing material. Due to the specific catalytic exothermic reaction of the O-MEA on H2/CO, the sensor shows great selectivity for H2 and CO at 150 °C of the integrated microheater in the MEMS device, with the theoretical detection limit of 0.3 ppm for H2 and 0.29 ppm for CO. The MEMS heater, capable of instantaneous temperature changes in pulse operation mode, offers a novel approach for thermal modulation of the sensor, which is crucial for the adsorption and reaction of H2/CO molecules on the sensing layer surface. Consequently, we investigate the gas-sensing capabilities of the sensor under pulse heating modes (PHMs) of the MEMS heater and then propose the gas-sensing mechanism. The results indicate that PHMs significantly not only reduce the operating temperature and power consumption but also enhance the sensor's functionality by providing multivariable response signals, paving the way for intelligent gas detection. Based on the high selectivity to H2 and CO, transforming the transient sensing curves into two-dimensional images via Gramian Angular Field (GAF) model and subsequent modeling using a convolutional neural network (CNN) algorithm, we have realized efficient and intelligent recognition of H2 and CO. This work provides insight for the development of low-power, high-performance MEMS gas sensors and further intelligence of individual MEMS sensors.

Fe3O4@uio66 core-shell composite for detection of electrolyte leakage from lithium-ion batteries.

Fe3O4is an environmentally friendly gas sensing material with high response, but the cross-response to various analytes and poor thermal stability limit its practical applications. In this work, we prepared Fe3O4@uio66 core-shell composite via a facile method. The selective response to volatile organic compounds, especially to electrolyte vapors of lithium-ion batteries, as well as long-term stability of Fe3O4@uio66 has been dramatically enhanced compared to pure Fe3O4, due to the preconcentrator feature and thermal stability of the uio66 thin shell. Real-time detection of electrolyte leakage for an actual punctured lithium-ion battery was further demonstrated. The Fe3O4@uio66 sensor, after aging for 3 months, was able to detect the electrolyte leakage in 30 s, while the voltage of the punctured battery was maintained at the same level as that of a pristine battery over 6 h. This practical test results verified ability of the Fe3O4@uio66 sensor with long-term aging stability for hours of early safety warning of lithium-ion batteries.