Design And Research Of Detection System For Multi-Component Exhaled Gas Diagnostic Marker Based On MEMS Micro-hotplate Sensors

During the breathing process,targeted chemical markers in the blood can enter the exhaled gas through the gas diffusion of the alveolar and alveolar capillaries,which can reflect the metabolism of the human body and predict the occurrence of the disease.It is generally considered that multiple components of exhaled gases are closely related to disease,thus the detection of highly targeted expiratory markers can reflect the metabolic changes of the corresponding tissue cells under the premise of non-invasive and painless.It also can provide a basis for the diagnosis of the disease,or real-time monitoring of the development of the disease.There are many methods for detecting compounds in exhaled gases,such as traditional mass spectrometry,chromatographic analysis or high-precision chemical analysis instruments.Although the accuracy is high,their operation is complicated and depends on large-scale special equipment,which cannot meet the requirement of real-time monitoring.The gas sensors are the most promising methods for detecting exhaled gas because of their advantages of good sensitivity,rapid response,and simple operation.However,they still suffer from several issues,such as poor selectivity and low moisture resistance for multi-component gases.To this end,this paper intends to develop a detection method for targeted expiratory markers in a multi-component gas environment,and further improve its accuracy by optimizing the human exhaled gas collection system,sensor array and pattern recognition system,and finally establish a rapid detection method for trace diagnostic analytes in human exhaled gases.The specific research contents are as follows:1.A micro-hotplate gas sensor based on MEMS technology is designed,which is suitable for depositing gas sensitive materials in the dispensing process.Through simulation and experimental data,the MEMS micro-hotplate sensor has a heating power of only 60 mW when heated to 400?,and it takes only 20 ms to reach thermal stable state.Compared with the traditional ceramic tube or ceramic planar structure of the indirectly heated device,the heating power dissipation and thermal response performance of MEMS micro-hotplate sensor are greatly improved.Thus the MEMS micro-hotplate sensor can provide stable miniaturization for the performance evaluation of the metal oxide semiconductor gas sensing material.2.A acetone gas sensor is fabricated by loading electrospun WO3 nanofibers on MEMS micro-hot plate,which exhibits low detection limit(0.1 ppm).It is highly expected such high sensitivity sensor to be used for the detection and analysis of exhaled breath target acetone in diabetic patients.In addition,the prepared sensor has a sensitivity of 105 for 100 ppm acetone gas,and the response and recovery times are?10 s and?7 s,respectively.Compared with the WO3 nanosheet synthesized from hydrothermal method,the gas sensing performances of electrospun WO3 nanofibers show a large improvement in sensitivity and selectivity3.Conventional metal oxide semiconductor gas sensors operate at a certain temperature,and the characteristic of the sensor to gas response is only sensitivity.Limited by the sensitive mechanism,the sensor has a certain cross-response,and thus difficult to identify the multi-component gas mixture.This paper expands the "feature space" of the sensor by operating temperature modulation of the gas sensor,enabling the oxide semiconductor gas sensor to recognize multi-component mixed gas.Specifically,the temperature modulation test was carried out on the micro-hot plate sensor device using W03 nanofiber as a sensitive material,and the multi-component mixed gas was well recognized4.The detection of exhaled gases in humans is usually in a high humidity environment,so it is necessary to study the anti-humidity interference of gas sensors.Based on the unique properties of ionic liquids,this study developed an ionogel humidity sensor based on ionic liquids and SiO2 composites,which demonstrated excellent humidity sensing performance and explored the possible humidity sensitivity mechanism of SiO2/IL sensing materials.By simply adjusting the anion of the ionic liquid,the sensor's sensitivity to humidity response can be adjusted,which provides a route for designing the gas sensor against humidity interference.In addition,the fast response and high sensitivity of the SiO2/[Bmim]Br humidity sensor enable successful real-time monitoring of respiratory rate.