Research On Detection And Discrimination Of Volatile Organic Compounds Based On Temperature-modulated FBAR Virtual Sensor Array

Gas sensors have always been an important research direction in the field of sensors.Real-time monitoring,effective identification and discrimination of volatile organic compounds(VOCs)are of great significance in various fields such as environmental monitoring,security,health and medical care.However,gas sensor technology still faces many challenges:for example,how to build gas detectors system with small size,high sensitivity,fast response and low cost.Film bulk acoustic reaonator(FBAR)has attracted a lot of attention because of its high sensitivity,small size,fast response,low cost,easy arraying and output of various sensing parameters.Based on this research hotspot,this paper develops an electronic nose system(e-nose)based on a single FBAR with temperature modulation(TC-FBAR)as a multiparameter virtual sensor array.Through self-assembly modification and PCA and LDA algorithm analysis,the e-nose realizes real-time detection,identification and discrimination of six VOCs such as methanol and ethanol vapors.The main research contents and results of this paper are as follows:1.The TC-FBAR device was successfully fabricated by the standard MEMS process,and the working principle and sensing characteristics of the device were analyzed from the mass loading effect.The 20-bilayer self-assembled PSS/PDDA thin films was used to modify TC-FBAR as the sensitive layer,and the performance of the device was compared and analyzed before and after modification.2.Using SiO₂material as the temperature compensation layer,the TC-FBAR with a temperature frequency coefficient TCF of 2.8798 ppm/°C was successfully processed,which was 10 times lower than the TCF of the conventional FBAR,thus significantly reducing the influence of temperature on the frequency shift of the sensor device.At the same time,the heater is integrated with TC-FBAR to form the core part of the virtual sensor array.The pulsed temperature cycled operation(TCO)innovatively eliminates the drift of the frequency shift baseline,ensuring that the temperature of the TC-FBAR virtual sensor array is stable during the working process.3.The real-time static detection and dynamic detection can be used to obtain the frequency shift and impedance responses of the six VOCs at four different temperatures by the TC-FBAR VSA based on temperature modulation.Through the analysis of PCA and LDA algorithms,the VSA achieves efficient identification and discrimination of six VOCs,and the correct discrimination rate for each VOC vapor is over 97%.Two concentration-independent constants were obtained by fitting the isothermal adsorption curve,revealing the reason why temperature modulation affects the adsorption and desorption of different VOCs on the sensor surface.At the same time,the limit of detection(LOD),sensitivity and repeatability of TC-FBAR VSA are researched,which show that the VSA has the advantages of low LOD,high sensitivity,good repeatability and stability.