A Multi-scale Microbial Aerosol Detection Method Based On The Microfluidic AC Impedance Sensor

The pathogenic microorganisms in the air threaten human health.The smaller the particle size is,the deeper the microbial aerosol enters the human body,which would cause great harm to the human.Therefore,the detection of small particle size microbial aerosol is of great significance.However,there are the following difficulties existing in the detection of microbial aerosol:(1)The aerosol samples collected from the air contain a large number of impurity particles,and the content of pathogenic microorganism aerosol is relatively low,affecting the detection effect.(2)The particle sizes of pathogenic microorganism aerosols are different,and it is difficult for existing microfluidic chips to simultaneously purify aerosols with more than three particle sizes.(3)The existing automated methods are not effective when detecting microbial aerosols with similar shapes.Therefore,the subject proposed a microbial aerosol detection method based on the microfluidic AC impedance sensor.The specific research contents of the paper are as follows:(1)Based on the principles of aerosol purification kinetics and enrichment kinetics using microfluidic chips,this paper designed a multi-scale aerosol purification chip structure;the chip structural parameters were optimized and the optimal chip inlet flow rate was selected;The purification effect of the multi-scale aerosol purification chip was analyzed through experiments.(2)Based on the theory of electrochemical impedance spectroscopy,an equivalent circuit for microparticle impedance detection was derived;Taking Aspergillus niger spores,Staphylococcus griseus spores and polystyrene microspheres as research objects,based on the different dependence of the impedance modulus of different particles on frequency,a microbial classification model(IDV)based on the difference in impedance changes was proposed.(3)A microelectrode for impedance detection of microbial aerosols was designed.The multi-scale aerosol purification chip was coupled with the microelectrode to obtain a microfluidic AC impedance sensor which realized the integration of purification and detection of microbial aerosol;The purification function of the integrated sensor was tested through experiments on latex microspheres with different particle sizes;Taking Aspergillus niger spores,Staphylococcus griseus spores and polystyrene microspheres as experimental objects,the microbial aerosol detection function of the integrated sensor was tested through experiments.The experimental results show that The Multi-scale aerosol purification chip proposed in this paper could simultaneously purify and enrich particles within four particle size ranges.What’s more,the classification accuracy of the IDV classification model is 96.67%,which is6.47%higher than the SVM classification model and the detection limit of the IDV classification model is 1×10~3CFU/m L.Additionally,Integrated sensors can simultaneously purify and enrich particles with particle sizes of 20μm,10μm,5μm and 3μm.The accuracy of the integrated sensor for detecting Aspergillus niger spores,Staphylococcus aureus and nanospheres is 90%,86%and 96%.Therefore,the microfluidic AC impedance sensor could realize the accurate detection of multi-scale microbial aerosol without labels.