Development Of Miniaturized Microfluidic Electrical Impedance Measurement System Used For Aerosol Particle Detection

The concentration of aerosol particles in the atmosphere has a serious impact on climate change,air quality and public health.Detecting the changing of aerosol concentration and studying its size distribution and composition have attracted scientists all over the world.At present,the collection and detection technologies of aerosol particles are relatively mature,but the mainstream detection technologies are relatively complex and expensive,which is not conducive to large-scale promotion.Microfluidic chips are simple to manufacture,small in size and easy to integrate.Integrating microfluidic chips with aerosol collection system makes it possible to build a small,portable and simple aerosol real-time detection system.Based on this,the topic proposed to design a miniaturized microfluidic electrical impedance detection system combined with the virtual impactor manufactured by micro-machining,to build a realtime aerosol sampling and analysis system.The aerosol sampling and analysis system is composed of aerosol sampling system and aerosol analysis system.The aerosol sampling system consists of a second-order virtual impactor and a miniature aerosol collection bottle.Aerosol particles in the air are sucked into the virtual impactor by an air pump,and then are drove into the PBS solution in the aerosol collection bottle.Aerosol analysis system,also namely miniaturized microfluidic impedance flow cytometer,is composed of microfluidic impedance chip and impedance measurement circuit.The microfluidic impedance chip is manufactured using micromanufacturing technology,and its working principle is the same as Coulter Counter.Measurement circuit generates sinusoidal excitation voltage and inputted to microfluidic chip excitation voltage input electrode port,and the current difference of the two output electrodes is converted to the voltage difference.Then the amplitude and phase of the differential signal are converted to two easily measured DC voltage signals through internal circuit.Each time a particle flows through the microfluidic chip,the output ports of the amplitude and phase voltage both output a bipolar pulse signal.In this project,microspheres with diameters ranging from 500 nm to 15μm are firstly used to verify the particles detection and identification ability of the system.,and the relationship between the volume of microsphere and the size of signal pulse was studied.The result showed that the two parameters have a strong positive correlation.Then the biological microspheres were prepared by mixing E.coli liquid and aminomodified polystyrene microsphere liquid to explore the identification ability of the system for biological microspheres and non-biological microspheres.Finally,the smoke particles of ordinary cigarette and e-cigarette were collected and analyzed respectively,and the particle size distribution of the two samples was compared.It was found that the particle size of the smoke particles produced by e-cigarettes was smaller than that produced by ordinary cigarettes.