Research On Generation Device And Application Of Microfluidic Bubble Based On Single-phase Fluid Drive

With the development of industrialization and accelerated urbanization,atmospheric pollution has become increasingly serious,and more and more microorganisms are entrapped in the air.The increase of microorganisms can lead to the generation and spread of diseases and pose a threat to human health.Especially since the discovery of New Coronavirus pneumonia in 2019,it has spread rapidly around the world and seriously affected people’s productive life.Airborne transmission is one of the main ways of the spread of New Coronavirus,a virus detection device in the air that is easy to operate and flexible with accurate results can help people discover the viruses contained in the air early and help people respond in advance,which is of great significance to prevent the spread of the virus.Microfluidics is a rapidly developing technique for manipulating fluids in microscale space in recent years,and has received a great deal of attention from scholars due to its low manufacturing cost,flexibility in operation,and speed in its application to detection.In this paper,a single-phase liquid-driven air microbubble preparation microfluidic chip is developed based on microfluidic chip technology and applied to air detection.Compared with traditional atmospheric monitoring methods,this chip has the characteristics of high throughput and simple operation,and can realize real-time qualitative and quantitative analysis when testing air.Firstly,the microfluidic chip structure is designed.Compared with the traditional chip that prepares microbubbles by controlling two phases of fluid,the chip only needs to manipulate one phase of liquid to complete the preparation of microbubbles,and the size of the prepared microbubbles is uniform with good monodispersity.The experimental results show that the larger the liquid phase injection flow rate is in a certain range,the smaller the size of the generated microbubbles will be;when the injection flow rate exceeds a certain value Q,no more microbubbles will be generated in the chip.The size of this critical flow rate Q is related to the chip parameters,the longer the external phase tube length L,the larger the external phase tube diameter D,and the smaller the chip tilt angle θ,the larger the critical flow rate for microbubble generation will be.Finally,the bubble generation mechanism is analyzed by combining Bernoulli’s equation,and the empirical equation affecting the bubble generation law inside the microfluidic chip is fitted;the experiments on fluorescent particles in air show that the chip has the potential to be applied to air detection.Then,a PDMS surface with superhydrophobic properties was prepared using the template method to reduce the problems of liquid blockage during the use of the chip,and the surface was used as the inner wall of the chip to reduce the resistance to fluid flow.Using glass as the template,we firstly processed the micro-weave on the glass surface by laser lithography,and studied the effect of laser parameters on the morphology of the micro-weave and selected the best laser processing parameters;then we used this parameter as the basic parameter to study the effect of micro-weave depth and width on the wettability of PDMS,and achieved the adjustable wettability of PDMS with the contact angle up to 162°.PDMS surface was used as the inner wall to prepare microfluidic chips with different wettability properties,and the effect of the contact angle of the inner wall on the critical flow rate of the chip was tested;the larger the contact angle,the higher the critical flow rate.Finally,COMSOL Mulphysics software was used to simulate the flow field inside the microfluidic chip,analyze the bubble generation process in the microfluidic channel,investigate the effect of the liquid phase flow rate on the bubble size,investigate the effect of the channel parameters on the bubble generation situation,and compare the simulation results with the preliminary experimental results to verify that the deviation value between the simulation results and the experimental results of most experimental groups is less than 10%,which shows that the simulation model can predict the experimental results well and also verify the accuracy of the experimental results.