| Microfluidic systems have broad application prospects in the fields of biomedical testing,chemical analysis,and drug development due to the characteristics of integration,high efficiency,and ability to avoid cross-contamination.The current parallel sequencing gene sample preparation process has been unable to meet the needs of fast and high-throughput parallel sequencing technology.This paper proposes a microfluidic gene sequencing pretreatment system for the preparation of gene samples for parallel sequencing.Using air pressure-driven bubble mixing technology and bubble-enhanced ultrasonic technology,the extraction and shearing of gene samples can be realized in a microfluidic system.,opening the prospect for the future implementation of complete molecular protocols on a single microfluidic platform.In this paper,the mathematical model of sound wave scattering caused by a single bubble is studied,and the characteristics of a single oscillating bubble that converts sound energy into mechanical energy and scatter to the surroundings are analyzed,and the pressure scattered by a single bubble into the surrounding liquid is obtained.A mathematical model of sound wave attenuation caused by multiple bubbles was established,and the efficiency of sound wave conversion into mechanical energy in the bubble suspension was analyzed.The mathematical model of ultrasonic reflection on the measuring cylinder wall is established,and the reflection and transmittance of the ultrasonic wave perpendicularly incident on the measuring cylinder are obtained.The force model of the oscillating bubbles in the sound field considering the rising state of the bubbles was established,and based on this mathematical model,a multiphase flow numerical simulation model of the coupling of the flow field and the sound field was established.CFD was used to simulate the impact of the bubble disturbance on the entire system under different gas driving pressures.Influence of acoustic field and flow field distribution characteristics in solution.The influence of bubble disturbance on the pressure distribution,velocity field distribution and sound pressure level distribution inside the measuring cylinder solution is simulated to study the flow field and sound field characteristics.Aiming at the problem that the agglomeration of magnetic bead solution affects the effect of gene extraction in the process of gene extraction by magnetic bead method,a mixing method of rising air bubbles driven by air pressure was proposed.The inert gas is injected into the bottom of the microcavity to generate bubbles to form a vortex in the sample solution to realize the mixing function and avoid the agglomeration of magnetic beads during magnetic mixing.Carry out the numerical simulation model of gas-liquid-solid multiphase flow for the mixing of rising bubbles in the microcavity,simulate the influence of different driving pressures and different inlet cross-section shapes on the gas-pressure-driven bubble mixing characteristics in the microcavity,and obtain the optimal inlet cross-section and air pressure range.A set of air pressure-driven mixing test platform was built,and the vortex formation and flow field distribution in the microcavity were observed by fluorescence PIV method,and the relationship between driving pressure,bubble volume,vortex characteristics and mixing characteristics was analyzed,and the air pressure-driven bubble mixing was verified.method feasibility.On this basis,the mixing effect of the bubbles in the microcavity was tested under different driving pressures,and the relationship between the mixing efficiency of the bubbles and the driving pressure was obtained.Aiming at the problem of thermal damage to gene samples easily caused by microfluidic ultrasonic gene shearing,the bubble-enhanced ultrasonic gene shearing technology was studied,and the input of sound energy was reduced by the method of bubble-enhanced ultrasound to reduce the thermal damage of gene samples.In order to predict the effectiveness of bubble-enhanced ultrasonic technology,a simulation model of bubble oscillation in the sound field was established,and the dynamic response characteristics of the bubble in the sound field under different driving parameters and the enhancement effect on the sound field intensity were studied through numerical simulation.On this basis,a set of pressure-adjustable ultrasonic water bath bubble-enhanced gene shear test device was built,and the experimental research on the bubble-enhanced ultrasonic gene shear characteristics was carried out by changing the gas driving pressure and ultrasonic action time.The test results show that the air bubbles have an obvious enhancement effect on ultrasonic gene shearing,and the enhancement effect has an effect on both long and short gene chains.Based on the above results,this paper further carried out the study of an ultrasonic microfluidic gene shearing chip with a lateral channel array,and achieved ultrasonic enhancement on the chip by trapping a large number of bubbles in the microfluidic channel through the lateral channel array with closed ends.Through numerical simulation and experimental testing,the enhancement effect of different driving voltages and different bubble volumes on the ultrasonic effect was analyzed,and the rapid gene shearing without thermal damage on the chip was realized under the optimized structural parameters.Finally,the genomic DNA sample was extracted from mouse muscle tissue using the bubble mixing gene extraction technology,and the preparation of the genomic DNA sequencing sample was realized by using the microfluidic bubble-enhanced ultrasonic gene shearing chip.In addition,in order to evaluate the performance of on-chip gene cleavage,an on-chip gene cleavage test was performed using standard Lambda DNA,and the obtained results were compared with commercial instruments.Excellent performance,good fragmentation size distribution(300～500bp)and a yield of more than 90%,fully meet the requirements of parallel sequencing technology gene samples,and have broad application prospects. |
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