Research On Fabrication Method Of Fused Silica Microchannel In Microfluidic Chip

Microfluidic chips have the advantages of low sample consumption,low pollution,fast analysis and high detection efficiency.In recent years,with the continuous development of manufacturing technology,microfluidic chips have been widely used in disease diagnosis,food safety detection,gene analysis,new drug synthesis and other fields.The fabrication of microfluidic chips involves many disciplines such as fluid physics,new materials,microelectronics,chemistry and biology,and has become a hot research field.Quartz and glass are the traditional materials for the manufacture of biochemical analysis reactions and measurement containers.Because of their excellent optical properties and chemical stability,they are one of the main substrates for the fabrication of microfluidic chips.Microchannel is the most important basic unit in microfluidic chip.The processing of microchannel is very important for the fabrication of microfluidic chip.In this dissertation,the processing methods of microchannels on fused quartz materials are studied.In order to reduce the generation of thermal cracks and improve the quality of microchannels,the mothed of laser-induced plasma processing is used in this dissertation.Starting with the heat transfer in the process,the theoretical analysis and Simulation of the physical process in different stages are carried out.Finally,the processing equipment is improved and the experiment is completed to verify the theoretical analysis and simulation results.Among the samples,the length of microchannel is more than 2 mm and the surface is smooth.The quality of microchannel is better than that of microchannel manufactured by nanosecond laser thermal processing method.This method has a good application prospect in the future stacking miniaturization of microfluidic chips.The main research contents are as follows:1.Based on the Fourier heat conduction equation,the physical principle of laser-induced plasma processing fused quartz is systematically expounded.These include heat transfer in materials,temperature and thermal stress distribution of materials,generation and development of plasma,impact of plasma on materials,and shielding effect of plasma on laser.2.The physical processes of fused quartz irradiated by different modes of laser are simulated,and the simulation data of temperature and stress on fused quartz surface are obtained,and the differences caused by different beams are compared.The temperature distribution of the material surface is obviously affected by the intensity distribution of the beam.The highest temperature is in the region of energy concentration.The larger temperature gradient along the edge of the spot leads to the increase of thermal stress.In addition,the distribution of temperature and thermal stress along the longitudinal direction of fused quartz mid-axis is also obtained by simulation,and its evolution process is analyzed.3.The micropore model of fused quartz is established,and the temperature and thermal stress of fused quartz micropores irradiated by laser are simulated.Different simulation results are obtained by changing the parameters of beam mode,beam focus position and micropore morphology,and the influence of these parameters on the processing process is analyzed.4.The generation of plasma during processing is studied.The effects of two-photon absorption and avalanche breakdown on plasma generation are analyzed and compared.The region of plasma generation under TEM00 and TEM01 irradiation is estimated.For simplified fused quartz geometry model,the impact force of plasma on fused quartz surface irradiated by TEM00 and TEM01 beams was calculated by LSDW one-dimensional model.5.According to the geometric model of fused quartz micropore,the plasma motion in the micropore is simulated by hydrodynamics.The data of temperature,velocity and pressure distribution during plasma evolution are obtained by simulation.The differences of plasma motion under TEM00 and TEM01 mode beam irradiation are compared and analyzed.6.The experimental platform is built.It can collect spectra to judge whether the plasma is produced during the processing,so as to control the processing progress and realize the laserinduced plasma processing of fused quartz.The morphology of fused quartz microchannel was observed and analyzed,and the surface of microchannel was scanned by SEM.The microstructure of microchannel was analyzed,and the rationality of the simulation model was verified.Innovations are made in the following aspect:1.Because the time of the laser pulse is short,it is difficult to measure the physical parameters of the sample in the process.In addition,for the samples with complex morphology,it is difficult to obtain the data by solving the physical equation directly.In this paper,the micropore on fused quartz is simulated by finite element method,and the distributions of temperature and thermal stress of the fused silica under laser pulse irradiation are obtained.The theory of hydrodynamics is applied to the modeling of plasma and the interaction between laser and plasma in the micropore is simulated.2.Because fused quartz is processed by laser-induced plasma,the traditional laser processing system needs to be improved.In the existing laser processing system,the function of plasma detection is added,and the formation of microchannels is promoted by detecting the plasma state and adjusting the focus position.The reformed equipment reduces manual interference and realizes automatic processing to a certain extent.