Study On The Process Of Fabricating PMMA Microfluidic Chips By Femtosecond Laser

As a rapid detection technology,microfluidic chip technology is of great value in the fields of public health and safety events and biomedical research and development.Based on the current status of laser transmission welding polymer microfluidic chip where welding additives are generally used,and the fact that the domestic and foreign research on additive-free transmission welding polymer by femtosecond laser is insufficient,we conduct an in-depth study on the laser preparation of microfluidic chip and then propose a method of laser transmission welding PMMA materials without additives by using infrared femtosecond laser with the purpose of reducing the welding process,preparation cost and its difficulty.The main contents of this study are as follows.First of all,by studying the various microfluidic chip preparation techniques(including microgroove processing and material bonding)and summarizing their advantages and disadvantages,choose the laser preparation of microfluidic chips;and then,after investigating the current status of research on laser processing technology at home and abroad,select two processing methods suitable for the preparation of microfluidic chip,the UV femtosecond laser preparation of microgrooves and the infrared femtosecond laser additive-free transmission welding.Secondly,investigate the effects of laser pulse energy density,pulse frequency and scanning speed on the shape of processed PMMA microgrooves,and then analyse the effects of laser scanning with different transverse scan spacing and longitudinal feed repetition on the shape of microgrooves.Then,the degree of influence of the process parameters on the microgroove morphology was investigated using the method of extreme difference analysis.Finally,the ablation thresholds of PMMA material are determined:F_th(26)=0.697 J/cm² and F_th(1)=2.0426 J/cm².Thirdly,the relationship between laser scanning processing speed,laser pulse frequency and laser average output power and width and depth of the welding line and welding strength is studied,and the optimal combination of process parameters is determined by using the response surface method of Box-Behnken's experimental design:when the laser pulse frequency is 1 MHz,the laser scanning speed is 0.8 mm/s and the laser average output power is 13.39 W,the welding strength of the sample can reach 33.5 MPa,69.8%of the strength of the PMMA base material.Finally,based on the theories of finite elements and laser transmission welding temperature field,use the Z-scanning technology to measure the nonlinear absorption coefficient of PMMA,establish a simulation model of the temperature field during the process of laser welding.The results of the experiment show a trend of change consistent with the values of the simulation.