| Microfluidic chips have been widely studied and applied in biological detection,medical diagnosis,chemical analysis and other fields in recent years.Microfluidic chips can be mass-produced by injection molding,but bonding is often independent of molding and cannot be automated or mass-produced.Compared with the conventional hotkey of dozens of minutes,a mould hot or just a few minutes,but the bonding process to control the mould temperature accurately and efficiently is a problem need to solve,bonding temperature close to the glass transition temperature of polymer materials,polymer flow under pressure of microchannel deformation or collapse,bonding strength and micro channel deformation coordination between the need to control.On the other hand,before bonding,the chip forming quality is required,and the process needs to ensure that the chip microchannel complex system,residual stress and current warping deformation and other forming indexes are good,to reduce the influence on the chip bonding quality.The main research work and achievements are as follows:1)Based on the design of in-mold bonding process,a bonding experimental platform was built,and a local high dynamic temperature control scheme was designed.Experiments verified the accuracy and efficiency of the temperature control process.Within 40 s,the temperature of the bonding base reached the required temperature,the temperature fluctuation range of the bonding interface was ±0.7 ℃,and the temperature difference between the upper and lower surface of the chip was ±1℃.High dynamic temperature is realized to accurately control the temperature of the bonding interface.2)Before the bonding experiment,the orthogonal experiment was used to analyze the three key indicators of microchannel complex system,residual stress and macroscopic warping deformation of injection molding microfluidic chip.It was found that the single objective optimization results were different,and the single factor optimization could not meet the overall quality control.Therefore,gray relational analysis was applied to the multi-objective optimization molding process,and the microchannel complex system of microfluidic chip was more than90%,the residual stress value was the minimum,the distribution was the minimum,and the warpage deformation value of substrate was 41μm,and the cover was 54μm.Provide high quality chips for subsequent bonding.3)The influence of bonding process parameters on chip bonding quality was studied through the in-mold bonding experiment platform.When the bonding temperature is lower than Tg,the bonding pressure increases the bonding strength more significantly.As the bonding temperature rises above Tg,the bonding strength and microchannel deformation also increase significantly.When the bonding temperature is109℃,the microchannel on the chip is close to blocking.The bonding pressure can be increased at lower temperature or the bonding temperature can be increased at lower pressure to achieve a certain bonding quality.4)In view of the significant viscoelastic properties of polymer chip bonding process,the viscoelastic constitutive model of the material was established through compression creep experiment to study its deformation mechanism,and the in-mold bonding process was simulated by ANSYS software.The results show that bonding temperature is the most significant factor affecting bonding quality.The experimental and simulation results coordinate the bonding strength and microchannel deformation,and obtain the selection principle of bonding parameters suitable for different applications.In view of the good agreement between the simulation model and the experimental results,the microchannel size compensation scheme is verified by numerical simulation method,which can achieve 1.77 MPa bonding strength and good microchannel.There are 61 figures,19 tables and 98 references. |
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