Numerical Simulation And Bonding Test Of Injection Molding Of COC Microfluidic Chip

With the development of science and technology and the deepening of micro-control technology research,there is an increasing demand for disposable low-cost chips.However,how to realize efficient,low-cost and mass manufacturing of microfluidic chips is a key problem faced by commercialization of microfluidic technology.In this paper,COC-8007(cycloolefin copolymer)was used as the material to study the injection molding and thermocompression bonding of COC chips,so as to improve the processing quality of the chips and provide some theoretical guidance for the batch production of microfluidic chips.Based on the injection molding theory,numerical simulation was carried out to reduce the warpage of COC chip,and the injection molding process parameters were optimized.Through numerical simulation,it is found that the warpage of chip is mainly caused by uneven shrinkage.Firstly,PB test is used to screen the factors that have significant influence on shrinkage deformation,and L₂₇(3¹³)orthogonal test is designed to optimize shrinkage deformation.Then,taking the amount of uneven shrinkage warpage as the optimization index,combining orthogonal test and signal-to-noise ratio method,the injection molding process parameters are optimized to obtain the optimal process parameter combination.Based on the optimization results of orthogonal test,the second-order response surface method is used to further simulate and optimize the parameters and establish the relationship between quality index and process parameters and predict the influence of process parameters on uneven shrinkage warpage,In order to obtain the optimal process parameter combination of uneven shrinkage warpage of chip.The optimal combination of process parameters is mold temperature 70.31?,melt temperature 239.97?,holding pressure 105MPa and holding time 21.63s.The single factor test method is used to simulate and analyze the influence law of various influencing factors on uneven shrinkage and warping deformation,and relevant conclusions are obtained.With the increase of die temperature,the warpage first increases and then decreases.With the increase of melt temperature and packing pressure,the warping deformation decreases;When the holding time is between 6 and12 seconds,the warping deformation decreases with the increase of time,and after more than 12 seconds,the warping deformation hardly changes;Injection pressure has little effect on warpage.In this paper,the chip was fabricated with the above-mentioned optimal injection molding process parameters,and the bonding test was carried out.The influence of bonding process parameters on the deformation and bonding strength of the chip microchannel was studied by single factor test.The results show that increasing the bonding pressure can increase the bonding strength and reduce the bonding time.Increasing bonding temperature and time can accelerate the diffusion of molecules between bonding surfaces,increase the intermolecular force and increase the bonding strength;However,too high bonding temperature,too high bonding pressure and too long bonding time will cause serious chip deformation and even destroy the chip microstructure.Considering the deformation of the microchannel and the bonding strength of the chip,the bonding temperature of 78?,the bonding pressure of 0.16MPa and the bonding time of 240s were determined as the optimized process parameters.Experiments of bonding and droplet generation were carried out with these parameters.The micro-channel deformation of the chip is small,the bonding strength reaches 0.076MPa,and uniform and stable droplets can be generated.The chip meets the use requirements.