Research On Key Technology Of Injection Molding Of The Microfluidic Chip With Micro Cylinder Arrays

Polymer microfluidic chip is a typical microstructure product, which has a biggish dimension span. In injection molding, shrinkage, warpage and burn must be overcome, and microstructure partial replication and breakage have to be avoided. Therefore, the research into injection molding technology of complex microstructure product is great significance and importance in reality.Microfluidic chip with micro cylinder arrays was studied, which was 100mm long, 16mm wide and 1.5mm thickness, and side wall was 0.5mm thickness. About 13000 diameter of 100μm and height of 50um cylinders and 1000 diameter of 50μm and height of 15um cylinders was designed respectively within 2mm wide rectangle and 6.23mm high rapezoid on the surface. The influence of process parameters on the quality of micro cylinder arrays were investigated, the cause and influence rules of warpage were analyzed, and the solutions were proposed in the plastic injection process.Firstly, the influence of process parameters on the quality of micro cylinder arrays and warpage were investigated by single-factor experiment. In the experiments, the change rule of process parameters on the quality of micro cylinder arrays and warpage were observed by changing process parameters in turn, and the process parameters range were conformed.Secondly, based on the single-factor tests, the six factors and five levels orthogonal table was designed by the Minitab software. The non-interaction and interaction between process parameters were analyzed by the Minitab software, aimed at optimizing the quality of micro cylinder arrays and warpage. The experiments show that the most important factors influencing the quality of micro cylinder arrays and warpage are the mold temperature and injection rate, and melt temperature is a secondary factor, and there exist marked interaction between melt temperature and injection rate.Thirdly, the short shot experiment was studied based on the orthogonal experiment. First, injection rate was changed, but injection volume stayed the same, the relationship between injection rate and melt front shape was investigated by observing the melt front shape, and the injection rates range were conformed. Second, injection volume was changed, but injection rate stayed the same, the relationship between injection volume and product shape and the defects positions were studied through observing product shape, and the structure of microfluidic was studied, the injection rate switch positions and three stages injection molding were conformed. The injection rates were changed in turn, the change rule of the micro cylinder arrays height and warpage were studied, and the variation range of injection rates was confirmed.Lastly, then the influence of injection rates and switch positions of injection rates on the microfluidic chip quality were studied by the orthogonal experiment, aimed at optimizing the quality of micro cylinder arrays and warpage, and the process parameters were optimized. The experimental results suggest that the third-stage injection rate is predominant factor which effects warpage. The second-stage and third-stage injection rate are predominant factors which effect the micro cylinder height. The injection rates switch position influence the quality of microfluidic chip, and the bigger the gap of injection rate, the bigger the effect. The qualified microfluidic chip has been largely produced and used.