Research On Injection Molding Of Micro Structure Replication Based On Micro-fluidic Chip

Nowadays micro injection molding technology has been increasingly matured, and there are a lot research on the micro injection molding at home and abroad. However, the filling mechanism of micro structure parts and the interaction between melt and micro structure still need to be further investigated in order to improve the research of micro structure injection molding.Micro-fluidic chip, a kind of typical plastic part with micro structure, was selected to study. There is a "cross" shape micro-channel on its surface. The key point of this research is the micro channel replication fidelity. In the past, the analysis of replication fidelity was focused on the longitudinal micro channel. But in this study transverse micro channel was emphasized, and the difference of them was compared. The research results will have reference value to improve the replication fidelity of complicated micro structure.Based on a kind of new electrothermic variotherm injection molding technology, the injection molding experiments of micro-fluidic chip were done. According to the experience, a better set of process parameters was chosen, and the mold temperature was selected as a variable parameter, the other parameters were kept constant. The control device was adjusted to be heated and cooled the mold rapidly, then the micro-fluidic chips were molded in different mold temperatures. Afterwards, cutting the longitudinal and transverse micro channels of chip in the specified location respectively, and the micro channel section shape of two directions and photographed them were observed.The replication fidelity of longitudinal and transverse micro channels for chip in the different mold temperatures were analyzed and compared. Because of the difference of the interaction relationship between melt and micro-convexity of cavity, it could be found that there existed significant difference between them, and the opening shape of both sides for transverse micro-channel was also inconsistent. Based on the basic theory of melt filling, the mathematical expression which could describe the size of opening round for transverse micro-channel was built. Using the electric variotherm system, a series of molding experiments were done. The results show that the measured opening round of transverse micro-channel is agreed with the calculated result on the whole.In order to further verify the reliability of above conclusions, and compare the molding difference between electric heating mold(electrothermic variotherm injection molding) and oil heating mold(oil constant injection molding), the oil constant injection molding experiments were done for micro-fluidic chips in the same condition. To a certain extent, the results of oil heating experiments could be verified the conclusions of electric heating experiments, and the micro channels replication fidelity of chip for electrothermic variotherm injection molding were obvious better than the one of oil constant injection molding, then the advantages of electric heating is analyzed. Finally, the opening deformation of transverse micro-channels for both oil heating and electric heating experiments were analyzed, the exclusive method was used to find out the cause of this problem, and the related solutions were put forward.