Research On Injection Molding Process For Micro Structure Parts Based On Microfluidic Chip

With the rapid development of micro system technologies, micro structure parts are used widely in biomedical science, environmental engineering, precise instrument, aerospace, information communication and so on. Polymer micro structure parts are a kind of parts, which have the traditional dimension size with microstructure, such as microfluidic chip, microsensor, micro-pump, microlens array, light guide plate etc. Its extensive and commercial applications benefit from various replication technologies, which injection molding is the effective means to achieve mass and economical production. However, injection molding of micro structure parts needs to face many problems such as multi-scale flowing, heat transfer, etc. its quality control is quite complicated, especially the choice of process parameters, because it do not only influence the replication accuracy of microstructure, but also affect the molding quality of polymer parts. According to the demand of National Key Technologies Program of China (2006BAF04B13), the microfluidic chip is taken as an example to study the relative theory and key technology of microstructure parts molding thoroughly.Firstly, a kind of microfluidic chip with quite simple single-cross microchannel was chosen as research object. Through many molding experiments, the rules and mechanisms that how process parameters affected the chip molding qualities were analyzed, and the defects forming mechanisms for chip parts and the improving methods were studied. By means of single-factor and orthogonal experiments of each process parameter, the degree of interaction among parameter was analyzed, the process control towards injection molding was optimized, and then the process control solutions and technologies to reduce and even eliminate the defects were proposed.Secondly, based on numerical simulation, theoretical analysis, melt rheological experiments and visualized experiments of melt filling process, the mechanism and flow law during the melt filling to microstructure cavity were studied, the forming reasons of replication defects and defect levels in microchannel of chip parts were analyzed, and the reasonable principle of process parameters for parts with micro structure was gained and the mechanism of the influence on replication quality of molding parts was proposed, the process control theory on microstructure injection molding was improved.Thirdly, aimed at the significant effect of mold surface temperature and temperature distribution on molding qualities of microfluidic chips, and the finite space on the micro-injection machine and mold, a new kind of mold with heat pipe transfer and Peltier cooling device was studied and designed. Rapid heating and cooling, precise temperature control can be gained.Fourthly, considering the complicated microchannel network of microfluidic chips in practical application, a kind of microfluidic chip with double-cross microchannel was chosen to study the applicability of the rules on complicated microstfucture parts, which was obtained from simple single-cross microfluidic chip molding. The control standards of injection process parameters on micro structure was also modified and improved.Lastly, based on the experimental results of process control optimization, the replication accuracy of different microchannels of microfluidic chips was studied. The results showed that the optimized process control can guarantee the replication accuracy of microchannel structures. Within the reasonable range of process parameters, the microchannels replicated by batch production have consistency, moreover, microchannel replication accuracy of single chips also have consistency. Therefore, injection molding technology has the ability of successfully manufacturing microfluidic chips in mass and has promising prospect.