Study On Microfluidic Chip Injection Molding Quality And Ultrasonic-aid Injection Molding

The development of MEMS technology provides a broad application prospect for micro-injection molding products. Nowadays micro plastic parts have been widely used in biomedicine, precision instruments, aerospace and communication, etc., quality requirements for plastic parts are constantly raised. So the phenomenon of thickness nonuniformity and micro-channel replication inconsistency have currently become the main problems which hinder further quality improvement of the plastic parts, especially for those bigger parts with micro-structures.Microfluidic chip was chosen as the studied object, aimed at improving its thickness uniformity and replication fidelity. The cause and prevention of the thickness nonuniformity and replication inconsistency were focused on. And ultrasonic-aid injection molding technology was explored, in order to improve micro-injection molding products quality further.Firstly, based on Moldflow simulation, the cavity pressure value molding the microfluidic chip could be got. Setting this value as insert loading condition, the insert deformation was caculated by ANSYS Workbench, injection molding experiments were done accordingly. The results show that the chip thickness nonuniformity is mainly caused by micro deformation of the insert during molding process, the simulated insert deformation is as approximately30um as the final product thickness nonuniformity, and they have the same deformation trend. Improvements methods about mold design were proposed.Secondly, considering microfluidic chips structural features, injection molding process of microfluidic chip were analyzed deeply, the multi-stage injection molding technology was applied in the molding process. According to the molding characteristics of runner and chips, multi-stage injection molding parameters were set. Runner was filled in the low injection speed, the chip was filled in high injection speed. After short shot experiments and analysis of micro-channel quality, the results show that the structures of micro-channels are entirely filled in the high injection speed stage, the formation and growth of frozen layer are suppressed, and the width and corner radius of the micro-channel is reduced to some extent, and the replication consistency is better, the overall quality of microfluidic chip is further improved by multi-stage injection molding. Finally, the existing injection mold was transformed as ultrasonic-aid injection mold, the ultrasonic waves was directly applied in the end of the sprue. Using crystalline material PP and non-crystalline material PMMA and PC, ultrasonic-aid injection molding experiments were done to analyze the influence of ultrasonic waves on the microstructure replication and the crystalline degree.