Abstract: Microfluidic chip, a kind of thin wall plastic parts with microchannels, is widely applied in biology, chemistry, and biomedicine. Compared with hot embossing, microfluidic chip injection molding is more efficient and suitable for mass production, but its quality control is much more complex. It’s indicated in experiments that the incomplete replication of the microchannels and the sink mark for microfluidic chips are the chief defects to the molding. Negative influences are caused by these defects on the bonding of microfluidic chips and electrophoresis separation of the sample liquid. Computer simulation, theoretical analysis and visual test show that the stagnant flow of the melt in micro-channel and the difference of shrinking directions of the parts of chips are the main reasons for molding defects. Using the orthogonal experiment method (Taguchi method), the influence of different process parameters (mold temperature, injection rate, injection pressure and melt temperature) on the molding process for the incomplete replication is discussed. The results show that mold temperature is the decisive parameter to the replication fidelity of the microchannels, injection rate and melt temperature are the secondary factors, injection pressure is less important than the others, but a high injection pressure must be maintained.

Key words: Computer simulation, Defects, Injection molding, Microchannels, Microfluidic chip, Replication fidelity