Enhancing structural replication of microfluidic chips: Parameter optimization and mold insert modification

Abstract

The demolding process in micro‐injection molding constitutes a critical phase, exerting a decisive influence on the quality of polymer microstructures. In this study, the demolding forces of PMMA microfluidic chips were measured under different demolding temperatures, packing pressures, and demolding speeds by using pure nickel (Ni) mold insert. The dimensional deviations of the microchannels with different aspect ratios were analyzed. In addition, the effect of mold insert modification on the demolding force was further analyzed. The results showed that the effect of demolding temperature on the demolding force was the most significant, and the peak demolding force decreased with the decrease in temperature. The width of the microchannels increased and the depth decreased after demolding, while the opposite results were observed for the micro‐mixing structures. However, the dimensional deviation of the micro‐mixing structures was larger than that of the microchannels. Using the optimal molding parameters, the peak demolding force could be reduced from 114.0 N at 110°C to 47.0 N, a decrease of 58.8%. It is noteworthy that, when the microchannel was narrower than 100 μm, achieving precise replication of microchannel dimensions became progressively more challenging as the microchannel width decreased. Using the Ni‐WS2 mold insert with low surface energy and low friction coefficient, the demolding force could be further reduced by 38.3%. The effect of the molding quality of microfluidic chip microstructures on the mixing performance of heavy metals was demonstrated by micro‐mixing experiments.Highlights Demolding temperature crucially affects microstructure dimensions. Optimal parameters and modified mold insert reduce demolding force by 38.3%. Dimensional deviation increases with the increase of microchannel aspect ratio. Optimized microfluidic chip enhances Co2+ chemiluminescence by 6.42%.