Microfluidic chips have become a critical component in advanced applications such as biochemical analysis, medical diagnostics, drug development, and environmental monitoring because of their ability to precisely control fluid flow at the microscale. The functionality of these chips is highly dependent on the precision and dimensional stability of microchannel structures formed on them. While injection molding is an efficient method for a mass production of microfluidic chips, it is required to minimize undesirable deformation due to thermal and mechanical stresses, which can degrade the overall performance. This study investigated global (Macro-scale) and local (Micro-scale) deformation behaviors of injection-molded microfluidic chips. Effects of processing parameters, including mold temperature, melt temperature, filling time, and packing pressure, were investigated. The Taguchi-based design of experiments approach was employed to systematically analyze these effects and to determine optimal conditions to minimize deformation.

In the present study, a numerical investigation of an insert injection molding process was carried out for the development of thermoplastic microfluidic chip plates with metal electrodes. Insert injection molding technology enables efficient realization of a plastic-metal hybrid structure and various efforts have been undertaken to produce novel components in several application fields. The microfluidic chip with metal inserts was proposed as a representative example and its molding process was analyzed. The important characteristics of the filling stage, such as the effects of filling time and thickness of the part cavity, were characterized. Furthermore, the detailed distributions of pressure and temperature at the end of the filling stage were investigated, revealing the significance of metal insert temperature.

In the present study, replication of microstructured surfaces by microinjection molding was carried out. For a fabrication of mold inserts, nickel microstructures having various characteristic dimensions were fabricated by nickel electroforming onto Si mother microstructures. In addition, reverse nickel microstructures based on the electroformed nickel microstructures were successfully realized by electroforming with passivation process. The fabricated nickel microstructures were used as mold inserts for a replication of microstructured surfaces by microinjection molding. Microinjection molding experiment was carried out under three different processing conditions, which revealed effects of a packing stage and mold wall temperature. The microinjection-molded microstructured surfaces were characterized by using an atomic force microscope (AFM). It was found that mold wall temperature could enhance replication quality, resulting in the precise microstructured surfaces.