Investigation of injection molding parameters on the uniformity of porous array of polymer microfluidic chip

The uniformity of the porous array seriously affects the performance of the injection-molded parts. In this study, a uniform hole array chip constituted by 384 holes whose radiuses are 1.30 mm is fabricated by precision injection molding technology. To capture the relevance between the uniform dimension of the porous array and the injection molding process parameters, single factor experiment was adopted. Besides, the condensed state of the hole array was studied to give a further explanation of the inner relationship between the hole array and the most sensitive injection process. As for the measurement, the diameter of the hole which next to the gate and away from the gate was investigated by means of universal tool-measuring microscope, and the standard deviation of the hole diameter was chosen to estimate the uniformity of the hole array. Furthermore, the crystal state and interface state were characterized by polarized light microscopy (PLM), used to explain why the difference of those holes appeared. The results reveal that the impact of process parameters on the uniformity of the hole array was ranked as follows: melt temperature, cooling time, mold temperature, injection pressure, injection speed and packing pressure. Besides, the analysis of the condensed state on different melt temperature indicates that the larger grain size is less favorable to the uniform molding, as the melt temperature increases, the difference of cortical thickness between the dynamic template and fixed template sides decreases, product uniformity is improved.