(Invited) Microneedle Array Features in Precise Moulding of Biocompatible Polymers

Microneedle array features were fabricated by micro-injection molding using biocompatible polymers such as polycarbonate (PC), polypropylene (PP) and polylacticacid (PLA). PC and PP based microneedle array features with high aspect ratio for needle height was fabricated by several injection molding techniques. Injection compression molding and injection molding with super critical carbon dioxide fluid with or without vacuum process inside the cavity of mold were performed. Effects of process parameters on processability and surface replication of the molded parts were evaluated. The height replication ratio for micro-needle was improved by using injection compression molding. Moreover, the effect of vacuum process inside cavity of mold under filling process was small. However the height replication ratio for micro-needle showed the highest values using the injection molding with super critical carbon dioxide fluid with vacuum inside the cavity of mold process.  In addition, hydroxyapatite (HAp) particle dispersed PLA composites based microneedle array features were also fabricated by twin screw extrusion and micro-injection molding. The viscosity of PLA was reduced by HAp dispersion because of acceleration of hydrolysis degradation during both processing. The micro-needle array of HAp/PLA composites for application to biomedical parts was obtained and the needle height was improved by the optimum composition of HAp to polymer.