Biodegradable polymer needle with various tip angles and effect of vibration and surface tension on easy insertion

This paper proposes a fabrication method of microneedles with various tip angles made of biodegradable polymer (polylactic acid, referred to herein as PL A). It was confirmed by finite element method (FEM) simulation that stress concentration occurs more severely at the tip area, as the needle becomes thin, and tip angle becomes sharp. Masks for silicon cavities (negative dies for micromolding) with various tip angles are designed. The fabrication process involves etching a groove on the surface of a silicon die, molding the polymer into this groove, and then releasing it. The resistance force during inserting a fabricated needle to an artificial skin of silicone rubber was investigated. Effectiveness of sharp tip angle and thin shank for easy insertion is confirmed. Imitating mosquito´s needle, the effectiveness of vibrating needle, and giving surface tension to object surface was also confirmed.