Fabrication of Microneedle from Stretched Biodegradable Polymer Sheet by 3D Laser Machining

Abstract

Polylactic acid (PLA) microneedles have been usually fabricated by injection molding. Herein, we consider microneedles that mimic the maxillae of mosquito proboscises, which have sharp tips with jagged harpoon-like protrusions. In case of such microneedles, filling the melting PLA resin up to the tip of the mold trough without burrs is challenging. To address this issue, we have proposed a new microneedle fabrication method in this paper. In this method, the needle with the desired shape was obtained from a PLA sheet by femtosecond laser machining. The needle was turned by 90°, and its tip further cut obliquely with the laser for three-dimensional (3D) sharpening. Tensile and buckling tests were conducted by using a test piece cut out from the PLA sheet. It was experimentally established that the strength and Young’s modulus along the sheet’s stretch direction are higher than those along its perpendicular direction. The 3D sharpened PLA microneedle successfully penetrated an artificial skin made of polydimethylsiloxane. A pair of microneedles were alternately vibrated against each other, mimicking the motion of mosquito two maxillae. With this alternate vibration, the resistance force during insertion was found to be lower compared to that without vibration.