Mechanical finite element analysis of needle tip shape to develop insertable polymer-based microneedle without plastic deformation.

Bioabsorbable polymer microneedles are highly attractive as modernized medical devices for efficient yet safe transdermal drug delivery and biofluid biopsy. In this study, the elastoplastic deformation of polymer microneedles, having a high aspect ratio (over 5-10), is investigated using poly(lactic) acid polymer approved by the United States Food and Drug Administration to be generally considered safe. Microneedle geometries are comprehensively analyzed for tip geometries comprising the tip diameter (ϕ) and tip taper length (l) of 100 designs. Elastoplastic analysis is conducted using the finite element method to determine the typical geometries of the polymer microneedles to avoid elastoplastic deformation accompanied by fatal fracture based on the mechanical properties of the polymer materials. The design principles of microneedle geometries based on polymer material properties are important guidelines for developing polymer microneedles, overcoming their mechanical weakness, and ensuring excellent functions.