Innovative design of hollow polymeric microneedles for transdermal drug delivery

Abstract

Hypodermic injections give the best results in terms of drug administration efficiency, but benefit from a negative image among patients due to the fear of pain linked to needles. Transdermal drug delivery (TDD) has thus been greatly developed in the past ten years in order to be able to by-pass the skin protective layers in a minimally invasive way. With the advent of micro electro mechanical systems, opportunities have appeared, particularly in the area of microneedles. In this paper we present a new design of hollow polymeric microneedles aimed at being used for TDD by allowing injection of a liquid in the non-innerve part of the dermis. The design has been studied in order to be able to manufacture these microneedles arrays using techniques that may be applicable to industrial production at low cost. The envisioned microfabrication processes and their stacking are presented which involve injection micromolding and excimer laser ablation. Microneedles are also numerically characterized in terms of mechanics and microfluidics showing that the design also involves interesting features in terms of needles resistance and microfluidic. Due to the innovative double-molding technique, the micro-needles are indeed emptied leaving a cavity. An outlet channel on the side of the needle allows fluid flowing out of the needles. The characteristics of this outlet channel contribute to flow homogenization when several needles are placed in an array pattern. This microneedle design thus combines interesting characteristics in terms of ease of fabrication at large scale, mechanical resistance and fluid dynamics.