Design rules for a tunable merged-tip microneedle

Abstract

This publication proposes the use of an elasto-capillarity-driven self-assembly for fabricating a microscale merged-tip structure out of a variety of biocompatible UV-curable polymers for use as a microneedle platform. In addition, the novel merged-tip microstructure constitutes a new class of microneedles, which incorporates the convergence of biocompatible polymer micropillars, leading to the formation of a sharp tip and an open cavity capable of both liquid trapping and volume control. When combined with biocompatible photopolymer micropillar arrays fabricated with photolithography, elasto-capillarity-driven self-assembly provides a means for producing a complex microneedle-like structure without the use of micromolding or micromachining. This publication also explores and defines the design rules by which several fabrication aspects, such as micropillar dimensions, shapes, pattern array configurations, and materials, can be manipulated to produce a customizable microneedle array with controllable cavity volumes, fracture points, and merge profiles. In addition, the incorporation of a modular through-hole micropore membrane base was also investigated as a method for constitutive payload delivery and fluid-sampling functionalities. The flexibility and fabrication simplicity of the merged-tip microneedle platform holds promise in transdermal drug delivery applications.

Drug delivery: self-assembly of microneedles

The fabrication of merged-tip microneedles by elasto-capillarity-driven self-assembly is investigated in photocurable polymers, revealing design parameters for their potential use in drug delivery. Microneedles can be used for delivery of drug payloads by perforating the skin. However, existing needle fabrication processes typically rely on expensive approaches such as etching, embossing, and molding. Now, a team from Seoul National University led by Noo Li Jeon, explore design parameters for fabrication by elastic-capillary-driven self-assembly: photolithography is used to fabricate closely spaced polymer micropillars, the tips of which crosslink to form a microneedle. A number of microneedle geometries are studied, for different UV-curable polymers, suggesting the possibility of their use in drug delivery.