3D printed microneedle assemblies

A three-dimensionally printed microneedle assembly, comprising:

• an array of microneedles formed by exposure of a liquid resin comprised of photopolymers to a light source layer-by-layer through a series of patterns projected onto the liquid resin, wherein, for at least a plurality of the microneedles included in the array, each microneedle of the plurality of microneedles comprises:
• a needle shaft;
• and
• a plurality of cantilevered barbs, each of the cantilevered barbs having a first end that protrudes transversely from the needle shaft of the respective microneedle, a second end that points in a downward direction towards a base of the needle shaft, and a curved surface between the first end and the second end that is formed by removal of un-crosslinked monomers from one or more layers comprised of a crosslinking gradient.

A method for fabricating an array of microneedles, comprising:

• printing an array of microneedles having a tip and a needle shaft by exposing polymers to a light source layer-by-layer through a series of patterns projected onto a photocurable liquid resin including monomer material, the patterns being horizontal cross sections of the array of microneedles;
• and
• forming one or more cantilevered layers by exposure to the light source for a first predetermined curing time to create initially horizontal, cantilevered barbs extending transversely from the needle shaft from a first end to a second end, wherein the cantilevered barbs have a crosslinking gradient with a higher degree of crosslinking at an upper portion of the cantilevered barbs and a lower degree of crosslinking at a bottom portion of the cantilevered barbs, the cantilevered barbs including at least some un-crosslinked monomers,
• rinsing the printed array of microneedles to remove an amount of un-crosslinked monomers from the cantilevered layers, where the removal of un-crosslinked monomers causes shrinkage of the cantilevered layers to induce a curvature to a surface of the cantilevered barbs between the first end and the second end such that the second end points in a downward direction towards a base of the needle shaft, and
• post-curing the rinsed array of microneedles to fixate the curvature in the surface of the cantilevered barbs.

A microneedle assembly formed according to a method comprising the steps of:

• printing an array of microneedles having a tip and a needle shaft by exposing polymers to a light source layer-by-layer through a series of patterns projected onto a photocurable liquid resin including monomer material, the patterns being horizontal cross sections of the array of microneedles;
• and
• forming one or more cantilevered layers by exposure to the light source for a first predetermined curing time to create initially horizontal, cantilevered barbs extending transversely from the needle shaft from a first end to a second end, wherein the cantilevered barbs have a crosslinking gradient with a higher degree of crosslinking at an upper portion of the cantilevered barbs and a lower degree of crosslinking at a bottom portion of the cantilevered barbs, the cantilevered barbs including at least some un-crosslinked monomers,
• rinsing the printed array of microneedles to remove an amount of un-crosslinked monomers from the cantilevered layers, where the removal of un-crosslinked monomers causes shrinkage of the cantilevered layers to induce a curvature to a surface of the cantilevered barbs between the first end and the second end such that the second end points in a downward direction towards a base of the needle shaft, and
• post-curing the rinsed array of microneedles to fixate the curvature in the surface of the cantilevered barbs.