Advances in the processing of materials on a micro-scale have led to the development and introduction of devices that employ very small needles – microneedles – that deliver drugs by mechanically perforating the out skin layer and allowing for transdermal absorption of the active compound. These processing techniques incorporate one or more technologies that enable the precise machining, extrusion, casting, and/or forming of from one to an array or grid of microneedles.
Microneedles are generally arranged in so-called microfibricated arrays. They are synthesized by reactive ion etching techniques on silicon or other types of material, in order to create microscopic arrays of needles, measuring 100-1000µm in length and 10-15µm in tip diameter. When these needles are inserted into skin, they pierce the stratum corneum and create microconduits for transport across the stratum corneum.
Microneedles may be small enough to capture the convenience of patches but large enough to create micrometer-scale pathways across the skin for drug delivery of even the largest macromolecules. Microneedles can be painlessly inserted into the skin of human subjects and their use does not need any medical expertise.
