An array of porous microneedles for transdermal monitoring of intercellular swelling.

An array of porous microneedles was developed for minimally-invasive transdermal electrolytic connection through the human skin barrier, the stratum corneum. The length of microneedle was designed to be 100 μm so that it penetrates into the epidermis layer without pain. Each microneedle was supported by a thicker cylindrical post protruding from a planar substrate to realize its effective penetration even into elastic human skin. Since this support (post and substrate) was equally porous as the needles, the needle chip was entirely permeable for electrolyte. This ion-conductive porous microneedle array was applied to the transdermal conductometry with small direct current for local monitoring of intercellular swelling, edema. The porous needle-based electrode system could be a platform for various transdermal electrical diagnosis and treatments.