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 pro-
truding from a planar substrate to realize its effective penetra-
tion 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.

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