Porous microneedle-based wearable device for monitoring of transepidermal potential

lWe have developed an open-tip porous microneedle (PMN) array.lThe open-tip PMN electrode makes a minimally invasive connection to the subepidermal region.lIt measures the transepidermal potential (TEP), a possible index of skin functions.lThe TEP was monitored for hours by a patch-type PMN-based potentiometric device. Transepidermal potential (TEP), an electrical potential difference of tens of millivolts that is generated along the thickness direction of the epidermis, is a possible indicator of epidermal function, including the permeability barrier of skin. Herein, a patch-type wearable device for minimally invasive monitoring of TEP was developed by utilizing a porous microneedle (PMN) array made of an epoxy resin. In order to measure the potential of the subepidermal tissue, the entire surface of the PMN except for the needle tip was coated by a thin film of insulating parylene C. The open-tip PMN was integrated with a wearable potentiometric device composed of a pair of screen-printed Ag/AgCl electrodes. By optimizing the porosity and the size of the liquid junction, the TEP of tens of mV at a subject's forearm was successfully monitored over a 4 h period. [Display omitted]