Abstract: This disclosure provides self-applied wearable devices configured to electrically stimulate a user, generate and/or collect a user's electrophysiological data via electrodes, in contact with the outer layer of skin, that hydrate the skin surface using iontophoresis, reverse iontophoresis, and/or a combination thereof. The wearable devices provided herein increase conductivity and/or move biological ions and/or polar molecules from the electrode into the outer skin layer of skin surface to reduced impedance between the outer skin layer and electrode, wherein the impedance between electrodes is matched and/or minimized. This disclosure also provides systems comprising the same, and methods for making and using the same.