Functional electrical stimulation (FES) has been used to revitalise the muscles of people suffering from various kinds of injury. However, when human skin is incorporated into electrical circuits, it must not be treated as a passive component. Skin’s electrical properties must be known when electrodes deliver electrical stimulation to the body, whether by hydrogel electrodes or by electrodes embedded in apparel. Failure to address this issue increases the risk of skin burns due to too high current through the skin/electrode interface. We have demonstrated that there is a relationship between electrode size and measured voltage. The rise of voltage with a reduction of electrode size can be explained by the diminution of the skin contact area with resulting higher skin/electrode impedances. Thus, finding an electrical skin model that represents the behaviour of human skin is important for circuit design and the product development process.
Patterned iridium oxide film as neural electrode interface: Biocompatibility and improved neurite outgrowth with electrical stimulation