Analysis of skin-electrode impedance using concentric ring electrode

A significant contributor to artefact generation in surface electromyography (sEMG) and, functional electrical stimulation (FES) intensity is the skin-to-electrode impedance (Z(S/E)). While using electrolytic gels may initially lower Z(S/E), the impedance may not remain stable. It can vary over time due to changes in underlying structures such as sweat glands and physical deformations due to movements. An experiment seeking to identify major factors in the reduction of Z(S/E), and therefore mitigate these artefacts, was performed by varying a series of control factors on the concentric ring electrode (CRE). Unlike conventional disc electrodes, CREs have small surface areas which may exacerbate Z(S/E) changes. The factors tested were electrode material, electrode size, skin preparation, and surface pressure. This work analyzes how these factors in their various combinations effect changes in Z(S/E) and suggests protocols for improving recording or stimulation with CREs via lowered and consistent Z(S/E).