Additively Manufactured Dry Electrodes for Biosignal Measurements

The acquisition of electrophysiological signals, such as electrocardiography or electromyography, is an integral part of medical diagnostics and therapy. In the clinical environment, these signals are typically recorded using adhesive gel electrodes which have particularly good electrical characteristics. Outside this environment, however, these electrodes are not practical, since they have to be placed manually and can only be used once. Instead, the use of dry electrodes can be beneficial, especially in complex systems such as wearables or prostheses. Unfortunately, these electrodes are not widely commercially available and their electrical characteristics are hardly documented. One major challenge is the occurring high interface impedance between the electrode and the skin. In this study, dry electrodes with different contact surfaces made of conductive polylactide acid are designed, additively manufactured and the corresponding electrode-skin impedances are examined on human subjects. The influences of different electrode radii as well as surface structures on the electrode-skin interface impedance are compared with each other. The result of the investigation is that the impedance decreases as the contact area increases, which corresponds to the electrical equivalent circuit. However, the chosen structuring of the surface has a negative impact on the impedance, although the effective electrode surface was expected to be increased.