A dynamic measurement system for evaluating dry bio-potential surface electrodes

In this paper, a dynamic measurement system (DMS) is presented for assessing performance of wearable and dry bio-potential surface electrodes (DBSEs) in air, especially motion artifacts. A pair of perforated membranes is assembled on the two ends of the barrel which contains electrolyte to simulate surface of the skin. The pressure of electrode/membrane can be controlled and measured, one of electrodes can move on membrane by the motion controller. Experimental results show maximum coefficient of variation (CV) of electrical impedance spectra (EIS) and dynamic open circuit potential variation (DOCP, so-called motion artifacts) of gold electrode pair are, respectively, 4.3% and 7.2% in continuous measurements, 12.6% and 22% in discontinuous measurements, the pressure and the length of motion track between electrode and membrane are strongly linear correlation with DOCP variations. EIS and DOCP of five types of electrodes were measured on DMS and their parameters of equivalent circuit (EC) of EIS and DOCP variation show larger is equivalent capacitance in electrode/electrolyte interface, less is DOCP variation. DOCP variations of two batches of electrode performed respectively on DMS and on skin have approximate 0.64 of Pearson correlation coefficient. In general, the DMS provides a powerful tool to investigate the mechanism of DOCP variation and evaluates the static or dynamic performance of electrodes. However, parameters of EC model by fitting EIS can predict the motion artifact and help the design of electrode and its integrated wearable garments.