Mechanism of pressure induced baseline shift in bioelectric signals measurement using wearable electrodes

In this paper, we present an objective evaluation method to study the pressure induced abrupt baseline shift in bioelectric signals measurement using textile electrodes. The evaluation was carried out on a hollow simulator, made from a Teflon tube with two pieces of filtration membranes at each end to mimic human skin, which filled with saline solution. An electrode pair was set to contact with the membranes under controllable pressure. The baseline of bioelectric signals, indicated by open circuit potential (OCP) of the electrode pair, was continuously recorded when increasing the electrode-membrane contact pressure stepwise. Electrochemical impedances of the electrode pair were also measured at each pressure step. The results shown that the OCP and impedance decreased with electrode contact pressure. Mechanism of the abrupt baseline shift was analyzed using a capacitor model which well explained this phenomenon.