Soft ionic-hydrogel electrodes for electroencephalography signal recording

Wet gel electrodes have been widely used for electroencephalography (EEG) signal recording, which generally causes skin abrasion and longer preparation time. In this paper, we present soft ionic-hydrogel based electrodes to overcome such drawbacks. In order to conveniently measure the EEG signals, we design the claw-like and patch-like structures for robust connection between metal (Ag/AgCl) electrodes and skin scalps. Next, we experimentally show that the soft ionic-hydrogel based electrodes have similar performance with the conventional wet gel electrodes in terms of the short-circuit noise, electrical impedance, and skin-electrode contact impedance on unprepared human skin, significantly better than dry electrodes and water-based electrodes. We further perform the EEG measurements and steady-state visual evoked potentials (SSVEP) experiments with five subjects to verify the effectiveness of the soft ionic-hydrogel based electrodes. The experimental results demonstrate that our developed soft ionic-hydrogel electrodes can record high-quality EEG signals in a fast and clean way, being a compelling option for EEG-based brain-computer interfaces.