Assessing a novel micro-seepage electrode with flexible and elastic tips for wearable EEG acquisition

Electroencephalogram (EEG) electrodes play an important role in the applications of wearable brain-computer interfaces (BCI). Although traditional wet gel-based electrodes can obtain low contact impedance and high signal-to-noise ratio (SNR), cumbersome procedures including skin preparation, gelling, and hair cleaning make them inconvenient to use. Dry electrodes can avoid these shortcomings; however, they can hardly achieve impedance and SNR as good as wet electrodes. This study aims to develop a novel micro-seepage electrode, which possesses both high convenience of dry electrode and low contact impedance of wet electrode, and assess contact impedance, comfort level, and EEG signal quality of the proposed electrode. The proposed micro-seepage electrode can continuously provide a small amount of electrolyte from flexible brush-pen like tips to scalp, which keeps the scalp-electrode interface moist like that of wet electrodes. The electrode can be put on and taken off easily like dry electrode, and there is also no need to wash hair after use. This study investigated the contact impedance of the electrode with regard to electrolyte type, recording duration, and contact pressure on the occipital area. In addition, this study compared SNR and classification accuracy of steady-state visual evoked potentials (SSVEPs) between the proposed electrode and the wet electrode. The proposed electrode can be set up very quickly. The flexible and elastic tips make it comfortable to wear. Using the contact lens cleaning solution as electrolyte, the average impedance of the electrode was 12.1 kΩ@10 Hz. The impedance kept below 20 kΩ for more than 8 h on volunteers’ scalp. The SNR and classification accuracy of SSVEPs obtained by the proposed electrodes were comparable to those of wet electrodes. The proposed micro-seepage electrode can provide a comfortable and convenient solution for high-quality EEG acquisition.