Ten-Hour Stable Noninvasive Brain-Computer Interface Realized by Semidry Hydrogel-Based Electrodes

Noninvasive brain computer interface(BCI)has been extensively studied from many aspects in the past decade.In order to broaden the practical applications of BCI technique,it is essential to develop electrodes for electroencephalogram(EEG)collection with advanced characteristics such as high conductivity,long term efectiveness,and biocompatibility.In this study,we devcloped a silver-nanowire/PVA hydrogc/mclamine sponge(AgPHMS)semidry EEG electrode for long lasting monitoring of EEG signal.Benefiting from the water storage capacity of PVA hydrogel,the clectrolyte solution can be continuously released to the scalpelctrode interface during used.The electrolyte solution can infiltrate the stratum corneum and reduce the scalp-electrode impedance to 10k0-15k0.The flexible structure enabls the electrode with mechanical stability,increases the wearing comfort,and reduces the scalp-electrode gap to reduce contact impedance.As a result,a long-term BCI application based on measurements of motion-onset visual evoked potentials(mVEPs)shows that the 3-hour BCI accuracy of the new electrode(77%to 100%)is approximately the same as that of conventional eletrodes supported by a conductive gel during the first hour.Furthermore,the BCI system based on the new electrode can retain low contact impedance for 10 hours on scalp,which greatly improved the ability of BCI technique.