Highly uniform non-invasive BCI microneedle array electrodes using a facile micro-nano process for high-quality EEG signal acquisition

Microneedle array electrodes (MNAEs) are non-invasive dry electrodes with easy-to-use and low impedance characteristics, which have broad application prospects in brain-computer interface (BCI)-related scientific research, medical, health and entertainment fields. The micro-electromechanical system process has been extensively demonstrated to fabricate the MNAEs efficiently. Most of the current reports use the mechanical dicing method, which is complicated and lacks the study of multiple channels for microneedle electrodes. In this study, an MNAE was fabricated based on photolithography and an etching process, which is facile and low-cost. The prepared microneedle arrays represent a regular structure and high consistency. The MNAEs exhibited superb durability, with a contact impedance as low as 2.6 kΩ@10 Hz, which is significantly better than commercial claw-shaped dry and wet electrodes. The results of electroencephalogram (EEG, including visual evoked potential and cognitive engagement measurements) and electrooculogram showed that the MNAEs outperformed the commercial electrodes in terms of sensitivity, signal-to-noise ratio, and stability. The signal amplitude was enhanced by more than 39% - 44% over the commercial wet electrodes. The prepared electrodes demonstrate leading performance in terms of impedance characteristics, wearing comfort, and durability. This study paves the way for the development of high-performance, low-cost BCI dry electrodes and their practical applications in human-machine interface interactions.