A systematic evaluation of EEG electrode geometry for enhanced signals: an experimental approach

The advancement of neural recording technologies is critical for improving our understanding of brain function and enhancing the efficacy of brain–computer-interfaces. Electroencephalography (EEG), is a non-invasive technique for recording brain electrical activity via scalp electrodes. The geometry and material of electrodes significantly influence signal quality and noise. Here, we investigated the effect of electrode geometry on EEG performance. Time-domain analysis of the selected nanostructured pin-shaped gold-based dry electrodes, showed an in-phase conductance of 0.9 mS (effective resistance ~ 1.1 kΩ) without applied pressure. Also, impedance spectroscopy revealed a reduced electrode–skin impedance of ~ 300 kΩ at 100 Hz, with the bulk resistance of ~ 1.95 Ω, consistent with expected interface behavior. EEG performance was evaluated using steady-state visually evoked potential (SSVEP) and alpha modulation paradigms. In the SSVEP task (15 Hz stimulus), dry electrodes achieved a signal-to-noise ratio of 1.27 dB, comparable to 1.30 dB for standard wet Ag/AgCl electrodes. Alpha modulation analysis showed alpha-ratio of 2.43 a.u. vs. 1.83 a.u. for wet electrodes, and random forest classifier which completely distinguished eyes-open/eyes-closed states, confirmed the high-fidelity signal capturing. The scalable and cost-effective fabrication process offers long-term stability for clinical and research EEG, paving the way for future innovations in neural recording devices.