Characterizing contact impedance, signal quality and robustness as a function of the cardinality and arrangement of fingers on dry contact EEG electrodes

Continuous monitoring of patients´ electroencephalography (EEG) outside of clinical settings will be valuable for detecting the onset of medical conditions such as epilepsy, as well as for enabling patients with physically disabling conditions like amyotrophic lateral sclerosis (ALS) to communicate using a brain-computer interface (BCI). This requires the development of a wearable dry-contact EEG system that takes into account not only the signal quality but also the robustness of the system for everyday use. To this end, we investigate whether certain designs of dry electrodes lend themselves to better characteristics overall with respect to these factors. Five different metallic finger-based dry electrodes were designed and scalp electrode impedance was used to compare them under varying capping conditions, followed by an evaluation of how well they captured steady state visually evoked potentials (SSVEP). Our findings indicate that configurations with a relatively low density of fingers can more effectively penetrate through hair on the scalp and are more robust to varying conditions. This was confirmed to be a statistically significant observation through a one-sided paired t-test that resulted in a p-value <; 0.004.