Noninvasive electroencephalogram sensors based on all-solution-processed trapezoidal electrode array

Abstract

Conventional wet electrodes, such as a silver/silver chloride electrode, are limited for electroencephalogram (EEG) sensors directly attached to the scalp with existing hair due to their incomplete contact and increased impedance. In this study, an all-solution-processed trapezoidal electrode array is demonstrated for highly sensitive and reliable detection of EEG signals even when in direct contact with the scalp. The proposed noninvasive EEG sensors based on nanocomposites consisting of single-wall carbon nanotube random networks incorporated into a gelatin matrix exhibited a relatively low contact impedance of 11.16 × 102 Ω and a high sensitivity of 14.81 dB regardless of existing hair for real-time EEG recording without conductive gels or electrolytes. Furthermore, the origin of such advances induced by the soft and conductive electrode array is investigated by analyzing the effective contact area and signal-to-noise ratio on different scalp positions from 20 different subjects. A trapezoidal EEG electrode penetrates the dense hair and bypasses the hair shaft owing to its deformable shape induced by the soft and flexible nanocomposite film.