Validation of Soft Multipin Dry EEG Electrodes

Abstract

Current developments towards multipin, dry electrodes in electroencephalography (EEG) are promising for applications in non-laboratory environments. Dry electrodes do not require the application of conductive gel, which mostly confines the use of gel EEG systems to the laboratory environment. The aim of this study is to validate soft, multipin, dry EEG electrodes by comparing their performance to conventional gel EEG electrodes. Fifteen healthy volunteers performed three tasks, with a 32-channel gel EEG system and a 32-channel dry EEG system: the 40 Hz Auditory Steady-State Response (ASSR), the checkerboard paradigm, and an eyes open/closed task. Within-subject analyses were performed to compare the signal quality in the time, frequency, and spatial domains. The results showed strong similarities between the two systems in the time and frequency domains, with strong correlations of the visual (ρ = 0.89) and auditory evoked potential (ρ = 0.81), and moderate to strong correlations for the alpha band during eye closure (ρ = 0.81–0.86) and the 40 Hz-ASSR power (ρ = 0.66–0.72), respectively. However, delta and theta band power was significantly increased, and the signal-to-noise ratio was significantly decreased for the dry EEG system. Topographical distributions were comparable for both systems. Moreover, the application time of the dry EEG system was significantly shorter (8 min). It can be concluded that the soft, multipin dry EEG system can be used in brain activity research with similar accuracy as conventional gel electrodes.

Me-Doped Ti–Me Intermetallic Thin Films Used for Dry Biopotential Electrodes: A Comparative Case Study

“…Conversely, the Ti-Al system deposited on PU substrates exhibited very high values of contact impedance for all tested frequencies. Notwithstanding the differences between the Ti-Me films and the conventional Ag/AgCl reference electrodes, the observed level of interfacial impedance does not necessarily affect the quality of the signals recorded with state-of-the-art biosignal amplifiers [13,37,65]. The stability of the interfacial contact and the balance between the electrode pair (reduced variability) and its reproducibility over time [66,67] are equally important aspects in the development of reliable biopotential dry electrodes.…”

“…To overcome the limitations of conventional gel-based electrodes, improved hydrogels [2,[5][6][7] and semi-dry [8][9][10][11] and dry electrodes [3,[12][13][14] have been proposed and increasingly used in recent years. Semi-dry electrodes have been suggested as a compromise between conventional gel-based and completely dry electrodes.…”

“…On bare skin, dry electrodes normally exhibit higher contact impedances than the conventional gel-based wet electrodes, but when combined with state-of-the-art electronics, following a short settling time, the electrodes can record bioelectric signals with signal-to-noise ratios similar to the gel electrodes. Moreover, the use of soft, flexible substrate materials fosters the adaptivity of the electrode to the body shape, increasing the long-term wearing comfort and improving the electrode-skin contact, especially during body motion [3,[12][13][14]. Dry electrodes are thus user-friendly solutions offering improved applicability without the need for hydrogels or other types of wet electrolytes [3,[12][13][14][15][16][17].…”

“…Moreover, the use of soft, flexible substrate materials fosters the adaptivity of the electrode to the body shape, increasing the long-term wearing comfort and improving the electrode-skin contact, especially during body motion [3,[12][13][14]. Dry electrodes are thus user-friendly solutions offering improved applicability without the need for hydrogels or other types of wet electrolytes [3,[12][13][14][15][16][17].…”

“…Production cost, complexity, and reproducibility as well as constraints in electrode shape, mechanical characteristics, and durability have limited these materials to prototypes thus far. Coated elastomers have been suggested primarily with Ag [24], Ag/AgCl [11,13,16,25], gold (Au) [26], and titanium (Ti) [17,27,28]. While silverbased coatings are known to provide excellent electrochemical and thus bioelectric signal characteristics, their biocompatibility in long-term repetitive applications remains an often discussed and questioned limitation [29].…”