Novel Multipin Electrode Cap System for Dry Electroencephalography

Abstract

Current usage of electroencephalography (EEG) is limited to laboratory environments. Self-application of a multichannel wet EEG caps is practically impossible, since the application of state-of-the-art wet EEG sensors requires trained laboratory staff. We propose a novel EEG cap system with multipin dry electrodes overcoming this problem. We describe the design of a novel 24-pin dry electrode made from polyurethane and coated with Ag/AgCl. A textile cap system holds 97 of these dry electrodes. An EEG study with 20 volunteers compares the 97-channel dry EEG cap with a conventional 128-channel wet EEG cap for resting state EEG, alpha activity, eye blink artifacts and checkerboard pattern reversal visual evoked potentials. All volunteers report a good cap fit and good wearing comfort. Average impedances are below 150 kΩ for 92 out of 97 dry electrodes, enabling recording with standard EEG amplifiers. No significant differences are observed between wet and dry power spectral densities for all EEG bands. No significant differences are observed between the wet and dry global field power time courses of visual evoked potentials. The 2D interpolated topographic maps show significant differences of 3.52 and 0.44% of the map areas for the N75 and N145 VEP components, respectively. For the P100 component, no significant differences are observed. Dry multipin electrodes integrated in a textile EEG cap overcome the principle limitations of wet electrodes, allow rapid application of EEG multichannel caps by non-trained persons, and thus enable new fields of application for multichannel EEG acquisition.

Novel passive ceramic based semi-dry electrodes for recording electroencephalography signals from the hairy scalp

“…For the SSVEPs paradigm, the average temporal crosscorrelation between semi-dry/wet electrodes was 0.937 ± 0.027 (n=10) across the nine recording electrode pairs with ten subjects, with the highest at Oz (0.993) and the lowest at C3 (0.904) ( Figure 10B). The correlation results suggest that signals of the semi-dry and wet electrodes pairs were highly similar, and the correlation coefficients of all positions matches or exceeds the reported levels of most existing dry electrodes, ranging from 0.32 to 0.94 [17,25,36,[41][42][43][44][45]. Furthermore, the correlation coefficients of all positions were around 0.9, suggesting that the semi-dry electrodes' performances were robust against factors such as hair thickness.…”

Ag:TiN‐Coated Polyurethane for Dry Biopotential Electrodes: From Polymer Plasma Interface Activation to the First EEG Measurements

“…Therefore, the signals were filtered using a bandpass with cut‐off frequencies at 1–40 Hz and automatically selected data sequences of 10 s were analyzed. Further details about the EEG monitoring and analysis procedures can be found elsewhere …”

“…Moreover, incorrect and/or uncomfortable skin contact may arise due to the stiff nature of some of the proposed base materials (aluminium, [3] steel, [11,12] silicon, [13,14] titanium, [15] and polycarbonate [16] ), and designspecific conceptual problems (micro-needle electrodes [13,14] and rigid planar plates/disks unable to interfuse the hair layer [15,16] ). Hence, in order to reduce some of the referred drawbacks, several authors focused not only on the development of new electrode designs, which allow an effective hair interfusion, [17][18][19][20] but also on the use of more compliant base materials, such as textiles [21] and, above all, flexible polymers. [22][23][24][25] Thermoplastic polyurethanes (TPU) have been extensively applied in several fields that range from technical coatings to biomedical applications, [26][27][28] due to their excellent balance between mechanical properties (high flexibility, dependent on the composition), chemical barrier behavior, soft tact, and biocompatibility, [29,30] thus being appropriate to be used as biopotential electrode base material.…”

Active Electrodes for Wearable EEG Acquisition: Review and Electronics Design Methodology

“…Silver-coated polymer bristles [14], dry foam electrodes [15], polymer electrodes made of polydimethylsiloxane (PDMS) [16] or polyurethane [17], and comb-shaped polymer electrodes [18] can provide soft contact to the skin while still providing low electrode impedance in the order of 20kΩ to 500kΩ, being promising alternatives for wearable EEG applications.…”