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Flexible Multi-Layer Semi-Dry Electrode for Scalp EEG Measurements at Hairy Sites

by 1,†, 1,†, 1, 2 and 1,*
School of Electronic and Information Engineering, South China University of Technology, Guangzhou 510641, China
School of Computer Science, The University of Sydney, Sydney 2006, Australia
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Micromachines 2019, 10(8), 518;
Received: 3 July 2019 / Revised: 26 July 2019 / Accepted: 31 July 2019 / Published: 4 August 2019
(This article belongs to the Special Issue Printable and Flexible Electronics for Sensors)
One of the major challenges of daily wearable electroencephalogram (EEG) monitoring is that there are rarely suitable EEG electrodes for hairy sites. Wet electrodes require conductive gels, which will dry over the acquisition time, making them unstable for long-term EEG monitoring. Additionally, the electrode–scalp impedances of most dry electrodes are not adequate for high quality EEG collection at hairy sites. In view of the above problems, a flexible multi-layer semi-dry electrode was proposed for EEG monitoring in this study. The semi-dry electrode contains a flexible electrode body layer, foam layer and reservoir layer. The probe structure of the electrode body layer enables the electrode to work effectively at hairy sites. During long-term EEG monitoring, electrolytes stored in the reservoir layer are continuously released through the foam layer to the electrode–scalp interface, ensuring a lower electrode–scalp contact impedance. The experimental results showed that the average electrode–scalp impedance of the semi-dry electrode at a hairy site was only 23.89 ± 7.44 KΩ at 10 Hz, and it was lower than 40 KΩ over a long-term use of 5 h. The electrode performed well in both static and dynamic EEG monitoring, where the temporal correlation with wet electrode signals at the hairy site could reach 94.25% and 90.65%, respectively, and specific evoked EEG signals could be collected. The flexible multi-layer semi-dry electrode can be well applied to scalp EEG monitoring at hairy sites, providing a promising solution for daily long-term monitoring of wearable EEGs. View Full-Text
Keywords: EEG; semi-dry electrode; flexible electrode; multi-layer EEG; semi-dry electrode; flexible electrode; multi-layer
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MDPI and ACS Style

Hua, H.; Tang, W.; Xu, X.; Feng, D.D.; Shu, L. Flexible Multi-Layer Semi-Dry Electrode for Scalp EEG Measurements at Hairy Sites. Micromachines 2019, 10, 518.

AMA Style

Hua H, Tang W, Xu X, Feng DD, Shu L. Flexible Multi-Layer Semi-Dry Electrode for Scalp EEG Measurements at Hairy Sites. Micromachines. 2019; 10(8):518.

Chicago/Turabian Style

Hua, Haoqiang, Wei Tang, Xiangmin Xu, David D. Feng, and Lin Shu. 2019. "Flexible Multi-Layer Semi-Dry Electrode for Scalp EEG Measurements at Hairy Sites" Micromachines 10, no. 8: 518.

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