Inexpensive Fabrication of Stretchable Dry EEG Electrodes Using Well Known Dry Film Photoresists

With the discovery of new brain diseases, clinical tests for electroencephalogram (EEG) have become more important. Commercially available wet Ag/AgCl electrodes apply conductive gel to the scalp of the subject before recording of the EEG signal. After applying the gel, the impedance is gradually decreased and the EEG signal can be received. In the long term, the conductive gel dries and the impedance increases again. The gel causes skin irritations in the course of time as well. Therefore, Ag/AgCl electrodes are inappropriate to be used in long term measurements. Dry electrodes are introduced as a gel free no preparation alternatives of wet electrodes in the literature. In this manuscript, a novel flexible and stretchable dry EEG electrode is demonstrated. The electrode features four conductive pads to contact the scalp. The stretchable electrodes are embedded in elastomer. A flexible polyimide layer supports the conductive electrodes to increase mechanical reliability in elongations. The electrodes are produced using a relatively straightforward and cost-effective fabrication method namely commercial dry film photolithography. The EEG signal is recorded with the fabricated electrode as well as wet Ag/AgCl electrodes. The received signals from the two electrodes feature relatively high correlation.