Evaluation of flexible multi-claw and multi-channel semi-dry electrodes for evoked electroencephalography recording

Abstract

Polydimethylsiloxane (PDMS) filled with copper sulphate crystals, TiO2 nanoparticles, and carbon nanotubes (CNTs) were used as flexible matrices to fabricate semi-dry multi-claws and 19-channel electrodes for electroencephalography (EEG) recording. Good adhesion of the flexible Cu-TiO2-CNT@PDMS substrate and internal CNT conductive network together reduce the contact resistance between EEG electrode and the scalp. The scalp-contact impedance of the flexible matrix was < 5 kΩ when coated with conductive gel, whereas the poured semi-dry electrodes were < 20 kΩ in the hair area. The correlation coefficient between the spontaneous EEG signals synchronously collected by commercial Ag/AgCl and the semi-dry electrodes was greater than 99.3%. With these flexible electrodes, the amplitude of the α-rhythm reached 6 μV in the frequency domain, the service life was more than 3 months, and the SNR of the EEG signal reached 8–12 dB in steady-state visual evoked potential. For the 19-channel high-density electrode, the real-time EEG impedance of each channel was < 26.3 kΩ, and the SNR of the EEG at rest was 6.3 dB. The high-density electrode showed the response of α- and β-rhythms in auditory evoked EEG, and the regularity of these two rhythms was extracted from feedback EEG signals of speech and semantic stimuli. The Cu-TiO2-CNT@PDMS matrix and its semi-dry electrodes provide new materials and new processes for the preparation of flexible semi-dry electrodes and offer a new strategy for the preparation of integrated high-density electrodes.