In-service characterization of a polymer wick-based quasi-dry electrode for rapid pasteless electroencephalography

A novel quasi-dry electrode prototype, based on a polymer wick structure filled with a specially designed hydrating solution is proposed for electroencephalography (EEG) applications. The new electrode does not require the use of a conventional electrolyte paste to achieve a wet, low-impedance scalp contact. When compared to standard commercial Ag/AgCl sensors, the proposed wick electrodes exhibit similar electrochemical noise and potential drift values. Lower impedances are observed when tested in human volunteers due to more effective electrode/skin contact. Furthermore, the electrodes exhibit an excellent autonomy, displaying an average interfacial impedance of 37±11 kΩ cm2 for 7 h of skin contact. After performing bipolar EEG trials in human volunteers, no substantial differences are evident in terms of shape, amplitude and spectral characteristics between signals of wick and commercial wet electrodes. Thus, the wick electrodes can be considered suitable to be used for rapid EEG applications (electrodes can be prepared without the presence of the patient) without the traditional electrolyte paste. The main advantages of these novel electrodes over the Ag/AgCl system are their low and stable impedance (obtained without conventional paste), long autonomy, comfort, lack of dirtying or damaging of the hair and because only a minimal cleaning procedure is required after the exam.P. Fiedler and J. Haueisen acknowledge financial support by the German Federal Ministry of Education and Research (03IPT605A) and the Free State of Thuringia by funds of the European Social Fund (2015FGR0085). P. Fiedler, P. Pedrosa, H. Gaspar, B. Vasconcelos, C. Fonseca, and J. Haueisen acknowledge financial support by the German Academic Exchange Service (D/57036536). C. Fonseca acknowledges funds from FCT Portuguese Foundation for Science and Technology, project PTDC/SAU-ENB/116850/2010, and J. M. Nobrega acknowledges FEDER funds through the COMPETE 2020 Programme and National Funds through FCT under project UID/CTM/50025/2013. P. Pedrosa, P. Fiedler, B. Vasconcelos, J. Haueisen and C. Fonseca acknowledge financial support by the Seventh Framework Programme, (Grant / Award Number: 'IAPP-610950').