Fabrication of chitosan/Au-TiO₂ nanotube-based dry electrodes for electroencephalography recording

In this paper, we describe a method for fabricating dry electrodes for use in recording electroencephalograms (EEGs), which are based on the use of chitosan (Ch), gold (Au) particles, and titanium dioxide (TiO₂) nanotube arrays deposited on titanium (Ti) thin sheets. The samples were characterized by scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and EEG signal collection. The TiO₂ nanotube arrays were grown on the Ti thin sheet by an electrochemical anodic oxidation method. The Au particles were deposited on the bottom and surface layers of the TiO₂ nanotube array using an electrochemistry-based multi-potential step technology. The fabricated dry Ch/Au-TiO₂ electrodes have an efficient conversion interface for ion current/electron current, a high biocompatible contact surface, and a fast electron transfer channel. To confirm that the Ch/Au-TiO₂ layer can be used in dry EEG electrodes, the impedance spectra of the electrodes in solution and skin were analyzed. The mean impedance values for skin were found to be approximately 169 ± 33.0 kΩ at 2.15 Hz and 67.4 ± 8.9 kΩ at 100 Hz. In addition, EEG signals from the forehead and sites with hair were collected using both the dry Ch/Au-TiO₂ electrode and a wet Ag/AgCl electrode for comparison purposes. It was found that high quality EEG signal recordings could be obtained using the dry electrodes. The fact that electrolytes are not required means that the electrodes are suitable for use in long-term bio-potential testing. - Graphical abstract: We prepared dry electrodes based on chitosan, Au micro/nano-particles, and TiO₂-nanotube-coated Ti films for use in the accurate monitoring of EEG bio-potentials on the forehead and sites with hair. - Highlights: • Chitosan (Ch)/Au-TiO₂/Ti thin films have been successfully prepared. • The Ch/Au-TiO₂/Ti thin films were used as dry electrodes and applied to EEG monitoring. • The EEG signal quality from the dry electrode is similar to that from wet electrode. • The Ch and Au-TiO₂ nanotubes improved the interfacial stability and electron flow. • The dry electrode has applications in the recording of various bio-potentials.