| With the in-depth development of medical,neuroscience,cognitive psychology and artificial intelligence and other disciplines in-depth development,EEG as an effective means to obtain brain information has been applied to medical detection,clinical diagnosis and brain computer interface and many other areas.Electroencephalogram（referred to as EEG below）can be used to not only detect epilepsy,brain damage,meningitis and other diseases,but also to achieve the brain and brain interface to control wheelchairs,robots,aircraft and other external equipment.EEG acquisition is the primary assignment in EEG research,the current collection methods are mainly wet electrode,semi-wet electrode,active dry electrode,dry electrode and so on.Wet electrode is the main way to acquire EEG,but there are many deficiencies,such as the need to apply conductive media,the complex operation process,poor comfort,limited testing environment.In this paper,a semi-flexible EEG dry electrode-Ch/Au-TiO2 dry electrode（chitosan/gold nanoparticles/titanium dioxide nanotubes dry electrode）based on novel nano-materials was designed and fabricated for overcoming the deficiency of wet electrode.The preparation process is as follows: the gold nanoparticles were electrodeposited on the titanium substrate with multi-potential step technique,the array of titanium dioxide nanotubes were prepared by anodic oxidation,electrodeposit gold nanoparticles once more,finally coated with chitosan as a contact medium between dry electrode and scalp.The working mechanism of the electrode is as follows: chitosan is still an strong absorption under the low humidity to ensure that the dry electrode and the scalp contact tightly;gold nanoparticles combine with titanium dioxide nanotubes and scalp to achieve high-speed ion current and electron current conversion,thereby lower the contact resistance between the dry electrode and the scalp,achieving EEG collection standards.Three kinds of methods scanning electron microscopy,energy spectrum,X-ray diffraction have been used to observe and analyze the characterization of Ch/Au-TiO2 dry electrode,the results show that: titanium dioxide nanotubes array has grown neatly on the titanium thin sheet,their outer diameter is less than 50nm;various gold nanoparticles have been deposited at the base,the bottom and the surface of the titanium dioxide nanotubes;the dry electrode surface has formed a chitosan/gold nanoparticles-titanium dioxide nanotubes/gold nanoparticles-titanium multilayer film structure.In this paper,the impedance characteristics of the dry electrode on the electrolyte and skin were calculated and evaluated,the results show that the impedance between the dry electrode and the skin of Ch/Au-TiO2 is 169 ±33.0kΩ at 2.15 Hz and 67.4±8.9 kΩ at 100 Hz.Through the comparison experiment of dry and wet electrode EEG acquisition,under the state of closed eyes and open eyes,the mean linear correlations of the waveforms of all the EEG signals were 88% and 89% respectively.By analyzing frequency domain of EEG signals collected by dry and wet electrodes under alpha wave and SSVEP EEG paradigm,achieve similar results,both show obvious characteristics.In summary,the dry electrode can achieve the standard wet electrode EEG acquisition result,the acquired EEG signal is stable,accurate and reliable. |
