The Challenging Scalp-Electrode Interface and the Evolution of Materials and Electrode integrated ICTs for Electroencephalography

Abstract

Electroencephalography (EEG) is a non-invasive technique used to measure theelectrical activity of the brain. The use of EEG is very important for the diagnosis oftraumatic brain events and mental states such as injury, stroke, depression and manyothers including the COVID-19 brain fog syndrome. The quality of EEG signals largelydepends on the nature of the interface between the surface of the electrode material andthe surface of the scalp from where the electrical brain signals are acquired. The scalpsurface is composed of an epidermic substrate with hair, grease, dirt, dandruff, skinpeels and eventually many different hair products. The electrodes must combine severalproperties including electrical conductivity, mechanical strength, biocompatibility andcorrosion resistance. They also must be manufactured with shapes designed toovercome the inherently complex nature of the scalp-electrode interface. This reviewreports the latest advances in the design of materials, surface coatings, conductive gelsand information and communication technologies being developed to increase thequality of measurement of brain electrical signals in EEG protocols.