Design, fabrication, and characterization of flexible electrodes for recording brain electrical activity

Abstract

Electroencephalography (EEG) is an essential technique for analyzing brain activity, widely used in medical diagnostics, brain-computer interfaces, and neuroergonomics. However, conventional electrodes, often wet, rigid or semi-flexible, have limitations in terms of comfort, morphological adaptability, and signal stability. This thesis aims to design, fabricate, and characterize new high-performance flexible electrodes that optimize EEG signal quality, flexibility, comfort, and ergonomics In this study, several conductive polymer composites were explored, including SEBS, SEBS MA, and EVA-based materials incorporating carbon nanotubes and carbon black. These materials were selected and optimized to combine electrical conductivity, flexibility, and mechanical stability. The fabrication of the multi-branched electrode configuration was carried out through chemical dissolution in a solvent, followed by mechanical compression, ensuring optimal integration at the scalp interface. The characterization of the electrodes was structured around three main aspects: - Mechanical properties: Evaluation of the storage modulus as a function of temperature to assess the flexibility and resistance of the composites. - Electrical properties: Analysis of conductivity and electrochemical impedance to optimize the quality of skin contact. - EG performance: Comparison of recorded signals with those obtained using commercial flexible electrodes to evaluate signal fidelity. The results demonstrate that SEBS-MA/8%wtCNT/2%wtCB-based flexible electrodes offer a promising alternative to conventional electrodes, providing an optimal balance between flexibility and conductivity. Furthermore, an in-depth analysis of EEG signals highlights improved flexibility and enhanced signal stability, particularly during prolonged recordings. These advances open new perspectives for portable EEG, particularly in the context of digital health applications and individualized monitoring, by enabling the development of flexible electrodes suited for the continuous and personalized recording of brain activity. They also represent an important driver for brain–computer interfaces, by meeting the growing demands of applied neuroscience.

Date	13 Apr 2026
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Ilyass Tabiai (Supervisor) & Éric David (Co-supervisor)