Fabrication Strategies and Performance Optimization Strategies of Flexible Brain–Computer Interface Electrodes

Brain-computer interface (BCI) provides a direct communication pathway between the brain and external devices and has been applied in neurological disease treatment, motor rehabilitation, and human-computer interaction. Electrodes play essential roles in recording and modulating neural signals, and their performance directly affects signal quality, spatial resolution, and long-term stability. Traditional rigid electrodes suffer from mechanical mismatch with brain tissue, which may induce tissue damage and reduce recording stability during long-term implantation. Flexible electrodes offer improved mechanical compatibility and have emerged as promising alternatives. Recent advances in materials science, micro/nanofabrication, and interface engineering have enhanced the electrical, mechanical, and biological performance of flexible BCI electrodes. This review summarizes neural signal characteristics, electrode requirements, fabrication strategies, and performance optimization approaches. The major fabrication methods include microelectromechanical systems (MEMS), printing and transfer, laser processing and thermal drawing, and electrospinning, while deposition and surface modification are discussed as functional enhancement strategies. The review also highlights challenges associated with large-scale manufacturing, long-term stability, and the physical and clinical limitations of invasive, semi-invasive, and noninvasive electrodes. Future directions involving intelligent, wireless, and self-powered systems, together with clinical translation, are discussed to promote the development of flexible electrodes for BCI applications.