A Flexible Fractal Electrode With EMI Shielding and Long‐Term Impedance Stability for High‐Fidelity Brain‐Computer Interfaces

ABSTRACT

Brain electrodes constitute critical components of brain‐computer interfaces (BCIs), facilitating the acquisition of neural signals and enabling direct interaction with external devices. However, brain electrodes are often hindered by susceptibility to electromagnetic interference (EMI) and unstable interfacial impedance, constraining their performance and reliability in BCI applications. To address these challenges, we introduce a novel flexible fractal electrode that simultaneously integrates robust EMI shielding capability with long‐term interfacial impedance stability. The flexible fractal electrode incorporates a biomimetic fractal architecture that effectively mitigates motion artifacts and maintains a stable interface impedance over eight hours. To enhance EMI resilience, second‐order fractal discretization structures are strategically incorporated into the electrode design. Compared with the continuous structure, this fractal discretization reduces EMI absorption by 57 dB at 10 GHz (from 74 to 17 dB) and by 59 dB at 11 GHz (from 61 to 2 dB). We further validated the electrode's functionality within a virtual reality‐enabled BCI system, achieving classification accuracies of 92% for visual evoked potentials and 90.7% for emotion recognition. By concurrently addressing impedance stability, and EMI resilience through structural design, the flexible fractal electrode establishes a promising pathway toward practical, high‐fidelity BCIs.