Soft, curved electrode systems capable of integration on the auricle as a persistent brain-computer interface

Area of Science:

• Biomedical Engineering
• Neuroscience
• Materials Science

Background:

• Noninvasive electroencephalogram (EEG) recording is crucial for neurological disorder diagnosis and brain-computer interfaces (BCIs).
• Current EEG electrode technologies face limitations in continuous use due to skin irritation and degradation of interface properties.

Purpose of the Study:

• To develop and evaluate novel soft, foldable fractal mesh electrodes for chronic, high-fidelity, and comfortable EEG acquisition.
• To assess the mechanical, electrical, and biocompatible properties of these electrodes for long-term skin integration.

Main Methods:

• Fabrication of soft, foldable electrodes in open, fractal mesh geometries.
• Mechanical and computational modeling to understand integration on irregular skin surfaces (auricle, mastoid).
• Biocompatibility and wearability assessments using cell-level tests and thermal imaging.
• Long-term EEG recording (2 weeks) during various daily activities.

Main Results:

• Electrodes demonstrated excellent conformability and intimate integration on complex skin topologies without significant loading.
• Biocompatibility and wearability were confirmed, with no significant skin irritation observed.
• High-fidelity EEG signals were consistently recorded for 2 weeks, even during vigorous activities like exercise, swimming, sleeping, and bathing.
• Successful demonstrations of a steady-state visually evoked potential (SSVEP)-based BCI text speller and P300 event-related potential elicitation.

Conclusions:

• The novel fractal mesh electrodes provide a breakthrough solution for comfortable, long-term, and high-fidelity noninvasive EEG monitoring.
• These electrodes significantly advance the potential for continuous neurological monitoring and practical brain-computer interface applications.