Stretchable, Hair-compatible, Adhesive and Paintable EEG Electrodes (SHAPE)

Long-term stable electroencephalography (EEG) recording from the hairy scalp is essential for understanding brain function, diagnosing neurological disorders, and brain-computer interfaces (BCI). While conductive liquid gel electrodes offer reliable signals, they suffer from dehydration over time and are difficult to connect. Recently, on-scalp formed hydrogel electrodes have been developed to achieve stable electrical contact with the skin for long-term EEG; however, their millimeter-range thickness makes them less breathable and hard to remove. We introduce a stretchable, hair-compatible, adhesive, and paintable EEG electrode (SHAPE) based on PEDOT:PSS and additives. SHAPE is viscous enough to be applied by hand using a brush onto the hairy scalp and self-dries into micrometer-thin conductive membranes, forming a low-impedance, long-term stable interface with the skin while remaining breathable and easy to remove. Additionally, SHAPE-coated metal foil can adhere reliably to SHAPE electrode even during sleep, enabling stable EEG recording for up to 48 hours. SHAPE effectively records high-quality visual-evoked potentials, including P300 and steady-state visual evoked potentials (SSVEP) for BCI.