Fig. 1. On-skin paintable biogel interface for high-fidelity EEG recording.

(A) Schematic illustration showing the concept of on-skin paintable biogel for hairy scalp for EEG recording (e.g., typical EEG signal and SSVEP). (B and C) Photographs and infrared camera images of biogel at high temperature (B) and room temperature (C), demonstrating the transition of biogel between fluidic state at high temperature and solid-like gel state at low temperature. (D and E) Photographs of direct painting biogel ink on skin (D) and in situ gelatinized adhesive biogel on skin after 2 to 3 min (E), showing its on-skin painting capability and good adhesion with skin. (F) Photograph and optical image of peeled-off on-skin painted biogel (upper) and the replicated skin texture structure on its surface (lower), showing its conformal contact with the corrugated skin surface. (G and H) Optical images of biogel painted on the hairy scalp (G) and clean scalp after removing biogel by water (H), showing its good contact with scalp with no hair interference and its easy removal. (I) Photographs showing the superior attachment of Ag/AgCl electrodes with painted biogels compared to commercial EEG paste.