On-scalp printing of personalized electroencephalography e-tattoos

This study introduces a full-head, on-scalp microjet printing technology for creating ultrathin, stretchable, self-drying EEG e-tattoos capable of high-fidelity electrophysiological monitoring on hairy scalps. The authors developed two biocompatible PEDOT:PSS-based inks—one optimized for low-impedance electrodes and one for high-conductivity interconnects—and paired them with a 5-axis robotic printing system guided by 3D head scans and a project-and-slice layout algorithm. Compared with conventional wet-gel EEG electrodes, the printed e-tattoos exhibited significantly lower and more stable contact impedance (<40 kΩ over 6 hours), superior skin conformability, strong mechanical adhesion, and robustness during motion. Performance was validated across multiple EEG modalities, including motor imagery and error-related potentials, demonstrating parity with gel electrodes while enabling long-term, comfortable, cap-free EEG acquisition.