On Dec. 2, 2024, a team of researchers reported they had conducted on-scalp digital printing of custom-designed, temporary-tattoo-like sensors, a groundbreaking advancement in noninvasive brain-monitoring technologies. Traditional electroencephalography (EEG) systems involve time-consuming manual electrode placement, conductive liquid gels, and cumbersome cables, which are prone to signal degradation and discomfort during prolonged use.

These skin-conformal EEG e-tattoo sensors enable comfortable, long-term, high-quality brain activity monitoring without the discomfort associated with traditional EEG systems. Using individual 3D head scans, custom sensor layout design, and a 5-axis microjet printing robot, created EEG e-tattoos with precise, tailored placement over the entire scalp. The inks for electrodes and interconnects have slightly different compositions to achieve low skin contact impedance and high bulk conductivity, respectively. After printing and self-drying, the inks form conductive, stretchable, and breathable thin films that ensure high signal fidelity, even over extended periods.

This technology paves the way for non-invasive, high-performance, and user-friendly brain monitoring that will enhance both patient care and the understanding of the human brain. On-scalp printed ultrathin e-tattoos could play a pivotal role in developing BCIs for various industries, including prosthetics, virtual reality (VR), and human-robot teaming. The study was published in Cell Biomaterials.