Hairlike EEG electrode for long-term non-invasive brain monitoring

• A hairlike device has been developed for long-term, non-invasive monitoring of the brain’s electrical activity.¹
• The lightweight, flexible electrode attaches directly to the scalp and delivers stable, high-quality EEG recordings.^{1 1}

Weekly enrichment (2026-07-20)

• The underlying study, “Stick-and-play bioadhesive hairlike electrodes for chronic EEG recording on human,” was published in npj Biomedical Innovations (2025) by a Penn State–led team (Salahuddin Ahmed, Marzia Momin, Tao Zhou and colleagues).²³
• The device is built by direct-ink-writing (DIW) 3D printing into four layers: a central conducting-polymer hydrogel electrode of PEDOT:PSS blended with hydrophilic polyurethane, sandwiched between two PDMS encapsulation layers, with a printed bioadhesive ring securing it to the scalp.²
• The hydrogel electrode material has high electrical conductivity (>11 S cm⁻¹) and high stretchability (~400%), while the assembled hairlike device stretches to an ultimate strain of about 200%.²
• Geometry mimics a hair strand: the scalp interface dot is 1.5 mm in diameter and the hairlike interconnect is 300 µm wide, and the print can be dyed to match different hair colors for discreet wear.²
• On the hairy scalp the device showed electrode–skin impedance of 14.83 kΩ at 100 Hz and 16.72 kΩ at 10 Hz — lower than a commercial gold electrode with EEG paste — and impedance stayed stable through 12 and 24 hours of continuous wear.²
• Mechanical robustness was confirmed over 10, 50, and 100 cyclic tensile loading cycles (10% max strain) with no impedance degradation, so the electrode stayed put during hair combing and cap donning/removal.²
• Functional recording: in two healthy subjects with dense hair, occipital recordings captured a clear ~10 Hz alpha peak in the eyes-closed state that vanished eyes-open, with fidelity comparable to (and sometimes exceeding) gold electrodes; signals used an Intan controller at 20 kHz sampling with a 60 Hz notch and 1–40 Hz band-pass filter (IRB protocol 00022808).²
• BCI/clinical implication: gel-free, session-to-session-stable scalp electrodes suited to chronic EEG and brain–machine interfaces; current limitations are a still-wired readout and validation in only two subjects, with wireless operation noted as future work.²³

Footnotes

1. https://www.sciencedaily.com/releases/2025/05/250502133950.htm ↩ ↩² ↩³

2. https://doi.org/10.1038/s44385-025-00009-x ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

3. https://www.eurekalert.org/news-releases/1082585 ↩ ↩²