Skin-inspired gradient hydrogel electrode keeps EEG signals sharp for over 14 hours

Noninvasive brain-computer interfaces promise to translate electrical activity from the scalp into commands for computers, but the electrodes that make this possible have long been caught in a design compromise. According to the researchers, current rigid or uniformly soft electrodes suffer from a mismatch with the scalp, causing motion artifacts and short operation times. A team reporting in npj Flexible Electronics says it has broken through this trade-off with a hydrogel electrode whose stiffness changes gradually from one end to the other, mimicking the layered structure of human skin.

The device, called a skin-mimetic adaptive gradient electrode, is soft at the interface with the scalp, where comfort and conformity matter most, and firm at the opposite end, where a solid connection to the electronic circuit is required.

The manufacturing approach behind the gradient relies on the Marangoni effect. By placing the hydrogel in a gradient temperature field, the team induced heterogeneous crosslinking, meaning the polymer network formed more densely in some regions than others.

The gradient design does more than tune stiffness. The crosslinking process also produces a gradient pore structure within the hydrogel, which the authors say enables sustained release of electrolyte. The authors link the gradient pore structure to sustained electrolyte release, which they associate with stable, high-quality recording over many hours of wear.

The electrode maintained stable, high-quality electroencephalographic recording for more than eight hours while the wearer moved freely, and for more than fourteen hours at rest. In a typing task used to gauge brain-computer interface function, accuracy stayed above 94 percent throughout the recording sessions.

The authors frame the advance as a demonstration of the potential of gradient-designed hydrogels for noninvasive BCIs in freely moving practicality.

Skin itself is the inspiration. The design is inspired by human skin's gradient structure, according to the researchers.

For now, the reported results establish that a gradient temperature field can induce heterogeneous crosslinking in a hydrogel, producing an electrode with gradual stiffness change and a gradient pore structure for sustained electrolyte release.

Subject of Research: A skin-mimetic hydrogel electrode with a stiffness gradient for long-term noninvasive brain-computer interface recording

Article Title: Skin-mimetic adaptive gradient electrode for ambulatory noninvasive brain-computer interfaces

Article References: Jiang, J., Chen, H., Huang, Z., Feng, Z., Zhou, S., Jia, H., Li, X., Huang, J., Xie, J., Liang, Y., Liang, Y., Tang, Z., Zhao, Z., Wei, W., Chen, H., Yang, L., Wang, H., Wang, J., Cao, S., … Lin, S. (2026). Skin-mimetic adaptive gradient electrode for ambulatory noninvasive brain-computer interfaces. npj Flexible Electronics. https://doi.org/10.1038/s41528-026-00650-5

Image Credits: AI Generated

DOI: 10.1038/s41528-026-00650-5

Keywords: brain-computer interface, hydrogel electrode, EEG, Marangoni effect, gradient stiffness, scalp electronics, motion artifacts, electrolyte release, wearable sensors, noninvasive BCI, Skin-mimetic, adaptive