Engineering Skin–Electrode Interfaces for High-Fidelity, Long-Term Electrophysiological Monitoring

High-fidelity electrophysiological signal acquisition is essential for long-term health monitoring, human–machine interaction, and intelligent prosthetics. Conductive hydrogels have become the gold-standard commercial electrode materials due to their excellent adhesion, stretchability, ionic conductivity, and biocompatibility. However, conventional preformed hydrogel electrodes face two major challenges in real-world applications: poor conformability on hairy areas such as the scalp and insufficient breathability leading to sweat accumulation and skin irritation. To address these limitations, skin–electrode interface engineering has been proven to be an effective strategy. This Spotlight on Applications first outlines the fundamental evaluation metrics for electrophysiological electrodes, including interfacial impedance, signal-to-noise ratio, mechanical properties, adhesion, breathability, and dynamic reliability. We then review recent advances from our group in phase-change hydrogels that enable rapid gelation and seamless penetration of hair barriers, as well as breathable architectures such as self-adhesive nanofilms and sweat-activated hydrogel nanomeshes that maintain long-term signal fidelity. Typical applications are highlighted, ranging from continuous health monitoring to interactive human–centric interfaces. Finally, we discuss remaining challenges and future directions toward closed-loop, biodegradable, and personalized electrophysiological platforms.