In Situ Formation of Mechanical Interlocking Skin and Electronics Interfaces through Dual-Phase Transition of Conductive Materials

The increasing demand for daily health monitoring has accelerated the development of wearable devices. However, conventional wearables, typically based on rigid materials and external fixation methods, suffer from interfacial instability during dynamic motion and heavy sweating, leading to signal distortion and device delamination. Skin-like wearable electronics and in situ fabrication strategies have emerged to improve conformability and signal stability. However, challenges remain in achieving a stable skin-device interface and reliable performance under dynamic conditions using simplified fabrication methods. Here, we present a flexible multiparameter monitoring device that integrates with the skin through a skin-electronics interface undergoing a dual-phase transition from hydrogel to liquid and subsequently to a solid state via in situ heating and photonic crosslinking. This transition forms mechanically interlocked structures that ensure robust adhesion and stable skin contact even under humid and high-acceleration conditions. Rapid curing enabled by an integrated heating layer and optical waveguide reduces the fabrication time to 1 min, allowing efficient on-demand deployment. The device achieves stable monitoring of ECG, PPG, acceleration, and temperature signals and supports Bluetooth data transmission under accelerations up to 11 g, as well as during swimming and showering. Furthermore, machine-learning-based motion recognition and individual identification models achieve 100% accuracy. This work advances in situ-fabricated wearable electronics by improving fabrication efficiency, interfacial robustness, and environmental adaptability, providing a promising platform for portable physiological monitoring.