Surface and Interfacial Engineering toward Durable Mechanically Coupled Flexible Electronics.

Mechanically coupled flexible electronics enable real-time, conformal monitoring of diverse mechanical signals. However, their operation in dynamic and complex environments places stringent demands on surface and interfacial reliability. Insufficient interfacial functionalization, unstable contact, as well as mechanical and electrical mismatch have emerged as key factors limiting device durability, signal fidelity, and practical deployment. This review summarizes the fundamental surface and interfacial challenges in mechanically coupled flexible electronics from the perspective of surface and interfacial physics, including contact instability, interfacial failure, stress concentration, and environmental degradation. To address these challenges, various material systems designed to enhance surface and interfacial performance are systematically reviewed, focusing on surface chemical modification, interfacial chemical engineering, as well as processing- and manufacturing-enabled physical reinforcement approaches. In addition to isolated chemical or physical methods, multiscale surface and interface architectures are further engineered through bioinspired interfaces, mechanical interlocking, adhesive interlayers, buffering layers, percolating interpenetrating networks, and homogeneous structural design. The resulting improvements in reliability and functional stability are illustrated through representative applications across multiple operating scenarios. Finally, current challenges and future directions are outlined in terms of standardization, environmental robustness, manufacturing repeatability, and large-scale implementation.