Harnessing cracks in metal films: Design strategies for stretchable conductors

Stretchable electronics are advancing rapidly to meet the demanding requirements of applications such as wearable health monitoring, soft robotics, human−machine interfaces, and biomedical systems, where reliable electromechanical performance under large deformation is essential. Metal film-based conductors are widely employed as key functional components, including stretchable interconnects/electrodes and strain sensors, owing to their high electrical conductivity and excellent compatibility with established microelectronics technologies. Depending on the targeted functionality, these metal films are engineered either as stretchable interconnects/electrodes that maintain strain-insensitive conductivity or as sensing elements that leverage strain-sensitive signal transduction. Despite their distinct roles, both types of components rely on crack-governed electromechanical responses. While several reviews have addressed metal film-based stretchable electronics, they typically focus separately on either stretchable interconnects/electrodes or strain sensors. A comparative analysis that systematically contrasts these two device categories, particularly in terms of crack regulation strategies and their underlying similarities and differences, remains lacking. To address this gap, this review synthesizes recent progress in metal film-based stretchable electronics, with an emphasis on elucidating the connections and distinctions in crack engineering and electromechanical response for each. Building on this framework, the review distills general principles for crack regulation, identifies key challenges, and outlines promising directions for future research. This review aims to provide a cohesive foundation to guide the rational design of next-generation metal film-based stretchable electronics. (Figure presented.).