Event‐Driven Elongation Monitor for Soft Devices Using a Deformation‐Activated Piezoconductive Switch

Stretchable devices have advanced in recent years, but challenges remain in managing deformations beyond design limits. Continuous power consumption for deformation monitoring hinders practical use. This underscores the need for a system capable of detecting loads beyond the allowable deformation of stretchable devices while minimizing energy consumption. Here, we developed a strain‐induced switching circuit based on a positive piezoconductive composite. This composite transitioned from a resistance value exceeding 10 MΩ to a conductive state under strain, exhibiting a switching ratio of 10 5 , enabling passive detection of excessive deformation, while it is decreased to 10 2 after 100 cycles of repeated use. The composite—made from silicone, ionic liquid, and nickel particles—offers tunable switching behavior by adjusting the nickel‐to‐polymer ratio and cross‐sectional geometry. By combining it with a stretchable, non‐contact power transfer system using printed liquid metal coils, we realized a low‐energy, event‐driven strain monitor embedded in stretchable devices. The liquid metal coils maintained stable power transmission even under 30% extension. We demonstrated applications in deformation detection of a plastic plate and strain‐triggered infrared communication. This achievement is expected not only to significantly enhance the safety and reliability of stretchable devices but also to contribute to the development of energy‐efficient, self‐protective devices.