A bi-directional thermal-driven actuator with conduction‐to‐insulation transformation behavior and its applications in overheating protection and early warning of fire

To endow an actuator with multi functions in response to heat, a layer of electrically conductive silicone rubber (SR) filled with 80 wt% silver powder was coated on a double-layered actuator consisting of two layers of SR filled with different thermal expansion microspheres to obtain a triple-layered actuator. The layer of electrically conductive SR had a little effect on the actuation properties of the triple-layered actuator. The triple-layered actuator exhibited bi-directional deformation and conduction‐to‐insulation transformation behavior during actuation process. The relationships between electrical conductivity, bending curvature and heating time were established. Applications of the actuator in overheating protection and early warning of fire were demonstrated.