A bimetallic strip is a composite material made of two or more metals or other materials with suitable properties.
Also known as a "thermostatic bimetal," this material relies on the differing thermal expansion coefficients of its constituent layers. When the temperature changes, the "active layer" (the one with the higher expansion coefficient) deforms more than the "passive layer" (the one with the lower expansion coefficient), causing the strip to bend toward the passive layer side; this change in curvature results in mechanical deformation. However, as the application areas for bimetals have expanded and bonding technologies have advanced, three-layer, four-layer, and even five-layer versions have emerged in recent times.
