Colossal thermal-mechanical actuation via phase transition in single-crystal VO2 microcantilevers

The spontaneous strain associated with the structural change in the metal-insulator transition in VO2 is orders of magnitude higher than thermal expansion mismatch used in bimetallic strips. Here we show that this strain can be leveraged to thermally activate bending of crystalline VO2-based bilayer microcantilevers at extremely large curvatures, making them suitable for thermal sensors, energy transducers and actuators with unprecedented sensitivities. The single-crystallinity, deposition conditions, and postdeposition treatments were utilized to control the metal-insulator domain structure along the cantilever, by which we achieved bending curvatures a few hundred times higher than conventional bilayer cantilevers with the same geometry.