Flexible, all-inorganic actuators based on vanadium dioxide and carbon nanotube bimorphs

Flexible actuators responsive to multiple stimuli are much desired in wearable electronics. However, general designs containing organic materials are usually subject to slow response and limited lifetime, or high triggering threshold. In this study, we develop flexible, all-inorganic actuators based on bimorph structures composed of vanadium dioxide (VO₂) and carbon nanotube (CNT) thin films. The drastic, reversible phase transition of VO₂ drives the actuators to deliver giant amplitude, fast response up to ∼100 Hz, and long lifetime more than 1 000 000 actuation cycles. The excellent electrical conductivity and light absorption of CNT thin films enable the actuators to be highly responsive to multiple stimuli including light, electric, and heat. The power consumption of the actuators can be much reduced by doping VO₂ to lower its phase transition temperature. These flexible bimorph actuators find applications in biomimetic inspect wings, millimeter-scale fingers, and physiological-temperature driven switches.