Tunable Photothermal Actuators Based on a Pre-programmed Aligned Nanostructure.

For various applications, it is challenging but essential to obtain complex tunable mechanical actuations in response to environmental stimuli. Here, a general and effective strategy is developed to produce multiple types of photomechanical actuation (from phototropic/apheliotropic bending to three-dimensional helical buckling) by manipulating the orientation of one-dimensional nanomaterials. These materials are manipulated to mimic plants that generate diverse mechanical motions through the orientation of cellulose fibrils. The photomechanical actuations can be completed in milliseconds and can be performed reversibly without detectable fatigue after 100 000 cycles. This capacity to produce multiple types of photomechanical actuation is further developed to produce complex integrated movements, as demonstrated by a light-manipulated robotic arm and a solar energy harvesting system.