Infrared-Triggered Actuators from Graphene-Based Nanocomposites

The emerging field of optical-triggered actuators based on polymeric nanocomposite continues to be the focus of considerable research in recent years because of their scientific and technological significance. In principle, dispersing nanofiller with unique characteristics in polymer matrix can not only provide superb enhancement of performance but also afford novel actuation schemes to the systems. Graphene, combining its unusual electrical, thermal, mechanical, and optical properties, can provide the ability to act as "energy transfer" and trigger unit in the realm of nanocomposite actuators. Herein, we demonstrate a new dimension to this 2D nanoscale material by showing the excellent light-triggered acutation of its thermoplastic polyurethane nanocomposites with significantly enhanced mechanical properties. These nanocomposite actuators with 1 wt % loading of sulfonated functionalized graphene sheets (sulfonated-graphene) exhibit repeatable infrared-triggered actuation performance which can strikingly contract and lift a 21.6 g weight 3.1 cm with 0.21 N of force on exposure to infrared light and demonstrate estimated energy densities of over 0.33 J/g. Some cases can even reach as high as 0.40 J/g. Dramatic improvement in mechanical properties is also obtained for the graphene nanocomposites with homogeneous dispersion. As the concentration of sulfonated-graphene increases, its nanocomposites show significantly enhanced mechanical properties, that is, the Young's modulus increases by 120% at only 1 wt % loading. Moreover, through comparative study of three kinds of graphene materials, it is found that this infrared-triggered actuation property is principally dependent on the integrity of the aromatic network of graphene and on its dispersion state within the matrix.