Natural sunlight-actuated shape memory materials with reversible shape change and self-healing abilities based on carbon nanotubes filled conductive polymer composites

Abstract

Light-responsive shape memory materials (SMMs) are a type of smart materials which utilize the convenient light energy to actuate shape changes of the materials. Although natural sunlight is the unlimited and clean energy on the earth, it is still a challenge to use sunlight to trigger shape changes of SMMs because sunlight is a relatively weak energy source. Herein, a type of natural sunlight-actuated SMMs with self-healing ability based on the carbon nanotubes/chlorinated poly(propylene carbonate) composites is fabricated by the facile melt blending. It is observed that the composites exhibit excellent shape memory properties, which can be triggered not only by IR light but also by sunlight. For pre-stretched composites with 200% strain, the contraction force produced during shape recovery under IR light is 2.6 ± 0.2 N, which can lift 550 times their own weight. In addition, the shortest shape recovery time of the sheet composites (a thickness of 0.2 mm) under natural sunlight is only 39 s. Subsequently, the composite-paper bilayer films are constructed and assembled into an artificial flower. It is interesting to note that this flower can open under sunlight and close after blocking the sunlight, which is similar to the heliophile flowers in nature. Moreover, it is found that the incision on the composite sheet can be fast healed under infrared irradiation, which exhibits light-actuated self-healing behavior. We hope that this work may stimulate new ideas and inspire in the development of natural sunlight-actuated SMMs and devices in future.