Intelligent actuators with the ability to interact with the environment have become an emerging topic. However, traditional actuators could not achieve more complex functions such as stimulus-dependent colorations. Although many dyed or luminescent actuators can display specific colors and alter their shapes, these actuations struggle with photobleaching, low luminous efficacy, or unfavorable response fatigue. Here, by mimicking the behaviors of chameleons, structural-color actuators that feature unprecedented capabilities of both sensitive vapochromic and robust vapomechanical responses have been achieved. These properties enable fast, stable, and sharp color alterations together with non-fatigued and programmable motions. With the state-of-the-art concept of interaction with the environment, these structural-color actuators may provide inspiration for further development in various research fields, including sensors, actuators, robotics, and smart systems.

In response to the changing environment, chameleons can adjust their skin colors to communicate and create disguise during locomotions. By mimicking their behaviors, we present structural-color actuators that can sense the environment and give responses of non-fatigued vivid color alterations and programmable shape transformations. Due to the sensitive vapochromic and robust vapomechanical response properties, these structural-color actuators exhibit fast color changes (less than 1 s) and non-fatigued shape transformations (more than 110 cycles) when exposed to specific vapors. On the basis of these extraordinary properties, we demonstrate the actuation processes of a rotating pinwheel and a closing/blooming flower with brilliant color changes, and a worm-like structural-color walker that can move forward straight and rhythmically with dynamic color changes. With these chameleon-like behaviors, these structural-color actuators could have important implications in sensing, communication, and disguise of soft robotics.

Introduction

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Zhao Y. Bioinspired living structural color hydrogels. Recently, various strategies have been established for designing actuators that are more similar to creatures in nature. By introducing dyes into the actuation systems, not only could the actuators alter their shapes but they could also adapt to the environment by displaying specific colors. In a seminal work, Morin et al. developed soft pneumatic robots with integrated microfluidics injected with dyed liquids that could change the color for display and camouflage, although this system requires continuous flow and manipulation of multiple liquids for specific color alteration and thus has a slow response time.In addition, the stability and durability of the dyed colors are limited by their photobleaching properties.Since then, different color elements that can change their optical properties, including luminescence and reflection, have been further developed to achieve various color actuations, but struggle with low luminous efficacy or unfavorable response fatigue.Furthermore, compared with the smart adaptations in nature, the overall actuation systems lack the ability of sensing the environment autonomously with coordinated responses of desired shape and color alterations. Consequently, to broaden the range of practical applications, a more ideal adaptive actuation system should be explored.