Nastic movements in plants that occur in response to environmental stimuli have inspired many man-made shape-morphing systems. Tendril is an exemplification serving as a parasitic grasping component for the climbing plants by transforming from a straight shape into a coiled configuration via the asymmetric contraction of internal stratiform plant tissues. Inspired by tendrils, this study using a three-dimensional (3D) printing approach developed a class of soft grippers with preprogrammed deformations being capable of imitating the general motions of plant tendrils, including bending, spiral, and helical distortions for grasping. These grippers initially in flat configurations were tailored from a polymer–paper bilayer composite sheet fabricated via 3D printing a polymer on the paper substrate with different patterns. The rough and porous paper surface provides a printed polymer that is well-adhered to the paper substrate which in turn serves as a passive strain-limiting layer. During printing, the melted polymer filament is stretched, enabling the internal strain to be stored in the printed polymer as memory, and then it can be thermally released, which will be concurrently resisted by the paper layer, resulting in various transformations based on the different printed geometries. These obtained transformations were then used for designing grippers to grasp objects with corresponding motions. Furthermore, a fully equipped robotic tendril with three segments was reproduced, where one segment was used for grasping the object and the other two segments were used for forming a tendril-like twistless spring-like structure. This study further helps in the development of soft robots using active polymer materials for engineered systems.

中文翻译：

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柔软的卷须夹爪：可编程聚合物-纸双层复合材料的形状变形

植物响应环境刺激而发生的剧烈运动激发了许多人造形状变形系统。卷须是通过内部层状植物组织的不对称收缩从笔直形状变为盘绕形态而成为攀援植物的寄生抓握组件的一个示例。受卷须的启发，这项使用三维（3D）打印方法的研究开发出了一类具有预编程变形的软抓手，它们能够模仿植物卷须的一般运动，包括弯曲，螺旋和螺旋形扭曲以便抓握。这些最初为扁平结构的抓手是通过在纸质基材上以不同图案进行3D打印聚合物而制成的聚合物-纸双层复合片材制成的。粗糙且多孔的纸表面提供了印刷好的聚合物，该聚合物良好地粘附到纸基材上，而纸基材又用作无源应变限制层。在打印过程中，融化的聚合物长丝会被拉伸，从而将内部应变存储在已打印的聚合物中作为记忆，然后可以将其热释放，并同时受到纸层的抵抗，从而导致基于不同层的各种转变印刷的几何形状。然后，将这些获得的转换用于设计抓取器以抓取具有相应运动的对象。此外，复制了具有三段的设备齐全的机器人卷须，其中一个段用于抓握物体，而另外两个段用于形成类似卷须的无扭转弹簧状结构。