Zhang Qiang, Kuang Xiao, Weng Shayuan, Zhao Zeang, Chen Haosen, Fang Daining, Qi H Jerry
The George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
State Key Laboratory for Turbulence and Complex System, College of Engineering, Peking University, Beijing, 100871, People's Republic of China.
ACS Appl Mater Interfaces. 2020 Apr 15;12(15):17979-17987. doi: 10.1021/acsami.0c02038. Epub 2020 Apr 3.
Inspired by diverse shape-shifting phenomena in nature, various man-made shape programmable materials have been developed for applications in actuators, deployable devices, and soft robots. However, fabricating mechanically robust shape-morphing structures with on-demand, rapid shape-transformation capability, and high load-bearing capacity is still a great challenge. Herein, we report a mechanically robust and rapid shape-shifting material system enabled by the volatilization of a non-fully-reacted, volatile component in a partially cured cross-linking network obtained from photopolymerization. Volume shrinkage induced by the loss of the volatile component is exploited to drive complex shape transformations. After shape transformation, the residual monomers, cross-linkers, and photoinitiators that cannot volatilize still exist in the network, which is ready for a further photopolymerization to significantly stiffen the initial material. Guided by analytic models and finite element analysis, we experimentally demonstrate that a variety of shape transformations can be achieved, including both 2D-to-3D and 3D-to-3D' transformations, such as a buckyball self-folding from a 2D hexagonal lattice sheet and multiple pop-up structures transforming from their initial compact configurations. Moreover, we show that an ultra-low-weight 3D Miura-ori structure transformed from a 2D sheet can hold more than 1600 times its weight after stiffness improvement via postcuring. This work provides a versatile and low-cost method to fabricate rapid and robust shape-morphing structures for potential applications in soft robots, deployable antennas, and optical devices.
受自然界中各种变形现象的启发，人们开发了各种人造形状可编程材料，用于致动器、可展开装置和软机器人等领域。然而，制造具有按需、快速形状转换能力和高承载能力的机械坚固的形状变形结构仍然是一个巨大的挑战。在此，我们报告了一种机械坚固且快速变形的材料系统，该系统由光聚合得到的部分固化交联网络中未完全反应的挥发性成分挥发所驱动。利用挥发性成分损失引起的体积收缩来驱动复杂的形状转变。形状转变后，网络中仍存在无法挥发的残留单体、交联剂和光引发剂，可通过进一步的光聚合显著增强初始材料的硬度。在分析模型和有限元分析的指导下，我们通过实验证明可以实现多种形状转变，包括二维到三维和三维到三维'的转变，例如从二维六边形晶格片自折叠形成巴基球以及多个弹出结构从其初始紧凑构型转变。此外，我们表明，通过二维片材转变得到的超低重量三维三浦折纸结构在经过后固化提高硬度后，可以承受超过其自身重量1600倍的重量。这项工作提供了一种通用且低成本的方法来制造快速且坚固的形状变形结构，用于软机器人、可展开天线和光学器件等潜在应用。
