用随机剪裁设计新型折纸材料,实现拉伸与剪切解耦。
Harnessing disorder to decouple extension and shear in kirigami metamaterials

- 通过随机剪裁打破周期性限制,实现拉伸与剪切的解耦。
- 所设计材料可编程调控各向异性,消除寄生剪切应变。
- 结合图神经网络与遗传算法,实现从目标性能反向设计结构。
折纸超材料通过周期性切割将刚性薄片转化为可变形结构,但其面板旋转相互关联,导致拉伸时必然伴随寄生剪切,且各向异性刚度只能在有限离散响应中选择,无法独立调节。生物组织通过有序无序(如皮肤纤维梯度排列、心肌分层各向异性)克服类似限制。本文首次将工程无序作为设计自由度,提出随机折纸可拓展至连续且更广阔的机械响应空间,包括近乎完全消除拉伸-剪切耦合的可编程各向异性。由于无序结构缺乏简单参数化,我们采用几何感知图神经网络(GNN)建立切割拓扑与非线性双向应力-应变响应之间的映射,并结合遗传算法逆向设计出满足两个正交轴目标响应的图案。GNN训练速度比图像模型快一个数量级,精度更高。制备的弹性体样品验证了预测的非线性各向异性响应,实现了从设计到实物的闭环。该工作将无序转化为调控方向刚度的变量,为软执行器及匹配生物组织各向异性的植入式器件提供了新方案。
原文摘要 · Abstract (English)
Kirigami turns stiff sheets into compliant, shape-morphing structures, but its reliance on periodic cut patterns comes at a cost: correlated panel rotations couple extension to shear, so stretching one axis drives a parasitic shear that cannot be suppressed, and also confine anisotropic stiffness to a narrow, discrete set of responses that cannot be tuned independently. Biological tissues overcome an analogous constraint through controlled disorder, such as graded fiber orientations in skin and hierarchical anisotropy in myocardium, achieving direction-dependent mechanics unavailable to regular architectures. Here, we show that engineered disorder is a design degree of freedom for kirigami, with stochastic kirigami accessing a continuous and far broader region of mechanical response than periodic patterns. This includes programmable anisotropy with near-complete elimination of extension-shear coupling. Because disordered patterns lack a simple parameterization, we navigate this design space with a geometry-aware graph neural network (GNN) that maps cut topology to the full nonlinear, bidirectional stress-strain response, coupled to a genetic algorithm that inverse-designs patterns reproducing target responses along two perpendicular axes. The GNN trains an order of magnitude faster and more accurately than image-based models. Fabricated elastomer samples reproduce the predicted nonlinear, anisotropic responses, closing the loop from design to physical component. By turning disorder into a variable to control directional stiffness, this work develops architected materials that stretch without parasitic shear, from soft actuators to tissue-interfacing devices matched to the anisotropy of living tissue.
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