Zhang Xu, Medina Lior, Cai Haogang, Aksyuk Vladimir, Espinosa Horacio D, Lopez Daniel
Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
Department of Mechanical Engineering, Northwestern University, Evanston, IL, 60208, USA.
Adv Mater. 2021 Feb;33(5):e2005275. doi: 10.1002/adma.202005275. Epub 2020 Dec 22.
Kirigami structures provide a promising approach to transform flat films into 3D complex structures that are difficult to achieve by conventional fabrication approaches. By designing the cutting geometry, it is shown that distinct buckling-induced out-of-plane configurations can be obtained, separated by a sharp transition characterized by a critical geometric dimension of the structures. In situ electron microscopy experiments reveal the effect of the ratio between the in-plane cut size and film thickness on out-of-plane configurations. Moreover, geometrically nonlinear finite element analyses (FEA) accurately predict the out-of-plane modes measured experimentally, their transition as a function of cut geometry, and provide the stress-strain response of the kirigami structures. The combined computational-experimental approach and results reported here represent a step forward in the characterization of thin films experiencing buckling-induced out-of-plane shape transformations and provide a path to control 3D configurations of micro- and nanoscale buckling-induced kirigami structures. The out-of-plane configurations promise great utility in the creation of micro- and nanoscale systems that can harness such structural behavior, such as optical scanning micromirrors, novel actuators, and nanorobotics. This work is of particular significance as the kirigami dimensions approach the sub-micrometer scale which is challenging to achieve with conventional micro-electromechanical system technologies.
折纸结构提供了一种很有前景的方法，可将平面薄膜转变为传统制造方法难以实现的三维复杂结构。通过设计切割几何形状，研究表明可以获得由结构的临界几何尺寸所表征的尖锐转变分隔开的不同屈曲诱导面外构型。原位电子显微镜实验揭示了面内切尺寸与薄膜厚度之比对面外构型的影响。此外，几何非线性有限元分析（FEA）准确预测了实验测量的面外模式、它们作为切割几何形状函数的转变，并提供了折纸结构的应力-应变响应。本文报道的计算-实验相结合的方法和结果代表了在表征经历屈曲诱导面外形状转变的薄膜方面向前迈出的一步，并为控制微米和纳米尺度屈曲诱导折纸结构的三维构型提供了一条途径。面外构型在创建能够利用这种结构行为的微米和纳米尺度系统方面具有很大的实用性，例如光学扫描微镜、新型致动器和纳米机器人。这项工作具有特别重要的意义，因为折纸尺寸接近亚微米尺度，而这对于传统微机电系统技术来说是具有挑战性的。
