Zhou Jian, Huang Richard, Moldovan Nicolaie, Stan Liliana, Wen Jianguo, Jin Dafei, Nelson David R, Košmrlj Andrej, Czaplewski David A, López Daniel
Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL 60439.
Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, NY 13902.
Proc Natl Acad Sci U S A. 2025 Mar 25;122(12):e2425200122. doi: 10.1073/pnas.2425200122. Epub 2025 Mar 19.
Thermally induced ripples are intrinsic features of nanometer-thick films, atomically thin materials, and cell membranes, significantly affecting their elastic properties. Despite decades of theoretical studies on the mechanics of suspended thermalized sheets, controversy still exists over the impact of these ripples, with conflicting predictions about whether elasticity is scale-dependent or scale-independent. Experimental progress has been hindered so far by the inability to have a platform capable of fully isolating and characterizing the effects of ripples. This knowledge gap limits the fundamental understanding of thin materials and their practical applications. Here, we show that thermal-like static ripples shape thin films into a class of metamaterials with scale-dependent, customizable elasticity. Utilizing a scalable semiconductor manufacturing process, we engineered nanometer-thick films with precisely controlled frozen random ripples, resembling snapshots of thermally fluctuating membranes. Resonant frequency measurements of rippled cantilevers reveal that random ripples effectively renormalize and enhance the average bending rigidity and sample-to-sample variations in a scale-dependent manner, consistent with recent theoretical estimations. The predictive power of the theoretical model, combined with the scalability of the fabrication process, was further exploited to create kirigami architectures with tailored bending rigidity and mechanical metamaterials with delayed buckling instability.
热致波纹是纳米厚薄膜、原子级薄材料和细胞膜的固有特征，会显著影响它们的弹性特性。尽管对悬浮热化薄片的力学进行了数十年的理论研究，但对于这些波纹的影响仍存在争议，关于弹性是与尺度相关还是与尺度无关存在相互矛盾的预测。到目前为止，由于无法拥有一个能够完全隔离和表征波纹效应的平台，实验进展受到了阻碍。这一知识空白限制了对薄材料的基本理解及其实际应用。在此，我们表明类似热的静态波纹将薄膜塑造成一类具有与尺度相关、可定制弹性的超材料。利用可扩展的半导体制造工艺，我们设计了具有精确控制的冻结随机波纹的纳米厚薄膜，类似于热波动膜的快照。对波纹悬臂梁的共振频率测量表明，随机波纹以与尺度相关的方式有效地重整化并增强了平均弯曲刚度以及样品间的变化，这与最近的理论估计一致。理论模型的预测能力与制造工艺的可扩展性相结合，进一步被用于创建具有定制弯曲刚度的kirigami结构和具有延迟屈曲不稳定性的机械超材料。
