Department of Mechanical Engineering, University of Colorado Boulder, Boulder, Colorado 80309, USA.
Soft Matter. 2017 Oct 25;13(41):7625-7632. doi: 10.1039/c7sm01404j.
Shape memory polymers (SMPs) can remember two or more distinct shapes, and thus can have a lot of potential applications. This paper presents combined experimental and theoretical studies on the wrinkling of single-crystal Si ribbons on SMPs and the temperature dependent evolution. Using the shape memory effect of heat responsive SMPs, this study provides a method to build wavy forms of single-crystal silicon thin films on top of SMP substrates. Silicon ribbons obtained from a Si-on-insulator (SOI) wafer are released and transferred onto the surface of programmed SMPs. Then such bilayer systems are recovered at different temperatures, yielding well-defined, wavy profiles of Si ribbons. The wavy profiles are shown to evolve with time, and the evolution behavior strongly depends on the recovery temperature. At relatively low recovery temperatures, both wrinkle wavelength and amplitude increase with time as evolution progresses. Finite element analysis (FEA) accounting for the thermomechanical behavior of SMPs is conducted to study the wrinkling of Si ribbons on SMPs, which shows good agreement with experiment. Merging of wrinkles is observed in FEA, which could explain the increase of wrinkle wavelength observed in the experiment. This study can have important implications for smart stretchable electronics, wrinkling mechanics, stimuli-responsive surface engineering, and advanced manufacturing.
形状记忆聚合物（SMPs）可以记住两种或更多不同的形状，因此具有很多潜在的应用。本文对 SMP 上单晶 Si 带的褶皱和温度相关的演化进行了组合实验和理论研究。利用热响应 SMP 的形状记忆效应，本研究提供了一种在 SMP 基底上构建单晶硅薄膜波浪形的方法。从绝缘体上硅（SOI）晶片获得的 Si 带被释放并转移到编程 SMP 的表面。然后，将这样的双层系统在不同温度下恢复，得到具有良好定义的 Si 带的波纹状轮廓。实验表明，波纹状轮廓随时间演变，而演变行为强烈依赖于恢复温度。在相对较低的恢复温度下，随着演化的进行，皱纹的波长和振幅都会随时间增加。进行了考虑 SMP 热机械行为的有限元分析（FEA），以研究 SMP 上 Si 带的褶皱，结果与实验吻合良好。在 FEA 中观察到褶皱的合并，这可以解释实验中观察到的褶皱波长的增加。本研究对于智能可拉伸电子产品、褶皱力学、刺激响应表面工程和先进制造具有重要意义。
