Wrinkling patterns are beneficial for a wide range of engineering applications including flexible electronics, tuned optics, sensoring, energy harvesting, surface wetting and biomedicine. Here we report on controllable multimode wrinkling patterns of metal (iron) films sputter deposited on flexible substrates with gradient modulus. It is found that disordered wrinkles (G1 wrinkling) form in the weakly crosslinking region at the early stage of film deposition. Disordered labyrinth wrinkles with larger wavelengths and ordered stripe wrinkles localized by cracks (both G2 wrinkling) appear in the strongly crosslinking region for the samples with small film thickness and large thickness, respectively. The coexistence of the labyrinth G1 wrinkling and labyrinth G2 wrinkling (or stripe G2 wrinkling) can be obtained by tuning the substrate modulus and film thickness. The morphologies, evolutions and mechanisms of such wrinkles are discussed in detail based on the stress theory. This study can promote better understanding of the substrate effect on the complex wrinkling patterns.

中文翻译：

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沉积在具有梯度模量的柔性基板上的铁膜溅射的多模褶皱图案

起皱模式有利于广泛的工程应用，包括柔性电子、调谐光学、传感、能量收集、表面润湿和生物医学。在这里，我们报告了金属（铁）薄膜溅射沉积在具有梯度模量的柔性基板上的可控多模褶皱图案。发现在成膜初期，在弱交联区形成无序皱褶（G1皱褶）。对于小膜厚和大膜厚的样品，在强交联区分别出现了波长较大的无序迷宫皱纹和裂纹局部化的有序条纹皱纹（均为G2皱纹）。通过调整基板模量和膜厚，可以得到迷宫G1起皱和迷宫G2起皱（或条纹G2起皱）并存的情况。基于应力理论详细讨论了此类皱纹的形态、演变和机制。这项研究可以促进更好地理解基材对复杂皱纹图案的影响。