Abstract.

Periodic wrinkling of a rigid capping layer on a deformable substrate provides a useful method for templating surface topography for a variety of novel applications. Many experiments have studied wrinkle formation during the compression of a rigid film on a relatively soft pre-strained elastic substrate, and most have focused on the regime where the substrate thickness can be considered semi-infinite relative to that of the film. As the relative thickness of the substrate is decreased, the bending stiffness of the film dominates, causing the bilayer to transition to either local wrinkling or a global buckling instability. In this work optical microscopy was used to study the critical parameters that determine the emergence of local wrinkling or global buckling of freestanding bilayer films consisting of a thin rigid polymer capping layer on a pre-strained elastomeric substrate. The thickness ratio of the film and substrate as well as the pre-strain were controlled and used to create a buckling phase diagram which describes the behaviour of the system as the ratio of the thickness of the substrate is decreased. A simple force balance model was developed to understand the thickness and strain dependences of the wrinkling and buckling modes, with excellent quantitative agreement being obtained with experiments using only independently measured material parameters.

Graphical abstract

中文翻译：

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独立的薄双层薄膜中出现局部起皱或整体弯曲。

摘要。

定期对可变形基板上的刚性覆盖层起皱，为各种新型应用提供了一种有效的模板化表面形貌的方法。许多实验研究了在相对柔软的预应变弹性基材上压缩硬质薄膜时形成的皱纹，并且大多数研究都集中在可以认为基材厚度相对于薄膜为半无限厚的状态。随着基材的相对厚度减小，薄膜的弯曲刚度起主导作用，导致双层转变为局部起皱或整体屈曲不稳定性。在这项工作中，光学显微镜被用来研究确定独立的双层薄膜出现局部起皱或整体弯曲的关键参数，这些双层薄膜由在预应变的弹性体基底上的薄的刚性聚合物覆盖层组成。控制膜和基板的厚度比以及预应变，并用于创建屈曲相图，该屈曲相图描述了随着基板厚度比的减小，系统的行为。开发了一个简单的力平衡模型以了解起皱和屈曲模式的厚度和应变相关性，并且仅使用独立测量的材料参数通过实验获得了极好的定量一致性。控制膜和基板的厚度比以及预应变，并用于创建屈曲相图，该屈曲相图描述了随着基板厚度比的减小，系统的行为。开发了一个简单的力平衡模型以了解起皱和屈曲模式的厚度和应变相关性，并且仅使用独立测量的材料参数通过实验获得了极好的定量一致性。控制膜和基板的厚度比以及预应变，并用于创建屈曲相图，该屈曲相图描述了随着基板厚度比的减小，系统的行为。开发了一个简单的力平衡模型以了解起皱和屈曲模式的厚度和应变相关性，并且仅使用独立测量的材料参数通过实验获得了极好的定量一致性。

图形概要