Wrinkled Interfaces: Taking Advantage of Anisotropic Wrinkling to Periodically Pattern Polymer Surfaces

Abstract

Periodically patterned surfaces can cause special surface properties and are employed as functional building blocks in many devices, yet remaining challenges in fabrication. Advancements in fabricating structured polymer surfaces for obtaining periodic patterns are accomplished by adopting "top-down" strategies based on self-assembly or physico-chemical growth of atoms, molecules, or particles or "bottom-up" strategies ranging from traditional micromolding (embossing) or micro/nanoimprinting to novel laser-induced periodic surface structure, soft lithography, or direct laser interference patterning among others. Thus, technological advances directly promote higher resolution capabilities. Contrasted with the above techniques requiring highly sophisticated tools, surface instabilities taking advantage of the intrinsic properties of polymers induce surface wrinkling in order to fabricate periodically oriented wrinkled patterns. Such abundant and elaborate patterns are obtained as a result of self-organizing processes that are rather difficult if not impossible to fabricate through conventional patterning techniques. Focusing on oriented wrinkles, this review thoroughly describes the formation mechanisms and fabrication approaches for oriented wrinkles, as well as their fine-tuning in the wavelength, amplitude, and orientation control. Finally, the major applications in which oriented wrinkled interfaces are already in use or may be prospective in the near future are overviewed.

Retraction of “Three-Axial Strain-Triggered Multimode Wrinkles with Tuneable Frictional and Optical Performances”

“…Inspired by the nature, the designs and applications of surface micro–nano structures have received a great deal of attention in the past few decades. − Among them, the lithography- or template-based strategies usually possess the advantages of high precision, good repeatability, and stability, but they also encounter some intrinsic disadvantages such as special equipment, high cost, and poor efficiency. On the contrary, the self-assembly based on stress-driven surface instability provides a cost-effective and reliable method to rapidly generate ordered micro–nano structures over large areas without the traditional lithography tools and masks. − Through stress-driven self-assembly, a variety of technical solutions have been developed to control surface wrinkle patterns in film–substrate systems. These techniques include expansion/contraction due to temperature variation, swelling/deswelling due to solvent diffusion, loading/unloading of external mechanical forces, growth/atrophy of biological tissues, surface tension of liquid, light-triggered structural transitions, − and so on.…”

Formation of aligned needle‐like crystals of 9,10‐dibromoanthracene in small droplets

“…As shown in Figure 6, the interval between droplets is determined by the wavelength of the sinusoidal wrinkles in the surface layer. As theoretically predicted, 36 the thickness of the oxidized surface layer controls the wavelength. Therefore, the duration of the oxidation using the UV-ozone treatment was varied from 50 to 110 min and the interval between droplets was measured (Figure S6).…”

“…34,35 While the oxidized surface layer becomes swollen with the solvent, in-plane expansion of the layer is restricted by the underlying PDMS sheet, which causes undulation on the layer owing to buckling instability. 36 Using appropriate methods, [37][38][39] the undulations (i.e., wrinkles or dimples) confine the solution to the concave portions. In addition, solute crystals form following solvent evaporation, but not always.…”

Recent advances in the construction and application of stretchable PEDOT smart electronic membranes

“…123 The shape and size of wrinkles depend on the modulus mismatch between the epidermis and elastomer, the magnitude of stress, and the duration of stimulation. 124 Reducing the thickness and Poisson's ratio of the epidermis and increasing the elastic modulus ratio between the skin and the substrate will result in smaller wrinkled pitches. The conductive layer with a dense wrinkled structure on the elastomer can maintain a stable conductive network when stretched.…”