Universal Method for Creating Hierarchical Wrinkles on Thin-Film Surfaces

Abstract

One of the most interesting topics in physical science and materials science is the creation of complex wrinkled structures on thin-film surfaces because of their several advantages of high surface area, localized strain, and stress tolerance. In this study, a significant step was taken toward solving limitations imposed by the fabrication of previous artificial wrinkles. A universal method for preparing hierarchical three-dimensional wrinkle structures of thin films on a multiple scale (e.g., nanometers to micrometers) by sequential wrinkling with different skin layers was developed. Notably, this method was not limited to specific materials, and it was applicable to fabricating hierarchical wrinkles on all of the thin-film surfaces tested thus far, including those of metals, two-dimensional and one-dimensional materials, and polymers. The hierarchical wrinkles with multiscale structures were prepared by sequential wrinkling, in which a sacrificial layer was used as the additional skin layer between sequences. For example, a hierarchical MoS wrinkle exhibited highly enhanced catalytic behavior because of the superaerophobicity and effective surface area, which are related to topological effects. As the developed method can be adopted to a majority of thin films, it is thought to be a universal method for enhancing the physical properties of various materials.

Multigenerational Crumpling of 2D Materials for Anticounterfeiting Patterns with Deep Learning Authentication

“…3,23,24 Furthermore, the out-of-plane characteristics of 2DM microstructures can be programmably designed across multiple length scales, producing various hierarchical topographies. 18,19,[24][25][26] The combination of multiscale features with specific orientations can serve as unique identifiers to classify and categorize the resulting 2DM hierarchies into specific subgroups. With the pre-categorization step, the search-andcompare algorithm only needs to be conducted within a smaller database, thus shortening the overall authentication time.…”

“…Several sequential deformation strategies have been investigated in the literature to enable the sophisticated design of hierarchical 2DM topographies. 18,25,26 However, the majority of reported methods involved repeated substrate dissolution and/or delicate 2DM film transfer, severely limiting the scalability of pattern fabrication and the capability of topographic tuning.…”

Multifunctionality and Mechanical Actuation of 2D Materials for Skin‐Mimicking Capabilities

“…By heating the samples above its glass transition temperature of polystyrene ( T g ≈ 100 °C), the prestrain will release, yielding well‐defined crumpled textures of deposited nanomaterials. This approach has been applied to various nanomaterials, including gold thin films, CNTs, and the large family of 2D materials (e.g., graphene, GO, MoS 2 , WS 2 , SnS 2 ). Large‐area coating techniques (such as spray coating, inkjet printing) can be easily involved in this approach since the thermally responsive substrate does not require any specialized equipment to stabilize the strains.…”

Laser Generation of Sub‐Micrometer Wrinkles in a Chalcogenide Glass Film as Physical Unclonable Functions

“…arising from the stress resistances of a bilayer structure made of a thin layer metal deposited on a elastomeric polymer, [7] or also from a laser-melted layer capped by a rigid oxide layer. [8][9][10] Numerous studies have been dedicated to wrinkles motivated by the understanding of the underlying physical process, [7,11] development of new methods, [12] or possible applications. [4] Here, we demonstrate a straightforward way to generate PUF-tags via formation of wrinkles on chalcogenide materials, i.e., semiconductor alloys containing at least one chalcogen chemical element from group VI (S, Se, and Te) alloyed, for example, with group IV or V elements like Ge, As or Sb atoms.…”