A dynamic surface pattern with a topography and fluorescence in response to environmental stimulus can enable information recording, hiding, and reading. Such patterns are therefore widely used in information security and anticounterfeiting. Here, we demonstrate a dynamic dual pattern using a supramolecular network comprising a copolymer containing pyridine (P4VP-nBA-S) and hydroxyl distyrylpyridine (DSP-OH) as the skin layer for bilayer wrinkling systems, in which both the wrinkle morphology and fluorescence color can be simultaneously regulated by visible light-triggered isomerization of DSP-OH, or acids. Acid-induced protonation of pyridines can dynamically regulate the cross-linking of the skin layer through hydrogen bonding, and the fluorescence of DSP-OH. On selective irradiation with 450 nm visible light or acid treatment, the resulting hierarchical patterned surface becomes smooth and wrinkled reversibly, and simultaneously its fluorescence changes dynamically from blue to orange-red. The smart surfaces with dynamic hierarchical wrinkles and fluorescence can find potential application in anticounterfeiting.
Regulating existing micro and nano wrinkle structures into desired configurations is urgently necessary yet remains challenging, especially modulating wrinkle direction and location on demand. In this work, we propose a novel light-controlled strategy for surface wrinkles, which can dynamically and precisely regulate all basic characteristics of wrinkles, including wavelength, amplitude, direction and location (λ, A, θ and Lc), and arbitrarily tune wrinkle topographies in two dimensions (2D). By considering the bidirectional Poisson's effect and soft boundary conditions, a modified theoretical model depicting the relation between stress distributions and the basic characteristics was developed to reveal the mechanical mechanism of the regulation strategy. Furthermore, the resulting 2D ordered wrinkles can be used as a dynamic optical grating and a smart template to reversibly regulate the morphology of various functional materials. This study will pave the way for wrinkle regulation and guide fabrication technology for functional wrinkled surfaces.
Structural color caused by thin‐film interference is widespread and simple in nature. Many researchers have already showed the reversible color change of structural color system, but it is difficult to regulate dynamically with tunable intensity and viewable angle. Herein, a dynamic structural color platform is reported by combining spontaneous thin film interference and wrinkling phenomenon in nature. This robust yet low cost strategy enables large‐scale and spatially arbitrary preparation of a uniform structural color surface through the whole visible spectral range. Furthermore, the prepared isotropic and anisotropic structural colors on disordered and ordered wrinkled thin films (WTFs) exhibit different optical properties that can be precisely and reversibly regulated by ultraviolet (UV) light and near‐infrared (NIR) light irradiation. This exquisite and tunable structural color platform may find applications in information storage, smart display, anticounterfeiting and encryption.
Dynamic micro-/nanowrinkle patterns with response to multienvironmental stimuli can offer a facile method for on-demand regulation of surface properties, thus allowing for generation of a smart surface. Here a practical yet robust strategy is described to fabricate redox, light and thermal responsive wrinkle by building dynamic double interpenetrating polymer network (IPN) as the top layer for a typical bilayer system. IPNs were constructed through the photochemical reaction of a mixture comprised of light-sensitive anthracene-containing polymer (PAN) and redox-sensitive disulfide-containing diacrylate monomer (DSDA). Thanks to the dynamic covalent reversible C–C bond in PAN and S–S bond in DSDA, the morphology of wrinkled surface not only can be reversibly and precisely (micrometer scale) tailored to all kinds of complicated hierarchical pattern permanently, but also can be controlled temporarily by irradiation of near-infrared light (NIR). A sine wave model is proposed to investigate the dynamics of real-time reversible wrinkle evolution. This general approach based on IPN allows independent multistimuli control over wettability and optical properties on the wrinkled surface, thus, presents a considerable alternative to implement a smart surface.
Obtaining a delamination-free wrinkled functional graphene surface in layered systems is an interesting challenge because the interface is usually too weak to withstand interfacial stress mismatch, which can trigger mechanical instability. In this paper, a general strategy is proposed toward addressing the delamination limitation imposed by fabricating conformal graphene wrinkles with bilayer systems of poly(methyl methacrylate) (PMMA) and polydimethylsiloxane (PDMS). To improve the interfacial strength, a postcuring transfer process is introduced to form a gradient interface layer without interfacial liquid between the PMMA and PDMS by entanglement of polymer chains during high-temperature curing. Compared to the conventional wet transfer of graphene,the transfer method can greatly enhance the interfacial strength. The chemical and mechanical mechanisms underlying the enhancement are revealed both experimentally and theoretically in terms of the transition from the buckled-induced delamination state to the delamination-free wrinkled state. Moreover, the light diffraction behaviors of multiscale graphene wrinkles are initially demonstrated to be an interesting continuous pattern induced by overlapping. The delamination-free conformal wrinkled functional graphene surface can provide valuable insight and design guidelines for the fundamental problems of deformed graphene and its applications in flexible functional devices.
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