The reversible surface patterns with fluorescence and topography can possibly enable information recording and reading and provide an important alternative to realize the higher information security. We demonstrated a reversible dual-pattern with simultaneously responsive fluorescence and topography using an anthracene (AN) and naphthalene diimide (NDI) containing copolymer (PAN-NDI-BA) as the skin layer, in which the reversible photodimerization of AN can simultaneously control the cross-linking and CT interaction between AN and NDI. Upon irradiation with UV light and thermal treatment, the resulting pattern assumes a reversible change between smooth and wrinkled states, and its fluorescence changes reversibly from red to white to blue-green. The smart surfaces with dynamic hierarchical wrinkles and fluorescence were achieved by selective irradiation with photomasks and can be employed for potential applications in smart displays and anticounterfeiting.
To avoid the losses caused by counterfeit commodity, documents and currency, various anticounterfeiting strategies have aroused an intensive interest and have been developed rapidly; however, obtaining unclonable anticounterfeiting technology that is sufficiently adaptable for industry-suitable authentication is still a challenge. Here, we report a facile yet effective anticounterfeiting strategy by utilizing pattern memory surface with NIR-driven dynamic wrinkles, which can be used as dynamic biomimetic fingerprints. The randomness and unpredictability of the wrinkles' morphology enable them to be analogous to the minutiae of fingerprints. The dynamic nature of the fingerprint-like wrinkles endows them with hidden information to further improve security levels, and their NIRresponsiveness can help maintain a nearly identical topography during the cycles of erasure and regeneration, thus truly realizing unclonable anticounterfeiting. On the basis of these characteristics of NIR-driven dynamic wrinkles, such as simple preparation and easy readout, unique and unclonable identity tags were fabricated for antique authentication, which can be further combined with fluorescence patterns to achieve multiple anticounterfeiting technologies.
On the process of deforming polymer, its morphologies can be vividly observed and reflected via the internal stress distribution under the polarized light due to its special stretched birefringence, which gives a new way to store and read information. Inspired by this vivid character, a novel crosslinked polyurethane (PU) is designed and used as matrix for coding information, in which aluminum acetylacetonate works as the crosslinker to form dynamical crosslinked structure with coordinated bonds. By tailoring these two bonds via a region-selective regulation, the information can be written in the crosslinked PU. Only under the polarized light, the coded information can be read as stress induced color on the deformed state. After its recovery, 2D pattern can be simultaneously formed on the surface of the film. Therefore, the information is expressed in multiple channels. Thanks to the dynamic character, the information can be also erased and rewritten. Therefore, it is a new method for information coding with a high security, which has a wide range of potential applications in data storage, anticounterfeiting labeling, information conversion, and other areas.
Understanding the evolution of self-wrinkling is critical to control the wrinkles that widely exist in nature and engineering. Using a single-layer film of photosensitive anthracene-functionalized poly(styrene-block-butadiene-block-styrene) (SBS-An) as a model, we investigated the generation of self-wrinkles on this film. Upon irradiation with UV light, the SBS-An film was designed to achieve a gradient structure with controllable elasticity and viscoelasticity. The inner stress is produced via UV-light-induced cross-linking, which drives the wrinkling. Importantly, the evolution of the wrinkles in this gradient film was a time-dependent kinetic process, which was traced by a microscope to understand the mechanism of wrinkling based on the polymer viscoelasticity. Theoretical calculations and simulations were also utilized to verify and support the experimental results. Furthermore, taking advantage of light, the precise temporal and spatial control of wrinkles could be achieved by photochemical boundaries, which permit various ordered wrinkles.
A dynamic diffraction grating (DDG) can realize on-demand in-situ regulation of light diffraction and is highly necessary in the next-generation optical devices; however, its fabrication remains challenging because of difficulties in generating a responsive pattern in the bulk material or on the surface. In this study, a facile and general approach to construct DDG is developed based on the near-infrared radiation (NIR)driven responsive 2D ordered surface pattern, which is fabricated by light-direct writing of wrinkles on a thin film of a photosensitive supramolecular polymer network comprised of a copolymer containing amino groups, anthracene carboxylic acid (ANA), and carbon nanotubes. The resulting surface pattern, which exhibits a height dependence on the NIR irradiation, can be used as the DDG whose optical diffraction can be regulated in-situ by NIR. Furthermore, because of the presence of a reversible ANA photodimer and hydrogen bonding in the supramolecular network, the patterned surface can be erased and rewritten by UV light with different wavelengths and self-healed by NIR irradiation. The results demonstrate a simple strategy for DDGs that will have a broad application in the fields of optics, electronics, and intelligent sensing.
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