Study On Dynamic Surface Wrinkle And Fluorescence Patterns

Various surface patterns exist everywhere in the nature,endowing the creatures with specific functions,especially the surface pattern with dynamic characteristics can effectively control the surface performance or feedback environmental information.Therefore,the study of surface patterns has attracted many researchers to devote themselves to it.Surface patterns can be divided into two categories,one is based on surface color,the other is based on topography.The surface color is mainly based on chemical chromophores which emit fluorescence or phosphorescence under specific excitation.And the surface topography can be fabricated via “top-down” and “bottom-up”.In the field of dynamic patterns,by taking advantage of photochromic materials or tunable supramolecular interactions,various dynamic patterns with reversible fluorescence have been fabricated and bear significant applications in information security and storage,sensors,and anti-counterfeiting.Compared with these reversible fluorescence patterns,however,it is substantially more challenging to fabricate responsive patterns with dynamically controlled topographies.As one important alternative process for generating patterned surfaces with a dynamic topography,the surface wrinkles of a stiff skin bound to an elastomeric substrate have been harnessed to create reversible patterns that are responsive to external stimuli and provide unique dynamic characteristics of surface topographies and their properties.Surface color and topography are always used for information recording and reading.But only one parameter that is fluorescence or topography,for the recording and reading of information,probably reduce the information capacity and security.And a reversible pattern with both fluorescence and topography will undoubtedly increase the information capacity and security.Here,we demonstrate two strategies to fabricate responsive,dynamic surface pattern with wrinkle and fluorescence,and used for two kinds of anti-counterfeiting materials.Reversible surface dual-pattern with wrinkled topography and fluorescence is realized by photo-tunable charge transfer interaction and used as anti-fake ink.And dynamic dual-pattern with wrinkle and fluorescence is achieved by utilizing infrared(IR)-driven reversible wrinkles with AIEgen-doped polymer as top-layer,which can be used as dynamic fingerprints for unclonable anti-counterfeiting.The details in the fabrication process and results are as follows:1.Reversible surface dual-pattern with simultaneously dynamic wrinkled topography and fluorescence.An anthracene(AN)and naphthalene diimide(NDI)containing copolymer(PAN-NDI-BA)are used as the skin layer with PDMS used as substrate.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.And this process with fluorescence and wrinkles is reversible under heating or 254 nm UV light.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 anti-counterfeiting ink.2.Dynamic biomimetic fingerprints with reversible wrinkled topography and fluorescence are fabricated by utilizing infrared(IR)-driven reversible wrinkles with various fluorescence molecules.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 IR-responsiveness can help maintain a nearly identical topography during the cycles of erasure and regeneration,thus truly realizing unclonable anti-counterfeiting.Based on these characteristics of IR-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 anti-counterfeiting technologies.