Highly Efficient and Environmentally Friendly Fabrication of Robust, Programmable, and Biocompatible Anisotropic, All‐Cellulose, Wrinkle‐Patterned Hydrogels for Cell Alignment

Abstract

unfolding, [2] and skin wrinkles communicate a change in the state of the body. [3] These exquisite self-wrinkling processes typically originate from heterogeneous growth rates during the growth process, which results in compressive strains on the constrained tissues or organs and leads to mechanical instability. [5,6] Hydrogels possess water-rich structures similar to the abovementioned biological tissues and are regarded as promising scaffolds in biomedical fields. [7][8][9] Given the importance of wrinkled structures, the similarity between hydrogels and biotissue, and the important role of the programmable structure of hydrogels in potential biomedical applications, [10,11] imitating the delicate architecture of biological tissues in a biocompatible, mechanically stable wrinkled hydrogel with programmable patterns can facilitate an understanding of the effects of surface topography on biological properties and will be of benefit to humanity. In fact, motivated by the distinct functionalities of wrinkled structures in biology, material scientists have attempted to mimic this structure in artificial systems. [12][13][14][15][16][17][18][19] Consequently, a series of strategies, including swelling mismatch, [20] prepatterning treatment, [21] or coating of a second layer on the substrate, [5] have been successfully conducted to generate a compressive strain that triggers a controllable wrinkling Wrinkled hydrogels from biomass sources are potential structural biomaterials. However, for biorelated applications, engineering scalable, structure-customized, robust, and biocompatible wrinkled hydrogels with highly oriented nanostructures and controllable intervals is still a challenge. A scalable biomass material, namely cellulose, is reported for customizing anisotropic, all-cellulose, wrinkle-patterned hydrogels (AWHs) through an ultrafast, auxiliary force, acid-induced gradient dual-crosslinking strategy. Direct immersion of a prestretched cellulose alkaline gel in acid and relaxation within seconds allow quick buildup of a consecutive through-thickness modulus gradient with acid-penetration-directed dual-crosslinking, confirmed by visual 3D Raman microscopy imaging, which drives the formation of selfwrinkling structures. Moreover, guided by quantitative mechanics simulations, the structure of AWHs is found to exhibit programmable intervals and aligned nanostructures that differ between ridge and valley regions and can be controlled by tuning the prestretching strain and acid treatment time, and these AWHs successfully induce cell alignment. Thus, a new avenue is opened to fabricate polysaccharide-derived, programmable, anisotropic, wrinkled hydrogels for use as biomedical materials via a bottom-up method.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Dynamic wrinkling pattern exhibiting tunable fluorescence for anticounterfeiting applications

“…In addition, wrinkles could also serve as graphical tags since the graphical images formed by wrinkles could be identified by naked eyes due to the light scattering caused by wrinkling pattern. Owing to the randomness, 3D topography, and nondeterministic process and unpredictability of the formation, wrinkling patterns caused by a surface mechanical instability [26][27][28][29][30][31][32] can realize a higher level of security in anticounterfeiting. Combining both responsive fluorescent behavior and the dynamic wrinkling pattern [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] into the same anticounterfeiting tag will undoubtedly enhance the information capacity and security.…”

Transparency Change Mechanochromism Based on a Robust PDMS‐Hydrogel Bilayer Structure

“…[ 39 ] Given the importance of wrinkling structures, the merits of PDMS and the biological similarity of a hydrogel, the PDMS‐hydrogel bilayer (PHB) structure with a robust interface provides a stable and water‐rich platform to generate surface wrinkles, which is ideal for many applications requiring high hydrophilicity. [ 22,29 ]…”

“…[18] Coating PDMS with a hydrogel anchored by micropillars is a creative approach to generate a more stable and effective hydrophilic surface, [19][20][21] as PDMS virtually does not swell in contact with water. [1] Thus, PDMS and hydrogel act as a perfect combination, because hydrogel contains water providing a very hydrophilic surface with remarkable biocompatibility and similarity to biological tissues, [22] and PDMS serves as a more rigid substrate for the soft hydrogel film. However, the PDMS substrate needs replica micro-molding via photosensitive chemistry to produce micropillar structures, and the modified interface of the PDMS and the hydrogel is just a physical conglutination with potential instability.…”

“…[39] Given the importance of wrinkling structures, the merits of PDMS and the biological similarity of a hydrogel, the PDMS-hydrogel bilayer (PHB) structure with a robust interface provides a stable and water-rich platform to generate surface wrinkles, which is ideal for many applications requiring high hydrophilicity. [22,29] Herein, we present a new method to prepare a covalently bonded PHB structure, which was obtained via in situ free radical copolymerization of acrylamide together with the surface alkenyl groups on α-zirconium phosphate (ZrP) nanosheets and on the surface of PDMS substrate in aqueous solution. Polyacrylamide (PAM) is chosen to build the polymer gel network as it is a widely-reported biocompatible polymer.…”

Photodynamic Pattern Memory Surfaces with Responsive Wrinkled and Fluorescent Patterns

“…Accordingly, as a naturally mechanical phenomenon, wrinkled patterning on film–substrate bilayer systems [ 8 ] resulting from compressive stress provides an intriguing avenue for overcoming the abovementioned obstacles and has attracted considerable research interest owing to the distinguished optical, [ 9 ] electrical, [ 10 ] biological, [ 11 ] and mechanical [ 9b,12 ] performances of the developed patterns. To date, manipulating the progress of stress relaxation and modulus within the wrinkled topologies based on indirect or direct actuation (e.g., light, temperature, pH, and solvents) has enabled the realization of dynamically tunable smart surfaces.…”