tissues could be organized into a helical assembly, [4][5][6] showing remarkable photonic properties and attractive structural anisotropy. The advantages of cellulosic sustainability and biocompatibility make it superior to other photonic materials to produce optical materials. Bioinspired cellulose's multiscale architecture has implemented a series of photonic building blocks, mainly including hydroxypropyl cellulose, [7] ethylcellulose, [8] and cellulose nanocrystal (CNC). [9,10] Among them, the self-assembly of CNCs into chiral photonic structures is the most representative. An artistic view (Figure 1a) shows a solid film formed by the selfassembly of CNCs, which is similar to the Bouligand structure of the beetle exoskeleton. [11,12] CNCs consist of each chain of β-(poly-1,4-D-glucose) stabilized via hydrogen bonds and hydrophobic interactions that provide mechanical stiffness to the solid film. [13] CNC-derived photonic materials have spawned a series of exciting applications in the fields of sensors, [14,15] optics, [16,17] electronics, [18] and engineering. [19,20] However, in many cases, the above materials rarely undergo elastic deformation but crack in bending, thus compromising their outstanding properties. In addition, the photonic structures of these materials are incompatible with humid and liquid environments because of their high hygroscopicity and water solubility.Cellulose nanocrystals (CNCs)-derived photonic materials have confirmed great potential in producing renewable optical and engineering areas. However, it remains challenging to simultaneously possess toughness, strength, and multi ple responses for developing high-performance sensors, intelligent coatings, flexible textiles, and multifunctional devices. Herein, the authors report a facile and robust strategy that poly(ethylene glycol) dimethacrylate (PEGDMA) can be converged into the chiral nematic structure of CNCs by ultraviolet-triggered free radical polymerization in an N,N-dimethylformamide solvent system. The resulting CNC-poly(PEGDMA) composite exhibits impressive strength (42 MPa), stretchability (104%), toughness (31 MJ m −3 ), and solvent resistance. Notably, it preserves vivid optical iridescence, displaying stretchable variation from red, yellow, to green responding to the applied mechanical stimuli. More interestingly, upon exposure to spraying moisture, it executes sensitive actuation (4.6° s −1 ) and multiple complex 3D deformation behaviors, accompanied by synergistic iridescent appearances. Due to its structural anisotropy of CNC with typical left-handedness, the actuation shows the capability to generate a high probability (63%) of right-handed helical shapes, mimicking a coiled tendril. The authors envision that this versatile system with sustainability, robustness, mechanochromism, and specific actuating ability will open a sustainable avenue in mechanical sensors, stretchable optics, intelligent actuators, and soft robots.The ORCID identification number(s) for the author(s) of this article can be found under https:/...

Designing a sustainable security model that carries multilevel information with numerous optical states will significantly enhance anti-counterfeiting abilities to deter counterfeits, ranging from artworks, currencies, and foods to medicines, but is enormously challenging. Herein, ambient-friendly, large-area, quadruple-level, and chiral luminescent materials are prepared by incorporating lanthanide complexes wrapped in poly(ethylene glycol) matrix into chiral nematic cellulose nanocrystal (CNC) films through a co-assembly strategy. Due to the regulation of the chiral nematic structures, the composite films enable full-color structural colors and tunable fluorescence. Notably, the brightest fluorescent film radiates right-handed circularly polarized luminescence with an asymmetric factor over −0.36, a lifetime up to 510 µs, and an absolute quantum yield up to 66.7%. More interestingly, a fascinating chirooptical behavior ranging from azure to khaki can be controlled by a polarizing filter at given 0° and 90° rotation angles. This anti-counterfeiting system showcases the comprehensive properties of bright and responsive photoluminescence, quadruple and convertible color, and flexible and solvent-resistant abilities. This CNC-derived photonic material can act as the multimodal security label on a model banknote, which greatly facilitates its development for practical applications.