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Naturally derived biopolymers have attracted great interest to construct photonic materials with multi-scale ordering, adaptive birefringence, chiral organization, actuation and robustness. Nevertheless, traditional processing commonly results in non-uniform organization across large-scale areas. Here, we report magnetically steerable uniform biophotonic organization of cellulose nanocrystals decorated with superparamagnetic nanoparticles with strong magnetic susceptibility, enabling transformation from helicoidal cholesteric (chiral nematic) to uniaxial nematic phase with near-perfect orientation order parameter of 0.98 across large areas. We demonstrate that magnetically triggered high shearing rate of circular flow exceeds those for conventional evaporation-based assembly by two orders of magnitude. This high rate shearing facilitates unconventional unidirectional orientation of nanocrystals along gradient magnetic field and untwisting helical organization. These translucent magnetic films are flexible, robust, and possess anisotropic birefringence and light scattering combined with relatively high optical transparency reaching 75%. Enhanced mechanical robustness and uniform organization facilitate fast, multimodal, and repeatable actuation in response to magnetic field, humidity variation, and light illumination.

 

Biological photonic structures can precisely control light propagation, scattering, and emission via hierarchical structures and diverse chemistry, enabling biophotonic applications for transparency, camouflaging, protection, mimicking and signaling. Corresponding natural polymers are promising building blocks for constructing synthetic multifunctional photonic structures owing to their renewability, biocompatibility, mechanical robustness, ambient processing conditions, and diverse surface chemistry. In this review, we provide a summary of the light phenomena in biophotonic structures found in nature, the selection of corresponding biopolymers for synthetic photonic structures, the fabrication strategies for flexible photonics, and corresponding emerging photonic-related applications. We introduce various photonic structures, including multi-layered, opal, and chiral structures, as well as photonic networks in contrast to traditionally considered light absorption and structural photonics. Next, we summarize the bottom-up and top-down fabrication approaches and physical properties of organized biopolymers and highlight the advantages of biopolymers as building blocks for realizing unique bioenabled photonic structures. Furthermore, we consider the integration of synthetic optically active nanocomponents into organized hierarchical biopolymer frameworks for added optical functionalities, such as enhanced iridescence and chiral photoluminescence. Finally, we present an outlook on current trends in biophotonic materials design and fabrication, including current issues, critical needs, as well as promising emerging photonic applications. 

Here, we report template‐assisted assembly of emissive carbon quantum dot (CQD) microcrystals on organized cellulose nanocrystals templates at the liquid–air interface. This large‐scale assembly is facilitated by the complementary amphiphilic character of CQDs and cellulose nanocrystals in the organized nematic phase. The resulting large microcrystals up to 200 μm across show unusually high emission that is not observed for limited CQDs aggregates. The dense crystal packing of CQDs in the layered fashion suppresses local molecular rotations and vibrations, thus restricting the intermolecular energy transfer and corresponding quenching phenomena. The as‐prepared crystals are mechanically stable and can be exploited for recyclable catalysis, enabling applications beyond the individual nanoparticles or disordered aggregates. The ligand‐templated assembly can be used to diversify CQD crystal architectures to guide formation of fibers, microplates, and micro‐flowers.

 

Here, we report template‐assisted assembly of emissive carbon quantum dot (CQD) microcrystals on organized cellulose nanocrystals templates at the liquid–air interface. This large‐scale assembly is facilitated by the complementary amphiphilic character of CQDs and cellulose nanocrystals in the organized nematic phase. The resulting large microcrystals up to 200 μm across show unusually high emission that is not observed for limited CQDs aggregates. The dense crystal packing of CQDs in the layered fashion suppresses local molecular rotations and vibrations, thus restricting the intermolecular energy transfer and corresponding quenching phenomena. The as‐prepared crystals are mechanically stable and can be exploited for recyclable catalysis, enabling applications beyond the individual nanoparticles or disordered aggregates. The ligand‐templated assembly can be used to diversify CQD crystal architectures to guide formation of fibers, microplates, and micro‐flowers.

 

The integration of chiral organization with photonic structures found in many living creatures enables unique chiral photonic structures with a combination of selective light reflection, light propagation, and circular dichroism. Inspired by these natural integrated nanostructures, hierarchical chiroptical systems that combine imprinted surface optical structures with the natural chiral organization of cellulose nanocrystals are fabricated. Different periodic photonic surface structures with rich diffraction phenomena, including various optical gratings and microlenses, are replicated into nanocellulose film surfaces over large areas. The resulting films with embedded optical elements exhibit vivid, controllable structural coloration combined with highly asymmetric broadband circular dichroism and a microfocusing capability not typically found in traditional photonic bioderived materials without compromising their mechanical strength. The strategy of imprinting surface optical structures onto chiral biomaterials facilitates a range of prospective photonic applications, including stereoscopic displays, polarization encoding, chiral polarizers, and colorimetric chiral biosensing.