Biological Material Interfaces as Inspiration for Mechanical and Optical Material Designs

Uncovering the Recent Progress of CNC-Derived Chirality Nanomaterials: Structure and Functions

Cellulose nanocrystal (CNC), as a renewable resource, with excellent mechanical performance, low thermal expansion coefficient, and unique optical performance, is becoming a novel candidate for the development of smart material. Herein, the recent progress of CNC-based chirality nanomaterials is uncovered, mainly covering structure regulations and function design. Undergoing a simple evaporation process, the cellulose nanorods can spontaneously assemble into chiral nematic films, accompanied by a vivid structural color. Various film structure-controlling strategies, including assembly means, physical modulation, additive engineering, surface modification, geometric structure regulation, and external field optimization, are summarized in this work. The intrinsic correlation between structure and performance is emphasized. Next, the applications of CNC-based nanomaterials is systematically reviewed. Layer-by-layer stacking structure and unique optical activity endow the nanomaterials with wide applications in the mineralization, bone regeneration, and synthesis of mesoporous materials. Besides, the vivid structural color broadens the functions in anti-counterfeiting engineering, synthesis of the shape-memory and self-healing materials. Finally, the challenges for the CNC-based nanomaterials are proposed.

Bio-Inspired Photoelectric Dual-Mode Sensor Based on Photonic Crystals for Human Motion Sensing and Monitoring

Photoelectric dual-mode sensors, which respond to strain signal through photoelectric dual-signals, hold great promise as wearable sensors in human motion monitoring. In this work, a photoelectric dual-mode sensor based on photonic crystals hydrogel was developed for human joint motion detection. The optical signal of the sensor originated from the structural color of photonic crystals, which was achieved by tuning the polymethyl methacrylate (PMMA) microspheres diameter. The reflective peak of the sensor, based on 250 nm PMMA PCs, shifted from 623 nm to 492 nm with 100% strain. Graphene was employed to enhance the electrical signal of the sensor, resulting in a conductivity increase from 9.33 × 10-4 S/m to 2 × 10-3 S/m with an increase in graphene from 0 to 8 mg·mL-1. Concurrently, the resistance of the hydrogel with 8 mg·mL-1 graphene increased from 160 kΩ to 485 kΩ with a gauge factor (GF) = 0.02 under 100% strain, while maintaining a good cyclic stability. The results of the sensing and monitoring of finger joint bending revealed a significant shift in the reflective peak of the photoelectric dual-mode sensor from 624 nm to 526 nm. Additionally, its resistance change rate was measured at 1.72 with a 90° bending angle. These findings suggest that the photoelectric dual-mode sensor had the capability to detect the strain signal with photoelectric dual-mode signals, and indicates its great potential for the sensing and monitoring of joint motion.

Silk-based intelligent fibers and textiles: structures, properties, and applications

Multifunctional fibers represent a cornerstone of human civilization, playing a pivotal role in numerous aspects of societal development. Natural biomaterials, in contrast to synthetic alternatives, offer environmental sustainability, biocompatibility, and biodegradability. Among these biomaterials, natural silk is favored in biomedical applications and smart fiber technology due to its accessibility, superior mechanical properties, diverse functional groups, controllable structure, and exceptional biocompatibility. This review delves into the intricate structure and properties of natural silk fibers and their extensive applications in biomedicine and smart fiber technology. It highlights the critical significance of silk fibers in the development of multifunctional materials, emphasizing their mechanical strength, biocompatibility, and biodegradability. A detailed analysis of the hierarchical structure of silk fibers elucidates how these structural features contribute to their unique properties. The review also encompasses the biomedical applications of silk fibers, including surgical sutures, tissue engineering, and drug delivery systems, along with recent advancements in smart fiber applications such as sensing, optical technologies, and energy storage. The enhancement of functional properties of silk fibers through chemical or physical modifications is discussed, suggesting broader high-end applications. Additionally, the review addresses current challenges and future directions in the application of silk fibers in biomedicine and smart fiber technologies, underscoring silk's potential in driving contemporary technological innovations. The versatility and sustainability of silk fibers position them as pivotal elements in contemporary materials science and technology, fostering the development of next-generation smart materials.

Interfacial Stereoelectronic Effect Induced by Anchoring Orientation

Heterogeneous interfaces in most devices play a key role in the material performance. Exploring the atomic structure and electronic properties of metal-molecule interfaces is critical for various potential applications, such as surface sensing, molecular recognition, and molecular electronic devices. This study unveils a ubiquitous interfacial stereoelectronic effect in conjugated molecular junctions by combining first-principles simulation and scanning tunneling microscopy break junction technology. Single-molecule junctions with same-side interfacial anchoring (cis configuration) exhibit higher conductance than those with opposite-side interfacial anchoring (trans configuration). The cis and trans configurations can undergo reversible conversions, resulting in a conductance switching. The stability of these configurations can be adjusted by an electric field, achieving precise regulation of conductance states. Our findings provide important insights for designing high-quality materials and enhancing the device performance.

Valorization of Seafood Waste for Food Packaging Development

Packaging plays a crucial role in protecting food by providing excellent mechanical properties as well as effectively blocking water vapor, oxygen, oil, and other contaminants. The low degradation of widely used petroleum-based plastics leads to environmental pollution and poses health risks. This has drawn interest in renewable biopolymers as sustainable alternatives. The seafood industry generates significant waste that is rich in bioactive substances like chitin, chitosan, gelatins, and alginate, which can replace synthetic polymers in food packaging. Although biopolymers offer biodegradability, biocompatibility, and non-toxicity, their films often lack mechanical and barrier properties compared with synthetic polymer films. This comprehensive review discusses the chemical structure, characteristics, and extraction methods of biopolymers derived from seafood waste and their usage in the packaging area as reinforcement or base materials to guide researchers toward successful plastics replacement and commercialization. Our review highlights recent advancements in improving the thermal durability, mechanical strength, and barrier properties of seafood waste-derived packaging, explores the mechanisms behind these improvements, and briefly mentions the antimicrobial activities and mechanisms gained from these biopolymers. In addition, the remaining challenges and future directions for using seafood waste-derived biopolymers for packaging are discussed. This review aims to guide ongoing efforts to develop seafood waste-derived biopolymer films that can ultimately replace traditional plastic packaging.

Bioinspired Nanolayered Structure Tuned by Extensional Stress: A Scalable Way to High-Performance Biodegradable Polyesters

The nacre-inspired multi-nanolayer structure offers a unique combination of advanced mechanical properties, such as strength and crack tolerance, making them highly versatile for various applications. Nevertheless, a significant challenge lies in the current fabrication methods, which is difficult to create a scalable manufacturing process with precise control of hierarchical structure. In this work, a novel strategy is presented to regulate nacre-like multi-nanolayer films with the balance mechanical properties of stiffness and toughness. By utilizing a co-continuous phase structure and an extensional stress field, the hierarchical nanolayers is successfully constructed with tunable sizes using a scalable processing technique. This strategic modification allows the robust phase to function as nacre-like platelets, while the soft phase acts as a ductile connection layer, resulting in exceptional comprehensive properties. The nanolayer-structured films demonstrate excellent isotropic properties, including a tensile strength of 113.5 MPa in the machine direction and 106.3 MPa in a transverse direction. More interestingly, these films unprecedentedly exhibit a remarkable puncture resistance at the same time, up to 324.8 N mm-1, surpassing the performance of other biodegradable films. The scalable fabrication strategy holds significant promise in designing advanced bioinspired materials for diverse applications.

Guidelines derived from biomineralized tissues for design and construction of high-performance biomimetic materials: from weak to strong

Living organisms in nature have undergone continuous evolution over billions of years, resulting in the formation of high-performance fracture-resistant biomineralized tissues such as bones and teeth to fulfill mechanical and biological functions, despite the fact that most inorganic biominerals that constitute biomineralized tissues are weak and brittle. During the long-period evolution process, nature has evolved a number of highly effective and smart strategies to design chemical compositions and structures of biomineralized tissues to enable superior properties and to adapt to surrounding environments. Most biomineralized tissues have hierarchically ordered structures consisting of very small building blocks on the nanometer scale (nanoparticles, nanofibers or nanoflakes) to reduce the inherent weaknesses and brittleness of corresponding inorganic biominerals, to prevent crack initiation and propagation, and to allow high defect tolerance. The bioinspired principles derived from biomineralized tissues are indispensable for designing and constructing high-performance biomimetic materials. In recent years, a large number of high-performance biomimetic materials have been prepared based on these bioinspired principles with a large volume of literature covering this topic. Therefore, a timely and comprehensive review on this hot topic is highly important and contributes to the future development of this rapidly evolving research field. This review article aims to be comprehensive, authoritative, and critical with wide general interest to the science community, summarizing recent advances in revealing the formation processes, composition, and structures of biomineralized tissues, providing in-depth insights into guidelines derived from biomineralized tissues for the design and construction of high-performance biomimetic materials, and discussing recent progress, current research trends, key problems, future main research directions and challenges, and future perspectives in this exciting and rapidly evolving research field.

Biopolymers for Hygroscopic Material Development

The effective management of atmospheric water will create huge value for mankind. Diversified and sustainable biopolymers that are derived from organisms provide rich building blocks for various hygroscopic materials. Here, a comprehensive review of recent advances in developing biopolymers for hygroscopic materials is provided. It is begun with a brief introduction of species diversity and the processes of obtaining various biopolymer materials from organisms. The fabrication of hygroscopic materials is then illustrated, with a specific focus on the use of biopolymer-derived materials as substrates to produce composites and the use of biopolymers as building blocks to fabricate composite gels. Next, the representative applications of biopolymer-derived hygroscopic materials for dehumidification, atmospheric water harvesting, and power generation are systematically presented. An outlook on future challenges and key issues worthy of attention are finally provided.

Towards predictive control of reversible nanoparticle assembly with solid-binding proteins

Although a broad range of ligand-functionalized nanoparticles and physico-chemical triggers have been exploited to create stimuli-responsive colloidal systems, little attention has been paid to the reversible assembly of unmodified nanoparticles with non-covalently bound proteins. Previously, we reported that a derivative of green fluorescent protein engineered with oppositely located silica-binding peptides mediates the repeated assembly and disassembly of 10-nm silica nanoparticles when pH is toggled between 7.5 and 8.5. We captured the subtle interplay between interparticle electrostatic repulsion and their protein-mediated short-range attraction with a multiscale model energetically benchmarked to collective system behavior captured by scattering experiments. Here, we show that both solution conditions (pH and ionic strength) and protein engineering (sequence and position of engineered silica-binding peptides) provide pathways for reversible control over growth and fragmentation, leading to clusters ranging in size from 25 nm protein-coated particles to micrometer-size aggregate. We further find that the higher electrolyte environment associated with successive cycles of base addition eventually eliminates reversibility. Our model accurately predicts these multiple length scales phenomena. The underpinning concepts provide design principles for the dynamic control of other protein- and particle-based nanocomposites.

ForceGen: End-to-end de novo protein generation based on nonlinear mechanical unfolding responses using a language diffusion model

Through evolution, nature has presented a set of remarkable protein materials, including elastins, silks, keratins and collagens with superior mechanical performances that play crucial roles in mechanobiology. However, going beyond natural designs to discover proteins that meet specified mechanical properties remains challenging. Here, we report a generative model that predicts protein designs to meet complex nonlinear mechanical property-design objectives. Our model leverages deep knowledge on protein sequences from a pretrained protein language model and maps mechanical unfolding responses to create proteins. Via full-atom molecular simulations for direct validation, we demonstrate that the designed proteins are de novo, and fulfill the targeted mechanical properties, including unfolding energy and mechanical strength, as well as the detailed unfolding force-separation curves. Our model offers rapid pathways to explore the enormous mechanobiological protein sequence space unconstrained by biological synthesis, using mechanical features as the target to enable the discovery of protein materials with superior mechanical properties.

Nanoparticle Assembly: From Self-Organization to Controlled Micropatterning for Enhanced Functionalities

Nanoparticles form long-range micropatterns via self-assembly or directed self-assembly with superior mechanical, electrical, optical, magnetic, chemical, and other functional properties for broad applications, such as structural supports, thermal exchangers, optoelectronics, microelectronics, and robotics. The precisely defined particle assembly at the nanoscale with simultaneously scalable patterning at the microscale is indispensable for enabling functionality and improving the performance of devices. This article provides a comprehensive review of nanoparticle assembly formed primarily via the balance of forces at the nanoscale (e.g., van der Waals, colloidal, capillary, convection, and chemical forces) and nanoparticle-template interactions (e.g., physical confinement, chemical functionalization, additive layer-upon-layer). The review commences with a general overview of nanoparticle self-assembly, with the state-of-the-art literature review and motivation. It subsequently reviews the recent progress in nanoparticle assembly without the presence of surface templates. Manufacturing techniques for surface template fabrication and their influence on nanoparticle assembly efficiency and effectiveness are then explored. The primary focus is the spatial organization and orientational preference of nanoparticles on non-templated and pre-templated surfaces in a controlled manner. Moreover, the article discusses broad applications of micropatterned surfaces, encompassing various fields. Finally, the review concludes with a summary of manufacturing methods, their limitations, and future trends in nanoparticle assembly.

Pseudomorphic Synthesis of Monodisperse Afterglow Carbon Dot-Doped SiO2 Microparticles for Photonic Crystals

Synthesizing monodisperse afterglow microparticles (MPs) is crucial for creating photonic crystal (PC) platforms with multiple optical states for optoelectronics. However, achieving high uniformity in both size and morphology is challenging for inorganic afterglow MPs using conventional methods. In this contribution, a novel approach for the synthesis of carbon dot (CD)-doped SiO2 MPs with tunable afterglow properties and size distributions is reported. These mechanism studies suggest that the pseudomorphic transformation of SiO2 MPs enables CD doping, providing a hydrogen bond-enriched environment for triplet state stabilization, which generates green afterglow while retaining the uniformity in size and morphology of the parent SiO2 MPs. Furthermore, the utility of CD-doped SiO2 MPs in the fabrication of rationally designed PC patterns is shown using a combined consecutive dip-coating and laser-assisted etching strategy. The pattern displays multiple optical responses under different lighting conditions, including angle-dependent structural colors and blue luminescence under daylight and upon 365-nm irradiation, respectively, as well as time-dependent green afterglow after ceasing UV excitation. The findings pave the way for further controlling the dynamics of spontaneous emissions by PCs to enable complicated optical states for advanced photonics.

Unrestricted Chiral Patterning by Laser Writing in Liquid Crystalline and Plasmonic Nanocomposite Thin Films

Obtaining hierarchical structures with arbitrarily controlled chirality remains a challenge. Here, thin films featuring chiroptically bipolar patterns are produced by a device utilizing microscale photothermal re-melting of materials exhibiting chirality synchronization. This device operates autonomously, guided by an algorithm that facilitates the homochiral growth of supramolecular organic helices through controlling their re-melting. The chirality synchronization phenomena of constitutionally achiral molecules grants availability of both handednesses of the helices, enabling unrestricted chiral writing in the film. The collective chiroptical response of assembled molecules is utilised to guide the patterning process, creating a foundation for optically secured information. The established methodology enables achieving dissymmetry factor values for circular dichroism (CD) a magnitude higher than previously reported, as confirmed with state-of-the-art, synchrotron-based Mueller matrix polarimetry (MMP). Moreover, the developed method is extended to nanocomposites comprising gold nanoparticles, providing the opportunity to tune the CD toward the plasmonic region. This strategic application of photothermal processing, specifically laser-directed melting, uncovers the potential to broaden the selection of nanostructured materials with precisely designed functionalities for photonic applications.

Fabrication of a Fish-Bone-Inspired Inorganic-Organic Composite Membrane

Biological materials have properties like great strength and flexibility that are not present in synthetic materials. Using the ribs of crucian carp as a reference, we investigated the mechanisms behind the high mechanical properties of this rib bone, and found highly oriented layers of calcium phosphate (CaP) and collagen fibers. To fabricate a fish-rib-bone-mimicking membrane with similar structure and mechanical properties, this study involves (1) the rapid synthesis of plate-like CaP crystals, (2) the layering of CaP-gelatin hydrogels by gradual drying, and (3) controlling the shape of composite membranes using porous gypsum molds. Finally, as a result of optimizing the compositional ratio of CaP filler and gelatin hydrogel, a CaP filler content of 40% provided the optimal mechanical properties of toughness and stiffness similar to fish bone. Due to the rigidity, flexibility, and ease of shape control of the composite membrane materials, this membrane could be applied as a guided bone regeneration (GBR) membrane.

Bioinspired Design Rules from Highly Mineralized Natural Composites for Two-Dimensional Composite Design

Discoveries of two-dimensional (2D) materials, exemplified by the recent entry of MXene, have ushered in a new era of multifunctional materials for applications from electronics to biomedical sensors due to their superior combination of mechanical, chemical, and electrical properties. MXene, for example, can be designed for specialized applications using a plethora of element combinations and surface termination layers, making them attractive for highly optimized multifunctional composites. Although multiple critical engineering applications demand that such composites balance specialized functions with mechanical demands, the current knowledge of the mechanical performance and optimized traits necessary for such composite design is severely limited. In response to this pressing need, this paper critically reviews structure-function connections for highly mineralized 2D natural composites, such as nacre and exoskeletal of windowpane oysters, to extract fundamental bioinspired design principles that provide pathways for multifunctional 2D-based engineered systems. This paper highlights key bioinspired design features, including controlling flake geometry, enhancing interface interlocks, and utilizing polymer interphases, to address the limitations of the current design. Challenges in processing, such as flake size control and incorporating interlocking mechanisms of tablet stitching and nanotube forest, are discussed along with alternative potential solutions, such as roughened interfaces and surface waviness. Finally, this paper discusses future perspectives and opportunities, including bridging the gap between theory and practice with multiscale modeling and machine learning design approaches. Overall, this review underscores the potential of bioinspired design for engineered 2D composites while acknowledging the complexities involved and providing valuable insights for researchers and engineers in this rapidly evolving field.

Untapped Potential of Deep Eutectic Solvents for the Synthesis of Bioinspired Inorganic-Organic Materials

Since the discovery of deep eutectic solvents (DESs) in 2003, significant progress has been made in the field, specifically advancing aspects of their preparation and physicochemical characterization. Their low-cost and unique tailored properties are reasons for their growing importance as a sustainable medium for the resource-efficient processing and synthesis of advanced materials. In this paper, the significance of these designer solvents and their beneficial features, in particular with respect to biomimetic materials chemistry, is discussed. Finally, this article explores the unrealized potential and advantageous aspects of DESs, focusing on the development of biomineralization-inspired hybrid materials. It is anticipated that this article can stimulate new concepts and advances providing a reference for breaking down the multidisciplinary borders in the field of bioinspired materials chemistry, especially at the nexus of computation and experiment, and to develop a rigorous materials-by-design paradigm.

Biomimetic Silk Architectures Outperform Animal Horns in Strength and Toughness

Structural biomimicry is an intelligent approach for developing lightweight, strong, and tough materials (LSTMs). Current fabrication technologies, such as 3D printing and two-photon lithography often face challenges in constructing complex interlaced structures, such as the sinusoidal crossed herringbone structure that contributes to the ultrahigh strength and fracture toughness of the dactyl club of peacock mantis shrimps. Herein, bioinspired LSTMs with laminated or herringbone structures is reported, by combining textile processing and silk fiber "welding" techniques. The resulting biomimetic silk LSTMs (BS-LSTMs) exhibit a remarkable combination of lightweight with a density of 0.6-0.9 g cm-3 , while also being 1.5 times stronger and 16 times more durable than animal horns. These findings demonstrate that BS-LSTMs are among the toughest natural materials made from silk proteins. Finite element simulations further reveal that the fortification and hardening of BS-LSTMs arise primarily from the hierarchical organization of silk fibers and mechanically transferable meso-interfaces. This study highlights the rational, cost-effective, controllable mesostructure, and transferable strategy of integrating textile processing and fiber "welding" techniques for the fabrication of BS-LSTMs with advantageous structural and mechanical properties. These findings have significant implications for a wide range of applications in biomedicine, mechanical engineering, intelligent textiles, aerospace industries, and beyond.

Tendon Repair and Regeneration Using Bioinspired Fibrillation Engineering That Mimicked the Structure and Mechanics of Natural Tissue

Replicating the controlled nanofibrillar architecture of collagenous tissue represents a promising approach in the design of tendon replacements that have tissue-mimicking biomechanics─outstanding mechanical strength and toughness, defect tolerance, and fatigue and fracture resistance. Guided by this principle, a fibrous artificial tendon (FAT) was constructed in the present study using an engineering strategy inspired by the fibrillation of a naturally spun silk protein. This bioinspired FAT featured a highly ordered molecular and nanofibrillar architecture similar to that of soft collagenous tissue, which exhibited the mechanical and fracture characteristics of tendons. Such similarities provided the motivation to investigate FAT for applications in Achilles tendon defect repair. In vitro cellular morphology and expression of tendon-related genes in cell culture and in vivo modeling of tendon injury clearly revealed that the highly oriented nanofibrils in the FAT substantially promoted the expression of tendon-related genes combined with the Achilles tendon structure and function. These results provide confidence about the potential clinical applications of the FAT.

Design and Evolution of Enhanced Peptide-Peptide Ligation for Modular Transglutaminase Assembly

Robust and precise tools are needed to enhance the functionality and resilience of synthetic nanoarchitectures. Here, we have employed directed evolution and rational design to build a fast-acting molecular superglue from a bacterial adhesion protein. We have generated the SnoopLigase2 coupling system, a genetically encoded route for efficient transamidation between SnoopTag2 and DogTag2 peptides. Each peptide was selected for rapid reaction by phage display screening. The optimized set allows more than 99% completion and is compatible with diverse buffers, pH values, and temperatures, accelerating the reaction over 1000-fold. SnoopLigase2 directs a specific reaction in the mammalian secretory pathway, allowing covalent display on the plasma membrane. Transglutaminase 2 (TG2) has a network of interactions and substrates amidst the mammalian cell surface and extracellular matrix. We expressed a modified TG2 with resistance to oxidative inactivation and minimal self-reactivity. SnoopLigase2 enables TG2 functionalization with transforming growth factor alpha (TGFα) in routes that would be impossible through genetic fusion. The TG2:TGFα conjugate retained transamidase activity, stably anchored TGFα for signal activation in the extracellular environment, and reprogrammed cell behavior. This modular toolbox should create new opportunities for molecular assembly, both for novel biomaterials and complex cellular environments.

Reconfigurable mechano-responsive soft film for adaptive visible and infrared dual-band camouflage

Learning from nature in terms of the camouflage used by species has enabled the continuous development of camouflage technologies for the visible to mid-infrared bands to prevent objects from being detected by sophisticated multispectral detectors, thereby avoiding potential threats. However, achieving visible and infrared dual-band camouflage without destructive interference while also realizing rapidly responsive adaptivity to the varying background remains challenging for high-demand camouflage systems. Here, we report a reconfigurable mechano-responsive soft film for dual-band camouflage. Its modulation ranges for visible transmittance and longwave infrared emittance can be up to 66.3% and 21%, respectively. Rigorous optical simulations are performed to elucidate the modulation mechanism of dual-band camouflage and identify the optimal wrinkles required to achieve the goal. The broadband modulation capability (figure of merit) of the camouflage film can be as high as 2.91. Other advantages, such as simple fabrication and a fast response, make this film a potential candidate for dual-band camouflage that can adapt to diverse environments.

Advanced Composites Inspired by Biological Structures and Functions in Nature: Architecture Design, Strengthening Mechanisms, and Mechanical-Functional Responses

The natural design and coupling of biological structures are the root of realizing the high strength, toughness, and unique functional properties of biomaterials. Advanced architecture design is applied to many materials, including metal materials, inorganic nonmetallic materials, polymer materials, and so on. To improve the performance of advanced materials, the designed architecture can be enhanced by bionics of biological structure, optimization of structural parameters, and coupling of multiple types of structures. Herein, the progress of structural materials is reviewed, the strengthening mechanisms of different types of structures are highlighted, and the impact of architecture design on the performance of advanced materials is discussed. Architecture design can improve the properties of materials at the micro level, such as mechanical, electrical, and thermal conductivity. The synergistic effect of structure makes traditional materials move toward advanced functional materials, thus enriching the macroproperties of materials. Finally, the challenges and opportunities of structural innovation of advanced materials in improving material properties are discussed.

Butterfly-Inspired Tri-State Photonic Crystal Composite Film for Multilevel Information Encryption and Anti-Counterfeiting

Counterfeiting is a worldwide issue and has long troubled legitimate businesses, while nowadays anti-counterfeiting materials and technology are still insufficient to combat the escalating counterfeit behaviors. Inspired by hindwing structure of Troides magellanus, a new kind of anti-counterfeiting material taking advantage of both physical and chemical structures to display multiple optical states is prepared. The chemical units (luminescent lanthanide) are blended with physical units (monodispersed colloidal particles) and mediating molecules, which are then assembled into a photonic crystal structure at room temperature in less than 10 s through a new assembly technique called molecule-mediated shear-induced assembly technique (MSAT). The as-prepared photonic crystal films feature three unique optical states, each displaying structural, fluorescent, and phosphorescent color under different lighting conditions, which integrates colors from both physical and chemical origins. Furthermore, by incorporating different luminescent materials into different parts of the photonic crystal pattern, a high-level information encryption system is designed to be capable of carrying three distinct types of information. Thanks to this powerful tool of MSAT, it is now possible to assemble different-sized, even irregular non-spherical units with monodispersed spherical units into high-quality photonic crystal films, which provides easy access to incorporating new features into photonic crystal systems.

Nanosilk Template-Guided/Induced Construction of Brush-/Flower-like 3D Nanostructures

Biomaterials with natural hierarchical structures typically exhibit extraordinary properties because of their multilevel structural designs. They offer many templates and models as well as inspiration for material design, particularly for fabricating structure-regulated, performance-enhanced, and function-enriched materials. Biopolymer-based nanocomposites with ingenious nanostructures constructed through ecofriendly and sustainable approaches are highly desirable to meet the multifunctional requirements of developing bioinspired materials. Herein, an all-silk fibroin-based nanocomposite with a brush-like nanostructure was constructed for the first time using a nanotemplate-guided assembly approach in which dissolved silk assembled directly on a silk nanowhisker (SNW) backbone to form peculiar nanobrushes based on the classical micelle model. Three-dimensional spider-like or centipede-like silk nanobrushes (SNBs) were fabricated by varying the SNW backbone length from 0.16 to 6 μm. The branches with average lengths of 32-290 nm were also adjustable. SNBs were further designed to regulate and induce biomineralization of hydroxyapatite (HAP) to form interesting flower-like nanostructures, in which the HAP nanosphere (diameters ∼16 nm) "core" was covered by SNBs with branches extending to form a "shell" (∼101 nm in length). Based on such protein nanotemplate-guided formation of nanoscale structures, practical hollow conduits with remarkable mechanical properties, biocompatibility, shape memory behavior, and bone engineering potential were fabricated. This study inspires the design of polymorphous biopolymer-based nanostructures with enhanced performance at multiple length scales where the weaknesses of individual building blocks are offset.

Engineered Living Materials For Sustainability

Recent advances in synthetic biology and materials science have given rise to a new form of materials, namely engineered living materials (ELMs), which are composed of living matter or cell communities embedded in self-regenerating matrices of their own or artificial scaffolds. Like natural materials such as bone, wood, and skin, ELMs, which possess the functional capabilities of living organisms, can grow, self-organize, and self-repair when needed. They also spontaneously perform programmed biological functions upon sensing external cues. Currently, ELMs show promise for green energy production, bioremediation, disease treatment, and fabricating advanced smart materials. This review first introduces the dynamic features of natural living systems and their potential for developing novel materials. We then summarize the recent research progress on living materials and emerging design strategies from both synthetic biology and materials science perspectives. Finally, we discuss the positive impacts of living materials on promoting sustainability and key future research directions.

Hierarchically structured bioinspired nanocomposites

Next-generation structural materials are expected to be lightweight, high-strength and tough composites with embedded functionalities to sense, adapt, self-repair, morph and restore. This Review highlights recent developments and concepts in bioinspired nanocomposites, emphasizing tailoring of the architecture, interphases and confinement to achieve dynamic and synergetic responses. We highlight cornerstone examples from natural materials with unique mechanical property combinations based on relatively simple building blocks produced in aqueous environments under ambient conditions. A particular focus is on structural hierarchies across multiple length scales to achieve multifunctionality and robustness. We further discuss recent advances, trends and emerging opportunities for combining biological and synthetic components, state-of-the-art characterization and modelling approaches to assess the physical principles underlying nature-inspired design and mechanical responses at multiple length scales. These multidisciplinary approaches promote the synergetic enhancement of individual materials properties and an improved predictive and prescriptive design of the next era of structural materials at multilength scales for a wide range of applications.

Mechanically robust bamboo node and its hierarchically fibrous structural design

Although short bamboo nodes function in mechanical support and fluid exchange for bamboo survival, their structures are not fully understood compared to unidirectional fibrous internodes. Here, we identify the spatial heterostructure of the bamboo node via multiscale imaging strategies and investigate its mechanical properties by multimodal mechanical tests. We find three kinds of hierarchical fiber reinforcement schemes that originate from the bamboo node, including spatially tightened interlocking, triaxial interconnected scaffolding and isotropic intertwining. These reinforcement schemes, built on porous vascular bundles, microfibers and more-refined twist-aligned nanofibers, govern the structural stability of the bamboo via hierarchical toughening. In addition, the spatial liquid transport associated with these multiscale fibers within the bamboo node is experimentally verified, which gives perceptible evidence for life-indispensable multidirectional fluid exchange. The functional integration of mechanical reinforcement and liquid transport reflects the fact that the bamboo node has opted for elaborate structural optimization rather than ingredient richness. This study will advance our understanding of biological materials and provide insight into the design of fiber-reinforced structures and biomass utilization.

Preparation and Characterization of High Mechanical Strength Chitosan/Oxidized Tannic Acid Composite Film with Schiff Base and Hydrogen Bond Crosslinking

Chitosan-based composite films with good biodegradability, biocompatibility, and sustainability are extensively employed in the field of food packaging. In this study, novel chitosan/tannic acid (CTA) and chitosan/oxidized tannic acid (COTA) composite films with excellent mechanical and antibacterial properties were prepared using a tape casting method. The results showed that, when 20% tannic acid (TA) was added, the tensile strength of the CTA composite film was 80.7 MPa, which was 89.4% higher than that of the pure chitosan (CS) film. TA was oxidized to oxidized tannic acid (OTA) with laccase, and the phenolic hydroxyl groups were oxidized to an o-quinone structure. With the addition of OTA, a Schiff base reaction between the OTA and CS occurred, and a dual network structure consisting of a chemical bond and hydrogen bond was constructed, which further improved the mechanical properties. The tensile strength of 3% COTA composite film was increased by 97.2% compared to that of pure CS film. Furthermore, these CTA films with significant antibacterial effects against Escherichia coli (E. coli) are likely to find uses in food packaging applications.

Nanochitin: Chemistry, Structure, Assembly, and Applications

Chitin, a fascinating biopolymer found in living organisms, fulfills current demands of availability, sustainability, biocompatibility, biodegradability, functionality, and renewability. A feature of chitin is its ability to structure into hierarchical assemblies, spanning the nano- and macroscales, imparting toughness and resistance (chemical, biological, among others) to multicomponent materials as well as adding adaptability, tunability, and versatility. Retaining the inherent structural characteristics of chitin and its colloidal features in dispersed media has been central to its use, considering it as a building block for the construction of emerging materials. Top-down chitin designs have been reported and differentiate from the traditional molecular-level, bottom-up synthesis and assembly for material development. Such topics are the focus of this Review, which also covers the origins and biological characteristics of chitin and their influence on the morphological and physical-chemical properties. We discuss recent achievements in the isolation, deconstruction, and fractionation of chitin nanostructures of varying axial aspects (nanofibrils and nanorods) along with methods for their modification and assembly into functional materials. We highlight the role of nanochitin in its native architecture and as a component of materials subjected to multiscale interactions, leading to highly dynamic and functional structures. We introduce the most recent advances in the applications of nanochitin-derived materials and industrialization efforts, following green manufacturing principles. Finally, we offer a critical perspective about the adoption of nanochitin in the context of advanced, sustainable materials.

Biomimetic Chiral Photonic Materials with Tunable Metallic Colorations Prepared from Chiral Melanin-like Nanorods for UV Shielding, Humidity Sensing, and Cosmetics

Many biological species combine the helical organization of cellulose or chitin microfibrils with broadband light absorption of black melanin to produce brilliant structural colors with metallic and glossy effects and other diverse functions. In this work, based on core-shell CNC@PDA chiral nanorods consisting of cellulose nanocrystals (CNCs) as the core and melanin-like polydopamine (PDA) as the shell that can form well-defined chiral liquid crystal phases, we report chiral photonic materials that closely mimic the unique coloration mechanisms and functionalities mastered by several biological species. The photonic films formed by such single CNC@PDA nanorods have brilliant iridescent structural colors originating from selective reflection of circularly polarized lights by the helical organization of CNC@PDAs across the films. Furthermore, the colors of such films have background-independent brightness, high visibility, and metallic effects that arise from the light absorption of the PDA component. Especially, the color ranges and metallic effects of the films can be conveniently tuned by varying the thickness of the PDA shell. In addition, the UV absorption and hygroscopic properties of PDA endow these CNC@PDA films with efficient broadband UV shielding and sensitive humidity-induced dynamic color changes. Due to the mussel-like superior adhesion of PDA, CNC@PDA-based photonic coatings can be formed conformably onto diverse kinds of substrates. A shiny eye shadow with viewing angle-dependent colorful patterns was used to demonstrate the potential applications. With combinations of multiple unique properties in one photonic material fabricated from a single building block, these CNC@PDA-based films are expected to have potential applications in cosmetics, UV protection, anticounterfeiting, chiral reflectors, etc.

Silk Fiber Multiwalled Carbon Nanotube-Based Micro-/Nanofiber Composite as a Conductive Fiber and a Force Sensor

Silk cocoon fibers (SFs) are natural polymers that are made up of fibroin protein. These natural fibers have higher mechanical stability and good elasticity properties. In this work, we coated multiwalled carbon nanotubes (MWCNTs) on the surface of SFs using a simple stirring technique with vinegar as the medium. This SF-MWCNT micro-/nanofiber composite was prepared without any adhesives. The characterization results revealed that the SF-MWCNT micro-/nanofiber composite exhibited excellent electrical conductivity (995 Ω cm^-1), tensile strength (up to 200% greater elongation), and durability characteristics. In addition, this micro-/nanofiber composite shows a change in resistance from 1450 to 960 Ω cm^-1 for an applied mechanical force of 0.3-1 N kg^-1. Based on our findings, SF-MWCNT micro-/nanofiber composite-based conductive fibers (CFs) and force sensors (FSs) were developed.

Mechanically and electrically biocompatible hydrogel ionotronic fibers for fabricating structurally stable implants and enabling noncontact physioelectrical modulation

Narrowing the mechanical and electrical mismatch between tissue and implantable microelectronics is essential for reducing immune responses and modulating physioelectrical signals. Nevertheless, the design of such implantable microelectronics remains a challenge due to the limited availability of suitable materials. Here, the fabrication of an electrically and mechanically biocompatible alginate hydrogel ionotronic fiber (AHIF) is reported, which is constructed by combing ionic chelation-assisted wet-spinning and mechanical training. The synergistic effects of these two processes allow the alginate to form a highly-oriented nanofibril and molecular network, with a hierarchical structure highly similar to that of natural fibers. These favourable structural features endow AHIF with tissue-mimicking mechanical characteristics, such as self-stiffening and soft tissue-like mechanical properties. In addition, tissue-like chemical components, i.e., biomacromolecules, Ca²⁺ ions, and water, endow AHIF with properties including biocompatibility and tissue-matching conductivity. These advantages bring light to the application of AHIFs in electrically-conductive implantable devices. As a prototype, an AHIF is designed to perform physioelectrical modulation through noncontact electromagnetic induction. Through experimental and machine learning optimizations, physioelectrical-like signals generated by the AHIF are used to identify the geometry and tension state of the implanted device in the body. Such an intelligent AHIF system has promising application prospects in bioelectronics, IntelliSense, and human-machine interactions.

Rationally Tuning Phase Separation in Polymeric Membranes toward Optimized All-day Passive Radiative Coolers

The all-day passive radiative cooler has emerged as one of the state-of-the-art energy-saving cooling tool kits but routinely suffers from limited processability, high cost, and complicated fabrication processes, which impede large-scale applications. To address these challenges, this work exploits a polymer-based passive radiative cooler with optimized turbidity, reconfigurability, and recyclability. These cooling membranes are fabricated via selective condensation of octyl side chain-modified polyvinyl alcohol through a non-solvent-induced phase separation method. The rational tuning over spatial organization and distribution of the air-polymer interface renders optimized bright whiteness with solar reflectance at 96%. Meanwhile, the abundant -C-O-C- bonds endow such membranes with infrared thermal emittance over 90%. The optimized membrane realizes a subambient cooling of ∼5.7 °C with an average cooling power of ∼81 W m-2 under a solar intensity of ∼528 W m-2. Furthermore, the supramolecule nature of the developed passive radiative cooling membrane bears enhanced shape malleability and recyclability, substantially enhancing its conformability to the complex geometry and extending its life for an eco-friendly society.

Phase Behaviors of ABA Star Polymer and Nanoparticles Confined in a Sphere with Soft Inner Surface

The phase behaviors of an ABA star polymer and nanoparticles confined in a sphere with soft inner surface, which is grafted with homopolymer brushes have been studied by the self-consistent field theory (SCFT). The morphologies of mixture in the center slice of sphere were focused. Two cases are considered: one is that the nanoparticles interact with the B blocks and the other is that the nanoparticles preferentially wet the B blocks. Under the two conditions, through changing the block ratio of the ABA star polymer, the concentration and radius of the nanoparticles, the phase behaviors of the mixtures confined the soft sphere are studied systematically. With increasing the concentration of nanoparticles, the entropy and the steric repulsive interaction of nanoparticles, and the nanoparticle density distributions along the perpendicular line through the center of sphere are plotted. The phase diagram is also constructed to analyze the effects of the nanoparticle volume fraction and radius on morphologies of ABA star polymers, and to study the effect of confinement on the phase behaviors. The results in this work provide a useful reference for controlling the ordered structures in experiment, which is an effective way to fabricate the newly multifunctional materials.

Recent Progress in Responsive Structural Color

Structural color has been regarded as an ideal alternative to pigments because of the advantages of environmental friendliness, resistance to fading, and dynamic regulation. Responsive structural color can give real-time visible feedback to external stimuli and thus has great prospects in many applications, such as displays, sensing, anticounterfeiting, information storage, and healthcare monitoring. In this Perspective, we elucidate basic concepts, controllable fabrications, and promising applications of responsive structural colors. In particular, we systematically summarize the general regulation mode of all kinds of responsive structural color systems. First, we introduce the basic chromogenic structures as well as the regulation modes of responsive structural color. Second, we present the fabrication methods of patterned structural color. Then, the promising applications of responsive structural color systems are highlighted in detail. Finally, we present the existing challenges and future perspectives on responsive structural colors.

Recognition and Detection of Wide Field Bionic Compound Eye Target Based on Cloud Service Network

In this paper, a multidisciplinary cross-fusion of bionics, robotics, computer vision, and cloud service networks was used as a research platform to study wide-field bionic compound eye target recognition and detection from multiple perspectives. The current research status of wide-field bionic compound-eye target recognition and detection was analyzed, and improvement directions were proposed. The surface microlens array arrangement was designed, and the spaced surface bionic compound eye design principle cloud service network model was established for the adopted spaced-type circumferential hierarchical microlens array arrangement. In order to realize the target localization of the compound eye system, the content of each step of the localization scheme was discussed in detail. The distribution of virtual spherical targets was designed by using the subdivision of the positive icosahedron to ensure the uniformity of the targets. The spot image was pre-processed to achieve spot segmentation. The energy symmetry-based spot center localization algorithm was explored and its localization effect was verified. A suitable spatial interpolation method was selected to establish the mapping relationship between target angle and spot coordinates. An experimental platform of wide-field bionic compound eye target recognition and detection system was acquired. A super-resolution reconstruction algorithm combining pixel rearrangement and an improved iterative inverse projection method was used for image processing. The model was trained and evaluated in terms of detection accuracy, leakage rate, time overhead, and other evaluation indexes, and the test results showed that the cloud service network-based wide-field bionic compound eye target recognition and detection performs well in terms of detection accuracy and leakage rate. Compared with the traditional algorithm, the correct rate of the algorithm was increased by 21.72%. Through the research of this paper, the wide-field bionic compound eye target recognition and detection and cloud service network were organically provide more technical support for the design of wide-field bionic compound eye target recognition and detection system.

Polycaprolactone usage in additive manufacturing strategies for tissue engineering applications: A review

Polycaprolactone (PCL) has been extensively applied on tissue engineering because of its low-melting temperature, good processability, biodegradability, biocompatibility, mechanical resistance, and relatively low cost. The advance of additive manufacturing (AM) technologies in the past decade have boosted the fabrication of customized PCL products, with shorter processing time and absence of material waste. In this context, this review focuses on the use of AM techniques to produce PCL scaffolds for various tissue engineering applications, including bone, muscle, cartilage, skin, and cardiovascular tissue regeneration. The search for optimized geometry, porosity, interconnectivity, controlled degradation rate, and tailored mechanical properties are explored as a tool for enhancing PCL biocompatibility and bioactivity. In addition, rheological and thermal behavior is discussed in terms of filament and scaffold production. Finally, a roadmap for future research is outlined, including the combination of PCL struts with cell-laden hydrogels and 4D printing.

Deconstruction and Reassembly of Renewable Polymers and Biocolloids into Next Generation Structured Materials

This review considers the most recent developments in supramolecular and supraparticle structures obtained from natural, renewable biopolymers as well as their disassembly and reassembly into engineered materials. We introduce the main interactions that control bottom-up synthesis and top-down design at different length scales, highlighting the promise of natural biopolymers and associated building blocks. The latter have become main actors in the recent surge of the scientific and patent literature related to the subject. Such developments make prominent use of multicomponent and hierarchical polymeric assemblies and structures that contain polysaccharides (cellulose, chitin, and others), polyphenols (lignins, tannins), and proteins (soy, whey, silk, and other proteins). We offer a comprehensive discussion about the interactions that exist in their native architectures (including multicomponent and composite forms), the chemical modification of polysaccharides and their deconstruction into high axial aspect nanofibers and nanorods. We reflect on the availability and suitability of the latter types of building blocks to enable superstructures and colloidal associations. As far as processing, we describe the most relevant transitions, from the solution to the gel state and the routes that can be used to arrive to consolidated materials with prescribed properties. We highlight the implementation of supramolecular and superstructures in different technological fields that exploit the synergies exhibited by renewable polymers and biocolloids integrated in structured materials.

Moderate conformational transition promotes the formation of a self-reinforced highly oriented silk fibroin network structure

A highly oriented molecular network structure (HOMNS) is a common and favorable design in natural and regenerated silks to achieve self-reinforcement of the material. However, the fundamental issues related to the formation of the HOMNS in silk fibroin materials and its influence on mechanical performance have not yet been addressed. By combining experimental characterization and molecular dynamics simulation, this work revealed that moderate conformational transition of silk fibroin promoted the formation of a low-density crosslinking molecular network among proteins. Such a molecular network is beneficial to further rearrangement of amorphous proteins in subsequent processing to form HOMNS. Here, a structure was confirmed that can strengthen the materials several times compared with the same material without HOMNS. These investigations improved the in-depth understanding of the fundamental questions related to the silk fibroin assembly, revealed their crucial structural remodeling, and paved the way for new fabrication strategies of mechanical-enhanced silk fibroin materials.

Recent advances in polymer scaffolds for biomedical applications

The review provides insights into current advancements in electrospinning-assisted manufacturing for optimally designing biomedical devices for their prospective applications in tissue engineering, wound healing, drug delivery, sensing, and enzyme immobilization, and others. Further, the evolution of electrospinning-based hybrid biomedical devices using a combined approach of 3 D printing and/or film casting/molding, to design dimensionally stable membranes/micro-nanofibrous assemblies/patches/porous surfaces, etc. is reported. The influence of various electrospinning parameters, polymeric material, testing environment, and other allied factors on the morphological and physico-mechanical properties of electrospun (nano-/micro-fibrous) mats (EMs) and fibrous assemblies have been compiled and critically discussed. The spectrum of operational research and statistical approaches that are now being adopted for efficient optimization of electrospinning process parameters so as to obtain the desired response (physical and structural attributes) has prospectively been looked into. Further, the present review summarizes some current limitations and future perspectives for modeling architecturally novel hybrid 3 D/selectively textured structural assemblies, such as biocompatible, non-toxic, and bioresorbable mats/scaffolds/membranes/patches with apt mechanical stability, as biological substrates for various regenerative and non-regenerative therapeutic devices.

Facile full-color printing with a single transparent ink

Structural colors are promising candidates for their antifading and eco-friendly characteristics. However, high cost and complicated processing inevitably hinder their development. Here, we propose a facile full-color structural-color inkjet printing strategy with a single transparent ink from the common polymer materials. This structural color arisen from total internal reflections is prepared by digitally printing the dome-shaped microstructure (microdome) with well-controlled morphology. By controlling the ink volume and substrate wettability, the microdome color can be continuously regulated across whole visible regions. The gamut, saturation, and lightness of the printed structural-color image are precisely adjusted via the programmable arrangement of different microdomes. With the advantages of simple manufacturing and widely available inks, this color printing approach presents great potential in imaging, decoration, sensing, and biocompatible photonics.

Spinning Methods Used for Construction of One- and Two-Dimensional Fibrous Protein Materials

Natural silk protein fibers have shown a great attraction to the researchers due to the extraordinary mechanical property, biocompatibility, and functional diversity. Unfortunately, the low yield and unevenness have hampered the scale use of the natural silk fibers. Herein, the appearance of the bioinspired artificial spinning strategy offers an effective way to fabricate silk fibers with controllable structures and functionality. This chapter describes an experimental method to prepare silk protein fibers on a large scale and summarizes the method to investigate the effects of the structure-property relationship of the recombinant protein fibers.

An Ultrastable Virus-Like Particle with a Carbon Dot Core and Expanded Sequence Plasticity

Ordered bio-inorganic hybridization has evolved for the generation of high-performance materials in living organisms and inspires novel strategies to design artificial hybrid materials. Virus-like particles (VLPs) are attracting extensive interest as self-assembling systems and platforms in the fields of biotechnology and nanotechnology. However, as soft nanomaterials, their structural stability remains a general and fundamental problem in various applications. Here, an ultrastable VLP assembled from the major capsid protein (VP1) of simian virus 40 is reported, which contains a carbon dot (C-dot) core. Co-assembly of VP1 with C-dots led to homogeneous T = 1 VLPs with a fourfold increase in VLP yields. The resultant hybrid VLPs showed markedly enhanced structural stability and sequence plasticity. C-dots and a polyhistidine tag fused to the inner-protruding N-terminus of VP1 contributed synergistically to these enhancements, where extensive and strong noncovalent interactions on the C-dot/VP1 interfaces are responsible according to cryo-EM 3D reconstruction, molecular simulation, and affinity measurements. C-dot-enhanced ultrastable VLPs can serve as a new platform, enabling the fabrication of new architectures for bioimaging, theranostics, nanovaccines, etc. The hybridization strategy is simple and can easily be extended to other VLPs and protein nanoparticle systems.

3D electron-beam writing at sub-15 nm resolution using spider silk as a resist

Electron beam lithography (EBL) is renowned to provide fabrication resolution in the deep nanometer scale. One major limitation of current EBL techniques is their incapability of arbitrary 3d nanofabrication. Resolution, structure integrity and functionalization are among the most important factors. Here we report all-aqueous-based, high-fidelity manufacturing of functional, arbitrary 3d nanostructures at a resolution of sub-15 nm using our developed voltage-regulated 3d EBL. Creating arbitrary 3d structures of high resolution and high strength at nanoscale is enabled by genetically engineering recombinant spider silk proteins as the resist. The ability to quantitatively define structural transitions with energetic electrons at different depths within the 3d protein matrix enables polymorphic spider silk proteins to be shaped approaching the molecular level. Furthermore, genetic or mesoscopic modification of spider silk proteins provides the opportunity to embed and stabilize physiochemical and/or biological functions within as-fabricated 3d nanostructures. Our approach empowers the rapid and flexible fabrication of heterogeneously functionalized and hierarchically structured 3d nanocomponents and nanodevices, offering opportunities in biomimetics, therapeutic devices and nanoscale robotics.

Mapping of Supramolecular Chirality in Insect Wings by Microscopic Vibrational Circular Dichroism Spectroscopy: Heterogeneity in Protein Distribution

The supramolecular chirality of the hindwing of Anomala albopilosa (male) was investigated using a microscopic vibrational circular dichroism (VCD) system, denoted as MultiD-VCD. The source of intense infrared (IR) light for the system was a quantum cascade laser. Two-dimensional maps of IR and VCD spectra were taken by scanning the surface area (ca. 2 mm × 2 mm) of the insect hindwing tissue. The spectra ranged from 1500 to 1700 cm^-1, and the maps have a spatial resolution of 100 μm. The distribution of proteins, including their supramolecular structures, was analyzed from the location-dependent spectral shape of the VCD bands assigned to amides I and II. The results revealed that the hindwing consists of segregated domains of proteins with different secondary structures: an α-helix (in one part of the membrane), a hybrid of α-helix and β-sheet (in another part of the membrane), and a coil (in a vein).

Facet Selectivity Guided Assembly of Nanoarchitectures onto Two-Dimensional Metal-Organic Framework Nanosheets

Facet-selective nanostructures in living systems usually exhibit outstanding optical and enzymatic properties, playing important roles in photonics, matter exchange, and biocatalysis. Bioinspired construction of facet-selective nanostructures offers great opportunities for sophisticated nanomaterials, but remains a formidable task. We have developed a macromolecule-mediated strategy for the assembly of upconversion nanoparticles (UCNPs)/two-dimensional metal-organic frameworks (2DMOFs) heterostructures with facet selectivity. Both experimental and theoretical results demonstrate that polyvinylpyrrolidone (PVP) can be utilized as an interface-selective mediator to further promote the facet-selective assembly of MOFs onto the surface of UCNPs. The UCNPs/2DMOFs nanostructures with facet selectivity display specific optical properties and show great advantages in anti-counterfeiting. Our demonstration of UCNPs/2DMOFs provides a vivid example for the controlled fabrication of facet-selective nanostructures and can promote the development of advanced functional materials for applications in biosensing, energy conversion, and information assurance.

Mechanical Training-Driven Structural Remodeling: A Rational Route for Outstanding Highly Hydrated Silk Materials

Highly hydrated silk materials (HHSMs) have been the focus of extensive research due to their usefulness in tissue engineering, regenerative medicine, and soft devices, among other fields. However, HHSMs have weak mechanical properties that limit their practical applications. Inspired by the mechanical training-driven structural remodeling strategy (MTDSRS) in biological tissues, herein, engineered MTDSRS is developed for self-reinforcement of HHSMs to improve their inherent mechanical properties and broaden potential utility. The MTDSRS consists of repetitive mechanical training and solvent-induced conformation transitions. Solvent-induced conformation transition enables the formation of β-sheet physical crosslinks among the proteins, while the repetitive mechanical loading allows the rearrangement of physically crosslinked proteins along the loading direction. Such synergistic effects produce strong and stiff mechanically trained-HHSMs (MT-HHSMs). The fracture strength and Young's modulus of the resultant MT-HHSMs (water content of 43 ± 4%) reach 4.7 ± 0.9 and 21.3 ± 2.1 MPa, respectively, which are 8-fold stronger and 13-fold stiffer than those of the as-prepared HHSMs, as well as superior to most previously reported HHSMs with comparable water content. In addition, the animal silk-like highly oriented molecular crosslinking network structure also provides MT-HHSMs with fascinating physical and functional features, such as stress-birefringence responsibility, humidity-induced actuation, and repeatable self-folding deformation.

Photochromic Polyamide 6 Based on Spiropyran Synthesized via Hydrolyzed Ring-Opening Polymerization

We report photochromic polyamide 6 (PA6) which was synthesized by hydrolyzed ring-opening polymerization of ε-caprolactam with spiropyran (SP) embedded in the polymer chains. It indicated that crystallinity degree of the resulting copolymers was decreased since only PA6 segments can crystallize with increasing content of SP modifier. Meanwhile, toughness of photochromic PA6 was decreased. The photochromic property analysis indicated that the sample with more flexibility and more content of SP was more sensitive to UV light at the beginning of irradiation than other samples and its color after being irradiated for 1 min tended to reddish. Investigation revealed that the UV-vis absorbance of SP-PA6-3 had negligible decay after 10 cycles, which indicated SP-modified PA6 possessed excellent photoresponse reversibility and fatigue resistance.