Bioinspired structural materials

The effect of salidroside on the bone and cartilage properties in broilers

Leg disorders frequently occur in fast-growing broiler chickens, constituting severe health and welfare problems. Although salidroside (SAL) promotes osteogenesis and inhibits apoptosis of chondrocytes in rats, it remains to be determined whether SAL can effectively improve bone growth in broilers. The present study was designed to investigate the effects of dietary SAL supplementation on bone and cartilage characteristics in broiler chickens. Ninety-six Arbor Acres broiler chickens were randomly divided into 4 groups: control, low-dose SAL, medium-dose SAL, and high-dose SAL groups. The broiler chickens were raised until 42 d of age, with samples of bone and cartilage collected for biomechanical testing and bone metabolism index detection. The results showed that SAL significantly increased the vertical external diameter, cross-sectional moment of inertia, and cross-sectional area of the femur and tibia. Additionally, SAL enhanced bone mineral density and strength, as evidenced by significant increases in stiffness, Young's modulus, ultimate load, and fracture work of the femur and tibia. Furthermore, SAL influenced the relative content of phosphate, carbonate, and amide I in cortical bone. Moreover, SAL upregulated the expression of osteogenic genes (Collagen-1, RUNX2, BMP2, and ALP) in a dose-dependent manner and maintained the homeostasis of the extracellular matrix (ECM) of chondrocytes. These results indicated that SAL promoted leg health in broilers by improving bone and cartilage quality and enhancing chondrocyte activity.

Upcycling biowaste into advanced carbon materials via low-temperature plasma hybrid system: applications, mechanisms, strategies and future prospects

This review focuses on the recent advances in the sustainable conversion of biowaste to valuable carbonaceous materials. This study summarizes the significant progress in biowaste-derived carbon materials (BCMs) via a plasma hybrid system. This includes systematic studies like AI-based multi-coupling systems, promising synthesis strategies from an economic point of view, and their potential applications towards energy, environment, and biomedicine. Plasma modified BCM has a new transition lattice phase and exhibits high resilience, while fabrication and formation mechanisms of BCMs are reviewed in plasma hybrid system. A unique 2D structure can be designed and formulated from the biowaste with fascinating physicochemical properties like high surface area, unique defect sites, and excellent conductivity. The structure of BCMs offers various activated sites for element doping and it shows satisfactory adsorption capability, and dynamic performance in the field of electrochemistry. In recent years, many studies have been reported on the biowaste conversion into valuable materials for various applications. Synthesis methods are an indispensable factor that directly affects the structure and properties of BCMs. Therefore, it is imperative to review the facile synthesis methods and the mechanisms behind the formation of BCMs derived from the low-temperature plasma hybrid system, which is the necessity to obtain BCMs having desirable structure and properties by choosing a suitable synthesis process. Advanced carbon-neutral materials could be widely synthesized as catalysts for application in environmental remediation, energy conversion and storage, and biotechnology.

Cartilage and bone injectable hydrogels: A review of injectability methods and treatment strategies for repair in tissue engineering

Cartilage and bone are crucial tissues causing disability in the elderly population, often requiring prolonged treatment and surgical intervention due to limited regenerative capacity. Injectable hydrogels that closely mimic the extracellular matrix (ECM) of native hard tissue have attracted attention due to their minimally invasive application and ability to conform to irregular defect sites. These hydrogels facilitate key biological processes such as cell migration, chondrogenesis in cartilage repair, osteoinduction, angiogenesis, osteoconduction, and mineralization in bone repair. This review analyzes in-vitro and in-vivo biomedical databases over the past decade to identify advancements in hydrogel formulations, crosslinking mechanisms, and biomaterial selection for cartilage and bone tissue engineering. The review emphasizes the effectiveness of injectable hydrogels as carriers for cells, growth factors, and drugs, offering additional therapeutic benefits. The relevance of these findings is discussed in the context of their potential to serve as a robust alternative to current surgical and non-surgical treatments. This review also examines the advantages of injectable hydrogels, such as ease of administration, reduced patient recovery time, and enhanced bioactivity, thereby emphasizing their potential in clinical applications for cartilage and bone regeneration with emphasis on addressing the shortcomings of current treatments.

Itaconic acid/cellulose-based hydrogels with fire-resistant and anti-freezing properties via vat photopolymerization 3D printing

Hydrogel-born materials have garnered significant interest due to their inherent flame retardant properties and eco-friendly characteristics. In light of the diminishing petroleum reserves and the escalating environmental challenges, there is an urgent impetus to exploit high-value applications of naturally occurring resources and to advance research in sustainable manufacturing technologies. In this vein, we describe an innovative and sustainable methodology for the development and production of flame-retardant hydrogels. This approach perfectly integrates renewable itaconic acid and cellulose derivatives with rapid vat photopolymerization (VP) 3D printing technology, which affords a green and efficient route for materials processing. Specifically, the biomass-based ink formulated for 3D printing demonstrates excellent visible-light curing properties, achieving a maximum double-bond conversion of 45.3 % within 10 min of exposure to visible-light LED under ambient conditions. Moreover, the resultant 3D-printed biomass-based hydrogels exhibit commendable flame-retardant performance, as evidenced by a V-0 flammability rating and a Limiting Oxygen Index (LOI) value of 60.2 %. They also possess desirable mechanical attributes (95.2 kPa) and exceptional thermal stability, enduring high temperatures for up to 12 min. Notably, these hydrogels exhibit remarkable freeze tolerance, maintaining their functionality even at profoundly low temperatures. This study demonstrates a novel strategy for the design and production of flame-retardant materials, contributing to the pursuit of green sustainability.

Super-Strong, Super-Stiff, and Super-Tough Fluorescent Alginate Fibers with Outstanding Tolerance to Extreme Conditions

The combination of multiple physical properties is of great importance for widening the application scenarios of biomaterials. It remains a great challenge to fabricate biomolecules-based fibers gaining both mechanical strength and toughness which are comparable to natural spider dragline silks. Here, by mimicking the structure of dragline silks, a high-performance fluorescent fiber Alg-TPEA-PEG is designed by non-covalently cross-linking the polysaccharide chains of alginate with AIEgen-based surfactant molecules as the flexible contact points. The non-covalent cross-linking network provides sufficient energy-dissipating slippage between polysaccharide chains, leading to Alg-TPEA-PEG with highly improved mechanical performances from the plastic strain stage. By successfully transferring the extraordinary mechanical performances of polysaccharide chains to macroscopic fibers, Alg-TPEA-PEG exhibits an outstanding breaking strength of 1.27 GPa, Young's modulus of 34.13 GPa, and toughness of 150.48 MJ m-3, which are comparable to those of dragline silk and outperforming other artificial materials. More importantly, both fluorescent and mechanical properties of Alg-TPEA-PEG can be well preserved under various harsh conditions, and the fluorescence and biocompatibility facilitate its biological and biomedical applications. This study affords a new biomimetic designing strategy for gaining super-strong, super-stiff, and super-tough fluorescent biomaterials.

Butterfly wing-inspired superhydrophobic photonic cellulose nanocrystal films for vapor sensors and asymmetric actuators

Cellulose nanocrystals (CNCs)-based stimuli responsive photonic materials demonstrate great application potential in mechanical and chemical sensors. However, due to the hydrophilic property of cellulose molecular, a significant challenge is to build a water-resistant photonic CNCs material. Here, inspired by butterfly wings with vivid structural color and superhydrophobic property, we have designed a CNCs based superhydrophobic iridescent film with hierarchical structures. The iridescent colored layer is ascribed to the chiral nematic alignment of CNCs, the superhydrophobic layer is ascribed to the micro-nano structures of polymer microspheres. Specially, superhydrophobic iridescent CNCs film could be used as an efficient colorimetric humidity sensor due to the existence of 'stomates' on superhydrophobic layer, which allowed the humid gas to enter into and out from the humidity responsive chiral nematic layers. Meanwhile, superhydrophobic iridescent films show out-standing self-cleaning and anti-fouling performance. Moreover, when the one side of the CNCs film was covered with superhydrophobic layer, the Janus film displays asymmetric expansion and bending behaviors as well as responsive structural colors in hydrous ethanol. This CNCs based hierarchical photonic materials have promising applications including photonic sensors suitable for extreme environment and smart photonic actuators.

Bio-inspired designs: leveraging biological brilliance in mechanical engineering-an overview

Nature's evolutionary mastery has perfected design over the years, yielding organisms superbly adapted to their surroundings. This research delves into the promising domain of bio-inspired designs, poised to revolutionize mechanical engineering. Leveraging insights drawn from prior conversations, we categorize innovations influenced by life on land, in water, and through the air, emphasizing their pivotal contributions to mechanical properties. Our comprehensive review reveals a wealth of bio-inspired designs that have already made substantial inroads in mechanical engineering. From avian-inspired lightweight yet robust materials to hydrodynamically optimized forms borrowed from marine creatures, these innovations hold immense potential for enhancing mechanical systems. In conclusion, this study underscores the transformative potential of bio-inspired designs, offering improved mechanical characteristics and the promise of sustainability and efficiency across a broad spectrum of applications. This research envisions a future where bio-inspired designs shape the mechanical landscape, fostering a more harmonious coexistence between human technology and the natural world.

Crack-Deflecting Lattice Metamaterials Inspired by Precipitation Hardening

Lattice structures, comprising nodes and struts arranged in an array, are renowned for their lightweight and unique mechanical deformation characteristics. Previous studies on lattice structures have revealed that failure often originates from stress concentration points and spreads throughout the material. This results in collapse failure, similar to the accumulation of damage at defects in metallic crystals. Here the precipitation hardening mechanism found in crystalline materials is employed to deflect the initial failure path, through the strategic placement of strengthening units at stress concentration points using the finite element method. Both the mesostructure, inspired by the arrangement of crystals, and the inherent microstructure of the base materials have played crucial roles in shaping the mechanical properties of the macro-lattices. As a result, a groundbreaking multiscale hierarchical design methodology, offering a spectrum of design concepts for engineering materials with desired properties is introduced.

A Versatile Microporous Design toward Toughened yet Softened Self-Healing Materials

Realizing the full potential of self-healing materials in stretchable electronics necessitates not only low modulus to enable high adaptivity, but also high toughness to resist crack propagation. However, existing toughening strategies for soft self-healing materials have only modestly improves mechanical dissipation near the crack tip (ГD), and invariably compromise the material's inherent softness and autonomous healing capabilities. Here, a synthetic microporous architecture is demonstrated that unprecedently toughens and softens self-healing materials without impacting their intrinsic self-healing kinetics. This microporous structure spreads energy dissipation across the entire material through a bran-new dissipative mode of adaptable crack movement (ГA), which substantially increases the fracture toughness by 31.6 times, from 3.19 to 100.86 kJ m-2, and the fractocohesive length by 20.7 times, from 0.59 mm to 12.24 mm. This combination of unprecedented fracture toughness (100.86 kJ m-2) and centimeter-scale fractocohesive length (1.23 cm) surpasses all previous records for synthetic soft self-healing materials and even exceeds those of light alloys. Coupled with significantly enhanced softness (0.43 MPa) and nearly perfect autonomous self-healing efficiency (≈100%), this robust material is ideal for constructing durable kirigami electronics for wearable devices.

Advances in the Development of Gradient Scaffolds Made of Nano-Micromaterials for Musculoskeletal Tissue Regeneration

The intricate hierarchical structure of musculoskeletal tissues, including bone and interface tissues, necessitates the use of complex scaffold designs and material structures to serve as tissue-engineered substitutes. This has led to growing interest in the development of gradient bone scaffolds with hierarchical structures mimicking the extracellular matrix of native tissues to achieve improved therapeutic outcomes. Building on the anatomical characteristics of bone and interfacial tissues, this review provides a summary of current strategies used to design and fabricate biomimetic gradient scaffolds for repairing musculoskeletal tissues, specifically focusing on methods used to construct compositional and structural gradients within the scaffolds. The latest applications of gradient scaffolds for the regeneration of bone, osteochondral, and tendon-to-bone interfaces are presented. Furthermore, the current progress of testing gradient scaffolds in physiologically relevant animal models of skeletal repair is discussed, as well as the challenges and prospects of moving these scaffolds into clinical application for treating musculoskeletal injuries.

Three-Dimensional Semiconductor Network as Regulators of Energy Metabolism Drives Angiogenesis in Bone Regeneration

Insufficient vascularization is a primary cause of bone implantation failure. The management of energy metabolism is crucial for the achievement of vascularized osseointegration. In light of the bone semiconductor property and the electric property of semiconductor heterojunctions, a three-dimensional semiconductor heterojunction network (3D-NTBH) implant has been devised with the objective of regulating cellular energy metabolism, thereby driving angiogenesis for bone regeneration. The three-dimensional heterojunction interfaces facilitate electron transfer and establish internal electric fields at the nanoscale interfaces. The 3D-NTBH was found to noticeably accelerate glycolysis in endothelial cells, thereby rapidly providing energy to support cellular metabolic activities and ultimately driving angiogenesis within the bone tissue. Molecular dynamic simulations have demonstrated that the 3D-NTBH facilitates the exposure of fibronectin's Arg-Gly-Asp peptide binding site, thereby regulating the glycolysis of endothelial cells. Further evidence suggests that 3D-NTBH promotes early vascular network reconstruction and bone regeneration in vivo. The findings of this research offer a promising research perspective for the design of vascularizing implants.

Hierarchically mimicking outer tooth enamel for restorative mechanical compatibility

Tooth enamel, and especially the outer tooth enamel, is a load-resistant shell that benefits mastication but is easily damaged, driving the need for enamel-restorative materials with comparable properties to restore the mastication function and protect the teeth. Synthesizing an enamel analog that mimics the components and hierarchical structure of natural tooth enamel is a promising way to achieve these comparable mechanical properties, but it is still challenging to realize. Herein, we fabricate a hierarchical enamel analog with comparable stiffness, hardness, and viscoelasticity as natural enamel by incorporating three hierarchies of outer tooth enamel based on hierarchical assembly of enamel-like hydroxyapatite hybrid nanowires with polyvinyl alcohol as a matrix. This enamel analog possesses enamel-similar inorganic components and a nanowire-microbundle-macroarray hierarchical structure. It exhibits toughness of 19.80 MPa m1/2, which is 3.4 times higher than natural tooth enamel, giving it long-term fatigue durability. This hierarchical design is promising for scalable production of enamel-restorative materials and for optimizing the mechanical performance of engineering composites.

Dual-Asymmetric Janus Membranes Based on Two-Dimensional Nanowebs with Superspreading Surface for High-Performance Desalination

Distillation membranes with hydrophobic surfaces and defined pores are considered a promising solution for seawater desalination. Most existing distillation membranes exhibit three-dimensional (3D) stacking bulk structures, where the zigzag water-repellent channels often lead to limited permeability and high energy costs. Here, we created two-dimensional nanowebs directly from the polymer/sol solution to construct dual-asymmetric Janus membranes. By tailoring the phase separation rate, the polymer phase evolved into continuous hydrophilic webs in situ weld on the microporous hydrophobic layer. The webs possess true-nanoscale architectures (internal fiber diameter of ∼20 nm, pore size of ∼140 nm) with enhanced roughness, serving as a superspreading surface to reach a water contact angle of 0° in 1.7 s. Benefiting from the architecture and wettability dual asymmetries, the obtained Janus membrane shows high-efficiency desalination performance (salt rejection >99%, flux of 11 kg m-2 h-1, and energy efficiency of 79%) with a thickness of 6.7 μm. Such a fascinating nanofibrous web-based Janus membrane may inspire the design of advanced liquid separation materials.

Mechanically Tunable, Compostable, Healable and Scalable Engineered Living Materials

Advanced design strategies are essential to realize the full potential of engineered living materials, including their biodegradability, manufacturability, sustainability, and ability to tailor functional properties. Toward these goals, we present mechanically engineered living material with compostability, healability, and scalability - a material that integrates these features in the form of a stretchable plastic that is simultaneously flushable, compostable, and exhibits the characteristics of paper. This plastic/paper-like material is produced in scalable quantities (0.5-1 g L-1), directly from cultured bacterial biomass (40%) containing engineered curli protein nanofibers. The elongation at break (1-160%) and Young's modulus (6-450 MPa) is tuned to more than two orders of magnitude. By genetically encoded covalent crosslinking of curli nanofibers, we increase the Young's modulus by two times. The designed engineered living materials biodegrade completely in 15-75 days, while its mechanical properties are comparable to petrochemical plastics and thus may find use as compostable materials for primary packaging.

Advances in Bioceramics for Bone Regeneration: A Narrative Review

Large osseous defects resulting from trauma, tumor resection, or fracture render the inherent ability of the body to repair inadequate and necessitate the use of bone grafts to facilitate the recovery of both form and function of the bony defect sites. In the United States alone, a large number of bone graft procedures are performed yearly, making it an essential area of investigation and research. Synthetic grafts represent a potential alterative to autografts due to their patient-specific customizability, but currently lack widespread acceptance in the clinical space. Early in their development, non-autologous bone grafts composed of metals such as stainless steel and titanium alloys were favorable due to their biocompatibility, resistance to corrosion, mechanical strength, and durability. However, since their inception, bioceramics have also evolved as viable alternatives. This review aims to present an overview of the fundamental prerequisites for tissue engineering devices using bioceramics as well as to provide a comprehensive account of their historical usage and significant advancements over time. This review includes a summary of commonly used manufacturing techniques and an evaluation of their use as drug carriers and bioactive coatings-for therapeutic ion/drug release, and potential avenues to further enhance hard tissue regeneration.

Scalable Macroscopic Engineering from Polymer-Based Nanoscale Building Blocks: Existing Challenges and Emerging Opportunities

Natural materials exhibit exceptional properties due to their hierarchical structures spanning from the nano- to the macroscale. Replicating these intricate spatial arrangements in synthetic materials presents a significant challenge as it requires precise control of nanometric features within large-scale structures. Addressing this challenge depends on developing methods that integrate assembly techniques across multiple length scales to construct multiscale-structured synthetic materials in practical, bulk forms. Polymers and polymer-hybrid nanoparticles, with their tunable composition and structural versatility, are promising candidates for creating hierarchically organized materials. This review highlights advances in scalable techniques for nanoscale organization of polymer-based building blocks within macroscopic structures, including block copolymer self-assembly with additive manufacturing, polymer brush nanoparticles capable of self-assembling into larger, ordered structures, and direct-write colloidal assembly. These techniques offer promising pathways toward the scalable fabrication of materials with emergent properties suited for advanced applications such as bioelectronic interfaces, artificial muscles, and other biomaterials.

One-Pot Hybridization of Microfibrillated Cellulose and Hydroxyapatite as a Versatile Route to Eco-Friendly Mechanical Materials

Hydroxyapatite was crystallized in an alkaline dispersion of mechanically fibrillated cellulose to prepare their composites with hydroxyapatite contents of 26-86 wt %. The composite powder was uniaxially pressed at 120 °C and 300 MPa to obtain the compacts. Three-point bending tests revealed that the bending strengths of the compacts were 40-100 MPa, and the elastic moduli were 4-9 GPa. The composite containing 43% hydroxyapatite showed the largest bending strength and the largest work of fracture, and the composite containing 62% hydroxyapatite showed the largest elastic modulus. The composites, derived from the bioderived eco-friendly materials, showed the mechanical properties comparable to those of engineering plastics such as polyamide-6. Scanning electron microscopic observation of the fracture surface showed that the organic phase was discontinuous when the hydroxyapatite weight fraction was increased from 43% to 62%, and the compacts with a discontinuous organic phase lost toughness.

From bone to nacre - development of biomimetic materials for bone implants: a review

The field of bone repair and regeneration has undergone significant advancements, yet challenges persist in achieving optimal bone implants or scaffolds, particularly load-bearing bone implants. This review explores the current landscape of bone implants, emphasizing the complexity of bone anatomy and the emerging paradigm of biomimicry inspired by natural structures. Nature, as a master architect, offers insights into the design of biomaterials that can closely emulate the mechanical properties and hierarchical organization of bone. By drawing parallels with nacre, the mollusk shells renowned for their exceptional strength and toughness, researchers have endeavored to develop bone implants with enhanced biocompatibility and mechanical robustness. This paper surveys the literature on various nacre-inspired composites, particularly ceramic/polymer composites like calcium phosphate (CaP), which exhibit promising similarities to native bone tissue. By harnessing the principles of hierarchical organization and organic-inorganic interfaces observed in natural structures, researchers aim to overcome existing limitations in bone implant technology, paving the way for more durable, biocompatible, and functionally integrated solutions in orthopedic and dental applications.

On the crack resistance and damage tolerance of 3D-printed nature-inspired hierarchical composite architecture

Materials scientists have taken a learn-from-nature approach to study the structure-property relationships of natural materials. Here we introduce a nature-inspired composite architecture showing a hierarchical assembly of granular-like building blocks with specific topological textures. The structural complexity of the resulting architecture is advanced by applying the concept of grain orientation internally to each building block to induce a tailored crack resistance. Hexagonal grain-shaped building blocks are filled with parallel-oriented filament bundles, and these function as stiff-blocks with high anisotropy due to the embedded fiber reinforcements. Process-induced interfacial voids, which provide preferential crack paths, are strategically integrated with cracks to improve fracture toughness at the macroscopic scale. This study discusses the structural effects of the local/global orientations, stacking sequences, feature sizes, and gradient assemblies of granular blocks on crack tolerance behavior. Alternating stacking sequences induce cracks propagating in the arrestor direction, which boost the fracture energy up to 2.4 times higher than the same layup stacking sequence. Gradient arrangements of feature sizes from coarse to fine or fine to coarse result in the coexistence of stiffness and toughness. Our approach to applying crystallographic concepts to complex composite architectures inspires for original models of fracture mechanics.

Revealing chemistry-structure-function relationships in shark vertebrae across length scales

Shark cartilage presents a complex material composed of collagen, proteoglycans, and bioapatite. In the present study, we explored the link between microstructure, chemical composition, and biomechanical function of shark vertebral cartilage using Polarized Light Microscopy (PLM), Atomic Force Microscopy (AFM), Confocal Raman Microspectroscopy, and Nanoindentation. Our investigation focused on vertebrae from Blacktip and Shortfin Mako sharks. As typical representatives of the orders Carcharhiniformes and Lamniformes, these species differ in preferred habitat, ecological role, and swimming style. We observed structural variations in mineral organization and collagen fiber arrangement using PLM and AFM. In both sharks, the highly calcified corpus calcarea shows a ridged morphology, while a chain-like network is present in the less mineralized intermedialia. Raman spectromicroscopy demonstrates a relative increase of glucosaminocycans (GAGs) with respect to collagen and a decrease in mineral-rich zones, underlining the role of GAGs in modulating bioapatite mineralization. Region-specific testing confirmed that intravertebral variations in mineral content and arrangement result in distinct nanomechanical properties. Local Young's moduli from mineralized regions exceeded bulk values by a factor of 10. Overall, this work provides profound insights into a flexible yet strong biocomposite, which is crucial for the extraordinary speed of cartilaginous fish in the worlds' oceans. STATEMENT OF SIGNIFICANCE: Shark cartilage is a morphologically complex material composed of collagen, sulfated proteoglycans, and calcium phosphate minerals. This study explores the link between microstructure, chemical composition, and biological mechanical function of shark vertebral cartilage at the micro- and nanometer scale in typical Carcharhiniform and Lamniform shark species, which represent different vertebral mineralization morphologies, swimming styles and speeds. By studying the intricacies of shark vertebrae, we hope to lay the foundation for biomimetic composite materials that harness lamellar reinforcement and tailored stiffness gradients, capable of dynamic and localized adjustments during movement.

Taming the Production of Bioluminescent Wood Using the White Rot Fungus Desarmillaria Tabescens

Although bioluminescence is documented both anecdotally and experimentally, the parameters involved in the production of fungal bioluminescence during wood colonization have not been identified to date. Here, for the first time, this work develops a methodology to produce a hybrid living material by manipulating wood colonization through merging the living fungus Desarmillaria tabescens with nonliving balsa (Ochroma pyramidale) wood to achieve and control the autonomous emission of bioluminescence. The hybrid material with the highest bioluminescence is produced by soaking the wood blocks before co-cultivating them with the fungus for 3 months. Regardless of the incubation period, the strongest bioluminescence is evident from balsa wood blocks with a moisture content of 700-1200%, highlighting the fundamental role of moisture content for bioluminescence production. Further characterization reveals that D. tabescens preferentially degraded hemicelluloses and lignin in balsa wood. Fourier-transform infrared spectroscopy reveals a decrease in lignin, while X-ray diffraction analysis confirms that the cellulose crystalline structure is not altered during the colonization process. This information will enable the design of ad-hoc synthetic materials that use fungi as tools to maximize bioluminescence production, paving the way for an innovative hybrid material that could find application in the sustainable production of light.

Organic-Inorganic Copolymerization Induced Oriented Crystallization for Robust Lightweight Porous Composite

Porous composites are important in engineering fields for their lightweight, thermal insulation, and mechanical properties. However, increased porosity commonly decreases the robustness, making a trade-off between mechanics and weight. Optimizing the strength of solid structure is a promising way to co-enhance the robustness and lightweight properties. Here, acrylamide and calcium phosphate ionic oligomers are copolymerized, revealing a pre-interaction of these precursors induced oriented crystallization of inorganic nanostructures during the linear polymerization of acrylamide, leading to the spontaneous formation of a bone-like nanostructure. The resulting solid phase shows enhanced mechanics, surpassing most biological materials. The bone-like nanostructure remains intact despite the introduction of porous structures at higher levels, resulting in a porous composite (P-APC) with high strength (yield strength of 10.5 MPa) and lightweight properties (density below 0.22 g cm-3). Notably, the density-strength property surpasses most reported porous materials. Additionally, P-APC shows ultralow thermal conductivity (45 mW m-1 k-1) due to its porous structure, making its strength and thermal insulation superior to many reported materials. This work provides a robust, lightweight, and thermal insulating composite for practical application. It emphasizes the advantage of prefunctionalization of ionic oligomers for organic-inorganic copolymerization in creating oriented nanostructure with toughened mechanics, offering an alternative strategy to produce robust lightweight materials.

Multifunctional Nacre-Like Nanocomposite Papers for Electromagnetic Interference Shielding via Heterocyclic Aramid/MXene Template-Assisted In-Situ Polypyrrole Assembly

Robust, ultra-flexible, and multifunctional MXene-based electromagnetic interference (EMI) shielding nanocomposite films exhibit enormous potential for applications in artificial intelligence, wireless telecommunication, and portable/wearable electronic equipment. In this work, a nacre-inspired multifunctional heterocyclic aramid (HA)/MXene@polypyrrole (PPy) (HMP) nanocomposite paper with large-scale, high strength, super toughness, and excellent tolerance to complex conditions is fabricated through the strategy of HA/MXene hydrogel template-assisted in-situ assembly of PPy. Benefiting from the "brick-and-mortar" layered structure and the strong hydrogen-bonding interactions among MXene, HA, and PPy, the paper exhibits remarkable mechanical performances, including high tensile strength (309.7 MPa), outstanding toughness (57.6 MJ m-3), exceptional foldability, and structural stability against ultrasonication. By using the template effect of HA/MXene to guide the assembly of conductive polymers, the synthesized paper obtains excellent electronic conductivity. More importantly, the highly continuous conductive path enables the nanocomposite paper to achieve a splendid EMI shielding effectiveness (EMI SE) of 54.1 dB at an ultra-thin thickness (25.4 μm) and a high specific EMI SE of 17,204.7 dB cm2 g-1. In addition, the papers also have excellent applications in electromagnetic protection, electro-/photothermal de-icing, thermal therapy, and fire safety. These findings broaden the ideas for developing high-performance and multifunctional MXene-based films with enormous application potential in EMI shielding and thermal management.

Coupling of Spectrin Repeat Modules for the Assembly of Nanorods and Presentation of Protein Domains

Modular protein engineering is a powerful approach for fabricating high-molecular-weight assemblies and biomaterials with nanoscale precision. Herein, we address the challenge of designing an extended nanoscale filamentous architecture inspired by the central rod domain of human dystrophin, which protects sarcolemma during muscle contraction and consists of spectrin repeats composed of three-helical bundles. A module of three tandem spectrin repeats was used as a rigid building block self-assembling via coiled-coil (CC) dimer-forming peptides. CC peptides were precisely integrated to maintain the spectrin α-helix continuity in an appropriate frame to form extended nanorods. An orthogonal set of customizable CC heterodimers was harnessed for modular rigid domain association, which could be additionally regulated by metal ions and chelators. We achieved a robust assembly of rigid rods several micrometers in length, determined by atomic force microscopy and negative stain transmission electron microscopy. Furthermore, these rigid rods can serve as a scaffold for the decoration of diverse proteins or biologically active peptides along their length with adjustable spacing up to tens of nanometers, as confirmed by the DNA-PAINT super-resolution microscopy. This demonstrates the potential of modular bottom-up protein engineering and tunable CCs for the fabrication of functionalized protein biomaterials.

Study of Self-Locking Structure Based on Surface Microstructure of Dung Beetle Leg Joint

Dung beetle leg joints exhibit a remarkable capacity to support substantial loads, which is a capability significantly influenced by their surface microstructure. The exploration of biomimetic designs inspired by the surface microstructure of these joints holds potential for the development of efficient self-locking structures. However, there is a notable absence of research focused on the surface microstructure of dung beetle leg joints. In this study, we investigated the structural characteristics of the surface microstructures present in dung beetle leg joints, identifying the presence of fish-scale-like, brush-like, and spike-like microstructures on the tibia and femur. Utilizing these surface microstructural characteristics, we designed a self-locking structure that successfully demonstrated functionality in both the rotational direction of the structure and self-locking in the reverse direction. At a temperature of 20 °C, the biomimetic closure featuring a self-locking mechanism was capable of generating a self-locking force of 18 N. The bionic intelligent joint, characterized by its unique surface microstructure, presents significant potential applications in aerospace and various engineering domains, particularly as a critical component in folding mechanisms. This research offers innovative design concepts for folding mechanisms, such as those utilized in satellite solar panels and solar panels for asteroid probes.

Bionic Design of High-Performance Joints: Differences in Failure Mechanisms Caused by the Different Structures of Beetle Femur-Tibial Joints

Beetle femur-tibial joints can bear large loads, and the joint structure plays a crucial role. Differences in living habits will lead to differences in femur-tibial joint structure, resulting in different mechanical properties. Here, we determined the structural characteristics of the femur-tibial joints of three species of beetles with different living habits. The tibia of Scarabaeidae Protaetia brevitarsis and Cetoniidae Torynorrhina fulvopilosa slide through cashew-shaped bumps on both sides of the femur in a guide rail consisting of a ring and a cone bump. The femur-tibial joint of Buprestidae Chrysodema radians is composed of a conical convex tibia and a circular concave femur. A bionic structure design was developed out based on the characteristics of the structure of the femur-tibial joints. Differences in the failure of different joint models were obtained through experiments and finite element analysis. The experimental results show that although the spherical connection model can bear low loads, it can maintain partial integrity of the structure and avoid complete failure. The cuboid connection model shows a higher load-bearing capacity, but its failure mode is irreversible deformation. As key parts of rotatable mechanisms, the bionic models have the potential for wide application in the high-load engineering field.

Nucleus-Spike 3D Hierarchical Superstructures via a Lecithin-Mediated Biomineralization Approach

3D hierarchical superstructures (3DHSs) are key products of nature's evolution and have raised wide interest. However, the preparation of 3DHSs composed of building blocks with different structures is rarely reported, and regulating their structural parameters is challenging. Herein, a simple lecithin-mediated biomineralization approach is reported for the first time to prepare gold 3DHSs composed of 0D nucleus and 1D protruding dendritic spikes. It is demonstrated that a hydrophobic complex by coordination of disulfiram (DSF) with a share of chloroauric acid is the key to forming the 3DHSs. Under the lecithin mediation, chloroauric acid is first reduced to form the 0D nucleus, followed by the spike growth through the reduction of the hydrophobic complex. The prepared 3DHSs possess well-defined morphology with a spike length of ≈95 nm. Notably, the hierarchical spike density is systematically manipulated from 38.9% to 74.3% by controlling DSF concentrations. Moreover, the spike diameter is regulated from 9.2 to 12.9 nm by selecting different lecithin concentrations to tune the biomineralization process. Finite-difference time-domain (FDTD) simulations reveal that the spikes form "hot spots". The dense spike structure endows the 3DHSs with sound performance in surface-enhanced Raman scattering (SERS) applications.

Ion-Specific Interactions Engender Dynamic and Tailorable Properties in Biomimetic Cationic Polyelectrolytes

Biomaterials such as spider silk and mussel byssi are fabricated by the dynamic manipulation of intra- and intermolecular biopolymer interactions. Organisms modulate solution parameters, such as pH and ion co-solute concentration, to effect these processes. These biofabrication schemes provide a conceptual framework to develop new dynamic and responsive abiotic soft material systems. Towards these ends, the chemical diversity of readily available ionic compounds offers a broad palette to manipulate the physicochemical properties of polyelectrolytes via ion-specific interactions. In this study, we show for the first time that the ion-specific interactions of biomimetic polyelectrolytes engenders a variety of phase separation behaviors, creating dynamic thermal- and ion-responsive soft matter that exhibits a spectrum of physical properties, spanning viscous fluids to viscoelastic and viscoplastic solids. These ion-dependent characteristics are further rendered general by the merger of lysine and phenylalanine into a single, amphiphilic vinyl monomer. The unprecedented breadth, precision, and dynamicity in the reported ion-dependent phase behaviors thus introduce a broad array of opportunities for the future development of responsive soft matter; properties that are poised to drive developments in critical areas such as chemical sensing, soft robotics, and additive manufacturing.

Simultaneous Color- and Dose-Controlled Thiol-Ene Resins for Multimodulus 3D Printing with Programmable Interfacial Gradients

Drawing inspiration from nature's own intricate designs, synthetic multimaterial structures have the potential to offer properties and functionality that exceed those of the individual components. However, several contemporary hurdles, from a lack of efficient chemistries to processing constraints, preclude the rapid and precise manufacturing of such materials. Herein, the development of a photocurable resin comprising color-selective initiators is reported, triggering disparate polymerization mechanisms between acrylate and thiol functionality. Exposure of the resin to UV light (365 nm) leads to the formation of a rigid, highly crosslinked network via a radical chain-growth mechanism, while violet light (405 nm) forms a soft, lightly crosslinked network via an anionic step-growth mechanism. The efficient photocurable resin is employed in multicolor digital light processing 3D printing to provide structures with moduli spanning over two orders of magnitude. Furthermore, local intensity (i.e., grayscale) control enables the formation of programmable stiffness gradients with ≈150× change in modulus occurring across sharp (≈200 µm) and shallow (≈9 mm) interfaces, mimetic of the human knee entheses and squid beaks, respectively. This study provides composition-processing-property relationships to inform advanced manufacturing of next-generation multimaterial objects having a myriad of applications from healthcare to education.

Super-Durable, Tough Shape-Memory Polymeric Materials Woven from Interlocking Rigid-Flexible Chains

Developing advanced engineering polymers that combine high strength and toughness represents not only a necessary path to excellence but also a major technical challenge. Here for the first time a rigid-flexible interlocking polymer (RFIP) is reported featuring remarkable mechanical properties, consisting of flexible polyurethane (PU) and rigid polyimide (PI) chains cleverly woven together around the copper(I) ions center. By rationally weaving PI, PU chains, and copper(I) ions, RFIP exhibits ultra-high strength (twice that of unwoven polymers, 91.4 ± 3.3 MPa), toughness (448.0 ± 14.2 MJ m-3), fatigue resistance (recoverable after 10 000 cyclic stretches), and shape memory properties. Simulation results and characterization analysis together support the correlation between microstructure and macroscopic features, confirming the greater cohesive energy of the interwoven network and providing insights into strengthening toughening mechanisms. The essence of weaving on the atomic and molecular levels is fused to obtain brilliant and valuable mechanical properties, opening new perspectives in designing robust and stable polymers.

Bio-Inspired Fluorescent Calcium Sulfate for the Conservation of Gypsum Plasterwork

In this work, the potential of bio-inspired strategies for the synthesis of calcium sulfate (CaSO4·nH2O) materials for heritage conservation is explored. For this, a nonclassical multi-step crystallization mechanism to understand the effect of calcein- a fluorescent chelating agent with a high affinity for divalent cations- on the nucleation and growth of calcium sulfate phases is proposed. Moving from the nano- to the macro-scale, this strategy sets the basis for the design and production of fluorescent nano-bassanite (NB-C; CaSO4·0.5H2O), with application as a fully compatible consolidant for the conservation of historic plasterwork. Once applied to gypsum (CaSO4·2H2O) plaster specimens, cementation upon hydration of nano-bassanite results in a significant increase in mechanical strength, while intracrystalline occlusion of calcein in newly-formed gypsum cement improves its weathering resistance. Furthermore, under UV irradiation, the luminescence produced by calcein molecules occluded in gypsum crystals formed upon nano-bassanite hydration allows the easy identification of the newly deposited consolidant within the treated gypsum plaster without altering the substrate's appearance.

Carbonic anhydrase encapsulation using bamboo cellulose scaffolds for efficient CO2 capture and conversion

Utilizing carbonic anhydrase (CA) to catalyze CO2 hydration offers a sustainable and potent approach for carbon capture and utilization. To enhance CA's reusability and stability for successful industrial applications, enzyme immobilization is essential. In this study, delignified bamboo cellulose served as a renewable porous scaffold for immobilizing CA through oxidation-induced cellulose aldehydation followed by Schiff base linkage. The catalytic performance of the resulting immobilized CA was evaluated using both p-NPA hydrolysis and CO2 hydration models. Compared to free CA, immobilization onto the bamboo scaffold increased CA's optimal temperature and pH to approximately 45 °C and 9.0, respectively. Post-immobilization, CA activity demonstrated effective retention (>60 %), with larger scaffold sizes (i.e., 8 mm diameter and 5 mm height) positively impacting this aspect, even surpassing the activity of free CA. Furthermore, immobilized CA exhibited sustained reusability and high stability under thermal treatment and pH fluctuation, retaining >80 % activity even after 5 catalytic cycles. When introduced to microalgae culture, the immobilized CA improved biomass production by ∼16 %, accompanied by enhanced synthesis of essential biomolecules in microalgae. Collectively, the facile and green construction of immobilized CA onto bamboo cellulose block demonstrates great potential for the development of various CA-catalyzed CO2 conversion and utilization technologies.

Bio-inspired synthesis of nanocrystalline calcite demonstrating significant improvement in mechanical properties of concrete: a construction-nanobiotechnology approach

The bioinspired synthesis of construction material, known as biocement, represents a significant advancement in addressing the environmental sustainability issues associated with traditional cement use in the built environment. Biocement is produced through the process of microbially induced bio-mineralization (MIBM), which offers a promising alternative or supplement to conventional cement, potentially reducing its consumption. Despite extensive literature on the application of biocement in construction biotechnology, the fundamental mechanisms underlying its ability to enhance concrete quality remain poorly understood. This study focuses on the kinetics of biomineral synthesis by two Bacillus species; Bacillus megaterium RB05 and Bacillus foraminis DRG5, to identify the most effective strain for biomineralization. Bioconcrete specimens were created by adding inoculum containing Bacillus megaterium RB05 cells with a nutrient solution to the concrete mixture in a layer-by-layer approach. After 28 days of water curing, nanoparticles of CaCO3, ranging in size from 27 to 82 nm, were produced in the bioconcrete specimens. The resulting concrete, containing nanocrystalline biogenic calcite, demonstrated significant improvements in mechanical properties. Specifically, compressive and tensile strengths of the bioconcrete, tested using a universal testing machine (UTM), increased by 7.69 ± 0.08% and 22 ± 0.1%, respectively, after 72 h of curing. Additionally, the biocement was found to exhibit an organic-inorganic hybrid nature, as identified by TEM, EDAX, FESEM, FTIR, and XRD analyses. The enhanced mechanical properties were attributed to the high surface-to-volume ratio and hybrid nature of the calcite nanoparticles. The findings of this investigation are encouraging, suggesting the potential development of future green and self-sustainable construction materials or bioconcrete.

Large-Area Layered Membranes with Precisely Controlled Nano-Confined Channels

Two-dimensional (2D) nanosheets-based membranes, which have controlled 2D nano-confined channels, are highly desirable for molecular/ionic sieving and confined reactions. However, it is still difficult to develop an efficient method to prepare large-area membranes with high stability, high orientation, and accurately adjustable interlayer spacing. Here, we present a strategy to produce metal ion cross-linked membranes with precisely controlled 2D nano-confined channels and high stability in different solutions using superspreading shear-flow-induced assembly strategy. For example, membranes based on graphene oxide (GO) exhibit interlayer spacing ranging from 8.0±0.1 Å to 10.3±0.2 Å, with a precision of down to 1 Å. At the same time, the value of the orientation order parameter (f) of GO membranes is up to 0.95 and GO membranes exhibit superb stability in different solutions. The strategy we present, which can be generalized to the preparation of 2D nano-confined channels based on a variety of 2D materials, will expand the application scope and provide better performances of membranes.

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.

Highly-Strong and Highly-Tough Alginate Fibers with Photo-Modulating Mechanical Properties

The good combination of high strength and high toughness is a long-standing challenge in the design of robust biomaterials. Meanwhile, robust biomaterials hardly perform fast and significant mechanical property changes under the trigger of light at room temperature. These limit the application of biomaterials in some specific areas. Here, photoresponsive alginate fibers are fabricated by using the designed azobenzene-containing surfactant as flexible contact point for cross-linking polysaccharide chains of alginate, which gain high mechanics through reinforced plastic strain and photo-modulating mechanics through isomerization of azobenzene. By transferring molecular motion into macro-scale mechanical property changes, such alginate fibers achieve reversible photo-modulations on the mechanics. Their breaking strength and toughness can be photo-modulated from 732 MPa and 112 MJ m-3 to 299 MPa and 27 MJ m-3, respectively, leading to record high mechanical changes among the developed smart biomaterials. With merits of good tolerance to pH and temperature, fast response to light, and good biocompatibility, the reported fibers will be suitable for working in various application scenarios as new smart biomaterials. This study provides a new design strategy for gaining highly-strong and highly-tough photoresponsive biomaterials.

Mechanical Regulation of Polymer Gels

The mechanical properties of polymer gels devote to emerging devices and machines in fields such as biomedical engineering, flexible bioelectronics, biomimetic actuators, and energy harvesters. Coupling network architectures and interactions has been explored to regulate supportive mechanical characteristics of polymer gels; however, systematic reviews correlating mechanics to interaction forces at the molecular and structural levels remain absent in the field. This review highlights the molecular engineering and structural engineering of polymer gel mechanics and a comprehensive mechanistic understanding of mechanical regulation. Molecular engineering alters molecular architecture and manipulates functional groups/moieties at the molecular level, introducing various interactions and permanent or reversible dynamic bonds as the dissipative energy. Molecular engineering usually uses monomers, cross-linkers, chains, and other additives. Structural engineering utilizes casting methods, solvent phase regulation, mechanochemistry, macromolecule chemical reactions, and biomanufacturing technology to construct and tailor the topological network structures, or heterogeneous modulus compositions. We envision that the perfect combination of molecular and structural engineering may provide a fresh view to extend exciting new perspectives of this burgeoning field. This review also summarizes recent representative applications of polymer gels with excellent mechanical properties. Conclusions and perspectives are also provided from five aspects of concise summary, mechanical mechanism, biofabrication methods, upgraded applications, and synergistic methodology.

Nanoscopic imaging of ancient protein and vasculature offers insight into soft tissue and biomolecule fossilization

Fossil bones have been studied by paleontologists for centuries. Despite this, empirical knowledge regarding the progression of biomolecular (soft) tissue diagenesis within ancient bone is limited; this is particularly the case for specimens spanning Pleistocene directly into pre-Ice Age strata. A nanoscopic approach is reported herein that facilitates direct imaging, and thus empirical observation, of soft tissue preservation state. Presented data include the first extensive nanoscopic (up to 150,000× magnification), three-dimensional (3D) images of ancient bone protein and vasculature; chemical signals consistent with collagen protein and membrane lipids, respectively, are also localized to these structures. These findings support the analyzed permafrost bones are not fully fossilized but rather represent subfossil bone tissue as they preserve an underlying collagen framework. Extension of these methods to specimens spanning the geologic record will help reveal changes biomolecular tissues undergo during fossilization and is a potential proxy approach for screening specimen suitability for molecular sequencing.

Study of the influence of macro-structure and micro-structure on the mechanical properties of stag beetle upper jaw

Macrostructural control of stress distribution and microstructural influence on crack propagation is one of the strategies for obtaining high mechanical properties in stag beetle upper jaws. The maximum bending fracture force of the stag beetle upper jaw is approximately 154, 000 times the weight of the upper jaw. Here, we explore the macro and micro-structural characteristics of two stag beetle upper jaws and reveal the resulting differences in mechanical properties and enhancement mechanisms. At the macroscopic level, the elliptic and triangular cross-sections of the upper jaw of the two species of stag beetles have significant effects on the formation of cracks. The crack generated by the upper jaws with a triangular section grows slowly and deflects easily. At the microscopic level, the upper jaw of the two species is a chitin cross-layered structure, but the difference between the two adjacent fiber layers at 45° and 50° leads to different deflection paths of the cracks on the exoskeleton. The mechanical properties of the upper jaw of the two species of stag beetle were significantly different due to the interaction of macro-structure and micro-structure. In addition, a series of bionic samples with different cross-section geometries and different fiber cross angles were designed, and mechanical tests were carried out according to the macro-structure and micro-structure characteristics of the stag beetle upper jaw. The effects of cross-section geometry and fiber cross angle on the mechanical properties of bionic samples are compared and analyzed. This study provides new ideas for designing and optimizing highly loaded components in engineering. STATEMENT OF SIGNIFICANCE: The upper jaw of the stag beetle is composed of a complex arrangement of chitin and protein fibers, providing both rigidity and flexibility. This structure is designed to withstand various mechanical stresses, including impacts and bending forces, encountered during its burrowing activities and interactions with its environment. The study of the upper jaw of the stag beetle can provide an efficient structural design for engineering components that are subjected to high loads. Understanding the relationship between structure and mechanical properties in the stag beetle upper jaw holds significant implications for biomimetic design and engineering.

Maneuvering the mineralization of self-assembled peptide nanofibers for designing mechanically-stiffened self-healable composites toward bone-mimetic ECM

Extracellular matrix (ECM) elasticity remains a crucial parameter to determine cell-material interactions (viz. adhesion, growth, and differentiation), cellular communication, and migration that are essential to tissue repair and regeneration. Supramolecular peptide hydrogels with their 3-dimensional porous network and tuneable mechanical properties have emerged as an excellent class of ECM-mimetic biomaterials with relevant dynamic attributes and bioactivity. Here, we demonstrate the design of minimalist amyloid-inspired peptide amphiphiles, CnPA (n = 6, 8, 10, 12) with tuneable peptide nanostructures that are efficiently biomineralized and cross-linked using bioactive silicates. Such hydrogel composites, CnBG exhibit excellent mechanical attributes and possess excellent self-healing abilities and collagen-like strain-stiffening ability as desired for bone ECM mimetic scaffold. The composites exhibited the formation of a hydroxyapatite mineral phase upon incubation in a simulated body fluid that rendered mechanical stiffness akin to the hydroxyapatite-bridged collagen fibers to match the bone tissue elasticity eventually. In a nutshell, peptide nanostructure-guided temporal effects and mechanical attributes demonstrate C8BG to be an optimal composite. Finally, such constructs feature the potential for adhesion, proliferation of U2OS cells, high alkaline phosphatase activity, and osteoconductivity.

Biomimetic Colored Coating toward Robust Display under Hostile Conditions

Structural colors particularly of the angle-independent category stemming from wavelength-dependent light scattering have aroused increasing interest due to their considerable applications spanning displays and sensors to detection. Nevertheless, these colors would be heavily altered and even disappear during practical applications, which is related with the variation of refractive index mismatch by liquid wetting/infiltrating. Inspired by bird feathers, we propose a simple deposition toward the coating with angle-independent structural color and superamphiphobicity. The coating is composed of ∼200 nm-sized channel-type structures between hollow silica and air nanostructures, exhibiting a robust sapphire blue color independent of intense liquid intrusion, which duplicates the characteristics of the back feather of Eastern Bluebird. A high color saturation and superamphiphobicity of the biomimetic coating are optimized by manipulating the coating parameters or adding black substances. Excellent durability under harsh conditions endows the coating with long-term service life in various extreme environments.

Nature's Load-Bearing Design Principles and Their Application in Engineering: A Review

Biological structures optimized through natural selection provide valuable insights for engineering load-bearing components. This paper reviews six key strategies evolved in nature for efficient mechanical load handling: hierarchically structured composites, cellular structures, functional gradients, hard shell-soft core architectures, form follows function, and robust geometric shapes. The paper also discusses recent research that applies these strategies to engineering design, demonstrating their effectiveness in advancing technical solutions. The challenges of translating nature's designs into engineering applications are addressed, with a focus on how advancements in computational methods, particularly artificial intelligence, are accelerating this process. The need for further development in innovative material characterization techniques, efficient modeling approaches for heterogeneous media, multi-criteria structural optimization methods, and advanced manufacturing techniques capable of achieving enhanced control across multiple scales is underscored. By highlighting nature's holistic approach to designing functional components, this paper advocates for adopting a similarly comprehensive methodology in engineering practices to shape the next generation of load-bearing technical components.

Well-Ordered Bicontinuous Nanohybrids from a Bottom-Up Approach for Enhanced Strength and Toughness

Biomimicking natural structures to create structural materials with superior mechanical performance is an area of extensive attention, yet achieving both high strength and toughness remains challenging. This study presents a novel bottom-up approach using self-assembled block copolymer templating to synthesize bicontinuous nanohybrids composed of well-ordered nanonetwork hydroxyapatite (HAp) embedded in poly(methyl methacrylate) (PMMA). This structuring transforms intrinsically brittle HAp into a ductile material, while hybridization with PMMA alleviates the strength reduction caused by porosity. The resultant bicontinuous PMMA/HAp nanohybrids, reinforced at the interface, exhibit high strength and toughness due to the combined effects of topology, nanosize, and hybridization. This work suggests a conceptual framework for fabricating flexible thin films with mechanical properties significantly surpassing those of traditional composites and top-down approaches.

Ultratough Supramolecular Polyurethane Featuring an Interwoven Network with Recyclability, Ideal Self-Healing and Editable Shape Memory Properties

Developing multifunctional polymers with excellent mechanical properties, outstanding shape memory characteristics, and good self-healing properties is a formidable challenge. Inspired by the woven cross-linking strategy, a series of supramolecular polyurethane (PU) with an interwoven network structure composed of covalent and supramolecular cross-linking nodes have been successfully synthesized by introducing the ureido-pyrimidinone (UPy) motifs into the PU skeleton. The best-performing sample exhibited ultrahigh strength (∼77.2 MPa) and toughness (∼312.7 MJ m-3), along with an ideal self-healing efficiency (up to 90.8% for 6 h) and satisfactory temperature-responsive shape memory effect (shape recovery rates up to 96.9%). Furthermore, it ensured recyclability. These favorable properties are mainly ascribed to the effective dissipation of strain energy due to the disassembly and reconfiguration of supramolecular nodes (i.e., quadruple hydrogen bonds (H-bonds) between UPy units), as well as the covalent cross-linking nodes that maintain the integrity of the polymer network structure. Thus, our work provides a universal strategy that breaks through the traditional contradictions and paves the way for the commercialization of high-performance multifunctional PU elastomers.

Single-Anion Conductive Solid-State Electrolytes with Hierarchical Ionic Highways for Flexible Zinc-Air Battery

Flexible zinc-air batteries are leading power sources for next-generation smart wearable electronics. However, flexible zinc-air batteries suffer from the highly-corrosive safety risk and limited lifespan due to the absence of reliable solid-state electrolytes (SSEs). Herein, a single-anion conductive SSE with high-safety is constructed by incorporating a highly amorphous dual-cation ionomer into a robust hybrid matrix of functional carbon nanotubes and polyacrylamide polymer. The as-fabricated SSE obtains dual-penetrating ionomer-polymer networks and hierarchical ionic highways, which contribute to mechanical robustness with 1200 % stretchability, decent water uptake and retention, and superhigh ion conductivity of 245 mS ⋅ cm-1 and good Zn anode reversibility. Remarkably, the flexible solid-state zinc-air batteries delivers a high specific capacity of 764 mAh ⋅ g-1 and peak power density of 152 mW ⋅ cm-2 as well as sustains excellent cycling stability for 1050 cycles (350 hours). This work offers a new paradigm of OH- conductors and broadens the definition and scope of OH- conductors.

Localized Ionic Reinforcement of Double Network Granular Hydrogels

Nature produces soft materials with fascinating combinations of mechanical properties. For example, the mussel byssus embodies a combination of stiffness and toughness, a feature that is unmatched by synthetic hydrogels. Key to enabling these excellent mechanical properties are the well-defined structures of natural materials and their compositions controlled on lengths scales down to tens of nanometers. The composition of synthetic materials can be controlled on a micrometer length scale if processed into densely packed microgels. However, these microgels are typically soft. Microgels can be stiffened by enhancing interactions between particles, for example through the formation of covalent bonds between their surfaces or a second interpenetrating hydrogel network. Nonetheless, changes in the composition of these synthetic materials occur on a micrometer length scale. Here, 3D printable load-bearing granular hydrogels are introduced whose composition changes on the tens of nanometer length scale. The hydrogels are composed of jammed microgels encompassing tens of nm-sized ionically reinforced domains that increase the stiffness of double network granular hydrogels up to 18-fold. The printability of the ink and the local reinforcement of the resulting granular hydrogels are leveraged to 3D print a butterfly with composition and structural changes on a tens of nanometer length scale.

Personalized PLGA/BCL Scaffold with Hierarchical Porous Structure Resembling Periosteum-Bone Complex Enables Efficient Repair of Bone Defect

Using bone regeneration scaffolds to repair craniomaxillofacial bone defects is a promising strategy. However, most bone regeneration scaffolds still exist some issues such as a lack of barrier structure, inability to precisely match bone defects, and necessity to incorporate biological components to enhance efficacy. Herein, inspired by a periosteum-bone complex, a class of multifunctional hierarchical porous poly(lactic-co-glycolic acid)/baicalein scaffolds is facilely prepared by the union of personalized negative mold technique and phase separation strategy and demonstrated to precisely fit intricate bone defect cavity. The dense up-surface of the scaffold can prevent soft tissue cell penetration, while the loose bottom-surface can promote protein adsorption, cell adhesion, and cell infiltration. The interior macropores of the scaffold and the loaded baicalein can synergistically promote cell differentiation, angiogenesis, and osteogenesis. These findings can open an appealing avenue for the development of personalized multifunctional hierarchical materials for bone repair.

Structure driven bio-responsive ability of injectable nanocomposite hydrogels for efficient bone regeneration

Injectable hydrogels are promising for treatment of bone defects in clinic owing to their minimally invasive procedure. Currently, there is limited emphasis on how to utilize injectable hydrogels to mobilize body's regenerative potential for enhancing bone regeneration. Herein, an injectable bone-mimicking hydrogel (BMH) scaffold assembled from nanocomposite microgel building blocks was developed, in which a highly interconnected microporous structure and an inorganic/organic (methacrylated hydroxyapatite and methacrylated gelatin) interweaved nano structure were well-designed. Compared with hydrogels lacking micro-nano structures or only showing microporous structure, the BMH scaffold enhanced the ingrowth of vessels and promoted the formation of dense cellular networks (including stem cells and M2 macrophages), across the entire scaffold at early stage after subcutaneous implantation. Moreover, the BMH scaffold could not only directly trigger osteogenic differentiation of the infiltrated stem cells, but also provided an instructive osteo-immune microenvironment by inducing macrophages into M2 phenotype. Mechanistically, our results reveal that the nano-rough structure of the BMH plays an essential role in inducing macrophage M2 polarization through activating mechanotransduction related RhoA/ROCK2 pathway. Overall, this work offers an injectable hydrogel with micro-nano structure driven bio-responsive abilities, highlighting harnessing body's inherent regenerative potential to realize bone regeneration.

Crossing length scales: X-ray approaches to studying the structure of biological materials

Biological materials have outstanding properties. With ease, challenging mechanical, optical or electrical properties are realised from comparatively `humble' building blocks. The key strategy to realise these properties is through extensive hierarchical structuring of the material from the millimetre to the nanometre scale in 3D. Though hierarchical structuring in biological materials has long been recognized, the 3D characterization of such structures remains a challenge. To understand the behaviour of materials, multimodal and multi-scale characterization approaches are needed. In this review, we outline current X-ray analysis approaches using the structures of bone and shells as examples. We show how recent advances have aided our understanding of hierarchical structures and their functions, and how these could be exploited for future research directions. We also discuss current roadblocks including radiation damage, data quantity and sample preparation, as well as strategies to address them.