Multiscale engineered artificial tooth enamel

Enamel-like Polymer-Infiltrated Ceramic Materials for Dental Applications

Polymer-infiltrated ceramic network (PICN) composites are recognized for their mechanical properties, closely resembling natural tooth enamel. However, the low fracture toughness of current PICN materials limits their broader use. This study draws inspiration from the natural enamel rod-sheath architecture to develop bionic PICN composites with an enamel-like structure, enhancing their fracture toughness for dental restorations. By simulating the morphology and arrangement of enamel rods, 3 types of zirconia ceramic scaffolds were designed and manufactured by digital light processing technology, which featured a straight-rod structure, a gnarled-rod structure, or a natural rod distribution structure. The scaffolds were surface treated and resin infiltrated to obtain enamel-structured PICN material, wherein the infiltrated resin formed a rod-sheath structure. With VITA Enamic (VE) as control, the enamel-like composites were characterized in detail for their microstructure, flexural strength, fracture toughness, flexural modulus, friction and wear properties, adhesive properties, and cell compatibility. Results show that the PICN with the natural rod distribution structure had the highest flexural strength and fracture toughness among the 3 PICN composites, but there was no significant difference in their moduli. Its strength and modulus were slightly lower than those of VE, but its toughness was 7.0 ± 0.6 MPa·m1/2, around 7 times that of VE. The fracture mode in the ceramic phase was mainly transgranular, while ductile fracturing of the resin phase contributed to toughening. Furthermore, it exhibited superior wear resistance when compared with VE and bovine enamel. After sandblasting and priming, its bond strength to bovine dentin was comparable to that of VE after standardized treatment. Cytotoxicity assays confirmed high cell viability and healthy morphology. Overall, these results indicate that the newly developed PICN composites offer significant improvement over current dental materials, making them promising candidates for bonded prosthetic applications.

Research Progress in Ceramic-Metal Composites: Designing Interface Structures for High Mechanical Performance

Ceramic-metal composites possess exceptional hardness and wear resistance, as well as high strength and ductility, rendering them highly promising for a wide range of applications. However, the performance of these composites can be significantly restricted by weak interfacial bonding, leading to crack formation at the interfaces; and ultimately, material failure. Therefore, poor interfacial bonding between ceramics and metals is a critical factor limiting the performance. Interfacial bonding strength can be enhanced by regulating the interface structure, which in turn, improves mechanical property. This review focuses on how to design strong interfacial structures in ceramic-metal composites, with particular emphasis on alumina ceramic-metal composites. It seeks to analyze the categorization of interfacial structures, design principles, and strategies for their formation, and examines the impact of interfacial bonding strength on the mechanical properties. Finally, it discusses the regulation of interfacial reactions, optimization of interface structures, integration of various interface designs, improvements in manufacturing technology, and the use of theoretical calculations to enhance interfacial bonding strength.

Interface Engineering for High Strength and High Toughness Ceramic Matrix Composites

Ceramics exhibit exceptional strength, hardness, and structural stability, rendering them indispensable as aerospace, national defense and biomedical applications. However, the presence of robust covalent or ionic bonds within the ceramic leads to its inherent poor fracture toughness. The incorporation of toughening phases into ceramics is widely recognized as an optimal toughening strategy for ceramic matrix composites (CMCs) based on chemical means, with the interplay between toughening phase and ceramic at the interface playing a crucial role in achieving superior mechanical properties. In this review, we briefly delineate the evolution of ceramic matrix composites, emphasizing that interface engineering constitutes an efficacious approach to augmenting the fracture toughness of these composites. Furthermore, we meticulously explore the structure-activity relationship between the composition and structure of the toughening phase and the mechanical attributes of CMCs. Additionally, we comprehensively summarize the impact of innovative biomimetic structures on the mechanical properties of these composites, unveiling the beneficial effects of interface regulation on energy dissipation. Ultimately, we systematically consolidate the mechanisms underpinning the influence of interface engineering on the mechanical properties of CMCs and propose solutions to existing interface challenges, paving the way for the development of next-generation CMCs that exhibit unparalleled strength and toughness.

A Gradient Enamel-Mimetic Composite via Crisscross Assembly of Aligned Hybrid Nanowires for Excellent Mechanical Performance

Materials with excellent comprehensive mechanical properties (e.g., strength and toughness, stiffness and damping, fatigue et al.) are highly desirable for engineering applications, while it is still challenged for design. Tooth enamel is a typical biomaterial with outstanding mechanical properties that originate from its multiscale and gradient structure. Some composites with enamel-like multiscale structures are successfully synthesized, but mimicking the gradient structure of tooth enamel is still difficult to realize. Here, an enamel analog is fabricated with a gradient structure similar to inner enamel based on the crisscross assembly of aligned hybrid nanowires through a magnetic-assisted freeze casting and subsequent mechanical compression strategy. The gradient enamel-mimetic composites exhibited high strength and toughness surpassing the natural tooth enamel, and simultaneously high stiffness and damping comparable to those of enamel, as well as high fatigue resistance. The interface reinforcement of gradient structure, crystal/amorphous and organic/inorganic, fundamentally accounted for high mechanical performance. The gradient design strategy provides an avenue for the engineering of structural materials with excellent mechanical properties.

Hierarchical Engineering of Single-Crystalline Mesoporous Metal-Organic Frameworks with Hollow Structures

Although the superiority of hierarchical structure has driven extensive demand for applications, establishing hierarchy in a long-range-ordered single crystal remains a formidable challenge due to the inherent competition and contradiction between single crystallinity and controllable hierarchical structure. Herein, we demonstrate a growth and dissociation kinetics cooperative strategy for synthesizing a family of hollow single-crystalline mesoporous metal-organic frameworks (meso-MOFs) with hierarchical structures. The approach employs a dual-template method, integrating both hard and soft templates. By adjusting the HCl/CH3COOH ratio, the reaction system's pH can be tuned to regulate the dissociation kinetics of the acid-sensitive seeds serving as hard templates for the formation of hollow structure, while simultaneously modifying the concentration of the dual acids to control the growth kinetics of meso-MOF shells. The competition between maintaining a single crystallinity and achieving a well-defined hierarchical structure can be effectively balanced. Driven by the two interfacial kinetics, we successfully obtained the octahedral meso-MOF nanoparticles that not only exhibit a well-defined hollow structure with precisely controllable hollow size (∼81-1120 nm) and tunable wall thickness (∼28.6-61.3 nm) but also retain their single-crystal integrity. Specifically, the dissociation kinetics of seeds governed the formation of hollow structures, while the growth kinetics of single-crystalline meso-MOF shells ensured uniform coverage and structural integrity. Based on this strategy, we further developed a series of novel hollow meso-MOFs with hierarchical nanostructures, including hollow open-capsule meso-MOFs, 2D hollow meso-MOFs, hollow interlayer-structured meso-MOFs, macro-meso-micro trimodal porous MOFs, and so on.

Integration of high strength, flexibility, and room-temperature plasticity in ceramic nanofibers

The developing cutting-edge technologies involving extreme mechanical environments, such as high-frequency vibrations, mechanical shocks, or repeated twisting, require ceramic components to integrate high strength, large bending strain, and even plastic deformation, which is difficult in conventional ceramic materials. The emergence of ceramic nanofibers (CNFs) offers potential solutions; unfortunately, this desirable integration of mechanical properties in CNFs remains unrealized to date, due to challenges in precisely modulating microstructures, reducing cross-scale defects, and overcoming inherent contradictions between mechanical attributes (particularly, high strength and large deformation are often mutually exclusive). Here, we report a nucleation regulation strategy for crystalline/amorphous dual-phase CNFs, achieving an extraordinary integration of high strength, superior flexibility, and room-temperature plasticity. This advancement stems from the optimized dual-phase structure featuring reduced nanocrystal aggregation, increased internal interfaces, and the elimination of fiber defects, thus fully activating the synergistic advantages and multiple deformation mechanisms of dual-phase configurations. Using TiO2, which is typically characterized by brittleness and low strength, as the proof-of-concept model, in-situ single-nanofiber mechanical tests demonstrate excellent flexibility, strength (~1.06 GPa), strain limit (~8.44%), and room-temperature plastic deformation. These findings would provide valuable insights into the mechanical design of ceramic materials, paving the way for CNFs in extreme applications and their widespread industrialization.

Nanoconfinement-induced shift in photooxidative degradation pathway of polystyrene

Polymer nanocomposites with high concentrations of nanoparticles (NPs) possess exceptional mechanical, transport, and thermal properties. To enable their widespread use in structural applications and functional coatings, it is crucial to understand how nanoconfinement and the polymer-NP interface influence polymer degradation under various environmental conditions, including prolonged UV exposure. In this study, we investigate the photooxidative degradation of polystyrene (PS)-confined in the interstices of SiO2 NP films. These nanocomposite films are prepared by the capillary rise infiltration (CaRI) of PS into interstices of SiO2 NP packings, and subsequently subjected to UV irradiation. Our investigation reveals that PS degradation progresses uniformly across the thickness, with degradation initiating from the center of the NP interstitial pores and extending towards the NP surface. We rationalize this degradation mechanism based on the disparity in the surface energies of PS and the NP surface, as well as slow oxygen diffusion through confined PS. We also demonstrate that packing smaller NPs at a given thickness or thicker packing of a specific NP size facilitates photooxidative degradation, highlighting the critical role of the number of interstitial pores in influencing degradation processes.

Unlocking property constraints through a multi-level ordered structure strategy

Materials with unprecedented and exotic properties are crucial for addressing energy and environmental crisis. However, many existing materials are approaching performance limits due to inherent physical constraints. Here, we report a multi-level ordered structure (MOS) strategy to address these challenges. Using magnetic material as a proof of concept, we demonstrate a resistive magnetic metal with high thermal stability, which is challenging due to the abundant free electrons in metals and inherent instability of the magnetized state, but highly sought after for future high-frequency and high-power applications. The obtained MOS material features multiple ordered characteristics across different levels, exhibiting large electrical resistivity surpassing its constituents by 2600%, while achieving an over 100% improvement in magnetic thermal stability that outperforms state-of-the-art commercial counterparts. Furthermore, it also achieves enhancements in coercivity, corrosion resistance and stiffness. The MOS strategy manipulates functional processes to simultaneously overcome multiple physical constraints and transcend performance bottlenecks.

Modulating the Structural Complexity of AuNCs Aggregates for Generation of Bright Luminescence

Self-assembly of coinage metal nanoclusters constitutes an important branch for the construction of bright luminescent materials. They also serve as a class of promising building blocks for the study of hierarchically organized assemblies due to their potential of generating high structural complexity. However, the strong intercluster interactions exert great difficulty and uncertainty on the modulation of the outcome aggregation structures. To explore a feasible methodology for constructing complex structures that combine order and disorder, accompanied by emerging desirable optical performances, herein we manipulate the supramolecular interactions of a gold nanocluster, namely, DPT-AuNCs through the incorporation of an amphiphilic cation, i.e., 1-dodecyl-3-methylimidazolium (DMI+). Diverse aggregation structures are obtained through coassembly, and a sea urchin-like aggregate with a complexity index of CI = 16.5 is formed by elevating the concentration of DMI+. Moreover, a positive correlation between structural complexity and emission intensity was observed, and strongly luminescent NCs-based aggregates were obtained. The mechanism for the emergence of structural complexity is demonstrated via kinetic studies, 1H NMR titration, theoretical computation, etc. The cation-π interaction is found to be vital for the association between DMI+ and DPT-AuNCs, which modulates the supramolecular interactions for assembly and in turn facilitates the growth of aggregates in multiple dimensions. The sea urchin-like aggregate is formed through a dynamic assembly process, mediated by the pre-equilibrium of DMI+ micelles at high concentrations. Finally, the luminescent NC aggregates can also be obtained by incorporating different types of amphiphilic cations, thus generalizing the method for constructing complex assembly structures.

Multiscale Engineered Bionic Solid-State Electrolytes Breaking the Stiffness-Damping Trade-Off

All-solid-state lithium metal batteries (LMBs) are regarded as next-generation devices for energy storage due to their safety and high energy density. The issues of Li dendrites and poor mechanical compatibility with electrodes present the need for developing solid-state electrolytes with high stiffness and damping, but it is a contradictory relationship. Here, inspired by the superstructure of tooth enamel, we develop a composite solid-state electrolyte composed of amorphous ceramic nanotube arrays intertwined with solid polymer electrolytes. This bionic electrolyte exhibits both high stiffness (Young's modulus=15 GPa, hardness=0.13 GPa) and damping (tanδ=0.08), breaking the trade-off. Thus, this composite electrolyte can not only inhibit Li dendrites growth but also ensure intimate contact with electrodes. Meanwhile, it also exhibits considerable Li+ transference number (0.62) and room temperature ionic conductivity (1.34×10-4 S cm-1), which is attributed to oxygen vacancies of the amorphous ceramic effectively decoupling the Li-TFSI ion pair. Consequently, the assembled Li symmetric battery shows an ultra-stable cycling (>2000 hours at 0.1 mA cm-2 at 60 °C, >500 hours at 0.1 mA cm-2 at 30 °C). Moreover, the LiFePO4/Li and LiNi0.8Co0.1Mn0.1O2/Li all-solid-state full cells both show excellent cycling performance. We demonstrate that this bionic strategy is a promising approach for the development of high-performance solid-state electrolytes.

Bioinspired Materials for Controlling Mineral Adhesion: From Innovation Design to Diverse Applications

The advancement of controllable mineral adhesion materials has significantly impacted various sectors, including industrial production, energy utilization, biomedicine, construction engineering, food safety, and environmental management. Natural biological materials exhibit distinctive and controllable adhesion properties that inspire the design of artificial systems for controlling mineral adhesion. In recent decades, researchers have sought to create bioinspired materials that effectively regulate mineral adhesion, significantly accelerating the development of functional materials across various emerging fields. Herein, we review recent advances in bioinspired materials for controlling mineral adhesion, including bioinspired mineralized materials and bioinspired antiscaling materials. First, a systematic overview of biological materials that exhibit controllable mineral adhesion in nature is provided. Then, the mechanism of mineral adhesion and the latest adhesion characterization between minerals and material surfaces are introduced. Later, the latest advances in bioinspired materials designed for controlling mineral adhesion are presented, ranging from the molecular level to micro/nanostructures, including bioinspired mineralized materials and bioinspired antiscaling materials. Additionally, recent applications of these bioinspired materials in emerging fields are discussed, such as industrial production, energy utilization, biomedicine, construction engineering, and environmental management, highlighting their roles in promoting or inhibiting aspects. Finally, we summarize the ongoing challenges and offer a perspective on the future of this charming field.

Osteomimix: A Multidimensional Biomimetic Cascade Strategy for Bone Defect Repair

Despite advancements in biomimetic mineralization techniques, the repair of large-scale bone defects remains a significant challenge. Inspired by the bone formation process, a multidimensional biomimetic cascade strategy is developed by replicating the biomineralization cascade, emulating the hierarchical structure of bone, and biomimicking its biological functions for efficient bone regeneration. This strategy involves the photocrosslinking of sodium methacrylate carboxymethyl cellulose-stabilized amorphous magnesium-calcium phosphate with methacrylate-modified type I collagen to create a self-mineralizing hydrogel. The hydrogel is then integrated with either naturally derived or synthetic oriented bulk scaffolds. The resulting composite, named Osteomimix, provides excellent mechanical support and can be customized for irregular bone defects using CAD/CAM technology. Through in vitro and in vivo studies, this work finds that Osteomimix exhibits spontaneous in situ biomimetic mineralization in a cell-free environment, while modulating immune responses and promoting vascularized bone formation in a cell-dependent manner. Built on bone-specific insights, this strategy achieves biomimicry across temporal, spatial, and functional dimensions, facilitating the seamless integration of artificial constructs with the natural tissue repair dynamics.

Crystallographic plane-induced selective mineralization of nanohydroxyapatite on fibrous-grained titanium promotes osteointegration and biocorrosion resistance

The (002) crystallographic plane-oriented hydroxyapatite (HA) and anatase TiO2 enable favorable hydrophilicity, osteogenesis, and biocorrosion resistance. Thus, the crystallographic plane control in HA coating and crystalline phase control in TiO2 is vital to affect the surface and interface bioactivity and biocorrosion resistance of titanium (Ti) implants. However, a corresponding facile and efficient fabrication method is absent to realize the HA(002) mineralization and anatase TiO2 formation on Ti. Herein, we utilized the predominant Ti(0002) plane of the fibrous-grained titanium (FG Ti) to naturally form anatase TiO2 and further achieve a (002) basal plane oriented nanoHA (nHA) film through an in situ mild hydrothermal growth strategy. The formed FG Ti-nHA(002) remarkably improved hydrophilicity, mineralization, and biocorrosion resistance. Moreover, the nHA(002) film reserved the microgroove-like topological structure on FG Ti. It could enhance osteogenic differentiation through promoted contact guidance, showing one order of magnitude higher expression of osteogenic-related genes. On the other hand, the nHA(002) film restrained the osteoclast activity by blocking actin ring formation. Based on these capacities, FG Ti-nHA(002) improved new bone growth and binding strength in rabbit femur implantation, achieving satisfactory osseointegration within 2 weeks.

Biomimetic Janus Particles Induced In Situ Interfacial Remineralization for Dentin Hypersensitivity

Dentin hypersensitivity (DH), caused by the exposure of dentin tubules, is a common complaint of dental patients. Although occlusion of the exposed tubules is the primary treatment approach, the complex oral environment, and multiple simultaneous requirements often hinder its implementation. In this study, strawberry‐shaped hemispheric Janus particles (JPs) are synthesized, and their use in the treatment of DH is evaluated in vitro and in an animal model. The hemispheric side of the JPs is modified with polymers of quaternary ammonium salts (QASs) to form a superhydrophobic coating with antibiofilm properties, while the flat side is modified with catechol groups able to form strong bonds with dentin. Even after 1 h of ultrasonication or 1000 rounds of thermal cycling, the dentin tubules are completely occluded by the JPs. Moreover, biofilm formation is not observed, and the area of living bacteria is less than 1% compared to the blank control and sodium fluoride (NaF)‐treated groups. In a rat model, the dentin tubules in the fixed specimens are completely occluded at day 3, much earlier than the occlusion obtained with commonly used NaF. These results demonstrate that JPs can provide a novel approach to the treatment of DH.

3D printing of biological tooth with multiple ordered hierarchical structures

Natural teeth fulfill functional demands by their heterogeneity. The composition and hydroxyapatite (HAp) nanostructured orientation of enamel differ from those of dentin. However, mimicking analogous materials still exhibit a significant challenge. Herein, a bottom-up, sequential approach was formulated by combining shear-induced and magnetic-assisted 3D printing technology, enabling the fabrication of the intricate microstructure of a multi-material dental crown, where the HAp nanostructure is highly ordered and almost perpendicular to each other at the dentinoenamel junction (DEJ). The HAp nanorods were first induced to achieve high orientation in each printed line, then formed a plane with a vertical structure of DEJ under the shear force and magnetic field at dentin and enamel, respectively, and finally 3D-printed into a dental crown with bilayered parts exhibiting site-specific composition, texture, and outstanding biocompatibility. This novel approach can be applied to design and fabricate natural tooth crowns, indicating the potential for multi-level and multi-dimensional texture control.

Dynamic Peptide Nanoframework-Guided Protein Coassembly: Advancing Adhesion Performance with Hierarchical Structures

Hierarchical structures are essential in natural adhesion systems. Replicating these in synthetic adhesives is challenging due to intricate molecular mechanisms and multiscale processes. Here, we report three phosphorylated peptides featuring a hydrophobic self-assembly motif linked to a hydrophilic phosphorylated sequence (pSGSS), forming peptide fibril nanoframeworks. These nanoframeworks effectively coassemble with elastin-derived positively charged proteins (PCP), resulting in complex coacervate-based adhesives with hierarchical structures. Our method enables the controlled regulation of both cohesion and adhesion properties in the adhesives. Notably, the complex adhesives formed by the dityrosine-containing peptide and PCP demonstrate an exceptional interfacial adhesion strength of up to 30 MPa, outperforming most known supramolecular adhesives and rivaling cross-linked chemical adhesives. Additionally, these adhesives show promising biocompatibility and bioactivity, making them suitable for applications such as visceral hemostasis and tissue repair. Our findings highlight the utility of bioinspired hierarchical assembly combined with bioengineering techniques in advancing biomedical adhesives.

Design and Development of Infiltration Resins: From Base Monomer Structure to Resin Properties

The resin infiltration concept is one of the most widely used minimally invasive restorative techniques in restorative dentistry with the most outstanding therapeutic effect, and it is also one of the key research directions in restorative dentistry. "Infiltration resin" is the specialty restorative material for the technology, which is the key factor to success. The specialized restorative material is commonly known as "infiltrant/infiltration resins" "resins infiltrant" "infiltrant" or "resins," which will be consistently referred to as "infiltration resins" throughout the article. The paper aims to provide a comprehensive overview of infiltration resins by introducing the development of their therapeutic mechanisms, basic components, current challenges, and future trends, Based on existing literature, we analyze and compare how changes in the base monomer's structure and ratio affect the effectiveness of infiltration resins, from the material's structure-effective relationship. After compiling the information, the existing solution strategies have been listed to offer substantial support and guidance for future research endeavors.

Poly(vinyl alcohol) potentiating an inert d-amino acid-based drug for boron neutron capture therapy

Since the discovery of d-amino acids, they have been considered inactive and have not been used as potent drugs. Here, we report that simple mixing with poly(vinyl alcohol) (PVA) unleashed latent potentials of d-amino acids in boron neutron capture therapy (BNCT). PVA formed boronate esters with seemingly useless boronated d-amino acids and induced tumor-associated amino acid transporter-superselective internalization and prolonged intracellular retention, accomplishing complete cure of tumors. The superselective internalization was achieved by switching the internalization pathway from ineffective pass through the transporter to the transporter-mediated endocytosis. The acidic environment in the endo-/lysosome dissociated the boronate esters and elicited the stealthiness of the drugs, preventing their externalization and prolonging intracellular retention time. In a subcutaneous tumor model, this system accomplished surprisingly high tumor-selective accumulation that could not be achieved by conventional approaches and induced drastic BNCT effects. PVA may be a unique material to unlock potentials of seemingly inert molecules.

Multiscale integral synchronous assembly of cuttlebone-inspired structural materials by predesigned hydrogels

The overall structural integrity plays a vital role in the unique performance of living organisms, but the integral synchronous preparation of different multiscale architectures remains challenging. Inspired by the cuttlebone's rigid cavity-wall structure with excellent energy absorption, we develop a robust hierarchical predesigned hydrogel assembly strategy to integrally synchronously assemble multiple organic and inorganic micro-nano building blocks to different structures. The two types of predesigned hydrogels, combined with hydrogen, covalent bonding, and electrostatic interactions, are layer-by-layer assembled into brick-and-mortar structures and close-packed rigid micro hollow structures in a cuttlebone-inspired structural material, respectively. The cuttlebone-inspired structural materials gain crack growth resistance, high strength, and energy absorption characteristics beyond typical energy-absorbing materials with similar densities. This hierarchical hydrogel integral synchronous assembly strategy is promising for the integrated fabrication guidance of bioinspired structural materials with multiple different micro-nano architectures.

Digital light printing of zirconia/resin composite material with biomimetic graded design for dental application

OBJECTIVE

Stress concentration and excessive wear on the opposite jaw teeth are the main problems that lead to the failure of all-ceramic crown restoration. The objectives of this study were to: (1) Synthesize the biomimetic gradient zirconia/resin composites. (2) Control the porosity and structure so that the mechanical properties of the biomimetic gradient zirconia/resin composites are close to enamel and dentin.

METHODS

Biomimetic uniform zirconia scaffolds with different widths (1.6 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.2 mm) and Biomimetic gradient (1.6 mm-2.2 mm) zirconia scaffolds were designed using 3DMax and Magics, fabricated by digital light processing 3D printing, and then infiltrated into dental resin for mechanical testing, finite element simulation and cytotoxicity testing.

RESULTS

Results show that the ceramic-polymer composites exhibit a significant enhancement in strength (1.37-fold increase) and toughness (2.08-fold increase) compared to zirconia ceramic scaffold (P < 0.05), highlighting the effectiveness of our structural design. In addition, the gradient design further improves the mechanical strength of the composites. Notably, the gradient composite crown exhibits a bending strength of 138.3 (±16.7) MPa, a toughness of 9.0 (±0.5) MJ/m³, and a compressive strength of 113.7 (±2.6) MPa, values that are comparable to those of natural enamel and dentin, and shows good biosafety.

CONCLUSION

Biomimetic gradient zirconia/dental resin materials were precisely fabricated through a series of studies, which is expected to further improve the clinical treatment effect. At the same time, the strategic design also provides new ideas for the performance improvement of other dental materials.

SIGNIFICANCE

Gradient zirconia/resin composite materials with mechanical properties matching natural teeth were precisely fabricated, and are expected to significantly improve clinical treatment outcomes. Additionally, the strategic design provides new insights for enhancing the performance of other dental materials.

Simultaneously Strengthening and Toughening All-Natural Structural Materials via 3D Nanofiber Network Interfacial Design

Constructing structural materials from sustainable raw materials is considered an efficient way to reduce the potential threat posed by plastics. Nevertheless, challenges remain regarding combining excellent mechanical and thermal properties, especially the balance of strength and toughness. Here, we report a 3D nanofiber network interfacial design strategy to strengthen and toughen all-natural structural materials simultaneously. The introduced protonated chitosan at the interface between the surface oxidized 3D nanonetwork of bacterial cellulose forms the interfacial interlocking structure of nanonetworks, achieving a robust physical connection and providing enough physical contact sites for chemical crosslinking. The obtained sustainable structural material successfully integrates excellent mechanical and thermal properties on the nanoscale of cellulose nanofibers, such as light weight, high strength, and superior thermal expansion coefficient. The relationship between structural design and comprehensive mechanical property improvement is analyzed in detail, providing a universal perspective to design sustainable high-performance structural materials from nanoscale building blocks.

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 Nanofillers Reinforced Polymer-Inorganic Nanocomposite Film with Enhanced Mechanical Properties

Simultaneously improving the strength and toughness of polymer-inorganic nanocomposites is highly desirable but remains technically challenging. Herein, a simple yet effective pathway to prepare polymer-inorganic nanocomposite films that exhibit excellent mechanical properties due to their unique composition and structure is demonstrated. Specifically, a series of poly(methacrylic acid)x-block-poly(benzyl methacrylate)y diblock copolymer nano-objects with differing dimensions and morphologies is prepared by polymerization-induced self-assembly (PISA) mediated by reversible addition-fragmentation chain transfer polymerization (RAFT). Such copolymer nano-objects and ultrasmall calcium phosphate oligomers (CPOs) are used as dual fillers for the preparation of polymer-inorganic composite films using sodium carboxymethyl cellulose (CMC) as a matrix. Impressively, the strength and toughness of such composite films are substantially reinforced as high as up to 202.5 ± 14.8 MPa and 62.3 ± 7.9 MJ m-3, respectively. Owing to the intimate interaction between the polymer-inorganic interphases at multiple scales, their mechanical performances are superior to most conventional polymer films and other nanocomposite films. This study demonstrates the combination of polymeric fillers and inorganic fillers to reinforce the mechanical properties of the resultant composite films, providing new insights into the design rules for the construction of novel hybrid films with excellent mechanical performances.

Direct Immobilization of Folic Acid Molecules on Hydroxyapatite Nanoparticles with Substitution and Coordination Phenomena

We successfully synthesized folic acid (FA) immobilized hydroxyapatite (HA) nanoparticles without using a mediative reagent (e.g., silane coupling agent), and the immobilization states were evaluated and discussed. The HA nanoparticles with higher biocompatibility have two different planes, namely, c- and m-planes. These plane surfaces are rich in phosphate groups (P-site) and Ca2+ ions (C-site), respectively. We suggested that during the synthesis of the HA nanoparticles, the P-site substitution and C-site coordination with the addition of organic molecules containing -COO- ions can occur. Thus, it is possible to simultaneously immobilize two molecules to one HA nanoparticle. In this study, we successfully synthesized FA-immobilized HA nanoparticles by P-site substitution and C-site coordination reactions, which were named as substitution type and coordination type. In the substitution type, when FA was reacted with HA during the nucleation stage, the PO43- ions of HA decreased as the FA ratio of coverage surface area increased, and the crystalline phase was changed significantly from the Ca deficient HA to the carbonated HA phase. Accordingly, it was indicated that FA was immobilized on HA by the P-site substitution. In the coordination type, since FA was reacted with HA after the completion of crystal growth, the crystalline phase was changed slightly as the FA ratio of coverage surface area increased, indicating that FA was immobilized on HA by the C-site coordination. From the above, we controlled the FA immobilization states on the HA nanoparticles by the P-site substitution and the C-site coordination through the FA addition timing in the synthesis. Since the -COO- ions in FA could be selectively substituted with the P-site in HA, it is possible to directly coordinate the foreign organic molecules to the Ca2+ ions in HA. Therefore, the immobilization technique of this study is expected to achieve two different drug molecules with diagnosis and therapy functions (i.e., theranostics) on one nanoparticle.

Monolithic DNApatite: An Elastic Apatite with Sub-Nanometer Scale Organo-Inorganic Structures

Hydroxyapatite (HA) exhibits outstanding biocompatibility, bioactivity, osteoconductivity, and natural anti-inflammatory properties. Pure HA, ion-doped HA, and HA-polymer composites are investigated, but critical limitations such as brittleness remain; numerous efforts are being made to address them. Herein, the novel self-crystallization of a polymeric single-stranded deoxyribonucleic acid (ssDNA) without additional phosphate ions for synthesizing deoxyribonucleic apatite (DNApatite) is presented. The synthesized DNApatite, DNA1Ca2.2(PO4)1.3OH2.1, has a repetitive dual phase of inorganic HA crystals and amorphous organic ssDNA at the sub-nm scale, forming nanorods. Its mechanical properties, including toughness and elasticity, are significantly enhanced compared with those of HA nanorod, with a Young's modulus similar to that of natural bone.

Bottom-Up Assembling Hierarchical Enamel-Like Bulk Materials with Excellent Optical and Mechanical Properties for Tooth Restoration

Enamel has good optical and mechanical properties because of its multiscale hierarchical structure. Biomimetic construction of enamel-like 3D bulk materials at nano-, micro-, mesh- and macro-levels is a challenge. A novel facile, cost-effective, and easy large-scale bottom-up assembly strategy to align 1D hydroxyapatite (HA) nanowires bundles to 3D hierarchical enamel structure with the nanowires bundles layer-by-layer interweaving orientation, is reported. In the strategy, the surface of oleate templated ultralong HA nanowires with a large aspect ratio is functionalized with amphiphilic 10-methacryloyloxydecyl dihydrogen phosphate (MDP). Furtherly, the MDP functionalized HA nanowire bundles are assembled layer-by-layer with oriented fibers in a single layer and cross-locked between layers at a certain angle at mesoscale and macroscale in the viscous bisphenol A-glycidyl methacrylate (Bis-GMA) ethanol solution by shear force induced by simple agitation and high-speed centrifugation. Finally, the excessive Bis-GMA and ethanol are removed, and (Bis-GMA)-(MDP-HA nanowire bundle) matrix is densely packed under hot pressing and polymerized to form bulk enamel-like materials. The composite has superior optical properties and comparable comprehensive mechanic performances through a combination of strength, hardness, toughness, and friction. This method may open new avenues for controlling the nanowires assembly to develop hierarchical nanomaterials with superior properties for many different applications.

Multiscale engineered artificial compact bone via bidirectional freeze-driven lamellated organization of mineralized collagen microfibrils

Bone, renowned for its elegant hierarchical structure and unique mechanical properties, serves as a constant source of inspiration for the development of synthetic materials. However, achieving accurate replication of bone features in artificial materials with remarkable structural and mechanical similarity remains a significant challenge. In this study, we employed a cascade of continuous fabrication processes, including biomimetic mineralization of collagen, bidirectional freeze-casting, and pressure-driven fusion, to successfully fabricate a macroscopic bulk material known as artificial compact bone (ACB). The ACB material closely replicates the composition, hierarchical structures, and mechanical properties of natural bone. It demonstrates a lamellated alignment of mineralized collagen (MC) microfibrils, similar to those found in natural bone. Moreover, the ACB exhibits a similar high mineral content (70.9 %) and density (2.2 g/cm3) as natural cortical bone, leading to exceptional mechanical properties such as high stiffness, hardness, and flexural strength that are comparable to those of natural bone. Importantly, the ACB also demonstrates excellent mechanical properties in wet, outstanding biocompatibility, and osteogenic properties in vivo, rendering it suitable for a broad spectrum of biomedical applications, including orthopedic, stomatological, and craniofacial surgeries.

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.

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.

Developing functional hydrogels for treatment of oral diseases

Oral disease is a severe healthcare challenge that diminishes people's quality of life. Functional hydrogels with suitable biodegradability, biocompatibility, and tunable mechanical properties have attracted remarkable interest and have been developed for treating oral diseases. In this review, we present up-to-date research on hydrogels for the management of dental caries, endodontics, periapical periodontitis, and periodontitis, depending on the progression of dental diseases. The strategies of hydrogels for treating oral mucosal diseases and salivary gland diseases are then classified. After that, we focus on the application of hydrogels related to tumor therapy and tissue defects. Finally, the review prospects the restrictions and the perspectives on the utilization of hydrogels in oral disease treatment. We believe this review will promote the advancement of more amicable, functional and personalized approaches for oral diseases.

A Superparamagnetic Composite Hydrogel Scaffold as In Vivo Dynamic Monitorable Theranostic Platform for Osteoarthritis Regeneration

Osteoarthritis (OA) is a prevalent disease, characterized by subchondral fractures in its initial stages, which has no precise and specific treatment now. Here, a novel multifunctional scaffold is synthesized by photopolymerizing glycidyl methacrylate-modified hyaluronic acid (GMHA) as the matrix in the presence of hollow porous magnetic microspheres based on hydroxyapatite. In vivo subchondral bone repairing results demonstrate that the scaffold's meticulous design has most suitable properties for subchondral bone repair. The porous structure of inorganic particles within the scaffold facilitates efficient transport of loaded exogenous vascular endothelial growth factor (VEGF). The Fe3O4 nanoparticles assembled in microspheres promote the osteogenic differentiation of bone marrow mesenchymal stem cells and accelerate the new bone generation. These features enable the scaffold to exhibit favorable subchondral bone repair properties and attain high cartilage repair scores. The therapy results prove that the subchondral bone support considerably influences the upper cartilage repair process. Furthermore, magnetic resonance imaging monitoring demonstrates that Fe3O4 nanoparticles, which are gradually replaced by new bone during osteochondral defect repair, allow a noninvasive and radiation-free assessment to track the newborn bone during the OA repair process. The composite hydrogel scaffold (CHS) provides a versatile platform for biomedical applications in OA treatment.

Superstrong, sustainable, origami wood paper enabled by dual-phase nanostructure regulation in cell walls

Constructing a crystalline-amorphous hybrid structure is an effective strategy to overcome the conflict between the strength and toughness of materials. However, achieving such a material structure often involves complex, energy-intensive processing. Here, we leverage the natural wood featuring coexisting crystalline and amorphous regions to achieve superstrong and ultratough wood paper (W-paper) via a dual-phase nanostructure regulation strategy. After partially removing amorphous hemicellulose and eliminating most lignin, the treated wood can self-densify through an energy-efficient air drying, resulting in a W-paper with high tensile strength, toughness, and folding endurance. Coarse-grained molecular dynamics simulations reveal the underlying deformation mechanism of the crystalline and amorphous regions inside cell walls and the failure mechanism of the W-paper under tension. Life cycle assessment reveals that W-paper shows a lower environmental impact than commercial paper and common plastics. This dual-phase nanostructure regulation based on natural wood may provide valuable insights for developing high-performance and sustainable film materials.

Insight from Boric Acid into Bioskeleton Formation: Inscribed Circle Effect on the Edge-Base Plate Growth

Complex morphologies in nature often arise from the assembly of elemental building blocks, leading to diverse and intricate structures. Understanding the mechanisms that govern the formation of these complex morphologies remains a significant challenge. In particular, the edge-base plate growth of biogenic crystals plays a crucial role in directing the development of intricate bioskeleton morphologies. However, the factors and regulatory processes that govern edge-base plate growth remain insufficiently understood. Inspired by biological skeletons and based on the soluble property of boric acid (BA) in both water and alcohols, we obtained a series of novel BA morphologies, including coccolith, and anemone biological skeletons. Here, we unveil the "inscribed circle effect", a concise mathematical model that reveals the underlying causative factors and regulatory mechanisms driving edge-base plate growth. Our findings illuminate how variations in solvent environments can exert control over the edge-base plate growth pathways, thereby resulting in the formation of diverse and complex morphologies. This understanding holds significant potential for guiding the chemical synthesis of bioskeleton materials.

Self-assembled branched polypeptides as amelogenin mimics for enamel repair

The regeneration of demineralized enamel holds great significance in the treatment of dental caries. Amelogenin (Ame), an essential protein for mediating natural enamel growth, is no longer secreted after enamel has fully matured in childhood. Although biomimetic mineralization based on peptides or proteins has made significant progress, easily accessible, low-cost, biocompatible and highly effective Ame mimics are still lacking. Herein, we construct a series of amphiphilic branched polypeptides (CAMPs) by facile coupling of the Ame's C-terminal segment and poly(γ-benzyl-L-glutamate), which serves to simulate the Ame's hydrophobic N-terminal segment. Among them, CAMP15 is the best biomimetic mineralization template with great self-assembly performance to guide the oriented crystallization of hydroxyapatite and is capable of inhibiting the adhesion of Streptococcus mutans and Staphylococcus aureus on the enamel surfaces. This work highlights the potential application of amphiphilic branched polypeptide as Ame mimics in repairing defected enamel, providing a promising strategy for prevention and treatment of dental caries.

Recent Advances in Functional Hydrogels for Treating Dental Hard Tissue and Endodontic Diseases

Oral health is the basis of human health, and almost everyone has been affected by oral diseases. Among them, endodontic disease is one of the most common oral diseases. Limited by the characteristics of oral biomaterials, clinical methods for endodontic disease treatment still face large challenges in terms of reliability and stability. The hydrogel is a kind of good biomaterial with an adjustable 3D network structure, excellent mechanical properties, and biocompatibility and is widely used in the basic and clinical research of endodontic disease. This Review discusses the recent advances in functional hydrogels for dental hard tissue and endodontic disease treatment. The emphasis is on the working principles and therapeutic effects of treating different diseases with functional hydrogels. Finally, the challenges and opportunities of hydrogels in oral clinical applications are discussed and proposed. Some viewpoints about the possible development direction of functional hydrogels for oral health in the future are also put forward. Through systematic analysis and conclusion of the recent advances in functional hydrogels for dental hard tissue and endodontic disease treatment, this Review may provide significant guidance and inspiration for oral disease and health in the future.

3D-printed bioinspired spicules: Strengthening and toughening via stereolithography

Recently, the replication of biological microstructures has garnered significant attention due to their superior flexural strength and toughness, coupled with lightweight structures. Among the most intriguing biological microstructures renowned for their flexural strength are those found in the Euplectella Aspergillum (EA) marine sponges. The remarkable strength of this sponge is attributed to its complex microstructure, which consists of concentric cylindrical layers known as spicules with organic interlayers. These features effectively impede large crack propagation, imparting extraordinary mechanical properties. However, there have been limited studies aimed at mimicking the spicule microstructure. In this study, structures inspired by spicules were designed and fabricated using the stereolithography (SLA) 3D printing technique. The mechanical properties of concentric cylindrical structures (CCSs) inspired by the spicule microstructure were evaluated, considering factors such as the wall thickness of the cylinders, the number of layers, and core diameter, all of which significantly affect the mechanical response. These results were compared with those obtained from solid rods used as solid samples. The findings indicated that CCSs with five layers or fewer exhibited a flexural strength close to or higher than that of solid rods. Particularly, samples with 4 and 5 cylindrical layers displayed architecture similar to natural spicules. Moreover, in all CCSs, the absorbed energy was at least 3-4 times higher than solid rods. Conversely, CCSs with a cylinder wall thickness of 0.65 mm exhibited a more brittle behavior under the 3-point bending test than those with 0.35 mm and 0.5 mm wall thicknesses. CCSs demonstrated greater resistance to failure, displaying different crack propagation patterns and shear stress distributions under the bending test compared to solid rods. These results underscore that replicating the structure of spicules and producing structures with concentric cylindrical layers can transform a brittle structure into a more flexible one, particularly in load-bearing applications.

Structure-optimized and microenvironment-inspired nanocomposite biomaterials in bone tissue engineering

Critical-sized bone defects represent a significant clinical challenge due to their inability to undergo spontaneous regeneration, necessitating graft interventions for effective treatment. The development of tissue-engineered scaffolds and regenerative medicine has made bone tissue engineering a highly viable treatment for bone defects. The physical and biological properties of nanocomposite biomaterials, which have optimized structures and the ability to simulate the regenerative microenvironment of bone, are promising for application in the field of tissue engineering. These biomaterials offer distinct advantages over traditional materials by facilitating cellular adhesion and proliferation, maintaining excellent osteoconductivity and biocompatibility, enabling precise control of degradation rates, and enhancing mechanical properties. Importantly, they can simulate the natural structure of bone tissue, including the specific microenvironment, which is crucial for promoting the repair and regeneration of bone defects. This manuscript provides a comprehensive review of the recent research developments and applications of structure-optimized and microenvironment-inspired nanocomposite biomaterials in bone tissue engineering. This review focuses on the properties and advantages these materials offer for bone repair and tissue regeneration, summarizing the latest progress in the application of nanocomposite biomaterials for bone tissue engineering and highlighting the challenges and future perspectives in the field. Through this analysis, the paper aims to underscore the promising potential of nanocomposite biomaterials in bone tissue engineering, contributing to the informed design and strategic planning of next-generation biomaterials for regenerative medicine.

High throughput automated characterization of enamel microstructure using synchrotron tomography and optical flow imaging

The remarkable damage-tolerance of enamel has been attributed to its hierarchical microstructure and the organized bands of decussated rods. A thorough characterization of the microscale rod evolution within the enamel is needed to elucidate this complex structure. While prior efforts in this area have made use of single particle tracking to track a single rod evolution to various degrees of success, such a process can be both computationally and labor intensive, limited to the evolution path of a single rod, and is therefore prone to error from potentially tracking outliers. Particle image velocimetry (PIV) is a well-established algorithm to derive field information from image sequences for processes that are time-dependent, such as fluid flows and structural deformation. In this work, we demonstrate the use of PIV in extracting the full-field microstructural distribution of rods within the enamel. Enamel samples from a wild African lion were analyzed using high-energy synchrotron X-ray micro-tomography. Results from the PIV analysis provide sufficient full-field information to reconstruct the growth of individual rods that can potentially enable rapid analysis of complex microstructures from high resolution synchrotron datasets. Such information can serve as a template for designing damage-tolerant bioinspired structures for advanced manufacturing. STATEMENT OF SIGNIFICANCE: Thorough characterization and analysis of biological microstructures (viz. dental enamel) allows us to understand the basis of their excellent mechanical properties. Prior efforts have successfully replicated these microstructures via single particle tracking, but the process is computationally and labor intensive. In this work, optical flow imaging algorithms were used to extract full-field microstructural distribution of enamel rods from synchrotron X-ray computed tomography datasets, and a field method was used to reconstruct the growth of individual rods. Such high throughput information allows for the rapid production/prototyping and advanced manufacturing of damage-tolerant bioinspired structures for specific engineering applications. Furthermore, the algorithms used herein are freely available and open source to broaden the availability of the proposed workflow to the general scientific community.

Nanoscale osseointegration of zirconia evaluated from the interfacial structure between ceria-stabilized tetragonal zirconia and cell-induced hydroxyapatite

BACKGROUND

The osseointegration of zirconia implants has been evaluated based on their implant fixture bonding with the alveolar bone at the optical microscopic level. Achieving nano-level bonding between zirconia and bone apatite is crucial for superior osseointegration; however, only a few studies have investigated nanoscale bonding. This review outlines zirconia osseointegration, including surface modification, and presents an evaluation of nanoscale zirconia-apatite bonding and its structure.

HIGHLIGHT

Assuming osseointegration, the cells produced calcium salts on a ceria-stabilized zirconia substrate. We analyzed the interface between calcium salts and zirconia substrates using transmission electron microscopy and found that 1) the cell-induced calcium salts were bone-like apatite and 2) direct nanoscale bonding was observed between the bone-like apatite and zirconia crystals without any special modifications of the zirconia surface.

CONCLUSION

Structural affinity exists between bone apatite and zirconia crystals. Apatite formation can be induced by the zirconia surface. Zirconia bonds directly with apatite, indicating superior osseointegration in vivo.

Mechanomaterials and Nanomechanics: Toward Proactive Design of Material Properties and Functionalities

While conventional mechanics of materials offers a passive understanding of the mechanical properties of materials in existing forms, a paradigm shift, referred to as mechanomaterials, is emerging to enable the proactive programming of materials' properties and functionalities by leveraging force-geometry-property relationships. One of the foundations of this new paradigm is nanomechanics, which permits functional and structural materials to be designed based on principles from the nanoscale and beyond. Although the field of mechanomaterials is still in its infancy at the present time, we discuss the current progress in three specific directions closely linked to nanomechanics and provide perspectives on these research foci by considering the potential research directions, chances for success, and existing research capabilities. We believe this new research paradigm will provide future materials solutions for infrastructure, healthcare, energy, and environment.

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.

Dual-Protection Inorganic-Protein Coating on Mg-Based Biomaterials through Tooth-Enamel-Inspired Biomineralization

Biocompatible magnesium alloys represent revolutionary implantable materials in dentistry and orthopedics but face challenges due to rapid biocorrosion, necessitating protective coatings to mitigate dysfunction. Directly integrating durable protective coatings onto Mg surfaces is challenging because of intrinsic low coating compactness. Herein, inspired by tooth enamel, a novel highly compact dual-protection inorganic-protein (inorganicPro) coating is in situ constructed on Mg surfaces through bovine serum albumin (BSA) protein-boosted reaction between sodium fluoride (NaF) and Mg substrates. The association of Mg ions and BSA establishes a local hydrophobic domain that lowers the formation enthalpy of NaMgF3 nanoparticles. This process generates finer nanoparticles that function as "bricks," facilitating denser packing, consequently reducing voidage inside coatings by over 50% and reinforcing mechanical durability. Moreover, the incorporation of BSA in and on the coatings plays two synergistic roles: 1) acting as "mortar" to seal residual cracks within coatings, thereby promoting coating compactness and tripling anticorrosion performance, and 2) mitigating fouling-accelerated biocorrosion in complex biosystems via tenfold resistance against biofoulant attachments, including biofluids, proteins, and metabolites. This innovative strategy, leveraging proteins to alter inorganic reactions, benefits the future coating design for Mg-based and other metallic materials with tailored anticorrosion and antifouling performances.

In Situ Polymerization of Hydrogel Electrolyte on Electrodes Enabling the Flexible All-Hydrogel Supercapacitors with Low-Temperature Adaptability

All-hydrogel supercapacitors are emerging as promising power sources for next-generation wearable electronics due to their intrinsic mechanical flexibility, eco-friendliness, and enhanced safety. However, the insufficient interfacial adhesion between the electrode and electrolyte and the frozen hydrogel matrices at subzero temperatures largely limit the practical applications of all-hydrogel supercapacitors. Here, an all-hydrogel supercapacitor is reported with robust interfacial contact and anti-freezing property, fabricated by in situ polymerizing hydrogel electrolyte onto hydrogel electrodes. The robust interfacial adhesion is developed by the synergistic effect of a tough hydrogel matrix and topological entanglements. Meanwhile, the incorporation of zinc chloride (ZnCl2) in the hydrogel electrolyte prevents the freezing of water solvents and endows the all-hydrogel supercapacitor with mechanical flexibility and fatigue resistance across a wide temperature range of 20 °C to -60 °C. Such all-hydrogel supercapacitor demonstrates satisfactory low-temperature electrochemical performance, delivering a high energy density of 11 mWh cm-2 and excellent cycling stability with a capacitance retention of 90% over 10000 cycles at -40 °C. Notably, the fabricated all-hydrogel supercapacitor can endure dynamic deformations and operate well under 2000 tension cycles even at -40 °C, without experiencing delamination and electrochemical failure. This work offers a promising strategy for flexible energy storage devices with low-temperature adaptability.

Anisotropic Liesegang pattern for the nonlinear elastic biomineral-hydrogel complex

The Liesegang pattern is a beautiful natural anisotropic patterning phenomenon observed in rocks and sandstones. This study reveals that the Liesegang pattern can induce nonlinear elasticity. Here, a Liesegang-patterned complex with biomineral-hydrogel repetitive layers is prepared. This Liesegang-patterned complex is obtained only when the biomineralization is performed under the supersaturated conditions. The Liesegang-patterned complex features a nonlinear elastic response, whereas a complex with a single biomineral shell shows a linear behavior, thus demonstrating that the Liesegang pattern is essential in achieving nonlinear elasticity. The stiff biomineral layers have buffered the concentrated energy on behalf of soft hydrogels, thereby exposing the hydrogel components to reduced stress and, in turn, enabling them to perform the elasticity continuously. Moreover, the nonlinear elastic Liesegang-patterned complex exhibits excellent stress relaxation to the external loading, which is the biomechanical characteristic of cartilage. This stress relaxation allows the bundle of fiber-type Liesegang-patterned complex to endure greater deformation.

Characterizing the microstructures of mammalian enamel by synchrotron phase contrast microCT

The enamel of mammalian teeth is a highly mineralized tissue that must endure a lifetime of cyclic contact and is inspiring the development of next-generation engineering materials. Attempts to implement enamel-inspired structures in synthetic materials have had limited success, largely due to the absence of a detailed understanding of its microstructure. The present work used synchrotron phase-contrast microCT imaging to evaluate the three-dimensional microstructure of enamel from four mammals including Lion, Gray Wolf, Snow Leopard, and Black Bear. Quantitative results of image analysis revealed that the decussation pattern of enamel consists of discrete diazone (D) and parazone (P) bands of rods organized with stacking arrangement of D+/P/D-/P in all mammals evaluated; the D+ and D- refer to distinct diazone bands with juxtaposed rod orientations from the reference plane. Furthermore, the rod orientations in the bands can be described in terms of two principal angles, defined here as the pitch and yaw. While the pitch angle increases from the outer enamel to a maximum (up to ≈ 40°) near the dentin enamel junction, minimal spatial variations are observed in yaw across the enamel thickness. There are clear differences in the decussation parameters of enamel across species that are interpreted here with respect to the structural demands placed on their teeth. The rod pitch and band width of enamel are identified as important design parameters and appear to be correlated with the bite force quotient of the four mammals evaluated. STATEMENT OF SIGNIFICANCE: The multi-functionality of tooth enamel requires both hardness and resistance to fracture, properties that are generally mutually exclusive. Ubiquitous to all mammalian teeth, the enamel is expected to have undergone adaptations in microstructure to accommodate the differences in diet, body size and bite force across animals. For the first time, we compare the complex three-dimensional microstructure of enamel from teeth of multiple mammalian species using synchrotron micro-computed tomography. The findings provide new understanding of the "design" of mammalian enamel microstructures, as well as how specific parameters associated with the decussation of rods appear to be engineered to modulate its fracture resistance.

Bioinspired Macroporous Materials of MXene Nanosheets: Ice-Templated Assembly and Multifunctional Applications

Biological macroporous materials, such as stems of the plants and bone of the animals, possess outstanding properties for powerful guarantee of creatures' survival through the well-aligned architecture constructed from limited components. Transition metal carbides or nitrides (MXenes), as novel 2D assemblies, have attracted numerous attentions in various applications due to their unique properties. Therefore, mimicking the bioinspired architecture with MXenes will boost the development of human-made materials with unparalleled properties. Freeze casting has been widely applied to fabricate bioinspired MXene-based materials and achieve the assembly of MXene nanosheets into 3D forms. This process solves the inherent restacking problems of MXenes, simultaneously preserving the unique properties of MXenes with a physical process. Here, the ice-templated assembly of MXene in terms of the freezing processes and their potential mechanisms is summarized. In addition, applications of MXene-based materials in electromagnetic interference shielding and absorption, energy storage and conversion, as well as piezoresistive pressure sensors are also reviewed. Finally, the current challenges and bottlenecks of ice-templated assembly of MXene are further discussed to guide the development of bioinspired MXene-based materials.

Entropy-Driven Design of Highly Impact-Stiffening Supramolecular Polymer Networks with Salt-Bridge Hydrogen Bonds

Impact-stiffening materials that undergo a strain rate-induced soft-to-rigid transition hold great promise as soft armors in the protection of the human body and equipment. However, current impact-stiffening materials, such as polyborosiloxanes and shear-thickening fluids, often exhibit a limited impact-stiffening response. Herein, we propose a design strategy for fabricating highly impact-stiffening supramolecular polymer networks by leveraging high-entropy-penalty physical interactions. We synthesized a fully biobased supramolecular polymer comprising poly(α-thioctic acid) and arginine clusters, whose chain dynamics are governed by highly specific guanidinium-carboxylate salt-bridge hydrogen bonds. The resulting material exhibits an exceptional impact-stiffening response of ∼2100 times, transitioning from a soft dissipating state (21 kPa, 0.1 Hz) to a highly stiffened glassy state (45.3 MPa, 100 Hz) with increasing strain rates. Moreover, the material's high energy-dissipating and hot-melting properties bring excellent damping performance and easy hybridization with other scaffolds. This entropy-driven approach paves the way for the development of next-generation soft, sustainable, and impact-resistant materials.

Bioinspired polysaccharide-based nanocomposite membranes with robust wet mechanical properties for guided bone regeneration

Polysaccharide-based membranes with excellent mechanical properties are highly desired. However, severe mechanical deterioration under wet conditions limits their biomedical applications. Here, inspired by the structural heterogeneity of strong yet hydrated biological materials, we propose a strategy based on heterogeneous crosslink-and-hydration (HCH) of a molecule/nano dual-scale network to fabricate polysaccharide-based nanocomposites with robust wet mechanical properties. The heterogeneity lies in that the crosslink-and-hydration occurs in the molecule-network while the stress-bearing nanofiber-network remains unaffected. As one demonstration, a membrane assembled by bacterial cellulose nanofiber-network and Ca2+-crosslinked and hydrated sodium alginate molecule-network is designed. Studies show that the crosslinked-and-hydrated molecule-network restricts water invasion and boosts stress transfer of the nanofiber-network by serving as interfibrous bridge. Overall, the molecule-network makes the membrane hydrated and flexible; the nanofiber-network as stress-bearing component provides strength and toughness. The HCH dual-scale network featuring a cooperative effect stimulates the design of advanced biomaterials applied under wet conditions such as guided bone regeneration membranes.