Layered nanocomposites inspired by the structure and mechanical properties of nacre

On-demand auxeticity and co-existing pre-tension induced compression stage in a sandwich design with kinematically constrained 3D suture tiles

By incorporating concepts from auxeticity, kinematic constraints, pre-tension induced compression (PIC), and suture tessellations, tiled sandwich composites are designed, demonstrating behaviors attributed to the synergy between auxeticity and pre-tension induced contact and compression, simultaneously triggered by a threshold strain. The designs can theoretically achieve on-demand Poisson's ratio in the widest range (-∞, +∞), and once triggered, the Poisson's ratio is stable under large deformation. Also, once the overall strain goes beyond the threshold, the designs enter into a PIC stage, ensuring the middle soft layer takes the tensile load, while the tiles are under compression via contact and the 3D articulation of the tooth-channel pairs. In this PIC stage, the tooth-channel pairs provide kinematic constraints via the contact and relative sliding between teeth and channels. The deformation mechanisms and mechanical properties of them are systematically explored via an integrated analytical, numerical, and experimental approach. Mechanical experiments are performed on 3D printed specimens. It is found that the length aspect ratio and the obliqueness of the teeth significantly influence the constraint angle and therefore the auxeticity and strength of the designs.

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.

Exploiting Saturation Regimes and Surface Effects to Tune Composite Design: Single Platelet Nanocomposites of Peptoid Nanosheets and CaCO3

Mineral-polymer composites found in nature exhibit exceptional structural properties essential to their function, and transferring these attributes to the synthetic design of functional materials holds promise across various sectors. Biomimetic fabrication of nanocomposites introduces new pathways for advanced material design and explores biomineralization strategies. This study presents a novel approach for producing single platelet nanocomposites composed of CaCO3 and biomimetic peptoid (N-substituted glycines) polymers, akin to the bricks found in the brick-and-mortar structure of nacre, the inner layer of certain mollusc shells. The significant aspect of the proposed strategy is the use of organic peptoid nanosheets as the scaffolds for brick formation, along with their controlled mineralization in solution. Here, we employ the B28 peptoid nanosheet as a scaffold, which readily forms free-floating zwitterionic bilayers in aqueous solution. The peptoid nanosheets were mineralized under consistent initial conditions (σcalcite = 1.2, pH 9.00), with variations in mixing conditions and supersaturation profiles over time aimed at controlling the final product. Nanosheets were mineralized in both feedback control experiments, where supersaturation was continuously replenished by titrant addition and in batch experiments without a feedback loop. Complete coverage of the nanosheet surface by amorphous calcium carbonate was achieved under specific conditions with feedback control mineralization, whereas vaterite was the primary CaCO3 phase observed after batch experiments. Thermodynamic calculations suggest that time-dependent supersaturation profiles as well as the spatial distribution of supersaturation are effective controls for tuning the mineralization extent and product. We anticipate that the control strategies outlined in this work can serve as a foundation for the advanced and scalable fabrication of nanocomposites as building blocks for nacre-mimetic and functional materials.

Sustainable liquid metal-induced conductive nacre

Nacre has inspired research to fabricate tough bulk composites for practical applications using inorganic nanomaterials as building blocks. However, with the considerable pressure to reduce global carbon emissions, preparing nacre-inspired composites remains a significant challenge using more economical and environmentally friendly building blocks. Here we demonstrate tough and conductive nacre by assembling aragonite platelets exfoliated from natural nacre, with liquid metal and sodium alginate used as the "mortar". The formation of GaOC coordination bonding between the gallium ions and sodium alginate molecules reduces the voids and improves compactness. The resultant conductive nacre exhibits much higher mechanical properties than natural nacre. It also shows excellent impact resistance attributed to the synergistic strengthening and toughening fracture mechanisms induced by liquid metal and sodium alginate. Furthermore, our conductive nacre exhibits exceptional self-monitoring sensitivity for maintaining structural integrity. The proposed strategy provides a novel avenue for turning natural nacre into a valuable green composite.

Highly Thermally Conductive Flexible Biomimetic APTES-BNNS/BC Nanocomposite Paper by Sol-Gel-Film Technology

Owing to the evolution of 5G technology, new energy vehicles, flexible electronics, miniaturization and integration of microelectronic devices, high-frequency and high-power devices, and thermal management of materials must consider additional limitations such as electrical insulation, excellent transverse heat transfer, flexibility, and weight. Boron nitride nanosheets (BNNSs) are ideal insulating materials with high thermal conductivity. However, the problem of the 3D thermal conductivity pathway and toughness strength of nanocomposite paper loaded with inorganic thermal conductivity fillers remains a huge challenge. In this study, we propose a new method for preparing ultrathin, large, and uniformly thick BNNS for quantitative production. Bulk hexagonal boron nitride (hBN) layers were exfoliated using a simple and low-cost hydrothermal reaction, and large-scale fewer-layered BNNSs were efficiently prepared by ball milling with a high yield (up to 80%). Based on the aforementioned step, a flexible insulating composite film with high thermal conductivity and a natural "brick-mud" shell structure was constructed via the sol-gel-film conversion method. After prestretching and hot-pressing treatment, the hydrogels became denser, and the modified BNNS formed a three-dimensional (3D) network structure with an ordered orientation and interconnections in the bacterial cellulose (BC) matrix. After 100 folding cycles, the tensile strength of the nanofiber composite film reached 53 MPa, and the strength retention rate exceeded 42%. By optimizing the modified BNNS content, the thermal conductivity reached 24 W/(m·K). This simple approach has wide application potential in the next-generation electronic devices, providing options for designing thermal interface materials with excellent electrical insulation, high thermal stability, and flexibility.

Bio-Inspired Functional Materials for Environmental Applications

With the global population expected to reach 9.7 billion by 2050, there is an urgent need for advanced materials that can address existing and developing environmental issues. Many current synthesis processes are environmentally unfriendly and often lack control over size, shape, and phase of resulting materials. Based on knowledge from biological synthesis and assembly processes, as well as their resulting functions (e.g., photosynthesis, self-healing, anti-fouling, etc.), researchers are now beginning to leverage these biological blueprints to advance bio-inspired pathways for functional materials for water treatment, air purification and sensing. The result has been the development of novel materials that demonstrate enhanced performance and address sustainability. Here, an overview of the progress and potential of bio-inspired methods toward functional materials for environmental applications is provided. The challenges and opportunities for this rapidly expanding field and aim to provide a valuable resource for researchers and engineers interested in developing sustainable and efficient processes and technologies is discussed.

Tough Hydrogels with Different Toughening Mechanisms and Applications

Load-bearing biological tissues, such as cartilage and muscles, exhibit several crucial properties, including high elasticity, strength, and recoverability. These characteristics enable these tissues to endure significant mechanical stresses and swiftly recover after deformation, contributing to their exceptional durability and functionality. In contrast, while hydrogels are highly biocompatible and hold promise as synthetic biomaterials, their inherent network structure often limits their ability to simultaneously possess a diverse range of superior mechanical properties. As a result, the applications of hydrogels are significantly constrained. This article delves into the design mechanisms and mechanical properties of various tough hydrogels and investigates their applications in tissue engineering, flexible electronics, and other fields. The objective is to provide insights into the fabrication and application of hydrogels with combined high strength, stretchability, toughness, and fast recovery as well as their future development directions and challenges.

Self-Assembly of Ultrathin, Ultrastrong Layered Membranes by Protic Solvent Penetration

Flexible membranes with ultrathin thickness and excellent mechanical properties have shown great potential for broad uses in solid polymer electrolytes (SPEs), on-skin electronics, etc. However, an ultrathin membrane (<5 μm) is rarely reported in the above applications due to the inherent trade-off between thickness and antifailure ability. We discover a protic solvent penetration strategy to prepare ultrathin, ultrastrong layered films through a continuous interweaving of aramid nanofibers (ANFs) with the assistance of simultaneous protonation and penetration of a protic solvent. The thickness of a pure ANF film can be controlled below 5 μm, with a tensile strength of 556.6 MPa, allowing us to produce the thinnest SPE (3.4 μm). The resultant SPEs enable Li-S batteries to cycle over a thousand times at a high rate of 1C due to the small ionic impedance conferred by the ultrathin characteristic and regulated ionic transportation. Besides, a high loading of the sulfur cathode (4 mg cm-2) with good sulfur utilization was achieved at a mild temperature (35 °C), which is difficult to realize in previously reported solid-state Li-S batteries. Through a simple laminating process at the wet state, the thicker film (tens of micrometers) obtained exhibits mechanical properties comparable to those of thin films and possesses the capability to withstand high-velocity projectile impacts, indicating that our technique features a high degree of thickness controllability. We believe that it can serve as a valuable tool to assemble nanomaterials into ultrathin, ultrastrong membranes for various applications.

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

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

The Use of Shells of Marine Molluscs in Spanish Ethnomedicine: A Historical Approach and Present and Future Perspectives

Since ancient times, the shells of marine molluscs have been used as a therapeutic and/or prophylactic resource. In Spain, they were part of practical guides for doctors or pharmacists until the 19th century. In general, seashells were prepared by dissolving in vinegar and were part of plasters or powders used as toothpaste, or to treat dyspepsia, heartburn and leprosy. Thus, the nacre or mother-of-pearl of various molluscs was regularly used in the Royal Colleges of Surgery and in hospitals during the times of the Cortes of Cadiz, as a medicine in galenic preparations based on powders. In contemporary Spanish ethnomedicine, seashells, with a high symbolic value, have been used as an amulet to prevent cracks in the breasts and promote their development during lactation, to avoid teething pain in young children, to eliminate stains on the face or to cure erysipelas. But, as in other countries, products derived from seashells have also been empirically applied. The two resources used traditionally have been the cuttlebone, the internal shell of cuttlefish and the nacre obtained from the external shells of some species. Cuttlebone, dried and pulverised, has been applied externally to cure corneal leukoma and in dental hygiene. In the case of nacre, a distinction must be made between chemical and physical remedies. Certain seashells, macerated in lemon juice, were used in coastal areas to remove spots on the face during postpartum. However, the most common practice in Spain mainland was to dissolve mother-of-pearl buttons in lemon juice (or vinegar). The substance thus obtained has been used to treat different dermatological conditions of the face (chloasma, acne), as well as to eliminate freckles. For the extraction of foreign bodies in the eyes, a very widespread traditional remedy has been to introduce small mother-of-pearl buttons under the lid. These popular remedies and practices are compared with those collected in classic works of medicine throughout history, and data on the pharmacological activity and pharmaceutical applications of the products used are provided. The use of cuttlebone powders is supported by different works on anti-inflammatory, immune-modulatory and/or wound healing properties. Nacre powder has been used in traditional medicines to treat palpitations, convulsions or epilepsy. As sedation and a tranquilisation agent, nacre is an interesting source for further drug development. Likewise, nacre is a biomaterial for orthopaedic and other tissue bioengineering applications. This article is a historical, cultural and anthropological view that can open new epistemological paths in marine-derived product research.

Divergent Deborah number-dependent transition from homogeneity to heterogeneity

Heterogeneous structures are ubiquitous in natural organisms. Native heterogeneous structures inspire many artificial structures that are playing important roles in modern society, while it is challenging to identify the relevant factors in forming these structures due to the complexity of living systems. Here, hybrid hydrogels consisting of flexible polymer networks with embedded stiff cellulose nanocrystals (CNCs) are considered an open system to simulate the generalized formation of heterogeneous core-sheath structures. As the result of the modified air drying process of hybrid hydrogels, the formation of heterogeneous core-sheath structure is found to be correlated to the relative evaporation speed. Specifically, the formation of such heterogeneity in xerogel fibers is found to be correlated with the divergence of Deborah number (De). During the transition of De from large to small values with accompanying morphologies, the turning point is around De = 1. The mechanism can be considered a relative humidity-dependent glass transition behavior. These unique heterogeneous structures play a key role in tuning water permeation and water sorption capacity. Insights into these aspects can prospectively contribute to a better understanding of the native heterogeneous structures for bionics design.

Selectively multilayered distribution of stereocomplex crystallite and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) ribbons to achieve highly ductile and strong poly(l-lactide) composites

Blending poly(l-lactide) (PLLA) with elastic polymers is an efficient way to obtain highly ductile materials (> 300 %), but it is accompanied by a significant reduction in strength. In this work, a special alternating multilayered composites with alternating stereocomplex crystallite (SC) (PLLA/poly(d-lactide) (PDLA) layer) and highly oriented Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) ribbons (PLLA/PHBV layer) is in situ constructed during laminated structuring process. Experimental results show that in situ formed PHBV ribbons are limitedly distributed in the thickness direction and align parallel to the layer interfaces. More interestingly, not only highly oriented shish crystals but also sparse lamellae of PLLA, which are arrested by SC, shish crystals, and PHBV ribbons, are in situ formed. Compared with sea-island structured composites prepared by traditional compression molding, the alternating multilayered composites show an increase in elongation at break from 8.7 % to 345.1 % and an increase in yield strength from 61.4 MPa to 73.2 MPa. During the tensile testing, the PLLA/PHBV layers firstly form micro-fibrils and micro-voids, driving the molecular chains of the PLLA/PDLA layer to respond in time to external forces through stress transfer of rich continuous layer interfaces. Since shear yielding and plastic deformation can easily penetrate the entire matrix, the alternating multilayered composites go a brittle-ductile transformation and the ductility is improved significantly. The increased strength of the alternating multilayered material is ascribed to the stiff shish crystals and SC. This work provides important guidance for the durable application of strong and ductile PLLA-based materials.

Nacre-mimetic cerium-doped nano-hydroxyapatite/chitosan layered composite scaffolds regulate bone regeneration via OPG/RANKL signaling pathway

Autogenous bone grafting has long been considered the gold standard for treating critical bone defects. However, its use is plagued by numerous drawbacks, such as limited supply, donor site morbidity, and restricted use for giant-sized defects. For this reason, there is an increasing need for effective bone substitutes to treat these defects. Mollusk nacre is a natural structure with outstanding mechanical property due to its notable "brick-and-mortar" architecture. Inspired by the nacre architecture, our team designed and fabricated a nacre-mimetic cerium-doped layered nano-hydroxyapatite/chitosan layered composite scaffold (CeHA/CS). Hydroxyapatite can provide a certain strength to the material like a brick. And as a polymer material, chitosan can slow down the force when the material is impacted, like an adhesive. As seen in natural nacre, the combination of these inorganic and organic components results in remarkable tensile strength and fracture toughness. Cerium ions have been demonstrated exceptional anti-osteoclastogenesis capabilities. Our scaffold featured a distinct layered HA/CS composite structure with intervals ranging from 50 to 200 μm, which provided a conducive environment for human bone marrow mesenchymal stem cell (hBMSC) adhesion and proliferation, allowing for in situ growth of newly formed bone tissue. In vitro, Western-blot and qPCR analyses showed that the CeHA/CS layered composite scaffolds significantly promoted the osteogenic process by upregulating the expressions of osteogenic-related genes such as RUNX2, OCN, and COL1, while inhibiting osteoclast differentiation, as indicated by reduced TRAP-positive osteoclasts and decreased bone resorption. In vivo, calvarial defects in rats demonstrated that the layered CeHA/CS scaffolds significantly accelerated bone regeneration at the defect site, and immunofluorescence indicated a lowered RANKL/OPG ratio. Overall, our results demonstrate that CeHA/CS scaffolds offer a promising platform for bone regeneration in critical defect management, as they promote osteogenesis and inhibit osteoclast activation.

Aligned Ice Templated Biomaterial Strategies for the Musculoskeletal System

Aligned pore structures present many advantages when conceiving biomaterial strategies for treatment of musculoskeletal disorders. Aligned ice templating (AIT) is one of the many different techniques capable of producing anisotropic porous scaffolds; its high versatility allows for the formation of structures with tunable pore sizes, as well as the use of many different materials. AIT has been found to yield improved compressive properties for bone tissue engineering (BTE), as well as higher tensile strength and optimized cellular alignment and proliferation in tendon and muscle repair applications. This review evaluates the work that has been done in the last decade toward the production of aligned pore structures by AIT with an outlook on the musculoskeletal system. This work describes the fundamentals of the AIT technique and focuses on the research carried out to optimize the biomechanical properties of scaffolds by modifying the pore structure, categorizing by material type and application. Related topics including growth factor incorporation into AIT scaffolds, drug delivery applications, and studies about immune system response will be discussed.

Bioinspired Additive Manufacturing of Hierarchical Materials: From Biostructures to Functions

Throughout billions of years, biological systems have evolved sophisticated, multiscale hierarchical structures to adapt to changing environments. Biomaterials are synthesized under mild conditions through a bottom-up self-assembly process, utilizing substances from the surrounding environment, and meanwhile are regulated by genes and proteins. Additive manufacturing, which mimics this natural process, provides a promising approach to developing new materials with advantageous properties similar to natural biological materials. This review presents an overview of natural biomaterials, emphasizing their chemical and structural compositions at various scales, from the nanoscale to the macroscale, and the key mechanisms underlying their properties. Additionally, this review describes the designs, preparations, and applications of bioinspired multifunctional materials produced through additive manufacturing at different scales, including nano, micro, micro-macro, and macro levels. The review highlights the potential of bioinspired additive manufacturing to develop new functional materials and insights into future directions and prospects in this field. By summarizing the characteristics of natural biomaterials and their synthetic counterparts, this review inspires the development of new materials that can be utilized in various applications.

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

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

Molecular Orientation-Regulated Bioinspired Multilayer Composites with Largely Enhanced Mechanical Properties

Natural nacre's hierarchical brick-and-mortar architecture motivates intensive studies on inorganic platelet/polymer multilayer composites, targeting mechanical property enhancement only by two strategies: optimizing the size and alignment of inorganic platelets and improving the interfacial interaction between inorganic platelets and polymers. Herein, a new strategy of polymer chain orientation to enhance the property of bioinspired multilayered composites is presented, which facilitates more stress to be transferred from polymer layers to inorganic platelets by simultaneous stiffening of multiple polymer chains. To this end, bioinspired multilayer films consisting of oriented sodium carboxymethyl cellulose chains and alumina platelets are designed and fabricated by three successive steps of water evaporation-induced gelation in glycerol, high-ratio prestretching, and Cu²⁺ infiltration. Regulating the orientation state of sodium carboxymethyl cellulose leads to a large enhancement of mechanical properties, including Young's modulus (2.3 times), tensile strength (3.2 times), and toughness (2.5 times). It is observed experimentally and predicted theoretically that the increased chain orientation induces failure mode transition in the multilayered films from alumina platelet pull-out to alumina platelet fracture because more stress is transferred to the platelets. This strategy opens an avenue toward rational design and manipulation of polymer aggregation states in inorganic platelet/polymer multilayer composites and allows a highly effective increase in modulus, strength, and toughness.

3D printing of conch-like scaffolds for guiding cell migration and directional bone growth

Regeneration of severe bone defects remains an enormous challenge in clinic. Developing regenerative scaffolds to directionally guide bone growth is a potential strategy to overcome this hurdle. Conch, an interesting creature widely spreading in ocean, has tough spiral shell that can continuously grow along the spiral direction. Herein, inspired by the physiological features of conches, a conch-like (CL) scaffold based on β-TCP bioceramic material was successfully prepared for guiding directional bone growth via digital light processing (DLP)-based 3D printing. Benefiting from the spiral structure, the CL scaffolds significantly improved cell adhesion, proliferation and osteogenic differentiation in vitro compared to the conventional 3D scaffolds. Particularly, the spiral structure in the scaffolds could efficiently induce cells to migrate from the bottom to the top of the scaffolds, which was like “cells climbing stairs”. Furthermore, the capability of guiding directional bone growth for the CL scaffolds was demonstrated by a special half-embedded femoral defects model in rabbits. The new bone tissue could consecutively grow into the protruded part of the scaffolds along the spiral cavities. This work provides a promising strategy to construct biomimetic biomaterials for guiding directional bone tissue growth, which offers a new treatment concept for severe bone defects, and even limb regeneration.

•

A conch-like scaffold was firstly developed for guiding directional bone growth.

•

The CL scaffolds efficiently induced cells “climbing stairs”- like-migrating.

•

The CL scaffolds showed improved bioactivities benefited from the spiral structure.

•

This work provided a new treatment concept for severe bone defects.

Review of Artificial Nacre for Oil–Water Separation

Due to their extraordinary prospective uses, particularly in the areas of oil–water separation, underwater superoleophobic materials have gained increasing attention. Thus, artificial nacre has become an attractive candidate for oil–water separation due to its superhydrophilicity and underwater superoleophobicity properties. Synthesized artificial nacre has successfully achieved a high mechanical strength that is close to or even surpasses the mechanical strength of natural nacre. This can be attributed to suitable synthesis methods, the selection of inorganic fillers and polymer matrices, and the enhancement of the mechanical properties through cross-linking, covalent group modification, or mineralization. The utilization of nacre-inspired composite membranes for emerging applications, i.e., is oily wastewater treatment, is highlighted in this review. The membranes show that full separation of oil and water can be achieved, which enables their applications in seawater environments. The self-cleaning mechanism’s basic functioning and antifouling tips are also concluded in this review.

Mechanical Behavior of Bamboo-Like Structures under Transversal Compressive Loading

Inspired by many biological structures in nature, biomimetic structures demonstrate significantly better mechanical performance than traditional engineering structures. The exceptional mechanical properties of natural materials are attributed to the hierarchical architecture of their structure. Consequently, the implementation of biomimetic structures in the design of lightweight structures with tailored mechanical properties has been constantly increasing in many fields of science and engineering. The bamboo structure is of particular interest because it combines a light weight and excellent mechanical properties, often surpassing those of several engineering materials. The objective of this study was to evaluate the mechanical behavior of bamboo-inspired structures subjected to transversal compressive loading. Structures consisting of bamboo-like thin-walled hexagonal building blocks (unit cells) with different dimensions were fabricated by stereolithography 3D printing and their mechanical performance was evaluated by mechanical testing, high-speed camera video recordings, and finite element simulations. The results of the elastic modulus, yield strength, and strain energy density at fracture were interpreted in terms of characteristic dimensions of the unit cell structure. The failure process was elucidated in the light of images of the fractured structures and simulation strain maps. The results of this study demonstrate that ultralight bamboo-like structures with specific mechanical characteristics can be produced by optimizing the dimensions and number density of the hexagonal unit cell.

Tribological Behavior of Bioinspired Surfaces

Energy losses due to various tribological phenomena pose a significant challenge to sustainable development. These energy losses also contribute toward increased emissions of greenhouse gases. Various attempts have been made to reduce energy consumption through the use of various surface engineering solutions. The bioinspired surfaces can provide a sustainable solution to address these tribological challenges by minimizing friction and wear. The current study majorly focuses on the recent advancements in the tribological behavior of bioinspired surfaces and bio-inspired materials. The miniaturization of technological devices has increased the need to understand micro- and nano-scale tribological behavior, which could significantly reduce energy wastage and material degradation. Integrating advanced research methods is crucial in developing new aspects of structures and characteristics of biological materials. Depending upon the interaction of the species with the surrounding, the present study is divided into segments depicting the tribological behavior of the biological surfaces inspired by animals and plants. The mimicking of bio-inspired surfaces resulted in significant noise, friction, and drag reduction, promoting the development of anti-wear and anti-adhesion surfaces. Along with the reduction in friction through the bioinspired surface, a few studies providing evidence for the enhancement in the frictional properties were also depicted.

Bio-inspired nacre-like composites with excellent mechanical properties, gas-barrier function and fire-retardant performances based on self-assembly between hyperbranched poly(amido amine)s and montmorillonite

The fabrication of mechanically robust multifunctional nanocomposite (NC) films using simple but effective strategies is a long-term challenge. Inspired by natural nacre, we designed and fabricated high-performance nacre-like NC films (Na-MTM/HBP) through the self-assembly of the hyperbranched poly(amido amine) (HBP) and montmorillonite (Na-MTM) using a vacuum filtration approach. The optimal Na-MTM/HBP NC film shows excellent mechanical strength (106 MPa), which can be attributed to the formation of numerous hydrogen bonds and the electrostatic interactions between hyperbranched HBP and Na-MTM nanosheets. Such films also exhibit excellent gas barrier and fire-fire-retardant owing to the high aspect ratio of the Na-MTM nanosheets. In this work, a class of high-performance NC films exhibiting good mechanical, gas barrier, and flame retardancy properties have been developed. These NC films have great potential in packing or coating materials.

Tensile and Viscoelastic Behavior in Nacre-Inspired Nanocomposites: A Coarse-Grained Molecular Dynamics Study

Organisms hold an extraordinarily evolutionary advantage in forming complex, hierarchical structures across different length scales that exhibit superior mechanical properties. Mimicking these structures for synthesizing high-performance materials has long held a fascination and has seen rapid growth in the recent past thanks to high-resolution microscopy, design, synthesis, and testing methodologies. Among the class of natural materials, nacre, found in mollusk shells, exhibits remarkably high mechanical strength and toughness. The highly organized "brick and mortar" structure at different length scales is a basis for excellent mechanical properties and the capability to dissipate energy and propagation in nacre. Here, we employ large-scale atomistic coarse-grained molecular dynamics simulations to study the mechanical and viscoelastic behavior of nacre-like microstructures. Uniaxial tension and oscillatory shear simulations were performed to gain insight into the role of complex structure-property relationships. Specifically, the role played by the effect of microstructure (arrangement of the crystalline domain) and polymer-crystal interactions on the mechanical and viscoelastic behavior is elucidated. The tensile property of the nanocomposite was seen to be sensitive to the microstructure, with a staggered arrangement of the crystalline tablets giving rise to a 20-30% higher modulus and lower tensile strength compared to a columnar arrangement. Importantly, the staggered microstructure is shown to have a highly tunable mechanical behavior with respect to the polymer-crystal interactions. The underlying reasons for the mechanical behavior are explained by showing the effect of polymer chain mobility and orientation and the load-carrying capacity for the constituents. Viscoelastic responses in terms of the storage and loss moduli and loss tangent are studied over three decades in frequency and again highlight the differences brought about by the microstructure. We show that our coarse-grained models offer promising insights into the design of novel biomimetic structures for structural applications.

Calcium carbonate: controlled synthesis, surface functionalization, and nanostructured materials

Calcium carbonate (CaCO₃) is an important inorganic mineral in biological and geological systems. Traditionally, it is widely used in plastics, papermaking, ink, building materials, textiles, cosmetics, and food. Over the last decade, there has been rapid development in the controlled synthesis and surface modification of CaCO₃, the stabilization of amorphous CaCO₃ (ACC), and CaCO₃-based nanostructured materials. In this review, the controlled synthesis of CaCO₃ is first examined, including Ca²⁺-CO₃^2- systems, solid-liquid-gas carbonation, water-in-oil reverse emulsions, and biomineralization. Advancing insights into the nucleation and crystallization of CaCO₃ have led to the development of efficient routes towards the controlled synthesis of CaCO₃ with specific sizes, morphologies, and polymorphs. Recently-developed surface modification methods of CaCO₃ include organic and inorganic modifications, as well as intensified surface reactions. The resultant CaCO₃ can then be further engineered via template-induced biomineralization and layer-by-layer assembly into porous, hollow, or core-shell organic-inorganic nanocomposites. The introduction of CaCO₃ into nanostructured materials has led to a significant improvement in the mechanical, optical, magnetic, and catalytic properties of such materials, with the resultant CaCO₃-based nanostructured materials showing great potential for use in biomaterials and biomedicine, environmental remediation, and energy production and storage. The influences that the preparation conditions and additives have on ACC preparation and stabilization are also discussed. Studies indicate that ACC can be used to construct environmentally-friendly hybrid films, supramolecular hydrogels, and drug vehicles. Finally, the existing challenges and future directions of the controlled synthesis and functionalization of CaCO₃ and its expanding applications are highlighted.

Self-Exfoliation of Flake Graphite for Bioinspired Compositing with Aramid Nanofiber toward Integration of Mechanical and Thermoconductive Properties

A self-grinding exfoliation strategy that depends on mutual shear friction between flake graphite particles is successfully developed to prepare pristine graphene with largely enhanced yield and productivity. Bioinspired assembly of pristine graphene nanosheets to an interconnected aramid nanofiber network is achieved by a continuous sol-gel-film transformation strategy and generates a flexible yet highly thermoconductive film. Flexible yet highly thermoconductive materials are essential for the development of next-generation flexible electronic devices. Herein, we report a bioinspired nanostructured film with the integration of large ductility and high thermal conductivity based on self-exfoliated pristine graphene and three-dimensional aramid nanofiber network. A self-grinding strategy to directly exfoliate flake graphite into few-layer and few-defect pristine graphene is successfully developed through mutual shear friction between graphite particles, generating largely enhanced yield and productivity in comparison to normal liquid-based exfoliation strategies, such as ultrasonication, high-shear mixing and ball milling. Inspired by nacre, a new bioinspired layered structural design model containing three-dimensional nanofiber network is proposed and implemented with an interconnected aramid nanofiber network and high-loading graphene nanosheets by a developed continuous assembly strategy of sol-gel-film transformation. It is revealed that the bioinspired film not only exhibits nacre-like ductile deformation behavior by releasing the hidden length of curved aramid nanofibers, but also possesses good thermal transport ability by directionally conducting heat along pristine graphene nanosheets.

Bioinspired Nanoheterogeneous Alternating Multiarched Architecture: Toward a Superior Strength-Toughness Integration

Strength and toughness are at odds with each other in coating design. Constructing strength-toughness-integrated coatings has long been a pursuit in materials design but is a challenge to achieve. Conventional wisdom suggests that growth of coatings is only a uniform cumulative growth on a two-dimensional plane. However, by constructing growth templates and controlling the alternation of heterogeneous materials, it subverts the traditional perception of cumulative growth in planes and creates the fact that the coating grows on a curved surface. Regulating the microstructure of the coating autonomously and matching the strength and toughness of heterogeneous materials, drawing inspiration from the multiarched structure in the nacre of red abalone, are crucial for achieving strength-toughness integration. Herein, we propose a new idea of coating deposition to achieve strength-toughness integration via preconstructing a nanoscale island-like discontinuous seed layer as a template for coating growth and then growing a nanoscale hard/soft heterogeneous multiarched architecture in situ. We refer to this architecture with intrinsic mechanical advantage as the "Nanoheterogeneous Alternating Multiarched" (NHAM) architecture. We design a nacre-like multiarched coating with a strength of 12.42 GPa and a K_IC value of 2.12 MPa·m^1/2, depositing the hard phase (TiSiCN layer) and the soft phase (Ag layer) with the unique NHAM architecture via physical vapor deposition technology, which exhibits a superior improvement in the strength-toughness integration compared to that reported in other studies (increased strength by at least 1 GPa without sacrificing toughness). The NHAM architecture strategy provides a pathway to design strength-toughness-integrated coatings. Two heterogeneous materials with well-matched strength and toughness can be deposited to achieve the NHAM architecture to greatly reflect the effect of strength-toughness integration.

Optical properties of novel luminescent nacre-like epoxy/graphene nanocomposite coating integrated with lanthanide-activated aluminate nanoparticles

Nacre structure has aragonite polygonal tablets, tessellated to generate separate layers, and exhibits adjacent layers and tablets within a layer bonded by a biopolymer. Herein, we report the development of nacre-like organic/inorganic hybrid nanocomposite coating consisting of epoxy tablets as well as rare-earth activated aluminate and graphene oxide tablet/tablet interfaces. The lanthanide-activated aluminate was prepared by the high temperature solid-state approach followed by the top-down technology to provide the phosphor nanoparticles (PNPs). Graphene oxide nanosheets were prepared from graphite. The prepared epoxy/graphene/phosphor nanocomposites were applied onto mild steel. Covalent bonds were formed between epoxy polymer chains resin and graphene oxide nanosheets. Those interface interactions results in tough surface, high tensile strength, and excellent durability. The usage of phosphor in the nanoparticle form guaranteed no agglomerations were produced throughout the hardening procedure by allowing better distribution of PNPs in the nacre-like matrix. The generated nacre-like substrates displayed reversible fluorescence. The excitation of the white colored nacre-like coats at 367 nm results in a green emission band at 518 nm as designated by CIE Lab and photoluminescence spectra. Various analysis methods were utilized to inspect the surface structure and elemental composition of the nacre-like coats. An improved hydrophobicity and mechanical characteristics were detected with increasing the phosphor concentration. Due to the astonishing characteristics of the prepared nacre-like composite paint, both ceramics and metals can benefit from the current simple strategy.

Bamboo-Based Biomaterials for Cell Transportation and Bone Integration

The construction of hierarchical porous structure in biomaterials is of great significance for improving nutrient transport and biological performance. However, it is still challenging to design porous bone substitutes with high strength and biological properties, which limits their clinical applications in load-bearing bone regeneration. Herein, based on hierarchical porous structure of renewable bamboo, the mineralized calcium phosphate/bamboo composite scaffolds with high strength and excellent transport performance are successfully prepared in combination of biotemplated approach and biomimetic mineralization. The mineralized biomaterials have simultaneously achieved high mechanical strength and low modulus, similar to those of cortical bone. Furthermore, the mineralized biomaterials exhibit good liquid transport capacity and can transport cells along anti-gravity direction. Based on density functional theory (DFT) calculations, the mineralized calcium phosphate reveals the optimal H₂ O adsorption energy (-0.651 eV) and low diffusion energy barrier (0.743 eV), which is conducive to enhance hydrophilicity and liquid transport performance. Moreover, owing to the synergistic effect of the porous structure of biotemplate and bioactive mineralized components, the mineralized biomaterials possess enhanced bone integration and osteoconduction properties. The present study shed light on deeper understanding of mineralized biosourced materials, offering a strategy of combining green chemistry with tissue engineering to prepare eco-friendly biomaterials.

Bioinspired, High-Strength, and Flexible MXene/Aramid Fiber for Electromagnetic Interference Shielding Papers with Joule Heating Performance

High-strength, flexible, and multifunctional characteristics are highly desirable for electromagnetic interference (EMI) shielding materials in the field of electric devices. In this work, inspired by natural nacre, we fabricated large-scale, layered MXene/amarid nanofiber (ANF) nanocomposite papers by blade-coating process plus sol-gel conversion step. The as-synthesized papers possess excellent mechanical performance, that is, exceptional tensile strength (198.80 ± 5.35 MPa), large strain (15.30 ± 1.01%), and good flexibility (folded into various models without fracture), which are ascribed to synergetic interactions of the interconnected three-dimensional network frame and hydrogen bonds between MXene and ANF. More importantly, the papers with extensive continuous conductive paths formed by MXene nanosheets present a high EMI shielding effectiveness of 13188.2 dB cm² g^-1 in the frequency range of 8.2-12.4 GHz. More interestingly, the papers show excellent Joule heating performance with a fast thermal response (<10 s) and a low driving voltage (≤4 V). As such, the large-scale MXene/ANF papers are considered as promising alternatives in a wide range of applications in electromagnetic shielding and thermal management.

The Interplay of Polymer Bridging and Entanglement in Toughening Polymer-Infiltrated Nanoparticle Films

Polymer-nanoparticle composite films (PNCFs) with high loadings of nanoparticles (NPs) (>50 vol %) have applications in multiple areas, and an understanding of their mechanical properties is essential for their broader use. The high-volume fraction and small size of the NPs lead to physical confinement of the polymers that can drastically change the properties of polymers relative to the bulk. We investigate the fracture behavior of a class of highly loaded PNCFs prepared by polymer infiltration into NP packings. These polymer-infiltrated nanoparticle films (PINFs) have applications as multifunctional coatings and membranes and provide a platform to understand the behavior of polymers that are highly confined. Here, the extent of confinement in PINFs is tuned from 0.1 to 44 and the fracture toughness of PINFs is increased by up to a factor of 12 by varying the molecular weight of the polymers over 3 orders of magnitude and using NPs with diameters ranging from 9 to 100 nm. The results show that brittle, low molecular weight (MW) polymers can significantly toughen NP packings, and this toughening effect becomes less pronounced with increasing NP size. In contrast, high MW polymers capable of forming interchain entanglements are more effective in toughening large NP packings. We propose that confinement has competing effects of polymer bridging increasing toughness and chain disentanglement decreasing toughness. These findings provide insight into the fracture behavior of confined polymers and will guide the development of mechanically robust PINFs as well as other highly loaded PNCFs.

In Situ Manipulation and Micromechanical Characterization of Diatom Frustule Constituents Using Focused Ion Beam Scanning Electron Microscopy

Biocomposite structures are difficult to characterize by bulk approaches due to their morphological complexity and compositional heterogeneity. Therefore, a versatile method is required to assess, for example, the mechanical properties of geometrically simple parts of biocomposites at the relevant length scales. Here, it is demonstrated how a combination of Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) and micromanipulators can be used to isolate, transfer, and determine the mechanical properties of frustule constituents of diatom Thalassiosira pseudonana (T.p.). Specifically, two parts of the diatom frustule, girdle bands and valves, are separated by FIB milling and manipulated using a sharp tungsten tip without compromising their physical or chemical integrity. In situ mechanical studies on isolated girdle bands combined with Finite Element Method (FEM) simulations, enables the quantitative assessment of the Young's modulus of this biosilica; E = 40.0 GPa. In addition, the mechanical strength of isolated valves could be measured by transferring and mounting them on top of premilled holes in the sample support. This approach may be extended to any hierarchical biocomposite material, regardless of its chemical composition, to isolate, transfer, and investigate the mechanical properties of selected constituents or specific regions.

Controlled Vertically Aligned Structures in Polymer Composites: Natural Inspiration, Structural Processing, and Functional Application

Vertically aligned structures, which are a series of characteristic conformations with thickness-direction alignment, interconnection, or assembly of filler in polymeric composite materials that can provide remarkable structural performance and advanced anisotropic functions, have attracted considerable attention in recent years. The past two decades have witnessed extensive development with regard to universal fabrication methods, subtle control of morphological features, improvement of functional properties, and superior applications of vertically aligned structures in various fields. However, a systematic review remains to be attempted. The various configurations of vertical structures inspired from biological samples in nature, such as vertically aligned structures with honeycomb, reed, annual ring, radial, and lamellar configurations are summarized here. Additionally, relevant processing methods, which include the transformation of oriented direction, external-field inducement, template method, and 3D printing method, are discussed in detail. The diverse applications in mechanical, thermal, electric, dielectric, electromagnetic, water treatment, and energy fields are also highlighted by providing representative examples. Finally, future opportunities and prospects are listed to identify current issues and potential research directions. It is expected that perspectives on the vertically aligned structures presented here will contribute to the research on advanced multifunctional composites.

Mechanically excellent nacre-inspired protective steel-concrete composite against hypervelocity impacts

Steel-concrete (SC) composite widely used in military defensive project is due to its impressive mechanical properties, long-lived service, and low cost. However, the growing use of hypervelocity kinetic weapons in the present war puts forward higher requirements for the anti-explosion and penetration performance of military protection engineering. Here, inspired by the special 'brick-and-mortar' (BM) structural feature of natural nacre, we successfully construct a nacre-inspired steel-concrete (NISC) engineering composite with 2510 kg/m³, possessing nacre-like lamellar architecture via a bottom-up assembling technique. The NISC engineering composite exhibits nacreous BM structural similarity, high compressive strength of 68.5 MPa, compress modulus of 42.0 GPa, Mohs hardness of 5.5, Young's modulus of 41.5 GPa, and shear modulus of 18.4 GPa, higher than pure concrete. More interestingly, the hypervelocity impact tests reveal the penetration capability of our NISC target material is obviously stronger than that of pure concrete, enhanced up to about 46.8% at the striking velocity of 1 km/s and approximately 30.9% at the striking velocity of 2 km/s, respectively, by examining the damages of targets, the trajectories, penetration depths, and residual projectiles. This mechanically integrated enhancement can be attributed to the nacre-like BM structural architecture derived from assembling the special steel-bar array frame-reinforced concrete platelets. This study highlights a key role of nacre-like structure design in promoting the enhanced hypervelocity impact resistance of steel-concrete composites.

Dynamic Mechanical Behaviors of Nacre-Inspired Graphene-Polymer Nanocomposites Depending on Internal Nanostructures

Nacre, a natural nanocomposite with a brick-and-mortar structure existing in the inner layer of mollusk shells, has been shown to optimize strength and toughness along the laminae (in-plane) direction. However, such natural materials more often experience impact load in the direction perpendicular to the layers (i.e., out-of-plane direction) from predators. The dynamic responses and deformation mechanisms of layered structures under impact load in the out-of-plane direction have been much less analyzed. This study investigates the dynamic mechanical behaviors of nacre-inspired layered nanocomposite films using a model system that comprises alternating multi-layer graphene (MLG) and polymethyl methacrylate (PMMA) phases. With a validated coarse-grained molecular dynamics simulation approach, we systematically study the mechanical properties and impact resistance of the MLG-PMMA nanocomposite films with different internal nanostructures, which are characterized by the layer thickness and number of repetitions while keeping the total volume constant. We find that as the layer thickness decreases, the effective modulus of the polymer phase confined by the adjacent MLG phases increases. Using ballistic impact simulations to explore the dynamic responses of nanocomposite films in the out-of-plane direction, we find that the impact resistance and dynamic failure mechanisms of the films depend on the internal nanostructures. Specifically, when each layer is relatively thick, the nanocomposite is more prone to spalling-like failure induced by compressive stress waves from the projectile impact. Whereas, when there are more repetitions, and each layer becomes relatively thin, a high-velocity projectile sequentially penetrates the nanocomposite film. In the low projectile velocity regime, the film develops crazing-like deformation zones in PMMA phases. We also show that the position of the soft PMMA phase relative to the stiff graphene sheets plays a significant role in the ballistic impact performance of the investigated films. Our study provides insights into the effect of nanostructures on the dynamic mechanical behaviors of layered nanocomposites, which can lead to effective design strategies for impact-resistant films.

Beyond homogeneous dispersion: oriented conductive fillers for high κ nanocomposites

Rational design of structures for regulating the thermal conductivities (κ) of materials is critical to many components and products employed in electrical, electronic, energy, construction, aerospace, and medical applications. As such, considerable efforts have been devoted to developing polymer composites with tailored conducting filler architectures and thermal conduits for highly improved κ. This paper is dedicated to overviewing recent advances in this area to offer perspectives for the next level of future development. The limitations of conventional particulate-filled composites and the issue of percolation are discussed. In view of different directions of heat dissipation in polymer composites for different end applications, various approaches for designing the micro- and macroscopic structures of thermally conductive networks in the polymer matrix are highlighted. Methodological approaches devised to significantly ameliorate thermal conduction are categorized with respect to the pathways of heat dissipation. Future prospects for the development of thermally conductive polymer composites with modulated thermal conduction pathways are highlighted.

Hybrid Bio-Inspired Structure Based on Nacre and Woodpecker Beak for Enhanced Mechanical Performance

Materials with high strength and toughness have always been pursued by academic and industrial communities. This work presented a novel hybrid brick-and-mortar-like structure by introducing the wavy structure of the woodpecker beak for enhanced mechanical performance. The effects of tablet waviness and tablet wave number on the mechanical performance of the bio-inspired composites were analyzed. Compared with nacre-like composites with a flat tablet, the strength, stiffness and toughness of the novel hybrid nacre-like composite with tablet wave surface increased by up to 191.3%, 46.6% and 811.0%, respectively. The novel failure mode combining soft phase failure and tablet fracture revealed the key to the high toughness of composites. Finite element simulations were conducted to further explore the deformation and stress distribution of the hybrid brick-and-mortar-like structure. It showed that the hybrid brick-and-mortar-like structure can achieve a much better load transfer, which leads to greater tensile deformation in tablet before fracture, thus improving strength and energy absorption. These investigations have implications in the design of composites with high mechanical performance for aerospace, automobile and other manufacturing industries.

Robust Biomimetic Nacreous Aramid Nanofiber Composite Films with Ultrahigh Thermal Conductivity by Introducing Graphene Oxide and Edge-Hydroxylated Boron Nitride Nanosheet

Dielectric materials with excellent thermally conductive and mechanical properties can enable disruptive performance enhancement in the areas of advanced electronics and high-power devices. However, simultaneously achieving high thermal conductivity and mechanical strength for a single material remains a challenge. Herein, we report a new strategy for preparing mechanically strong and thermally conductive composite films by combining aramid nanofibers (ANFs) with graphene oxide (GO) and edge-hydroxylated boron nitride nanosheet (BNNS-OH) via a vacuum-assisted filtration and hot-pressing technique. The obtained ANF/GO/BNNS film exhibits an ultrahigh in-plane thermal conductivity of 33.4 Wm⁻¹ K⁻¹ at the loading of 10 wt.% GO and 50 wt.% BNNS-OH, which is 2080% higher than that of pure ANF film. The exceptional thermal conductivity results from the biomimetic nacreous “brick-and-mortar” layered structure of the composite film, in which favorable contacting and overlapping between the BNNS-OH and GO is generated, resulting in tightly packed thermal conduction networks. In addition, an outstanding tensile strength of 93.3 MPa is achieved for the composite film, owing to the special biomimetic nacreous structure as well as the strong π−π interactions and extensive hydrogen bonding between the GO and ANFs framework. Meanwhile, the obtained composite film displays excellent thermostability (T_d = 555 °C, T_g > 400 °C) and electrical insulation (4.2 × 10¹⁴ Ω·cm). We believe that these findings shed some light on the design and fabrication of multifunctional materials for thermal management applications.

Biomimetic Nanocomposite Membranes with Ultrahigh Ion Selectivity for Osmotic Power Conversion

Ion transport in nanoconfinement exhibits significant features such as ionic rectification, ionic selectivity, and ionic gating properties, leading to the potential applications in desalination, water treatment, and energy conversion. Two-dimensional nanofluidics provide platforms to utilize this phenomenon for capturing osmotic energy. However, it is challenging to further improve the power output with inadequate charge density. Here we demonstrate a feasible strategy by employing Kevlar nanofiber as space charge donor and cross-linker to fabricate graphene oxide composite membranes. The coupling of space charge and surface charge, enabled by the stabilization of interlayer spacing, plays a key role in realizing high ion selectivity and the derived high-performance osmotic power conversion up to 5.06 W/m2. Furthermore, the output voltage of an ensemble of the membranes in series could reach 1.61 V, which can power electronic devices. The system contributes a further step toward the application of energy conversion.

Research Progress of Chitosan-Based Biomimetic Materials

Chitosan is a linear polysaccharide produced by deacetylation of natural biopolymer chitin. Owing to its good biocompatibility and biodegradability, non-toxicity, and easy processing, it has been widely used in many fields. After billions of years of survival of the fittest, many organisms have already evolved a nearly perfect structure. This paper reviews the research status of biomimetic functional materials that use chitosan as a matrix material to mimic the biological characteristics of bivalves, biological cell matrices, desert beetles, and honeycomb structure of bees. In addition, the application of biomimetic materials in wound healing, hemostasis, drug delivery, and smart materials is briefly overviewed according to their characteristics of adhesion, hemostasis, release, and adsorption. It also discusses prospects for their application and provides a reference for further research and development.

Numerical Optimization for the Geometric Configuration of Ceramics Perform in HCCI/ZTAP Wear-Resistant Composites Based on Actual Particle Model

In order to reduce the thermal stress in high chromium cast iron (HCCI) matrix composites reinforced by zirconia toughened alumina (ZTA) ceramic particles, finite element simulation is performed to optimize the geometric configuration of ceramics perform. The previous model simplifies the overall structure of the ceramic particle preform and adds boundary conditions to simulate the particles, which will cause uncontrollable error in the results. In this work, the equivalent grain models are used to describe the actual preform, making the simulation results closer to the actual experimental results. The solidification process of composite material is simulated, and the infiltration between molten iron and ceramic particles is realized. Thermal stress in solidification process and compression stress distribution are obtained. The results show that adding 10-mm round holes on the preform can improve the performance of the composite, which is helpful to prevent the cracks and increases the plasticity of the material.

Nacre-Inspired Strong and Multifunctional Soy Protein-Based Nanocomposite Materials for Easy Heat-Dissipative Mobile Phone Shell

Inspired by the hierarchically ordered "brick and mortar" (BM) architecture of natural nacre, in this study a rational assembly of boron nitride (BN) nanosheets was introduced into a mixture of trimethylolpropane triglycidyl ether (TTE) and soy protein isolate (SPI), and a strong and multifunctional SPI-based nanocomposite film with multinetwork structure was synthesized. At a low BN loading (<0.5%), the resulting multifunctional film was flexible, antiultraviolet, and nearly transparent and also displayed good thermal diffusion ability and exhibited an excellent combination of high tensile strength (36.4 MPa) and thermal conductivity (TC, 2.40 W·m^-1·K^-1), surpassing the performances of various types of petroleum-based plastics (displayed a tensile strength ranging from 1.9 to 21 MPa and TC ranging from 0.55-2.13 W·m^-1·K^-1), including nine different types of materials currently utilized for mobile phone shells, suggesting its vast potential in practical applications.

Recyclable and Light-Adaptive Vitrimer-Based Nacre-Mimetic Nanocomposites

Nacre's natural design consists of a perfect hierarchical assembly that resembles a brick-and-mortar structure with synergistic stiffness and toughness. The field of bioinspired materials often provides attractive architecture and engineering pathways which allow to explore outstanding property areas. However, the study of nacre-mimetic materials should not be limited to the design of its architecture but ought to include the understanding, operation, and improvement of internal interactions between their components. Here, we introduce a vitrimer prepolymer system that, once integrated into the nacre-mimetic nanocomposites, cures and cross-links with the presence of Lewis acid catalyst and further manifests associative dynamic exchange reactions. Bond exchanges are controllable by molecular composition and catalyst content and characterized by creep, shear-lag, and shape-locking tests. We exploit the vitrimer properties by laminating ca. 70 films into thick bulk materials, and characterize the flexural resistance and crack propagation. More importantly, we introduce recycling by grinding and hot-pressing. The recycling for highly reinforced nacre-mimetic nanocomposites is critically enabled by the vitrimer chemistry and improves the sustainability of bioinspired nanocomposites in cyclic economy. Finally, we integrate photothermal converters into the structures and use laser irradiation as external trigger to activate the vitrimer exchange reactions.

Polymer-infiltrated nanoplatelet films with nacre-like structure via flow coating and capillary rise infiltration (CaRI)

Alignment of highly anisotropic nanomaterials in a polymer matrix can yield nanocomposites with unique mechanical and transport properties. Conventional methods of nanocomposite film fabrication are not well-suited for manufacturing composites with very high concentrations of anisotropic nanomaterials, potentially limiting the widespread implementation of these useful structures. In this work, we present a scalable approach to fabricate polymer-infiltrated nanoplatelet films (PINFs) based on flow coating and capillary rise infiltration (CaRI) and study the processing-structure-property relationship of these PINFs. We show that films with high aspect ratio (AR) gibbsite (Al (OH)3) nanoplatelets (NPTs) aligned parallel to the substrate can be prepared using a flow coating process. NPTs are highly aligned with a Herman's order parameter of 0.96 and a high packing fraction >80 vol%. Such packings show significantly higher fracture toughness compared to low AR nanoparticle (NP) packings. By depositing NPTs on a polymer film and subsequently annealing the bilayer above the glass transition temperature of the polymer, polymer infiltrates into the tortuous NPT packings though capillarity. We observe larger enhancement in the modulus, hardness and scratch resistance of NPT films upon polymer infiltration compared to NP packings. The excellent mechanical properties of such films benefit from both thermally promoted oxide bridge formation between NPTs as well as polymer infiltration increasing the strength of NPT contacts. Our approach is widely applicable to highly anisotropic nanomaterials and allows the generation of mechanically robust polymer nanocomposite films for a diverse set of applications.