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Evolutionary selection in nature has led to hierarchical structuring as a fundamental optimization strategy for biological structures, maximizing functional performance while minimizing resource usage. Precise hierarchical organization of natural materials over a wide range of length scales gives rise to unique synergistic properties that could not be achieved by single components. Despite the clear advantages offered by hierarchically structuring matter, mastering hierarchical control based on the current synthetic toolbox is still a challenge. In this review, some recent advancements in the fabrication of hierarchical metal organic framework (MOF) materials are highlighted and the advantages that arise due to different kinds of MOF hierarchy are critically analyzed. The special focus of the review lies in highlighting the applications where MOF hierarchical materials can be most impactful and describing characterization techniques currently at the disposal of scientists for the precise characterization of MOF hierarchical structures across all length scales. Finally, the intent is to inspire reticular chemists to master hierarchical control of MOF materials so as to fully utilize the advantages MOFs offer for various applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Bone has a complex hierarchical structure with structural integration from nm to cm. The understanding of bone structure is developing rapidly due to improvements in available methodologies that allow unravelling structures across several length scales. These methods include advances in electron microscopy, in particular, focused ion beam scanning electron microscopy (FIB‐SEM), confocal laser scanning microscopy techniques, X‐ray imaging, X‐ray diffraction tomography (XRD‐CT), and tensor tomography (small angle X‐ray scattering tensor tomgraphy, SAXS‐TT and wide angle X‐ray scattering tensor tomgraphy, WAXS‐TT). Special emphasis is placed on the latter X‐ray techniques that are emerging into powerful tools. Through a review of selected recent results on the structure of the bone matrix as well as the lacuno‐canalicular network housing the osteocyte cells of bone, it is proposed that bone is more heterogeneous than typically described and that local variation in composition and crystallography may play a significant role in bone biology in health and disease. [ABSTRACT FROM AUTHOR]

The ForMAX beamline at the MAX IV Laboratory provides multiscale and multimodal structural characterization of hierarchical materials in the nanometre to millimetre range by combining small- and wide-angle X-ray scattering with full-field microtomography. The modular design of the beamline is optimized for easy switching between different experimental modalities. The beamline has a special focus on the development of novel fibrous materials from forest resources, but it is also well suited for studies within, for example, food science and biomedical research.

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. 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. [Display omitted] [ABSTRACT FROM AUTHOR]

Strontium ions can be removed from wastewater in fixed-bed reactors by adsorption on hierarchical materials (different pore sizes and phases). A detailed understanding of the materials multiscale structure is therefore crucial to optimize their sorption properties. This article presents a multi-technique approach developed to characterize the relationship between microstructure and adsorption in a range of Linde-type A (LTA) zeolite-geopolymer composites,. Two-dimensional scanning electron microscopy and 3D X-ray tomography were used to image the porous and solid phases at different length scales. Advanced numerical methods involving machine learning were applied to segment the images and provide quantitative morphological values describing the porous network geometry and the location and accessibility of the zeolite particles in the geopolymer. These results were then correlated with the materials sorption properties, measured in batch and column processes. Increasing the materials zeolite content (from 0 to 27 wt%) slowed down their adsorption kinetics but increased their maximal adsorption capacities from 20 to 49 mg.g−1 and Sr2+-selectivity at equilibrium. In breakthrough experiments, the material with highest zeolite content had a much higher breakthrough volume passing from 169 to 478 ml in the presented experimental conditions (much higher wastewater decontamination capacity), but a shallower breakthrough curve (lower column efficiency).

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.

In this study, in operandi SAXS experiments were conducted on samples of human hair with a varying degree of strain (2% within the elastic region and 10% beyond). Four different features in the SAXS patterns were evaluated: The intermediate filament distance perpendicular to and the distance from the meridional arc in the load direction, as well as the distances of the lipid bilayer peak in and perpendicular to the load direction. From the literature, one concludes that polar lipids in the cuticle are the origin of the lipid peak in the SAXS pattern, and this study shows that the observed strain in the lipids is much lower than in the intermediate filaments. We support these findings with SEM micrographs, which show that the scales in the cuticle deform much less than the cortex. The observed deformation of the intermediate filaments is very high, about 70% of the macrostrain, and the ratio of the transverse strain to the longitudinal strain at the nanoscale gives a Poisson ratio of νnano = 0.44, which is typical for soft matter. This work also finds that by varying the time period between two strain cycles, the typical strain recovery time is about 1000 min, i.e., one day. After this period, the structure is nearly identical to the initial structure, which suggests an interpretation that this is the typical time for the self-healing of hair after mechanical treatment. [ABSTRACT FROM AUTHOR]

Natural materials exhibit nano- to macro-scale structural hierarchy, whose novel properties are partially driven by their underlying nanostructural anisotropy. Here we expand on our mechanically-directed assembly technique, studying its ability to synthesize porous biopolymers with engineered 3-dimensional hierarchy and material properties. 3D-printing is used to create complex silicone molds into which cellulose or alginate prepolymer solutions are infiltrated and allowed to gel. By exposing these molded polymers to controlled treatments of polar solvent, tunable contractions can be induced. This applies precision mechanical strain on polymers as they further cross-link, leading to tunable nanoscale anisotropy within materials. A final critical-point drying step produces anisotropic, nanofibrillar aerogels exhibiting vibrant patterns of birefringence. Such materials present enhanced mechanical modulus and toughness. This approach appears generalizable across physically crosslinked polymers and can additionally be used to permanently align functional nanowires within materials. Taken together, mechanically-directed assembly is a straightforward, low-cost process to synthesize hierarchical materials with engineered chemical, electromagnetic, and mechanical properties

The mass production and disposal of non‐degradable fossil‐based plastics is responsible for alarming environmental and social issues when not managed responsibly. Towards manufacturing environmentally‐friendly materials, biopolymers, that is, polymers synthesized by living organisms, emerge as promising sustainable alternatives as they combine attractive mechanical properties, compostability, and renewable sourcing. In this review, we analyze the structural and mechanical properties of three of the most studied biopolymer classes: cellulose, chitin, and protein beta‐sheet structures. We first discuss the hierarchical structure of the biopolymers and how their rich interaction networks induce appealing mechanical properties. Then, we review different fabrication and processing methods to translate these attractive properties into macroscopic materials and composites. Finally, we discuss a nascent approach, which leverages the direct use of microorganisms, in the form of intact cells, tissues or dissociated biological matter (biomatter), as meso‐scale material building blocks. These non‐ or little pre‐processed biomatter building blocks are composed of the biopolymer structural elements (molecular‐nano scale), but also inherit the higher‐scale hierarchical characteristics. Processing‐structure–property relationships for biomatter‐based materials are discussed, emphasizing on the role of hierarchical arrangement, processing‐induced transformations, and intermolecular bonding, on the macroscopic mechanical properties. Finally, we present a perspective on the role of biopolymers in a circular economy. [ABSTRACT FROM AUTHOR]

Spider webs are incredible biological structures, comprising thin but strong silk filament and arranged into complex hierarchical architectures with striking mechanical properties (e.g., lightweight but high strength, achieving diverse mechanical responses). While simple 2D orb webs can easily be mimicked, the modeling and synthesis of 3D-based web structures remain challenging, partly due to the rich set of design features. Here, we provide a detailed analysis of the heterogeneous graph structures of spider webs and use deep learning as a way to model and then synthesize artificial, bioinspired 3D web structures. The generative models are conditioned based on key geometric parameters (including average edge length, number of nodes, average node degree, and others). To identify graph construction principles, we use inductive representation sampling of large experimentally determined spider web graphs, to yield a dataset that is used to train three conditional generative models: 1) an analog diffusion model inspired by nonequilibrium thermodynamics, with sparse neighbor representation; 2) a discrete diffusion model with full neighbor representation; and 3) an autoregressive transformer architecture with full neighbor representation. All three models are scalable, produce complex, de novo bioinspired spider web mimics, and successfully construct graphs that meet the design objectives. We further propose an algorithm that assembles web samples produced by the generative models into larger-scale structures based on a series of geometric design targets, including helical and parametric shapes, mimicking, and extending natural design principles toward integration with diverging engineering objectives. Several webs are manufactured using 3D printing and tested to assess mechanical properties. [ABSTRACT FROM AUTHOR]

In this study we report a computational approach towards multiscale architected materials analysis and design. A particular challenge in modeling and simulation of materials, and especially the development of hierarchical design approaches, has been to identify ways by which complex multi-level material structures can be effectively modeled. One way to achieve this is to use coarse-graining approaches, where physical relationships can be effectively described with reduced dimensionality. In this paper we report an integrated deep neural network architecture that first learns coarse-grained representations of complex hierarchical microstructure data via a discrete variational autoencoder and then utilizes an attention-based diffusion model solve both forward and inverse problems, including a capacity to solve degenerate design problems. As an application, we demonstrate the method in the analysis and design of hierarchical highly porous metamaterials within the context of nonlinear stress–strain responses to compressive deformation. We validate the mechanical behavior and mechanisms of deformation using embedded-atom molecular dynamics simulations carried out for copper and nickel, showing good agreement with the design objectives. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical architected materials achieve enhanced mechanical properties. • A deep learning approach based on an attention-based diffusion model is capable of providing both, forward and inverse predictions. • We discover hierarchical microstructure candidates for a specified nonlinear mechanical response. • We demonstrate single-shot end-to-end performance in both forward/inverse directions across the entire deformation regime. • Biologically inspired materials design for high-throughput discovery specifically for diverse nonlinear constitutive relationships is provided. Inspired by natural materials, hierarchical architected materials can achieve enhanced properties including achieving tailored mechanical responses. However, the design space for such materials is often exceedingly large, and both predicting mechanical properties of complex hierarchically organized materials and designing such materials for specific target properties can be extremely difficult. In this paper we report a deep learning approach using an attention-based diffusion model, capable of providing both, forward predictions of nonlinear mechanical properties as a function of the hierarchical material structure as well as solving inverse design problems in order to discover hierarchical microstructure candidates for a specified nonlinear mechanical response. We exemplify the method for a system of compressively loaded four-hierarchy level materials derived from a family of honeycomb structures, where patterns of distributed buckling events are unitary deformation events that control small- and large-scale deformation behavior. Our model offers exquisite single-shot end-to-end performance in both forward and inverse directions across the entire range of deformation regime, and is capable of rapidly discovering multiple solutions that satisfy a design objective in accordance with the known physical behavior elucidated by, and validated with, coarse-grained simulations. The model provides an effective way towards biologically inspired materials design for high-throughput discovery in order to achieve diverse nonlinear constitutive relationships. [ABSTRACT FROM AUTHOR]

Nature provides diverse models for manufacturing complex and hierarchical materials by controlling molecular assembly at scales ranging from sub-nano to macroscale. However, developing artificial strategies for manufacturing hierarchical materials with comparable machining capabilities to nature is extremely challenging. Here, a templated freezing assembly strategy is reported, enabling simultaneously regulating molecular assembly spatiotemporally to obtain hierarchical materials with structure control from sub-nano to macroscale. In this way, unique centimeter-scale freestanding nanofilms are assembled from diverse molecules, e.g., proteins and conjugated polymers. A generated silk fibroin (SF) nanofilm presents a tunable β-sheet fraction from 5% to 47%, fiber width from 30 to 3,000 nm, and micro-textures with desired shapes. Such a strategy will lay the foundation for customizing hierarchical functional materials from single or multi-component molecules, e.g., desired bio-scaffolds with controlled cell adhesion. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) or carborundum has unparalleled thermal stability and conductivity compared with many other materials. This feature together with its unique photoelectrical properties (tunable band gap: 2.39–3.33 eV), low thermal expansion, high strength, and good chemical and thermal stability makes it an ideal inert solid in catalysis. The evolution of methods for synthesizing SiC has also progressively endowed it with additional features at the multiscale. This review tracks the development of SiC from a secondary to a leading role material in catalysis. First, the intrinsic properties of SiC are discussed and compared with other state-of-the-art catalytic materials. The synthetic methods are systematically reviewed and compared. Then, the applications of SiC in catalysis are assessed, paying particular attention to those that involve C1 chemistry (Fischer–Tropsch Synthesis and the valorization of CO2 and CH4), photocatalysis and biomass conversion. Finally, the potential future applications of SiC are also addressed and discussed. [ABSTRACT FROM AUTHOR]

Simple Summary: Insects possess microscopic cuticular surface structures of different magnitudes. Such nano-, micro-, macro- and hierarchical structures often result in multifunctionality. In this review, we focus on hydrophobicity of the insect cuticle, since it often gives rise to other functions such as self-cleaning, anti-fogging, and anti-microbial activity. To do this, we reviewed the scientific literature on hydrophobic and superhydrophobic structures in insects. We found many insects possess unique structures and surface chemicals that make the cuticle waterproof. Among the many examples, we selected a few prominent ones to show the contribution of different levels of cuticular structures, as well as chemistry, in achieving hydrophobicity. We also discuss some instances of modern insect-inspired hydrophobic engineering designs. We show that insects are a great reservoir of inspiration for the guided design of novel materials with hydrophobic functionalities. Moreover, we also impart valuable insights on how material surfaces are important for biological systems. Insects demonstrate a wide diversity of microscopic cuticular and extra-cuticular features. These features often produce multifunctional surfaces which are greatly desired in engineering and material science fields. Among these functionalities, hydrophobicity is of particular interest and has gained recent attention as it often results in other properties such as self-cleaning, anti-biofouling, and anti-corrosion. We reviewed the historical and contemporary scientific literature to create an extensive review of known hydrophobic and superhydrophobic structures in insects. We found that numerous insects across at least fourteen taxonomic orders possess a wide variety of cuticular surface chemicals and physical structures that promote hydrophobicity. We discuss a few bioinspired design examples of how insects have already inspired new technologies. Moving forward, the use of a bioinspiration framework will help us gain insight into how and why these systems work in nature. Undoubtedly, our fundamental understanding of the physical and chemical principles that result in functional insect surfaces will continue to facilitate the design and production of novel materials. [ABSTRACT FROM AUTHOR]

In this study, in operandi SAXS experiments were conducted on samples of human hair with a varying degree of strain (2% within the elastic region and 10% beyond). Four different features in the SAXS patterns were evaluated: The intermediate filament distance perpendicular to and the distance from the meridional arc in the load direction, as well as the distances of the lipid bilayer peak in and perpendicular to the load direction. From the literature, one concludes that polar lipids in the cuticle are the origin of the lipid peak in the SAXS pattern, and this study shows that the observed strain in the lipids is much lower than in the intermediate filaments. We support these findings with SEM micrographs, which show that the scales in the cuticle deform much less than the cortex. The observed deformation of the intermediate filaments is very high, about 70% of the macrostrain, and the ratio of the transverse strain to the longitudinal strain at the nanoscale gives a Poisson ratio of νnano = 0.44, which is typical for soft matter. This work also finds that by varying the time period between two strain cycles, the typical strain recovery time is about 1000 min, i.e., one day. After this period, the structure is nearly identical to the initial structure, which suggests an interpretation that this is the typical time for the self-healing of hair after mechanical treatment.

Nanocrystalline layer-structured monoclinic Na2Ti3O7 is currently under consideration for usage in solid state electrolyte applications or electrochemical devices, including sodium-ion batteries, fuel cells, and sensors. Herein, a facile one-pot hydrothermal synthetic procedure is developed to prepare self-assembled moss-like hierarchical porous structure constructed by ultrathin Na2Ti3O7 nanotubes with an outer diameter of 6–9 nm, a wall thickness of 2–3 nm, and a length of several hundred nanometers. The phase and chemical transformations, optoelectronic, conductive, and electrochemical properties of as-prepared hierarchically-organized Na2Ti3O7 nanotubes have been studied. It is established that the obtained substance possesses an electrical conductivity of 3.34 × 10−4 S/cm at room temperature allowing faster motion of charge carriers. Besides, the unique hierarchical Na2Ti3O7 architecture exhibits promising cycling and rate performance as an anode material for sodium-ion batteries. In particular, after 50 charge/discharge cycles at the current loads of 50, 150, 350, and 800 mA/g, the reversible capacities of about 145, 120, 100, and 80 mA∙h/g, respectively, were achieved. Upon prolonged cycling at 350 mA/g, the capacity of approximately 95 mA∙h/g at the 200th cycle was observed with a Coulombic efficiency of almost 100% showing the retention as high as 95.0% initial storage. At last, it is found that residual water in the un-annealed nanotubular Na2Ti3O7 affects its electrochemical properties. [ABSTRACT FROM AUTHOR]

We derive a new homogenized model for heterogeneous porous media driven by inhomogeneous body forces. We assume that the fine scale, characterizing the heterogeneities in the medium, is larger than the pore scale, but nonetheless much smaller than the size of the material (the coarse scale). We decouple spatial variations and assume periodicity on the fine scale. Fine scale variations are formally reflected in a locally unbounded source for the arising system of partial differential equations. We apply the asymptotic homogenization technique to obtain a well-defined coarse scale Darcy-type model. The resulting problem is driven by an effective source which comprises both the coarse scale divergence of the average body force, and additional contributions which are to be computed solving a well-defined diffusion-type cell problem which is driven solely by fine scale variations of the given force. The present model can be used to predict the effect of externally applied magnetic (or electric) fields on ferrofluids (or electrolytes) flowing in porous media. This work can, in perspective, pave the way for investigations of the effect of applied forces on complex and heterogeneous hierarchical materials, such as systems of fractures or cancerous biological tissues.

[Display omitted] • Zeolite-in-geopolymers were investigated for nuclear wastewater decontamination. • Increasing the zeolite content strongly affects the porous and solid microstructure. • Increasing zeolite content slows down adsorption kinetics, but increases capacity. • Large zeolite particle clusters reduces the fixed-bed efficiency of the materials. Strontium ions can be removed from wastewater in fixed-bed reactors by adsorption on hierarchical materials (different pore sizes and phases). A detailed understanding of the materials multiscale structure is therefore crucial to optimize their sorption properties. This article presents a multi-technique approach developed to characterize the relationship between microstructure and adsorption in a range of Linde-type A (LTA) zeolite-geopolymer composites,. Two-dimensional scanning electron microscopy and 3D X-ray tomography were used to image the porous and solid phases at different length scales. Advanced numerical methods involving machine learning were applied to segment the images and provide quantitative morphological values describing the porous network geometry and the location and accessibility of the zeolite particles in the geopolymer. These results were then correlated with the materials sorption properties, measured in batch and column processes. Increasing the materials zeolite content (from 0 to 27 wt%) slowed down their adsorption kinetics but increased their maximal adsorption capacities from 20 to 49 mg.g−1 and Sr2+-selectivity at equilibrium. In breakthrough experiments, the material with highest zeolite content had a much higher breakthrough volume passing from 169 to 478 ml in the presented experimental conditions (much higher wastewater decontamination capacity), but a shallower breakthrough curve (lower column efficiency). [ABSTRACT FROM AUTHOR]

Investigating and understanding the intrinsic material properties of biogenic materials, which have evolved over millions of years into admirable structures with difficult to mimic hierarchical levels, holds the potential of replacing trial-and-error-based materials optimization in our efforts to make synthetic materials of similarly advanced complexity and properties. An excellent example is biogenic silica which is found in the exoskeleton of unicellular photosynthetic algae termed diatoms. Because of the complex micro- and nanostructures found in their exoskeleton, determining the intrinsic mechanical properties of biosilica in diatoms has only partly been accomplished. Here, a general method is presented in which a combination of in situ deformation tests inside an SEM with a realistic 3D model of the frustule of diatom Craspedostauros sp. (C. sp.) obtained by electron tomography, alongside finite element method (FEM) simulations, enables quantification of the Young's modulus (E = 2.3 ± 0.1 GPa) of this biogenic hierarchical silica. The workflow presented can be readily extended to other diatom species, biominerals, or even synthetic hierarchical materials. [ABSTRACT FROM AUTHOR]

Porous materials are ubiquitous systems with a large variety of applications from catalysis to polymer science, from soil to life science, from separation to building materials. Many relevant systems of biological or synthetic origin exhibit a hierarchy, defined as spatial organization over several length scales. Their characterization is often elusive, since many techniques can only be employed to probe a single length scale, like the nanometric or the micrometric levels. Moreover, some multiscale systems lack tridimensional order, further reducing the possibilities of investigation. 129Xe nuclear magnetic resonance (NMR) provides a unique and comprehensive description of multiscale porous materials by exploiting the adsorption and diffusion of xenon atoms. NMR parameters like chemical shift, relaxation times, and diffusion coefficient allow the probing of structures from a few angstroms to microns at the same time. Xenon can evaluate the size and shape of a variety of accessible volumes such as pores, layers, and tunnels, and the chemical nature of their surface. The dynamic nature of the probe provides a simultaneous exploration of different scales, informing on complex features such as the relative accessibility of different populations of pores. In this review, the basic principles of this technique will be presented along with some selected applications, focusing on its ability to characterize multiscale materials. [ABSTRACT FROM AUTHOR]

Biological systems must have the capability to withstand impacts generated during collisions due to combat and defense. Thus, evolution has created complex materials’ architectures at various length scales that are capable of withstanding repeated, low-to-medium-velocity impacts (up to 50 m/s). In this paper, we review impact resistant biological systems with a focus on their recurrent structural design elements, material properties, and energy absorbing mechanisms. We classify these impact resistant structures at the micro- and meso-scales into layered, gradient, tubular, sandwich, and sutured and show how they construct global hierarchical, composite, porous, and interfacial architectures. Additionally, we review how these individual structures and their design parameters can provide a tailored response. We conclude with a future outlook and discussion of their potential for impact resistant bioinspired designs.

Polysaccharides constitute over 90% of the carbohydrate mass in nature, which makes them a promising feedstock for manufacturing sustainable materials. Polysaccharide particles (PSPs) are used as effective scavengers, carriers of chemical and biological cargos, and building blocks for the fabrication of macroscopic materials. The biocompatibility and degradability of PSPs are advantageous for their uses as biomaterials with more environmental friendliness. This review highlights the progresses in PSP applications as advanced functional materials, by describing PSP extraction, preparation, and surface functionalization with a variety of functional groups, polymers, nanoparticles, and biologically active species. This review also outlines the fabrication of PSP-derived macroscopic materials, as well as their applications in soft robotics, sensing, scavenging, water harvesting, drug delivery, and bioengineering. The paper is concluded with an outlook providing perspectives in the development and applications of PSP-derived materials., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

Hierarchical zeolites have the potential to provide a breakthrough in transport limitation, which hinders pristine microporous zeolites and thus may broaden their range of applications. We have explored the use of Pd-doped hierarchical ZSM-5 zeolites for aerobic selective oxidation (selox) of cinnamyl alcohol and benzyl alcohol to their corresponding aldehydes. Hierarchical ZSM-5 with differing acidity (H-form and Na-form) were employed and compared with two microporous ZSM-5 equivalents. Characterization of the four catalysts by X-ray diffraction, nitrogen porosimetry, NH3 temperature-programmed desorption, CO chemisorption, high-resolution scanning transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy allowed investigation of their porosity, acidity, as well as Pd active sites. The incorporation of complementary mesoporosity, within the hierarchical zeolites, enhances both active site dispersion and PdO active site generation. Likewise, alcohol conversion was also improved with the presence of secondary mesoporosity, while strong Brønsted acidity, present solely within the H-form systems, negatively impacted overall selectivity through undesirable self-etherification. Therefore, tuning support porosity and acidity alongside active site dispersion is paramount for optimal aldehyde production.

Abstract Architected materials can exhibit mechanical properties that do not occur with ordinary solids. By integrating hierarchy and size effects, microarchitected metamaterials fabricated by two‐photon lithography with a metallic or ceramic coating can be ultrastrong but lightweight. However, the attainment of both strength and ductility is generally mutually exclusive. Inspired by the Pantheon dome in Rome, which can withstand high load while keeping low density, microarchitected domes with a gradient helix are designed and deposited in a hierarchical nanostructured aluminum film with ultrahigh strength and considerable plasticity. Despite having a thick coating, which usually causes catastrophic collapse, the thick‐walled metallic dome shows recoverability during compression. The compressive strength increases to 73 times that of current ductile‐like microlattices, leading to the metamaterial occupying the domain of the material property space that is hitherto empty. Detailed in situ experimental and computational work reveals the graceful (noncatastrophic) failure due to the helical twisting and plastic flow in the supra‐nanomaterial. It is a promising method of suppressing brittle failure via a combination of architectural and material design. It can be used to impart enhanced functionality, making programmable stiffness, and tailored energy absorption all possible.

Architected materials can exhibit mechanical properties that do not occur with ordinary solids. By integrating hierarchy and size effects, microarchitected metamaterials fabricated by two‐photon lithography with a metallic or ceramic coating can be ultrastrong but lightweight. However, the attainment of both strength and ductility is generally mutually exclusive. Inspired by the Pantheon dome in Rome, which can withstand high load while keeping low density, microarchitected domes with a gradient helix are designed and deposited in a hierarchical nanostructured aluminum film with ultrahigh strength and considerable plasticity. Despite having a thick coating, which usually causes catastrophic collapse, the thick‐walled metallic dome shows recoverability during compression. The compressive strength increases to 73 times that of current ductile‐like microlattices, leading to the metamaterial occupying the domain of the material property space that is hitherto empty. Detailed in situ experimental and computational work reveals the graceful (noncatastrophic) failure due to the helical twisting and plastic flow in the supra‐nanomaterial. It is a promising method of suppressing brittle failure via a combination of architectural and material design. It can be used to impart enhanced functionality, making programmable stiffness, and tailored energy absorption all possible. [ABSTRACT FROM AUTHOR]

Advances in additive manufacturing techniques have enabled the development of microarchitectured materials displaying a combination of low‐density and lightweight structures with high specific strength and toughness. The mechanical performance of microarchitectured materials can be assessed using standard techniques; however, when studying low‐ and ultralow‐density microarchitectured materials, standard characterization techniques can be subject to experimental artifacts. In addition, quantitative assessment and comparisons of microarchitectures with distinct lattice patterns are not always straightforward. Cancellous bone is a natural, ultralow‐density (porosity often exceeding 90%), irregular, cellular solid that has been thoroughly characterized in terms of microarchitecture and mechanical performance over the past 30 years. However, most of the literature on cancellous bone mechanical properties and microstructure–function relationships is in the medical literature and is not immediately accessible to materials designers. Herein, a brief review of state‐of‐the‐art approaches for characterizing the microarchitecture and mechanical performance of ultralow‐density cancellous bone is provided, including methods of addressing experimental artifacts during mechanical characterization of ultralow‐density cellular solids, methods of quantifying microarchitecture, and currently understood structure–function relationships. [ABSTRACT FROM AUTHOR]

Bi-layer absorbers, which include porous and hierarchical materials, benefit from their slight weight, garnering increased interest in electromagnetic wave dissipation adaptability. However, developing a simple manufacturing process and utilizing such unique structures with particular compounds to achieve rational electromagnetic wave dissipation performance remains a challenge. In this case, a novel hierarchical flower-like Mo 2 C particle and scraps' firewood-shaped La 0.6 Sr 0.4 MnO 3 were chemically synthesized and employed as the single component in each layer of a manufactured double-layer absorber. The mechanical and electromagnetic wave dissipation capability of optimized bilayer absorber samples was excellent. The best absorption was found in bilayer samples with a total thickness of just 1.2 mm, –39 dB dissipation intensity, and 3 GHz bandwidth at 5.4 GHz frequency. This performance was obtained by manipulating the order and layer thickness of the components, as well as modifying their morphology and microstructure. [Display omitted] [ABSTRACT FROM AUTHOR]

Nanocrystalline layer-structured monoclinic Na2Ti3O7 is currently under consideration for usage in solid state electrolyte applications or electrochemical devices, including sodium-ion batteries, fuel cells, and sensors. Herein, a facile one-pot hydrothermal synthetic procedure is developed to prepare self-assembled moss-like hierarchical porous structure constructed by ultrathin Na2Ti3O7 nanotubes with an outer diameter of 6–9 nm, a wall thickness of 2–3 nm, and a length of several hundred nanometers. The phase and chemical transformations, optoelectronic, conductive, and electrochemical properties of as-prepared hierarchically-organized Na2Ti3O7 nanotubes have been studied. It is established that the obtained substance possesses an electrical conductivity of 3.34 × 10−4 S/cm at room temperature allowing faster motion of charge carriers. Besides, the unique hierarchical Na2Ti3O7 architecture exhibits promising cycling and rate performance as an anode material for sodium-ion batteries. In particular, after 50 charge/discharge cycles at the current loads of 50, 150, 350, and 800 mA/g, the reversible capacities of about 145, 120, 100, and 80 mA∙h/g, respectively, were achieved. Upon prolonged cycling at 350 mA/g, the capacity of approximately 95 mA∙h/g at the 200th cycle was observed with a Coulombic efficiency of almost 100% showing the retention as high as 95.0% initial storage. At last, it is found that residual water in the un-annealed nanotubular Na2Ti3O7 affects its electrochemical properties.

Investigating and understanding the intrinsic material properties of biogenic materials, which have evolved over millions of years into admirable structures with difficult to mimic hierarchical levels, holds the potential of replacing trial-and-error-based materials optimization in our efforts to make synthetic materials of similarly advanced complexity and properties. An excellent example is biogenic silica which is found in the exoskeleton of unicellular photosynthetic algae termed diatoms. Because of the complex micro- and nanostructures found in their exoskeleton, determining the intrinsic mechanical properties of biosilica in diatoms has only partly been accomplished. Here, a general method is presented in which a combination of in situ deformation tests inside an SEM with a realistic 3D model of the frustule of diatom Craspedostauros sp. (C. sp.) obtained by electron tomography, alongside finite element method (FEM) simulations, enables quantification of the Young’s modulus (E = 2.3 ± 0.1 GPa) of this biogenic hierarchical silica. The workflow presented can be readily extended to other diatom species, biominerals, or even synthetic hierarchical materials.

Porous materials are ubiquitous systems with a large variety of applications from catalysis to polymer science, from soil to life science, from separation to building materials. Many relevant systems of biological or synthetic origin exhibit a hierarchy, defined as spatial organization over several length scales. Their characterization is often elusive, since many techniques can only be employed to probe a single length scale, like the nanometric or the micrometric levels. Moreover, some multiscale systems lack tridimensional order, further reducing the possibilities of investigation. 129Xe nuclear magnetic resonance (NMR) provides a unique and comprehensive description of multiscale porous materials by exploiting the adsorption and diffusion of xenon atoms. NMR parameters like chemical shift, relaxation times, and diffusion coefficient allow the probing of structures from a few angstroms to microns at the same time. Xenon can evaluate the size and shape of a variety of accessible volumes such as pores, layers, and tunnels, and the chemical nature of their surface. The dynamic nature of the probe provides a simultaneous exploration of different scales, informing on complex features such as the relative accessibility of different populations of pores. In this review, the basic principles of this technique will be presented along with some selected applications, focusing on its ability to characterize multiscale materials.

Surfactant‐templating is a versatile method to introduce tailored intracrystalline mesoporosity in zeolites. This method has been proven to be extremely effective to finely control both the amount of mesoporosity and the size of their mesopores, while maintaining the main features of the original zeolite, such as crystallinity, acidity, and hydrothermal stability. By building on the knowledge generated during the last 30 years in the field of amorphous mesoporous materials, the surfactant‐templating method has been successfully applied to develop intracrystalline mesoporosity into a variety of zeolite structures including FAU, BEA, MOR, LTL, and MFI. The improvement in both the textural and diffusional properties of the zeolite results in excellent catalytic performances in different industrially relevant processes, ranging from fluid catalytic cracking to the synthesis of active pharmaceutical ingredients. As a result of the excellent catalytic performances shown by the surfactant‐templated mesoporous Y zeolite, this is currently being used in several refineries, being the first industrial and large‐scale application of hierarchical zeolites. In this progress report, the literature regarding the surfactant‐templating method in zeolites is critically reviewed. [ABSTRACT FROM AUTHOR]

A large number of functional and catalytic materials exhibit porosity, often on different length scales and with a hierarchical structure. The assessment of pore sizes, pore geometry, and pore interconnectivity is complex and usually not feasible by classical spectroscopic and diffraction techniques. One of the most powerful methods to probe these parameters is nuclear magnetic resonance (NMR) spectroscopy of xenon, which is introduced into the pore system. Adsorbed to the pore walls, it acts as probe nucleus. In this tutorial review, an introduction into the basic principles of 129Xe NMR spectroscopy and the models developed to determine pore sizes in different materials are given. The possibilities and limitations of this method for obtaining insights into hierarchical structures of functional materials are highlighted and a review of recent works is presented. [ABSTRACT FROM AUTHOR]

The ForMAX beamline at the MAX IV Laboratory provides multiscale and multimodal structural characterization of hierarchical materials in the nanometre to millimetre range by combining small- and wide-angle X-ray scattering with full-field microtomography. The modular design of the beamline is optimized for easy switching between different experimental modalities. The beamline has a special focus on the development of novel fibrous materials from forest resources, but it is also well suited for studies within, for example, food science and biomedical research., (open access.)

Electrocatalytic water splitting offers a sustainable route for hydrogen production, enabling the clean and renewable alternative energy system of hydrogen economy. The scarcity and high-cost of platinum-group-metal (PGM) materials urge the exploration of high-performance non-PGM electrocatalysts. Herein, a unique hierarchical structure of Ni/V2O3 with extraordinary electrocatalytic performance (e.g., overpotentials as low as 22 mV at 20 mA·cm−2 and 94 mV at 100 mA·cm−2) toward hydrogen evolution reaction in alkaline electrolyte (1 M KOH) is reported. The investigation on the hierarchical Ni/V2O3 with a bimodal size-distribution also offers insight of interfacial engineering that only proper Ni/V2O3 interface can effectively improve H2O adsorption, H2O dissociation as well as H adsorption, for an efficient hydrogen production. [ABSTRACT FROM AUTHOR]

Abstract: We present the effect of different combinations of intracrystalline pore systems in hierarchical ZSM‐5 zeolites on their performance as MTO catalysts. We prepared ZSM‐5 zeolites with additional intracrystalline mesoporous, intracrystalline macropores and a novel ZSM‐5 type zeolite with intracrystalline meso and macropores. The catalytic results showed that both used catalysts with mesopores and macropores exhibited three times longer catalyst lifetime compared to a conventional catalyst. However, TGA analysis of the deactivated catalysts showed much larger coke content in the mesoporous catalyst than in the macroporous catalyst. Consequently, macropores predominantly led to reduced coke formation rate while additional mesopores predominantly enhanced the resistance against deactivation by coke. Combining both intracrystalline meso and macropores in one catalyst lead to a tenfold increase in catalyst lifetime. Besides the effect on the catalyst lifetime there was also a strong effect of the additional pore systems on the selectivity of the catalysts. The catalysts containing mesopores showed reduced selectivity to short chain olefins and increased selectivity to larger hydrocarbons in comparison to the catalysts without a mesopores system. [ABSTRACT FROM AUTHOR]

The adsorption and immersion of different fluids on a series of carbon molecular sieves was investigated. The carbon adsorbents with significantly different micro- and mesoporosity were characterized by means of nitrogen and argon adsorption at cryogenic temperatures, vapor adsorption at 298.15 K, liquid-immersion enthalpy and pH value measurements. The polarity and chain length of the fluid molecules used for adsorption and immersion were varied to study the texture and surface polarity, the accessibility of the pore systems and the adsorption mechanisms in micro- and mesoporous adsorbents. The experimental data are evaluated with regard to correlations between adsorption and immersion measurements. The obtained results affirm once again that vapor-sorption and liquid-immersion experiments extend the characterization tool for hierarchical materials in a meaningful manner. [ABSTRACT FROM AUTHOR]

Organization of nanoparticles is essential in order to control their light-matter interactions. We present cellulose nanocrystal suspension organization in flow towards a unidirectional state. Visualization of evolving polarization patterns of the cellulose nanocrystal suspensions is combined with steady and oscillatory shear rheology. Elucidation of the chiral nematic mesophase in a continuous process towards unidirectional order enables control of alignment in a suspension precursor for structural films and reveals thus far in situ unrevealed transition states that were not detectable by rheology alone. The coupled analytics enabled the suspensions of interest to be divided into rheological gels and rheological liquid crystal fluids with detailed information on the microtransition phases. Both populations experienced submicron organization and reached macro-scale homogeneity with unidirectional ordering in continued shear. We quantify the time, shear rate, and recovery time after shear to design an optimizing formation process for controlled wet structures as precursors for dry products. [ABSTRACT FROM AUTHOR]

Bijels are used to develop a new class of ultralight hierarchically porous aerogels exhibiting multimodal porosity across multiple length scales. Through in situ functionalization of a particle‐laden liquid interface wherein binary liquid pairs are kinetically trapped out of equilibrium through interfacial jamming, monolithic and freestanding carbon electrodes are produced with prescribed bulk densities down to ≈2 mg cm−3. Exemplary electrokinetic experiments indicate that the bicontinuity of the pore structure is essential for enhancing transport to and from the active electrode surfaces, demonstrating that these materials possess a superior ability to accumulate and transport charge when compared to analogous systems with restricted pore connectivity and fluid throughput. This approach offers a new synthetic route to bicontinuous and hierarchical aerogel materials with nested multimodal porosities. The flexibility of this scheme can address critical issues related to transport‐limited behaviors that arise in many technological fields, ranging from energy and catalysis research to remediation and sensing applications. [ABSTRACT FROM AUTHOR]

In order to obtain highly active catalytic materials for oxidation of carbon monoxide and volatile organic compounds (VOCs), monometallic platinum, copper, and palladium catalysts were prepared by using of two types of ZSM-5 zeolite as supports—parent ZSM-5 and the same one treated by HF and NH4F buffer solution. The catalyst samples, obtained by loading of platinum, palladium, and copper on ZSM-5 zeolite treated using HF and NH4F buffer solution, were more active in the reaction of CO and benzene oxidation compared with catalyst samples containing untreated zeolite. The presence of secondary mesoporosity played a positive role in increasing the catalytic activity due to improved reactant diffusion. The only exception was the copper catalysts in the reaction of CO oxidation, in which case the catalyst, based on untreated ZSM-5 zeolite, was more active. In this specific case, the key role is played by the oxidative state of copper species loaded on the ZSM-5 zeolites.

Inorganic-organic mesophase materials provide a wide range of tunable properties, which are often highly dependent on their nano-, micro-, or meso-scale compositions and structures. Among these are macroscopic orientational order and corresponding anisotropic material properties, the adjustability of which are difficult to achieve. This is due to the complicated transient and coupled transport, chemical reaction, and surface processes that occur during material syntheses. By understanding such processes, general criteria are established and used to prepare diverse mesostructured materials with highly aligned channels with uniform nanometer dimensions and controllable directionalities over macroscopic dimensions and thicknesses. This is achieved by using a micropatterned semipermeable poly(dimethylsiloxane) stamp to manage the rates, directions, and surfaces at which self-assembling phases nucleate and the directions that they grow. This enables mesostructured surfactant-directed silica and titania composites, including with functional guest species, and mesoporous carbons to be prepared with high degrees of hexagonal order, as well as controllable orthogonal macroscopic orientational order. The resulting materials exhibit novel anisotropic properties, as demonstrated by the example of direction-dependent photocurrent generation, and are promising for enhancing the functionality of inorganic-organic nanocomposite materials in separations, catalysis, and energy conversion applications., (© 2023 Wiley-VCH GmbH.)

Graphical abstract The photoelectric functional hierarchical materials were prepared by the simple ionic self-assembly strategy exhibits multiple stimuli-responsive switching behavior triggered by β-cyclodextrin (β-CD) inclusion, redox species, and pH. Abstract The photoelectric functional hierarchical materials have been successfully prepared by the simple ionic self-assembly (ISA) strategy from the cationic ferrocenyl surfactant, 16-alkyl (ferrocenyl-methyl)ammonium bromide (Fc16AB) and the anionic alizarin red (AR). The obtained complexes exhibited multiple stimuli-responsive switching behaviour triggered by β-cyclodextrin (β-CD) inclusion, redox species, and pH. The switching mechanism corresponding to each stimulus was studied in detail. Moreover, the fluorescent intensity of binary complexes could be modulated by the concentration of Fc16AB and redox of ferrocene part. The fluorescence switching mechanism upon redox stimulus was studied in detail. Both the complexes fabrication and transition mechanisms were found to be controlled by the inclusion equilibrium and the cooperative binding of noncovalent interactions, including the electrostatic interactions, π-π stacking, and amphiphilic hydrophobic association. This work provides a deep understanding of electro-photo molecular switching device. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Surfactant-modified zeolites were obtained by surface modification of *BEA-type zeolites. • The nitrate removal capacity increases with the increase of the zeolite external surface. • The highest ever observed nitrate removal capacity using surfactant-modified zeolite. Abstract Hierarchical *BEA-type nanosponges zeolite with a high external surface area (116 m2.g−1) and small crystal size, synthesized in the presence of a dual-porogenic organic compound, were modified with a cationic surfactant (HDTMA+Br−: hexadecyltrimethyl ammonium bromide) in order to create a new anion exchanger system: the surfactant-modified zeolite nanosponges (SMZ NS). For comparison, two other surfactant-modified *BEA-type zeolite materials, SMZ MC and SMZ NC , were obtained by modifying the synthesized conventional micron-size microcrytals and nanocrystals *BEA-type zeolite with HDTMA+Br−, respectively. Textural and structural properties were determined for the three prepared materials using N 2 adsorption/desorption analysis, XRD, SEM, and TEM. Nitrate adsorption isotherms were drawn in a large concentration range [0.8–24.2 mmol.L−1] and fitted with Langmuir isotherm model. The maximum nitrate removal capacity (1338 mmol.Kg−1/83 mg.g−1) was obtained for SMZ NS material. This value is the highest ever observed for nitrate removal using surfactant-modified zeolite. The nitrate removal kinetics were fitted with the pseudo second-order model for both materials SMZ NS and SMZ NC. [ABSTRACT FROM AUTHOR]