Self-supporting Structures Research Articles

Effect of oil and particles content on microstructure, rheology, and thermosensitive 3D printability of particles -stabilized high internal phase Pickering emulsions

In this study, soybean protein isolate (SPI) microgel/chitosan (CS) blending system prepared by gel fragmentation were used as particle-based emulsifiers. The presence of chitosan significantly reduced the particle size of the particles and decreased their contact angle (from 129° to 102°), thereby enhancing their wettability. These particles adsorbed onto the oil-water interface by rapidly decreasing the interfacial tension, forming stable O/W-type high internal phase Pickering emulsions. Confocal laser scanning microscopy analysis showed that the droplets were tightly packed together, and some of them were observed to have a polyhedral shape due to the packing, which is the basis for the formation of self-supporting structures. The rheological properties are closely related to the 3D printing results, increasing the oil and particles concentration improves the viscosity, energy storage modulus and gel strength of the system, while the excellent thixotropy facilitates the ability to 3D print these emulsions. At an oil content of 75% and a particles concentration of 3.0%, the accuracy and stability of the printed models were 97.9% and 99.2%, respectively. Introduction of curcumin and NaHCO3 led to a color change from yellow to reddish-brown during heating, enabling thermosensitive 3D printing of color changing HIPPEs. This study may broaden the range of applications of plant-based HIPPEs in 3D and thermosensitive 3D printing, as well as for the development of other innovative food products.

Calcium alginate/Polyaniline double network aerogel electrode for compressible and high electrochemical performance integrated supercapacitors

As a new type of energy storage device, supercapacitors have attracted more and more attention due to their excellent performance. However, the current electrode materials have limited specific surface area and cannot meet the needs of high energy storage. The aerogel material is a 3D network structure containing interconnected micro-nano structures, and also has hierarchical pores on the micro, meso and macro scales. The microporous and mesoporous structures can provide high specific surface area, while the macropores provide channels for the entry of active substances. In this study, calcium alginate (CA)/polyaniline (PANI)/reduced graphene oxide (RGO) aerogels based on double network structure with high mechanical property and excellent electrochemical performance are successfully constructed by sol-gel method. Due to the double network structure, the CA/PANI/RGO aerogel exhibits self-supported 3D porous network structures with high surface areas (330.3 m2/g). CA/PANI/RGO composite aerogel electrode shows high specific capacitance (908 F/g at 1 A/g) and excellent rate performance. The initial capacitance of more than 80 % can be maintained after 10,000 times of charge/discharge cycle test. Most importantly, the assembled flexible solid-state supercapacitor has high specific capacitance (885 F/g at 1 A/g) and mechanical flexibility (92.6 % of the capacitance retention after 1000 bending cycles).

A very simple synthesis of defect-rich PdAg nanosponges for highly selective hydrogenation of furfural

Furfuryl alcohol (FA) is an important chemical and has extensive applications in varied fields. To realize the highly selective hydrogenation of furfural (FF) to produce FA, the key is the preparation of the catalysts with excellent performance. Herein, a very simple wet chemical method is developed for the one-step preparation of PdAg nanosponges (NSs). Specifically, with Pd(OAc)2 and AgNO3 as precursors, and ethylene glycol (EG) as both solvent and reducing agent, PdAg NSs can be grown and assembled at mild temperature of 40 °C. Throughout the reaction, no any surfactants and additional reducing agents are applied. The as-prepared PdAg NSs possess 3D self-supported alloy structures, “clean” surface, abundant pores, high specific surface area and rich defects. In the FF hydrogenation reaction at 60 °C under 1.5 MPa H2 pressure in the mixed solvent of ethanol and water (1 : 4 in volume ratio), the self-supported PdAg-1 NSs (1 : 1 in Pd/Ag molar ratio) exhibit superior catalytic performance than other PdAg NSs, pure Pd sample and commercial Pd/C (10%). With PdAg-1 NSs as catalyst in the absence of support, 100% FF can be converted and the selectivity toward FA is as high as 97.1% at 36.0 h of reaction. After 4 cycles, PdAg-1 NSs still maintain the high catalytic activity in FF hydrogenation and high selectivity toward FA, which may originate from the 3D self-supported structures, high specific surface area, “clean” surface, rich defects and electronic synergistic effect between Pd and Ag. This simple fabrication of PdAg NSs introduces new ideas for the synthesis of other nanostructured bi- and multi-metallic catalysts for highly selective FF hydrogenation to FA and other advanced applications.

Free-standing medium-entropy porous needle-like FeCoCuNi phosphide nanowires-formed flower clusters/carbon fiber anode with high capacity and long durability for sodium-ion batteries

The drastic volume expansion and slow sodium-ion kinetics hinder the practical application of phosphides with high specific capacity and low discharge voltage in sodium-ion batteries (SIBs). Herein, we introduced entropy configuration into nanostructures and prepared a novel free-standing, three-dimensional, porous needle-like medium-entropy Fe, Co, Cu, Ni phosphide (ME-FCCNP) nanowires-formed flower clusters/carbon fiber cloth (CFC) anode (ME-FCCNP@CFC) for SIBs. The distorted lattices caused by medium-entropy configuration provide abundant sites for sodium-ion reactions and improve the electron transfer rate. The medium-entropy effects improve the mechanical stability, while the three-dimensional networks and porous needle-like nanowires provide sufficient space for the volume expansion. These combined properties enable the ME-FCCNP@CFC electrode to exhibit a high-rate capability of 170.8 mAh g−1 at 5.0 A g−1 and deliver a specific capacity of 325.8 mAh g−1 after 2000 cycles at 2.0 A g−1, far surpassing most of reported transition-metal phosphides. Moreover, the Na3V2(PO4)3 || ME-FCCNP@CFC full cell showcases a high-energy density of 256.8 Wh kg−1 and a long cycling life (267.8 mAh g−1 at 2.0 A g−1 with a capacity retention of 83.2 % after 1000 cycles). These results provide significantly promising implications for the anode design of SIBs by employing self-supporting and medium-entropy structures.

3D Bioprinting Using Universal Fugitive Network Bioinks.

Three-dimensional (3D) bioprinting has emerged with potential for creating functional 3D tissues with customized geometries. However, the limited availability of bioinks capable of printing 3D structures with both high-shape fidelity and desired biological environments for encapsulated cells remains a key challenge. Here, we present a 3D bioprinting approach that uses universal fugitive network bioinks prepared by loading cells and hydrogel precursors (bioink base materials) into a 3D printable fugitive carrier. This approach constructs 3D structures of cell-encapsulated hydrogels by printing 3D structures using fugitive network bioinks, followed by cross-linking printed structures and removing the carrier from them. The use of the fugitive carrier decouples the 3D printability of bioinks from the material properties of bioink base materials, making this approach readily applicable to a range of hydrogel systems. The decoupling also enables the design of bioinks for the biological functionality of the final printed constructs without compromising the 3D printability. We demonstrate the generalizable 3D printability by printing self-supporting 3D structures of various hydrogels, including conventionally non-3D printable hydrogels and those with a low polymer content. We conduct preprinting screening of bioink base materials through 3D cell culture to select bioinks with high cell compatibility. The selected bioinks produce 3D constructs of cell-encapsulated hydrogels with both high-shape fidelity and high cell viability and proliferation. The universal fugitive network bioink platform could significantly expand 3D printable bioinks with customizable biological functionalities and the adoption of 3D bioprinting in diverse research and applied settings.

Design and validation of 3D self-supporting structures and printing paths for multi-axis additive manufacturing

Additive manufacturing (AM) has become a widely used tool for fabricating components with complex geometries. However, the overhang effect induced by gravity often necessitates additional supports to prevent collapse and warping during the printing process. To address this issue, previous studies incorporated overhang constraints to the topology optimisation to create self-supporting structures. Nevertheless, these studies primarily focused on 3-axis AM, which deposits material in a single direction and often compromises structural stiffness to achieve self-supporting designs. In response, this study aims to design 3D self-supporting structures tailored for multi-axis AM. By leveraging the rotatable base platform of multi-axis systems, this approach automatically identifies optimised local build directions and the corresponding structural topology to minimise overhangs. The effectiveness of this approach is demonstrated through several numerical examples, with results validated numerically via printing simulations in VERICUT and physically using a multi-axis Wire Arc Additive Manufacturing (WAAM) machine. The results indicate that the performance degradation caused by 3-axis-based overhang constraints can be reduced to a negligible level with the multi-axis-based approach.

Study on Improving Fire Safety in Traditional Markets

In this study, we analyzed fire-safety management regulations and problems with fire-alarm equipment in traditional markets, as failures can cause significant damage in the event of a fire. We also present improvement measures based on analyzing major fire accidents. Traditional markets must designate the type of firefighting equipment installed at a store according to the number of stores, and apply this measure retroactively when the installation regulations are revised. If the market is designated as traditional, the equipment must be designated as a fire-safety management object, and the appointment of a fire safety manager, firefighting education and training, and self-inspection must be made mandatory. Fire-alarm equipment must be inspected regularly by a fire-safety manager, and fire-proof walls must be installed with self-supporting fire-resistant structures at certain sections. When designing a new traditional market, it must be designated after facility supplementation following safety inspection. In addition, traditional markets are required to have fire-detection equipment and automatic notification systems, and building-type traditional markets must retroactively install automatic sprinkler equipment.

Homogenization-based topology optimization for self-supporting additive-manufactured lattice-infilled structure

Lattice-infilled structures possess prominent properties at relatively low mass, which are of great significance in academic investigations and engineering fields such as aerospace science and biomedical applications. However, both the macro geometry and relative density distribution of the infilled microstructure exert considerable influence on performances of lattice-infilled structure and the structural manufacturability needs to be considered. In this work, an optimization design methodology for self-supporting additive-manufactured lattice-infilled structures is proposed, in which the macro geometry and relative density distribution of the microstructure are concurrently optimized. Microstructure is infilled after topology optimization and octree structure is introduced into the boundary layers of the lattice core to support the top shell during fabrication. The effectiveness of the proposed optimization design method for self-supporting additive-manufactured lattice-infilled structures was proved by both three-point-bending test and full-scale finite element simulation. Compared with the uniformly-infilled sample, mass-specific stiffness and strength of the topologyoptimized sample were improved by 41.2% and 112.1%, respectively. The proposed design method for lattice-infilled structures provides potential for designing additive-manufactured high-performance lightweight structures, which will broaden the boundaries of lattice structure in engineering applications.

A Direct Dry Synthesis Route for High Purity Catalytic Nanoporous Metallic Films

Control of catalyst morphology is important because it affects many catalytic related properties such as, active sites, surface energy, and surface area, which can lead to tunable catalytic activity. Nanoporous metallic networks (NPMs), a morphology of interest for catalysis, contain many uncoordinated atoms at the surface and highly curved ligaments that can have a large effect on catalytic performance. Nanoporous self-supported metal structures have been synthesized in the past by dealloying of a master alloy,[1] which is a wet chemical method. This technique uses an Au-Ag alloy, from which Ag is etched away and which always results in NPMs containing residual amounts of the sacrificial metal (Ag) preventing the formation of high-purity structures. It follows that the catalytic properties of pure NPMs formed by dealloying can not be studied due to metal 'impurities' remaining in the structure. Although these 'impurities' contribute to catalytic activity and stability, it is difficult to control their amount and the systematic investigation of the 'impurity' effect is almost impossible for these NPMs.Here, we present results obtained by using physical vapor deposition, in the form of glancing angle deposition (GLAD), together with plasma etching to form nanoporous ultra-thin metal mesh structures, in a unique and facile dry synthesis method,[2] unlike most wet chemical synthesis methods used to prepare catalysts, which result chemical waste. The nanostructured metal mesh films are suitable for catalysis as they are extremely pure and highly porous, and contain high curvature ligaments, different crystal motifs, and many grain boundaries. We present nanoporous gold films (NPGF) prepared by our method as an example material. We show that the electrochemical structural stability of the NPGF is remarkably higher than that of dealloyed nanoporous gold, which is a result of the high amount of grain boundaries. Furthermore, the electrocatalytic performance of CH3OH oxidation is measured and the results show high catalytic activity for pure NPGF.[3] Our GLAD method can be applied to various metals and enables precise mixing or doping of different materials composing the NPMs. The high porosity, active sites, and potential elemental mixing will lead to new catalysts, especially suitable for CO2 reduction to fuels and value-added chemicals.[1] G. Wittstock, M. Bäumer, W. Dononelli, T. Klüner, L. Lührs, C. Mahr, L. V. Moskaleva, M. Oezaslan, T. Risse, A. Rosenauer, A. Staubitz, J. Weissmüller, A. Wittstock, Chem. Rev. 2023, 123, 6716.[2] H. Kwon, H.-N. Barad, A. R. Silva Olaya, M. Alarcón-Correa, K. Hahn, G. Richter, G. Wittstock, P. Fischer, ACS Appl. Mater. Interfaces 2023, 15, 5620.[3] H. Kwon, H.-N. Barad, A. R. Silva Olaya, M. Alarcón-Correa, K. Hahn, G. Richter, G. Wittstock, P. Fischer, ACS Catal. 2023, 11656.

Topology Optimization of Self-supporting Structures for Additive Manufacturing via Implicit B-spline Representations

Owing to the rapid development in additive manufacturing, the potential to fabricate intricate structures has become a reality, emphasizing the importance of designing structures conducive to additive manufacturing processes. A crucial consideration is the ability to design structures requiring no additional support during manufacturing. This paper employs implicit B-spline representations for self-supporting structure design by integrating a topology optimization model with self-supporting constraints derived analytically from the implicit representation. This analytical derivation for detecting overhang regions enables accurate and efficient calculation of constraints, outperforming other B-spline-based methods. Compared to the traditional voxel-based methods, the implicit B-spline representation significantly expedites the optimization process by reducing the number of design variables. Additionally, several acceleration techniques are implemented to enhance the efficiency of our method, allowing simulations of 3D models with millions of finite elements to be completed within one and half an hour, excelling other B-spline-based methods and voxel-based methods. Various numerical experiments validate its excellent performance, confirming the effectiveness and efficiency of the proposed algorithm.

3D-Printed Flexible Microfluidic Health Monitor for In Situ Sweat Analysis and Biomarker Detection.

Wearable sweat biosensors have shown great progress in noninvasive, in situ, and continuous health monitoring to demonstrate individuals' physiological states. Advances in novel nanomaterials and fabrication methods promise to usher in a new era of wearable biosensors. Here, we introduce a three-dimensional (3D)-printed flexible wearable health monitor fabricated through a unique one-step continuous manufacturing process with self-supporting microfluidic channels and novel single-atom catalyst-based bioassays for measuring the sweat rate and concentration of three biomarkers. Direct ink writing is adapted to print the microfluidic device with self-supporting structures to harvest human sweat, which eliminates the need for removing sacrificial supporting materials and addresses the contamination and sweat evaporation issues associated with traditional sampling methods. Additionally, the pick-and-place strategy is employed during the printing process to accurately integrate the bioassays, improving manufacturing efficiency. A single-atom catalyst is developed and utilized in colorimetric bioassays to improve sensitivity and accuracy. A feasibility study on human skin successfully demonstrates the functionality and reliability of our health monitor, generating reliable and quantitative in situ results of sweat rate, glucose, lactate, and uric acid concentrations during physical exercise.

3D-printed photocatalytic scaffolds of BiVO4 by direct ink writing for acetaminophen mineralization

A novel methodology to obtain 3D printable BiVO4 precursor scaffolds (3DM-BiVO4) via robocasting, showing excellent periodicity, shape retention, and mechanical stability, is disclosed for the first time. The ceramic pastes (solids at 70 wt.-%) comprised of BiVO4 precursor, SiO2NPs, and a solution of deionized water: ethylene glycol (volume ratio 1:2, DI water: EG) exhibited enhanced rheology for the 3D printing of self-supported structures (3DM-BiVO4). The thermal treatment induced a monoclinic scheelite phase, and the ethylene glycol contributed to achieving a unique square flake-like particle morphology. 3DM-BiVO4 scaffolds were used as reusable monolithic photocatalysts, showing 72% acetaminophen mineralization at 240 min and pH = 9. This innovative approach opens avenues for designing 3D printable ceramic pastes, offering potential applications in tailoring-made monolithic photocatalyst fabrication by using SiO2NPs as an inorganic binder.

Solidified water at room temperature hosting tailored fluidic channels by using highly anisotropic cellulose nanofibrils

Highly anisotropic cellulose nanofibrils can solidify liquid water, creating self-supporting structures by incorporating a tiny number of fibrils. These fibrillar hydrogels can contain as much as 99.99 wt% water. The structure and mechanical properties of fibrillar networks have so far not been completely understood, nor how they solidify the bulk water at such low particle concentrations. In this work, the mechanical properties of cellulose fibrillar hydrogels in the dilute regime from a wt% perspective have been studied, and an elastoplastic model describing the network structure and its mechanics is presented. A significant insight from this work is that the ability of the fibrils to solidify water is very dependent on particle stiffness and the number of contact points it can form in the network structure. The comparison between the experimental results and the theoretical model shows that the fibrillar networks in the dilute regime form via a non-stochastic process since the fibrils have the time and freedom to find contact points during network formation by translational and rotational diffusion. The formed, dilute fibrillar network deforms by sliding fibril contacts upon straining the network beyond its elastic limit. Our results also show that before macroscopic failure, the fibril contacts are restored once the load is released. The exceptional properties of this solidified water are exploited to host fluidic channels, allowing directed fluid transportation in water. Finally, the microfluidic channels formed in the hydrogels are tailored by the layer-by-layer technique to be interactive against external stimuli, a characteristic envisioned to be useful in biomedical applications.

Novel Electrode Designs and Configurations in Secondary Iron-Air Batteries

Stationary energy storage solutions are urgently needed due to the challenges we face caused by the anthropogenic climate change. While Lithium-Ion batteries are still considered as state of the art within this field, the availability of lithium is limited.The iron-air battery system is mainly superior due to the low criticality of the active materials. Iron is cheap and abundant, while air is supplied by the ambient atmosphere. During discharging oxygen from ambient air is reduced (oxygen reduction reaction, ORR) and evolved during charging (oxygen evolution reaction, OER). One of the main challenges towards stable metal-air batteries is the air-electrode. Those usually consist of a catalyst, a conductive additive, and – depending on the electrode design- of a binder. Carbon-based materials offer an excellent intrinsic activity towards the oxygen reduction and a high specific surface area. However, carbon corrodes in the potential range of the oxygen evolution reaction. Our work focuses on the development of novel electrode formulations for PTFE-bonded electrodes and novel self-supported electrode structures - based on galvanic deposition of nickel - and their implementation in iron-air batteries.Within a first approach a mixed catalyst composed of MnO2 and NiO was investigated in a PTFE-bonded electrode with nickel as conductive additive. The electrode reached an initial activity of 0.77 V vs. RHE @ -25 mA cm-2 (ORR) and 1.57 V vs. RHE @ 25 mA cm-2 (OER) in 6 M KOH at room temperature. The potentials were stable for about 60 cycles (one cycle consisted of 60 min). MnO2 corrodes at OER potentials, which results in a decrease of activity. However, a partial substitution of MnO2 by NiO is beneficial for the cycling stability. In a second approach, a bifunctional nickel-cobalt-oxide based bifunctional catalyst was investigated within the same electrode system. An initial activity of 0.71 V vs. RHE and 1.63 V vs. RHE was observed for this system. Stable OER performance but a decrease ORR activity was observed within this system over time during cycling. To increase the cycling stability, dendritic nickel structures with a high intrinsic surface area were prepared with galvanic deposition. Our results indicate that the efficiency and stability of the battery can be improved by using this approach. Figure 1

"On-The-Fly" Synthesis of Self-Supported LDH Hollow Structures Through Controlled Microfluidic Reaction-Diffusion Conditions.

Layered double hydroxides (LDHs) are a class of functional materials that exhibit exceptional properties for diverse applications in areas such as heterogeneous catalysis, energy storage and conversion, and bio-medical applications, among others. Efforts have been devoted to produce millimeter-scale LDH structures for direct integration into functional devices. However, the controlled synthesis of self-supported continuous LDH materials with hierarchical structuring up to the millimeter scale through a straightforward one-pot reaction method remains unaddressed. Herein, it is shown that millimeter-scale self-supported LDH structures can be produced by means of a continuous flow microfluidic device in a rapid and reproducible one-pot process. Additionally, the microfluidic approach not only allows for an "on-the-fly" formation of unprecedented LDH composite structures, but also for the seamless integration of millimeter-scale LDH structures into functional devices. This method holds the potential to unlock the integrability of these materials, maintaining their performance and functionality, while diverging from conventional techniques like pelletization and densification that often compromise these aspects. This strategy will enable exciting advancements in LDH performance and functionality.

Layout and geometry optimization design for 3D printing of self-supporting structures

As the demand for high-performance structures in various scenarios continues to rise, the complexity of engineering structures also increases, necessitating the development of advanced design methods and the additive manufacturing (AM) of sophisticated structures. While the layout optimization method based on the ground structure technique can produce optimized designs, the gravity-induced overhang effect during the printing process often requires additional support materials. The use of additional support materials during the printing process can result in higher material costs or the need for post-processing to remove the support structures, significantly hindering the adoption of AM in practice. This paper presents an optimization framework to obtain self-support optimization designs and provides a practical validation for the effectiveness of the proposed framework. Firstly, a self-support point-line structure is obtained via the layout and geometry optimization, considering overhang constraints. Secondly, the point-line structure is transformed into a physical model with nodal expansion considered (i.e., taking into account the overlapping of members at nodes). Finally, the physical models are sliced and printed using both a plastic Fused Deposition Modeling (FDM) printer and a metal Wire Arc Additive Manufacturing (WAAM) printer. The results confirm that the proposed process is effective for both plastic and metal printing, demonstrating its exceptional versatility.

Metal-Organic-Framework-Based Nanoarrays for Oxygen Evolution Electrocatalysis.

The development of highly active and stable electrode materials for the oxygen evolution reaction (OER) is essential for the widespread application of electrochemical energy conversion systems. In recent years, various metal-organic frameworks (MOFs) with self-supporting array structures have been extensively studied because of their high porosity, abundant metal sites, and flexible and adjustable structures. This review provides an overview of the recent progress in the design, preparation, and applications of MOF-based nanoarrays for the OER, beginning with the introduction of the architectural advantages of the nanoarrays and the characteristics of MOFs. Subsequently, the design principles of robust and efficient MOF-based nanoarrays as OER electrodes are highlighted. Furthermore, detailed discussions focus on the composition, structure, and performance of pristine MOF nanoarrays (MOFNAs) and MOF-based composite nanoarrays. On the one hand, the effects of the two components of MOFs and several modification methods are discussed in detail for MOFNAs. On the other hand, the review emphasizes the use of MOF-based composite nanoarrays composed of MOFs and other nanomaterials, such as oxides, hydroxides, oxyhydroxides, chalcogenides, MOFs, and metal nanoparticles, to guide the rational design of efficient OER electrodes. Finally, perspectives on current challenges, opportunities, and future directions in this research field are provided.

Conceptual design of a novel megawatt portable nuclear power system by supercritical carbon dioxide brayton cycle coupled with heat pipe cooled reactor

In order to meet realistic requirements for flexible and reliable power supply in special scenarios such as remote areas and deep ocean exploration, a novel megawatt portable nuclear power system called SUPERHERO (SUPERcritical carbon dioxide cycle-HEat pipe ReactOr power system) is proposed in this paper. The system consists of a heat pipe-cooled reactor and a closed supercritical carbon dioxide (S–CO2) Brayton power cycle. Different cycle concepts were compared, and the simple recuperated cycle was adopted for compactness and simplicity of the system. The multi-objective optimization is performed to maximize cycle efficiency and minimize system volume, resulting in optimized parameters for a 1MWe system. By utilizing uranium nitride (UN) modular fuel elements and high heat transfer capacity potassium heat pipes, a compact reactor scheme with 3.13MWt is determined that can operate for 15 years without refueling. The neutronics and thermal analysis of the reactor are carried out, and the results show that the reactor has safety features such as a low peak factor, negative temperature feedback coefficient, sufficient reactivity compensation and control, and anti-failure of single heat pipe. The primary heat exchanger is also designed using the CFD method, and the heat exchange tubes combined with ribbed plates and self-supporting structures are used to enhance heat transfer and ensure structural stability. All these studies outline the general features of SUPERHERO, demonstrating that SUPERHERO has great development potential.

Numerical Simulation and Analysis of the Acoustic Properties of Bimodal and Modulated Macroporous Structures

In recent decades, cellular metallic materials have increasingly been used for control of reverberation and cutback. These materials offer a unique combination of expanded pores, high specific surfaces, improved structural performance, low weight, corrosion resistance at high temperatures, and a fixed/rigid pore network (i.e., at the boundaries, porosity does not change). This study examines the ability of sphere-packing models combined with numerical modelling and simulations to predict the acoustic properties of bimodal and modulated bottleneck-shaped macroporous structures that can realistically be achieved through liquid melts infiltration casting technique. The simulations show that porosity, openings, pore sizes and permeability of the material have significant effects on acoustics, and the predictions are consistent with experimental data substantiated in the literature. The modelling suggests that the creation of bimodal structures increases the capacity of the interstitial pores and pore contacts. The result is improved sound absorption properties and spectra, characterised by a pore volume fraction of 0.73 and a mean pore size to mean pore opening ratio of 4.8 for the 50% volume bimodal structure created at a 10 µm capillary radius. The importance of how pore structure-related parameters and existing fluid flow regimes can modulate the sound absorption performance of macroporous structures was revealed by numerical simulations of the sound absorption spectra for dual-porosity and dilated macroporous structures working from high-resolution tomography datasets. Sound absorption properties were optimised for structures having pore volume fractions between 0.68 and 0.76, maintaining the mean pore size to mean pore opening ratios between 4.0 and 6.0. Using this approach, enhanced and self-supporting macroporous structures may be designed and fabricated for efficient sound absorption in specific applications.

Advanced Synthetic Scaffolds Based on 1D Inorganic Micro-/Nanomaterials for Bone Regeneration.

Inorganic nanoparticulate biomaterials, such as calcium phosphate and bioglass particles, with chemical compositions similar to that of the inorganic component of natural bone, and hence having excellent biocompatibility and bioactivity, are widely used for the fabrication of synthetic bone graft substitutes. Growing evidence suggests that structurally anisotropic, or 1D inorganic micro-/nanobiomaterials are superior to inorganic nanoparticulate biomaterials in the context of mechanical reinforcement and construction of self-supporting 3D network structures. Therefore, in the past decades, efforts have been devoted to developing advanced synthetic scaffolds for bone regeneration using 1D micro-/nanobiomaterials as building blocks. These scaffolds feature extraordinary physical and biological properties, such as enhanced mechanical properties, super elasticity, multiscale hierarchical architecture, extracellular matrix-like fibrous microstructure, and desirable biocompatibility and bioactivity, etc. In this review, an overview of recent progress in the development of advanced scaffolds for bone regeneration is provided based on 1D inorganic micro-/nanobiomaterials with a focus on their structural design, mechanical properties, and bioactivity. The promising perspectives for future research directions are also highlighted.