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Bracket fungi sporocarps present promising environmentally friendly alternatives to harmful and wasteful structural applications with their high strength-to-weight ratio mechanical properties. Kingdom Fungi is estimated to have over three million species, yet only 4% of the species have been described by mycologists, and their mechanical behavior has been under-explored. This work aims to characterize the material behavior and mechanical properties of bracket fungi as a whole through micro-mechanical tensile testing combined with microstructural imaging and analysis of two representative species. The context layer from three distinctive fresh bracket sporocarps is used in this study. At the microstructure level, the bracket fungi have a preferred alignment in the hyphal network, which correlates to the radial direction. The bracket fungi exhibit an anisotropic mechanical behavior with higher ultimate tensile strength and elastic modulus in the radial direction, while the strain to failure is higher in the transverse direction. However, the bracket fungi exhibit an isotropic energy absorption, or toughness, behavior, with no statistically significant difference between the radial and transverse directions. The characterization of anisotropic mechanical properties and isotropic energy absorption will inspire the exploration of bracket fungi as a viable alternative to applications in various industries, such as aerospace and agriculture., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Little is known about the mechanical and material properties of hyphae, the single constituent material of Agaricomycetes fungi, despite a growing interest in fungus-based materials. In the Agaricomycetes (the mushrooms and allies), there are three types of hyphae that make up sporocarps: generative, skeletal, and ligative. All filamentous Agaricomycetes can be categorized into one of three categories of hyphal systems that compose them: monomitic, dimitic, and trimitic. Monomitic systems have only generative hyphae. Dimitic systems have generative and either skeletal (most common) or ligative. Trimitic systems are composed of all three kinds of hyphae. SEM imaging, compression testing, and theoretical modeling were used to characterize the material and mechanical properties of representative monomitic, dimitic, and trimitic sporocarps. Compression testing revealed an increase in the compression modulus and compressive strength with the addition of more hyphal types (monomitic to dimitic and dimitic to trimitic). The mesostructure of the trimitic sporocarp was tested and modeled, suggesting that the difference in properties between the solid material and the microtubule mesostructure is a result of differences in structure and not material. Theoretical modeling was completed to estimate the mechanical properties of the individual types of hyphae and showed that skeletal hyphae make the largest contribution to mechanical properties of fungal sporocarps. Understanding the contributions of the different types of hyphae may help in the design and application of fungi-based or bioinspired materials. STATEMENT OF SIGNIFICANCE: This research studies the material and mechanical properties of fungal sporocarps and their hyphae, the single constituent material of Agaricomycetes fungi. Though some work has been done on fungal hyphae, this research studies hyphae in context of the three hyphal systems found in Agaricomycetes fungi and estimates the properties of the hyphal filaments, which has not been done previously. This characterization was performed by analyzing the structures and mechanical properties of fungal sporocarps and calculating the theoretical mechanical properties of their hyphae. This data and the resulting conclusions may lead to a better design and implementation process of fungi-based materials in various applications using the properties now known or calculated., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Armillaria ostoyae (Romagn.) Herink is a highly pathogenic fungus that uses exploratory, cordlike structures called rhizomorphs to seek out new sources of nutrition, posing a parasitic threat to natural stands of trees, orchards, and vineyards. Rhizomorphs are notoriously difficult to destroy, and this resilience is due in large part to a melanized layer that protects the rhizomorph. While this structure has been previously observed, its structural and chemical defenses are yet to be discerned. Research was conducted on both lab-cultured and wild-harvested rhizomorph samples. While both environments produce rhizomorphs, only the wild-harvested rhizomorphs produced the melanized layer, allowing for direct investigation of its structure and properties. Imaging, chemical analysis, mechanical testing, and finite element modeling were used to understand the defense mechanisms provided by the melanized layer. Imaging showed a porous outer layer in both types of rhizomorphs, though the pores were smaller in the harvested melanized layer. This melanized layer contained calcium, which provides chemical defense against both human and natural control methods, but was absent from cultured samples. Nanoindentation resulted in a larger variance of hardness values for cultured rhizomorphs than for wild-harvested. Finite element analysis proved that the smaller pore structure of the melanized porous layer had the best balance between maximum deformation and resulting permanent deformation. These results allow for a better understanding of the defenses of this pathogenic fungus, which may lead to better control methods., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

With the increasing demand for orthopedic and dental reconstruction surgeries, there comes a shortage of viable bone substitutes. This study was therefore designed to assess the efficacy of porous fluorohydroxyapatite (FHA) as a potential bone substitute. For this, porous FHA scaffolds were fabricated using the freeze casting technique. They were then sintered at 1250, 1350 and, 1450 °C, and microstructural, mechanical, and in vitro properties were analyzed. The microstructure analyses revealed the porosity remained constant within the temperature range. However, the pore size decreased with increasing sintering temperature. The greatest compressive strength and elastic modulus were obtained at 1450 °C, which were 13.5 ± 4.0 MPa and 379 ± 182 MPa, respectively. These are comparable values to human trabecular bone and other porous scaffolds made using hydroxyapatite. This analysis has thus helped to attain an understanding of the mechanical and material properties of freeze-cast FHA scaffolds that have not been presented before. In vitro studies revealed an increasing rate of human osteoblast cell proliferation on freeze-cast FHA scaffolds with increasing sintering temperature, suggesting improved osteogenic properties. Additionally, osteoblasts cells were also shown to proliferate into the interior pores of all freeze-cast FHA scaffolds. These results indicate the potential of porous FHA scaffolds fabricated using the freeze-casting technique to be utilized clinically as bone substitutes., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Woodpeckers peck at trees without any reported brain injury despite undergoing high impact loads. Amongst the adaptations allowing this is a highly functionalized impact-absorption system consisting of the head, beak, tongue and hyoid bone. This study aims to examine the anatomical structure, composition, and mechanical properties of the skull to determine its potential role in energy absorption and dissipation. An acorn woodpecker and a domestic chicken are compared through micro-computed tomography to analyze and compare two- and three-dimensional bone morphometry. Optical and scanning electron microscopy with energy dispersive X-ray spectroscopy are used to identify the structural and chemical components. Nanoindentation reveals mechanical properties along the transverse cross-section, normal to the direction of impact. Results show two different strategies: the skull bone of the woodpecker shows a relatively small but uniform level of closed porosity, a higher degree of mineralization, and a higher cortical to skull bone ratio. Conversely, the chicken skull bone shows a wide range of both open and closed porosity (volume fraction), a lower degree of mineralization, and a lower cortical to skull bone ratio. This structural difference affects the mechanical properties: the skull bones of woodpeckers are slightly stiffer than those of chickens. Furthermore, the Young's modulus of the woodpecker frontal bone is significantly higher than that of the parietal bone. These new findings may be useful to potential engineered design applications, as well as future work to understand how woodpeckers avoid brain injury., (Published by Elsevier Ltd.)

Magnetic freeze casting utilizes the freezing of water, a low magnetic field and surface magnetized materials to make multi-axis strengthened porous scaffolds. A much greater magnetic moment was measured for larger magnetized alumina platelets compared with smaller particles, which indicated that more platelet aggregation occurred within slurries. This led to more lamellar wall alignment along the magnetic field direction during magnetic freeze casting at 75 mT. Slurries with varying ratios of magnetized particles to platelets (0:1, 1:3, 1:1, 3:1, 7:1, 1:0) produced porous scaffolds with different structural features and degrees of lamellar wall alignment. The greatest mechanical enhancement in the magnetic field direction was identified in the synergistic condition with the highest particle to platelet ratio (7:1). Magnetic freeze casting with varying ratios of magnetized anisotropic and isotropic alumina provided insights about how heterogeneous morphologies aggregate within lamellar walls that impact mechanical properties. Fabrication of strengthened scaffolds with multi-axis aligned porosity was achieved without introducing different solid materials, freezing agents or additives. Resemblance of 7:1 particle to platelet scaffold microstructure to wood light-frame house construction is framed in the context of assembly inspiration being derived from both natural and synthetic sources., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Bone consists of a hard mineral phase and a compliant biopolymer phase resulting in a composite material that is both lightweight and strong. Osteoporosis that degrades spongy bone preferentially over time leads to bone brittleness in the elderly. A porous ceramic material that can mimic spongy bone for a one-time implant provides a potential solution for the future needs of an aging population. Scaffolds made by magnetic freeze casting resemble the aligned porosity of spongy bone. A magnetic field applied throughout freezing induces particle chaining and alignment of lamellae structures between growing ice crystals. After freeze drying to extract the ice and sintering to strengthen the scaffold, cubes from the scaffold center are mechanically compressed along longitudinal (z-axis, ice growth direction) and transverse (y-axis, magnetic field direction) axes. The best alignment of lamellar walls in the scaffold center occurs when applying magnetic freeze casting with the largest particles (350nm) at an intermediate magnetic field strength (75mT), which also agrees with stiffness enhancement results in both z and y-axes. Magnetic moments of different sized magnetized alumina particles help determine the ideal magnetic field strength needed to induce alignment in the scaffold center rather than just at the poles., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Unlabelled: Woodpeckers avoid brain injury while they peck at trees up to 20Hz with speeds up to 7m/s, undergoing decelerations up to 1200g. Along with the head, beak and neck, the hyoid apparatus (tongue bone and associated soft tissues) is subjected to these high impact forces. The shape of the hyoid apparatus is unusual in woodpeckers and its structure and mechanical properties have not been reported in detail. High-resolution X-ray micro-computed tomography and scanning electron microscopy with energy dispersive X-ray spectroscopy were performed and correlated with nanoindentation mapping. The hyoid apparatus has four distinct bone sections, with three joints between these sections. Nanoindentation results on cross-sectional regions of each bone reveal a previously unreported structure consisting of a stiff core and outer, more compliant shell with moduli of up to 27.4GPa and 8.5GPa, respectively. The bending resistance is low at the posterior section of the hyoid bones, indicating that this region has a high degree of flexibility to absorb impact. These new structural findings can be applied to further studies on the energy dissipation of the woodpecker during its drumming behavior, and may have implications for the design of engineered impact-absorbing structures., Statement of Significance: Woodpeckers avoid brain injury while they peck at trees, which results in extreme impact conditions. One common adaptation in woodpeckers is the unusual shape of the elongated tongue, also called the hyoid apparatus. The relationship between the structure and mechanical properties of the bony part of the hyoid apparatus has not been previously reported. A three dimensional model of the bony tongue was developed, and the hardness and stiffness were evaluated. A new type of bone structure, which is opposite of typical skeletal bone structure was found. The combined microstructural and mechanical property analysis indicate possible energy absorption routes for the hyoid apparatus and are applicable to the design of engineered structures., (Copyright © 2016 Acta Materialia Inc. All rights reserved.)

The processing technique of freeze casting has been intensely researched for its potential to create porous scaffold and infiltrated composite materials for biomedical implants and structural materials. However, in order for this technique to be employed medically or commercially, it must be able to reliably produce materials in great quantities with similar microstructures and properties. Here we investigate the reproducibility of the freeze casting process by independently fabricating three sets of eight ZrO2-epoxy composite scaffolds with the same processing conditions but varying solid loading (10, 15 and 20 vol.%). Statistical analyses (One-way ANOVA and Tukey's HSD tests) run upon measurements of the microstructural dimensions of these composite scaffold sets show that, while the majority of microstructures are similar, in all cases the composite scaffolds display statistically significant variability. In addition, composite scaffolds where mechanically compressed and statistically analyzed. Similar to the microstructures, almost all of their resultant properties displayed significant variability though most composite scaffolds were similar. These results suggest that additional research to improve control of the freeze casting technique is required before scaffolds and composite scaffolds can reliably be reproduced for commercial or medical applications., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Marine organisms have developed a wide variety of protective strategies to thrive in their native environments. These biological materials, although formed from simple biopolymer and biomineral constituents, take on many intricate and effective designs. The specific environmental conditions that shape all marine organisms have helped modify these materials into their current forms: complete hydration, and variation in hydrostatic pressure, temperature, salinity, as well as motion from currents and swells. These conditions vary throughout the ocean, being more consistent in the pelagic and deep benthic zones while experiencing more variability in the nearshore and shallows (e.g. intertidal zones, shallow bays and lagoons, salt marshes and mangrove forests). Of note, many marine organisms are capable of migrating between these zones. In this review, the basic building blocks of these structural biological materials and a variety of protective strategies in marine organisms are discussed with a focus on their structure and mechanical properties. Finally, the bioinspired potential of these biological materials is discussed., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The boxfish (Lactoria cornuta) has a carapace consisting of dermal scutes with a highly mineralized surface plate and a compliant collagen base. This carapace must provide effective protection against predators as it comes at the high cost of reduced mobility and speed. The mineralized hydroxyapatite plates, predominantly hexagonal in shape, are reinforced with raised struts that extend from the center toward the edges of each scute. Below the mineralized plates are non-mineralized collagen fibers arranged in through-the-thickness layers of ladder-like formations. At the interfaces between scutes, the mineralized plates form suture-like teeth structures below which the collagen fibers bridge the gap between neighboring scutes. These sutures are unlike most others as they have no bridging Sharpey's fibers and appear to add little mechanical strength to the overall carapace. It is proposed that the sutured interface either allows for accommodation of the changing pressures of the boxfish's ocean habitat or growth, which occurs without molting or shedding. In both tension and punch testing the mineralized sutures remain relatively intact while most failures occur within the collagen fibers, allowing for the individual scutes to maintain their integrity. This complex structure allows for elevated strength of the carapace through an increase in the stressed area when attacked by predators in both penetrating and crushing modes., (Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)