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Current environmental crisis calls for new sustainable materials and products. Mycelium-based materials are grown by fungi onto solid ligno-cellulosic substrates and are promising sustainable materials which still face barriers to entry. This review discusses the challenges and prospects for making mycelium products. First, the technical challenges, properties needs and scientific knowledge gaps are reviewed. Then, methods to tailor the performance of mycelium-based materials are proposed, using synthetic or natural means. Living mycelium-based materials are also considered as an interesting alternative. The potential market opportunities for these products and their distribution are also discussed along with the public acceptance and perception. Overall, this paper complements current reviews on mycelium materials fabrication and properties by highlighting key gaps and challenges to address to allow these materials to enter the market. The paper suggests directions of future research and development for including mycelium-based products in daily life and improving the sustainability of the materials commonly used and their production. • One barrier to entry for mycelium products is their biodegradability. • Mycelium products could be made competitive thanks to their biodegradability. • Mycelium materials' properties can be tailored using synthetic or natural means. • Mycelium-based materials can also be used as living engineering materials. • Positive public perception could increase by adopting holistic views of the world. [ABSTRACT FROM AUTHOR]

Ceramic materials are ubiquitous in technologies operating under high mechanical, thermal or chemical constrains. Research in ceramic processing aims at creating ceramics with properties that are still challenging to obtain, such as toughness, transparency, conductivity, among others. Magnetic slip casting is a process where an external magnetic field is used to createcontrolled texture in ceramics. Over the past 20 years of research on magnetic slip casting, dense and textured ceramics of multiple chemistry were found to exhibit enhanced properties. This paper reviews the progress in the field of magnetic slip casting, details the processing parameters and the textures obtained for a diverse range of compositions. The structural and functional properties of the magnetically textured slip casted and sintered ceramics are presented. This overview of the magnetic slip casting process allows to identify critical directions for future advancement in advanced technical ceramics. [ABSTRACT FROM AUTHOR]

The architectures of biological hard materials reveal finely tailored complex assemblies of mineral crystals. Numerous recent studies associate the design of these local assemblies with impressive macroscopic response. Reproducing such exquisite control in technical ceramics conflicts with commonly used processing methods. Here, we circumvent this issue by combining the recently developed Magnetically Assisted Slip Casting (MASC) technique with the well‐established process of templated grain growth (TGG). MASC enables the local control over the orientation of platelets dispersed among smaller isotropic particles. After a high‐temperature pressureless heat treatment, the grains of the final ceramic follow the same orientation as of the initial platelets. This combination allows us to produce 95% dense alumina part with a grain orientation following any deliberate orientation. We successfully fabricated microstructures inspired from biological materials with ceramics that present periodically varying patterns with a programmable pitch down to a few tens of micrometers. The periodically textured dense ceramics exhibit matching variation of local hardness, confirming the capacity of the process to tailor local properties. This unique micrometer scale control over the local mechanical properties could be applied to adapt ceramic structures to complex loads using this inexpensive and scalable process. In systems where functional properties also depend on anisotropic grain orientation, the principle presented here could enable the creation of new multifunctional ceramics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single fungal hyphae increase in stiffness with time, up to 5 GPa. • Increase in mycelium density increases the mechanical properties of the composite. • Woodpiles porous structures lead to increased dense mycelium skin growth. • Woodpiles porous structures increase the stiffness by 6 times after 28 days mycelium growth. • Structural design in porous structure is an efficient method to improve the properties of growing bio-based materials. Mycelium-bound composites are biodegradable, eco-friendly materials grown by fungi onto solid ligno-cellulosic substrates. Mycelium is an interconnected network made of fungal cells that bind the substrates' particulates together. Uncompressed mycelium-bound composites have typically weak mechanical properties, similar to that of expanded polystyrene. In this paper, mycelium is grown onto porous woodpile struts structures to increase the final mechanical properties. The hypothesis is that increase in porosity can increase oxygen diffusion throughout the material and increase the development of dense mycelium network. Mycelium-bound composites grown from P. ostreatus onto bamboo microfibers substrates were studied to test this hypothesis. Constructing porous woodpile structures and monitoring the growth and the mechanical properties under compression, it was found that the porosity obtained through the design was able to increase dense fungal mycelium skin formation. As a result, the stiffness of the porous structures was multiplied by 6 after 28 days of growth. The specific modulus was in turned multiplied by 4 with the addition of 30 % macroscopic porosity. Despite the modest mechanical properties (stiffness about 0.5 MPa), the approach proposed illustrates how appropriate structural design can efficiently increase the properties of grown bio-based materials. [ABSTRACT FROM AUTHOR]

Natural composites are often heterogeneous to fulfil functional demands. Manufacturing analogous materials remains difficult, however, owing to the lack of adequate and easily accessible processing tools. Here, we report an additive manufacturing platform able to fabricate complex-shaped parts exhibiting bioinspired heterogeneous microstructures with locally tunable texture, composition and properties, as well as unprecedentedly high volume fractions of inorganic phase (up to 100%). The technology combines an aqueous-based slip-casting process with magnetically directed particle assembly to create programmed microstructural designs using anisotropic stiff platelets in a ceramic, metal or polymer functional matrix. Using quantitative tools to control the casting kinetics and the temporal pattern of the applied magnetic fields, we demonstrate that this approach is robust and can be exploited to design and fabricate heterogeneous composites with thus far inaccessible microstructures. Proof-of-concept examples include bulk composites with periodic patterns of microreinforcement orientation, and tooth-like bilayer parts with intricate shapes exhibiting site-specific composition and texture. [ABSTRACT FROM AUTHOR]

Biomimicry is an interdisciplinary design approach that provides solutions to engineering problems by taking inspiration from nature. Given the established importance of biomimicry for building a sustainable world, there is a need to develop effective curricula on this topic. In this study, a workshop was conducted twice in Singapore: once with 14 students from a local high school in Singapore, and once with 11 undergraduate students in engineering from the United States. The workshop aimed to better understand how students conceptualize biomimicry following the bottom-up and top-down biomimetic methods. The workshop contained a lecture and laboratory session, and data were collected via questionnaires, field observation, and participant presentations at the end of the laboratory session. A qualitative analysis revealed that the top-down biomimetic approach was initially understood using vague and generic terms. In contrast, the students described the bottom-up approach using precise and technical vocabulary. By naming the themes highlighting the students' conceptualizations, it was concluded that strengthening the principle that makes the natural object unique and increasing interdisciplinary knowledge are needed to help them perform the top-down approach. The results from this work should be confirmed with a more significant number of participants, and they could help develop a curriculum to teach the two approaches effectively by providing tools to help the students generalize their ideas and abstract meaning from systems. [ABSTRACT FROM AUTHOR]

Textured alumina ceramics with brick‐and‐mortar microstructures exhibit surprisingly high values of strength and toughness as compared to traditional ceramics. However, in full ceramic systems, pressure‐assisted sintering restricts their shaping potential, and the study of interfacial materials is still insufficient. Here, we fabricate textured alumina exhibiting elevated indentation fracture toughness using a high entropy oxide (HEO) (MgAlSiTiZr)O as the mortar. The HEO undergoes a single‐phase transformation at 1600°C, resulting in a crystallographic structure identical to that of ZrO2. Our HEO mortar is tough and has a high wetting behavior to alumina platelets used in the green body, which promotes densification via liquid phase sintering. Textured alumina ceramics with HEO mortar at concentrations varying from 0 to 90 wt% were fabricated using magnetically assisted slip casting and pressureless sintering through the templated grain growth process. A trade‐off between density and grain anisotropy led to the highest mechanical properties. Textured alumina with 10 wt% HEO exhibited over 95% relative density, an elastic modulus of 244 ± 29 GPa, a flexural strength of 329 ± 27 MPa, and an indentation fracture toughness of 6.80 ± 0.65 MPa∙m0.5, which is more than 1.9 times that of the usual polycrystalline alumina. Thanks to the mineral nature of HEO, the simplicity of the process, and the mechanical properties, the textured alumina with HEO mortar can be produced in complex shapes and could find applications in stringent environments. [ABSTRACT FROM AUTHOR]

Dense ceramics are irreplaceable in applications requiring high mechanical stiffness, chemical and temperature resistance and low weight. To improve their toughness, ceramics can be reinforced with elongated inclusions. Recent manufacturing strategies have been developed to control the orientations of disc-like microparticles in polymeric and ceramic matrices and to build periodic microstructures. Given the infinite number of possible microstructures available, modeling tools are required to select the potentially best design. Periodic microstructures can be involved in elastic wave scattering to dissipate mechanical energy from vibrations. In this paper, a model is proposed to determine the frequency bandgaps associated to periodic architectures in composites and ceramics and the influence of microstructural parameters are investigated. The results are used to define guidelines for the future fabrication of hard bulk ceramic materials that combine traditional ceramic's properties with high vibration resistance. [ABSTRACT FROM AUTHOR]

Crystallographic texture engineering in ceramics is essential to achieve direction-specific properties. Current texture engineering methods are time-consuming, energy extensive, or can lead to unnecessary diffusion of added dopants. Herein, we explore ultrafast high-temperature sintering (UHS) to prepare dense and textured alumina using templated grain growth (TGG). From a slurry containing alumina microplatelets coated with Fe 3 O 4 nanoparticles dispersed in a matrix of alumina nanoparticles, green bodies with oriented microplatelets were prepared using magnetic assisted slip casting (MASC). The effects of the sintering temperature, time and heating rate on the density and microstructure of the obtained ceramics were then studied. We found that TGG occurs for a temperature range between 1640 and 1780 °C and 10 s sintering time. Sintering at 1700 °C for 10 s led to dense and textured alumina with anisotropic grains thanks to the Fe 3 O 4 coating, which did not have the time to diffuse. The highest texture and relative density were obtained with a heating rate of ~5500 °C/min, leading to texture-dependent anisotropic mechanical properties. This study opens new avenues for fabricating textured ceramics in ultra-short times. [ABSTRACT FROM AUTHOR]

Mycelium-bound composites (MBCs) are materials obtained by growing fungi on a ligno-cellulosic substrate which have various applications in packaging, furniture, and construction industries. MBCs are particularly interesting as they are sustainable materials that can integrate into a circular economy model. Indeed, they can be subsequently grown, used, degraded, and re-grown. Integrating in a meaningful biocycle for our society therefore demands that MBCs fulfil antagonistic qualities which are to be at the same time durable and biodegradable. In this study, we conduct experiments using MBCs made from the fungus species Pleurotus ostreatus grown on bamboo microfibers substrate. By measuring the variations of the mechanical properties with time, we provide an experimental demonstration of a biocycle for such composites for in-door applications. We found that the biocycle can be as short as 5 months and that the use of sustainable coatings is critical to increase the durability of the composites while maintaining biodegradability. Although there are many scenarios of biocycles possible, this study shows a tangible proof-of-concept example and paves the way for optimization of the duration of each phase in the biocycle depending on the intended application and resource availability. [ABSTRACT FROM AUTHOR]

Mycelium-bound composites (MBCs) are materials obtained by growing fungi on a ligno-cellulosic substrate which have various applications in packaging, furniture, and construction industries. MBCs are particularly interesting as they are sustainable materials that can integrate into a circular economy model. Indeed, they can be subsequently grown, used, degraded, and re-grown. Integrating in a meaningful biocycle for our society therefore demands that MBCs fulfil antagonistic qualities which are to be at the same time durable and biodegradable. In this study, we conduct experiments using MBCs made from the fungus species Pleurotus ostreatus grown on bamboo microfibers substrate. By measuring the variations of the mechanical properties with time, we provide an experimental demonstration of a biocycle for such composites for in-door applications. We found that the biocycle can be as short as 5 months and that the use of sustainable coatings is critical to increase the durability of the composites while maintaining biodegradability. Although there are many scenarios of biocycles possible, this study shows a tangible proof-of-concept example and paves the way for optimization of the duration of each phase in the biocycle depending on the intended application and resource availability. [ABSTRACT FROM AUTHOR]

The transition from a linear to a circular economy is urgently needed to mitigate environmental impacts and loss of biodiversity. Among the many potential solutions, the development of entirely natural-based materials derived from waste is promising. One such material is mycelium-bound composites obtained from the growth of fungi onto solid lignocellulosic substrates, which find applications such as insulating foams, textiles, packaging, etc. During growth, the fungus degrades and digests the substrate to create a web-like stiff network called mycelium. The development of the mycelium is influenced by several factors, including the substrate composition. As food waste accounts for nearly 44% of total municipal solid waste, incorporating food in the substrate composition could be a means to increase the nutrients absorbed by the fungus. In this paper, we study the effects of the addition of food supplements on the growth of two fungal species, Ganoderma lucidum and Pleurotus ostreatus. The substrates, the food supplements, and the mycelia are characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, and optical microscopy. Our results show that addition of barley as a supplement significantly boosts the growth of G. lucidum and P. ostreatus. Using a common food as a nutritious enrichment for the development of mycelium is a simple and straightforward strategy to create waste-based mycelium-bound biocomposites for a large range of applications, on-site, therefore promoting a circular economy. [ABSTRACT FROM AUTHOR]

[Display omitted] • An organic waste-based ink was developed for 3D printing of mycelium-based engineered living materials (ELMs) in non-sterile conditions. • Mycelium growth and density improves with increasing nutrient content, which improves the mechanical strength of the 3D printed structure. • 3D printed mycelium-based ELMs exhibit self-healing behaviour. • 3D printed mycelium-based ELMs have the potential to act as a glue, joining different compatible materials together. There is an urgent need to change the way society produces and fabricates materials. Among the sustainable processes developed to date, 3D printing enables limited generation of waste. Living materials that are grown by microorganisms are also an interesting approach to fabricate biodegradable materials sustainably. 3D printing of living materials is nevertheless challenged by a high barrier to entry due to stringent sterilization requirements. In this study, the authors use a waste ingredient, coffee grounds, to fabricate mycelium materials using 3D printing in ambient conditions. Mycelium is the vegetative parts of the fungi which forms an interconnected network, covering air-material interfaces with a dense skin. An agar gel was chosen as the printing medium and supplemented with coffee grounds, malt and peptone to double the growth rate and density of the mycelium by Pleurotus ostreatus. Despite the jelly nature of the agar-based ink, 3D printing with a resolution of about 1 mm could be achieved using direct ink writing. The growth of the mycelium embedded in the ink was studied over 28 days and demonstrated that the mycelium was efficient in reinforcing the printed part, doubling its compressive modulus up to 60 kPa. Furthermore, the objects created by this ink exhibit self-healing and can be used for gluing components together. The approach taken in this work could be adapted by the user to accommodate for functionality requirements and the available local resources, thereby addressing some of the most pressing sustainable development goals. [ABSTRACT FROM AUTHOR]

Texture in ceramics can enhance their functional and structural properties. Current methods for texturation in dense ceramics employ plate-like particles or microplatelets as starting powders and processes that drive their orientation into specific directions. Using ultra-low magnetic fields combined with slip casting, it is possible to purposely orient magnetically responsive particles in any direction. Here, we explore the application of magnetic slip casting to bimodal slurries containing alumina nanoparticles and alumina microplatelets of various dimensions to create texture in ceramics with different grain sizes. After sintering, the obtained ceramics show anisotropic grains with controllable orientations, grain length of 3–7 μm, mild open porosity between 30–40 %, and interesting cracking behavior. Textured porous ceramics with tunable grain dimensions and orientations are promising for filtering, biomedical or composite applications. [ABSTRACT FROM AUTHOR]

Biomineralization, the process by which mineralized tissues grow and harden via biogenic mineral deposition, is a relatively lengthy process in many mineral-producing organisms, resulting in challenges to study the growth and biomineralization of complex hard mineralized tissues. Arthropods are ideal model organisms to study biomineralization because they regularly molt their exoskeletons and grow new ones in a relatively fast timescale, providing opportunities to track mineralization of entire tissues. Here, we monitored the biomineralization of the mantis shrimp dactyl club--a model bioapatite-based mineralized structure with exceptional mechanical properties--immediately after ecdysis until the formation of the fully functional club and unveil an unusual development mechanism. A flexible membrane initially folded within the club cavity expands to form the new club's envelope. Mineralization proceeds inwards by mineral deposition from this membrane, which contains proteins regulating mineralization. Building a transcriptome of the club tissue and probing it with proteomic data, we identified and sequenced Club Mineralization Protein 1 (CMP-1), an abundant mildly phosphorylated protein from the flexible membrane suggested to be involved in calcium phosphate mineralization of the club, as indicated by in vitro studies using recombinant CMP-1. This work provides a comprehensive picture of the development of a complex hard tissue, from the secretion of its organic macromolecular template to the formation of the fully functional club. [ABSTRACT FROM AUTHOR]

Disk-shaped microparticles experience an acoustic radiation force and torque in an ultrasonic standing wave. Hence, they are translated by the acoustic field, an effect called acoustophoresis, and rotated. The torque effect is also known from the "Rayleigh disk" which is described in literature for sound intensity measurements. In this paper, inviscid numerical simulations of acoustic radiation forces and torques for disks with radius ≪ wavelength in water are developed in good agreement with former analytical solutions, and the dependence on disk geometry, density, and orientation is discussed. Experiments with alumina disks (diameter 7.5 µm), suspended in an aqueous liquid in a silicon microchannel, confirm the theoretical results qualitatively at the microscale and ultrasonic frequencies around 2 MHz. These results can potentially be applied for the synthesis of disk-reinforced composite materials. The insights are also relevant for the acoustic handling of various disk-shaped particles, such as red blood cells. [ABSTRACT FROM AUTHOR]

Reinforced composites with controlled microstructure can achieve exceptional mechanical and functional properties. In recent years, scientists have placed in substantial efforts to fabricate reinforced composites with astounding properties through the design of these microstructures. To better understand the structure-property relationships of these materials, it is essential to characterise their microstructural features. However, standard characterisation techniques such as electron-based imaging are costly, time-consuming, and restricted to small-scale samples. In this work, we present a simple, inexpensive, and high-throughput alternative method to assess the surface microstructure of microplatelet reinforced composites. The method relies on directional reflectance microscopy (DRM), an optical technique that enables mapping of the filler orientation and weight fraction in these composites using surface reflectance data. We demonstrate the effective use of DRM on reflective microplatelet-reinforced polymeric composites that we prepared using 3D printing and mould casting techniques. Our experimental results showcase the potential of DRM as a high-throughput method to assess microstructural information in reinforced composites. This information could be used to understand how the microplatelets' alignments influence the materials' properties for devising new composite designs. [Display omitted]. [ABSTRACT FROM AUTHOR]

Natural ceramic composites present complex microstructures that lead to tortuous crack paths and confer them high toughness. Current microreinforced composites do not yet reach the same level of complexity in their microstructures, resulting in poorer properties. To achieve complex microstructuration, magnetically-assisted slip casting (MASC) was conducted using a setup with 4 degrees of freedom. Among all possible microstructures, a hybrid design between nacre-like and helicoidal arrangements was selected due to its ability to tilt and twist the crack path. The hybrid microstructured specimens fabricated, consisting of aluminum oxide microplatelets in a silicone matrix, were tested under compression and their mechanical performance compared. Although nacre-like composites exhibited the highest strength and toughness, helicoidal hybrids could show some ductility and higher stiffness. The fabrication strategy proposed here could thus be a simple route to study more complex microstructures in view of increasing the toughness of microplatelet reinforced composites. • Natural materials exhibit complex crack deflection paths that increase their toughness. • Hybrid microstructures between nacre-like and helicoidal arrangements were created. • PDMS composites with hybrid microstructures were tested under compression. • The hybrid microstructures at 90 ° angle had a high ductility at failure while being stiff. [ABSTRACT FROM AUTHOR]

4D printing empowers 3D printed structures made of hydrogels, liquid crystals or shape memory polymers, with reversible morphing capabilities in response to an external stimulus. To apply reversible shape-change to stiff lightweight materials such as microfiber reinforced polymers, we developed a composite ink that can be printed using direct-ink-writing (DIW), and that exhibits multistability around its glass transition temperature. After curing at room temperature, the flat print thermally morphs into a predefined shape upon heating at an actuation temperature and cooling down. The sample can then reversibly snap between multiple stable shapes when heated above its glass transition temperature thanks to pre-stress-induced multistability. The key that allows thermal morphing and pre-stress multistability is the microstructuring of the 3D printed composites by shear-induced alignment of reinforcing microfibers. This alignment leads to local anisotropy in thermomechanical properties and the build-up of pre-stresses. Furthermore, the ink composition can be tuned to generate shape-dependant reversible functional properties, such as electrical conductivity. Based on finite element modelling and experimental results, the method proposed here can be used for variety of compositions and designs, for applications where stiffness, reconfigurability and shape-dependent functionalities can be exploited. [Display omitted] [ABSTRACT FROM AUTHOR]

Mycelium-bound composites are promising materials for sustainable packaging, insulation, fashion, and architecture. However, moulding is the main fabrication process explored to date, strongly limiting the ability to design the complex shapes that could widen the range of applications. Extrusion is a facile and low energy-cost process that has not yet been explored for mycelium-bound composites with design freedom and structural properties. In this study, we combine cheap, easily and commonly available agricultural waste materials, bamboo microfibres, chitosan, and mycelium from Ganoderma l ucidum, to establish a composite mixture that is workable, extrudable and buildable. We study the impact of bamboo fibre size, chitosan concentration, pH and weight ratio of bamboo to chitosan to determine the optimum growth condition for the mycelium as well as high mechanical stiffness. The resulting materials have thus low energy costs, are sustainable and can be shaped easily. The developed composition is promising to further explore the use of mycelium-bound materials for structural applications using agricultural waste. Unlabelled Image • Mycelium-bound composites are sustainable alternative to current composites used in architecture, for example. • Having an extrudable composition to build mycelium-bound composites allows complex shaping and designing. • Chitosan addition to bamboo fibres provides workability, extrudability and buildability while allowing mycelium growth. [ABSTRACT FROM AUTHOR]