Fiber-reinforced polymers are widely used as lightweight materials in aircraft, automobiles, wind turbine blades, and sports products. Despite the beneficial weight reduction achieved in such applications, these composites often suffer from poor recyclability and limited geometries. 3D printing of liquid crystal polymers into complex-shaped all-fiber materials is a promising approach to tackle these issues and thus increase the sustainability of current lightweight structures. Here, we report a spin-printing technology for the manufacturing of recyclable and strong all-fiber lightweight materials. All-fiber architectures are created by combining thick print lines and thin spun fibers as reinforcing elements in bespoke orientations. Through controlled extrusion experiments and theoretical analyses, we systematically study the spinning process and establish criteria for the generation of thin fibers and laminates with unprecedented mechanical properties. The potential of the technology is further illustrated by creating complex structures with unique all-fiber architectures and mechanical performance.@en

Monolithic aerogels composed of crystalline nanoparticles enable photocatalysis in three dimensions, but they suffer from low mechanical stability and it is difficult to produce them with complex geometries. Here, an approach to control the geometry of the photocatalysts to optimize their photocatalytic performance by introducing carefully designed 3D printed polymeric scaffolds into the aerogel monoliths is reported. This allows to systematically study and improve fundamental parameters in gas phase photocatalysis, such as the gas flow through and the ultraviolet light penetration into the aerogel and to customize its geometric shape to a continuous gas flow reactor. Using photocatalytic methanol reforming as a model reaction, it is shown that the optimization of these parameters leads to an increase of the hydrogen production rate by a factor of three from 400 to 1200 µmol g−1 h−1. The rigid scaffolds also enhance the mechanical stability of the aerogels, lowering the number of rejects during synthesis and facilitating handling during operation. The combination of nanoparticle-based aerogels with 3D printed polymeric scaffolds opens up new opportunities to tailor the geometry of the photocatalysts for the photocatalytic reaction and for the reactor to maximize overall performance without necessarily changing the material composition.@en

Structural materials such as metals and fibre-reinforced plastics are stiff engineering materials used in many industrial fields. However, their high stiffness leads usually to the inability to dissipate energy via vibration damping. Contrarily, compliant materials such as rubbers and soft polymers exhibit an excellent damping behaviour, but lack in stiffness. Natural composites, such as wood, bone and seashells possess both high stiffness and high damping and thus combine properties that are generally mutually exclusive. In this study, the design principles of two biological composites, i.e. nacre and wood, were studied to design composites out of engineering materials which display a damping behaviour like the natural systems and are producible on a larger scale. The dynamic properties of nacre-inspired epoxy and flax fibre-reinforced composites were investigated and compared to structural engineering materials and to the biological materials served for the inspiration.@en

Structural materials such as metals and fibre-reinforced plastics are stiff engineering materials used in many industrial fields. However, their high stiffness leads usually to the inability to dissipate energy via vibration damping. Contrarily, compliant materials such as rubbers and soft polymers exhibit an excellent damping behaviour, but lack in stiffness. Natural composites, such as wood, bone and seashells possess both high stiffness and high damping and thus combine properties that are generally mutually exclusive. In this study, the design principles of two biological composites, i.e. nacre and wood, were studied to design composites out of engineering materials which display a damping behaviour like the natural systems and are producible on a larger scale. The dynamic properties of nacre-inspired epoxy and flax fibre-reinforced composites were investigated and compared to structural engineering materials and to the biological materials served for the inspiration.@en

Structural materials such as metals and fibre-reinforced plastics are stiff engineering materials used in many industrial fields. However, their high stiffness leads usually to the inability to dissipate energy via vibration damping. Contrarily, compliant materials such as rubbers and soft polymers exhibit an excellent damping behaviour, but lack in stiffness. Natural composites, such as wood, bone and seashells possess both high stiffness and high damping and thus combine properties that are generally mutually exclusive. In this study, the design principles of two biological composites, i.e. nacre and wood, were studied to design composites out of engineering materials which display a damping behaviour like the natural systems and are producible on a larger scale. The dynamic properties of nacre-inspired epoxy and flax fibre-reinforced composites were investigated and compared to structural engineering materials and to the biological materials served for the inspiration.@en

Structural materials such as metals and fibre-reinforced plastics are stiff engineering materials used in many industrial fields. However, their high stiffness leads usually to the inability to dissipate energy via vibration damping. Contrarily, compliant materials such as rubbers and soft polymers exhibit an excellent damping behaviour, but lack in stiffness. Natural composites, such as wood, bone and seashells possess both high stiffness and high damping and thus combine properties that are generally mutually exclusive. In this study, the design principles of two biological composites, i.e. nacre and wood, were studied to design composites out of engineering materials which display a damping behaviour like the natural systems and are producible on a larger scale. The dynamic properties of nacre-inspired epoxy and flax fibre-reinforced composites were investigated and compared to structural engineering materials and to the biological materials served for the inspiration.@en

Structural materials such as metals and fibre-reinforced plastics are stiff engineering materials used in many industrial fields. However, their high stiffness leads usually to the inability to dissipate energy via vibration damping. Contrarily, compliant materials such as rubbers and soft polymers exhibit an excellent damping behaviour, but lack in stiffness. Natural composites, such as wood, bone and seashells possess both high stiffness and high damping and thus combine properties that are generally mutually exclusive. In this study, the design principles of two biological composites, i.e. nacre and wood, were studied to design composites out of engineering materials which display a damping behaviour like the natural systems and are producible on a larger scale. The dynamic properties of nacre-inspired epoxy and flax fibre-reinforced composites were investigated and compared to structural engineering materials and to the biological materials served for the inspiration.@en

Structural materials combining high stiffness and damping capabilities are in high demand for passive damping applications in vibration control, precision manufacturing, and resilient buildings. However, the development of enhanced passive damping materials with high stiffness at low weight has been hindered by the mutually excluding nature of these mechanical properties. Motivated by the mechanical performance of biological materials such as bone and nacre, we exploit a simple casting and magnetically assisted manufacturing process to fabricate platelet-reinforced polymers with a stiff and damping staggered architecture. Dynamic mechanical analysis of our staggered architectures reveals an increase in the stiffness of the composites by a factor up to 4.5 while maintaining the strong damping response of the host polymer. Using an established micromechanical model, we can predict the damping figure of merit of such composites and provide guidelines for the creation of stiff and damping bio-inspired structures while considering boundary conditions of the manufacturing process. By reaching mechanical performance superior or comparable to bone and nacre, our bio-inspired strategy proves to be a promising pathway for the further development of low-power passive damping materials. @en

Lightweight biological materials such as bone, silk and wood demonstrate complex hierarchically structured shapes with outstanding mechanical properties by utilising directed self-assembly to grow structures. Here1, we demonstrate a bioinspired 3D printing approach to create lightweight structures with hierarchical architectures, complex geometries and unprecedented stiffness and toughness. Using the self-assembly of liquid crystal polymer molecules combined withorienting the molecular domains with the print path, we can reinforce the polymer according to the expected mechanical stresses. The resulting material is recyclable and leads to stiffness, strength and toughness that outperform state-ofthe- art 3D printed polymers by an order of magnitude and rival even high-performance composites. Thermotropic LCPs form nematic liquid crystalline domains when molten. These domains can be aligned in the FDM nozzle along the extrusion direction. After exiting the nozzle, solidification stops the thermal reorientation of the molecules due to the cessation of flow resulting in a skin-core morphology. The maximal Young’s modulus and strength were achieved when printing parallel (0°) to the loading direction (17 GPa stiffness and 400 MPa strength). The dependence of the modulus on the print direction can successfully be predicted using a classical laminate theory approach. It is possible to adapt the local material architecture to the specific loading conditions that are applied to the part by designing the filament deposition direction during 3D printing. We show 3D printed objects with stressadapted print line architecture with mechanical properties that are much stronger than state-of-the-art 3D printed polymers and rival the highest performance lightweight materials using a readily available polymer and a commercial desktop printer. In addition, we present a new approach to combine conventional 3D printing with in-situ spinning of fibres. By controlling the volume of molten polymer at the nozzle tip and rapidly translating the printhead, we are able to spin fibres with diameters down to 20 um, reaching tensile strength and Young’s modulus as high as 2.6 GPa and 208 GPa, respectively. These values are comparable to those of carbon fibres, which require energy-intensive fabrication processes. By spin-printing complex-shaped structures with unusual fibre-reinforcing architectures, we show that this new manufacturing platform opens new opportunities for the design and fabrication of lightweight parts combining recyclability and high mechanical performance. @en

Lightweight biological materials such as bone, silk and wood demonstrate complex hierarchically structured shapes with outstanding mechanical properties by utilising directed self-assembly to grow structures. Here1, we demonstrate a bioinspired 3D printing approach to create lightweight structures with hierarchical architectures, complex geometries and unprecedented stiffness and toughness. Using the self-assembly of liquid crystal polymer molecules combined withorienting the molecular domains with the print path, we can reinforce the polymer according to the expected mechanical stresses. The resulting material is recyclable and leads to stiffness, strength and toughness that outperform state-ofthe- art 3D printed polymers by an order of magnitude and rival even high-performance composites. Thermotropic LCPs form nematic liquid crystalline domains when molten. These domains can be aligned in the FDM nozzle along the extrusion direction. After exiting the nozzle, solidification stops the thermal reorientation of the molecules due to the cessation of flow resulting in a skin-core morphology. The maximal Young’s modulus and strength were achieved when printing parallel (0°) to the loading direction (17 GPa stiffness and 400 MPa strength). The dependence of the modulus on the print direction can successfully be predicted using a classical laminate theory approach. It is possible to adapt the local material architecture to the specific loading conditions that are applied to the part by designing the filament deposition direction during 3D printing. We show 3D printed objects with stressadapted print line architecture with mechanical properties that are much stronger than state-of-the-art 3D printed polymers and rival the highest performance lightweight materials using a readily available polymer and a commercial desktop printer. In addition, we present a new approach to combine conventional 3D printing with in-situ spinning of fibres. By controlling the volume of molten polymer at the nozzle tip and rapidly translating the printhead, we are able to spin fibres with diameters down to 20 um, reaching tensile strength and Young’s modulus as high as 2.6 GPa and 208 GPa, respectively. These values are comparable to those of carbon fibres, which require energy-intensive fabrication processes. By spin-printing complex-shaped structures with unusual fibre-reinforcing architectures, we show that this new manufacturing platform opens new opportunities for the design and fabrication of lightweight parts combining recyclability and high mechanical performance. @en

Researchers produce inorganic scaffolds using magnetic assembly to align preformed heterogeneous ceramic bricks, which are hot-pressed and infiltrated with an organic phase to generate a strong and tough composite that has a nacre-like brick-andmortar structure, interconnected with submicron interplatelet mineral bridges. The pioneering aspect of this study is the use of alumina platelets that are precoated with a ceramic layer that sinters at a lower temperature compared to the sintering temperature of the alumina platelets. Using precoated alumina platelets significantly minimize the processing time and material heterogeneity, which are commonly observed in fabrication processes that rely in co-sedimentation of particles exhibiting different size and density.@en

Researchers produce inorganic scaffolds using magnetic assembly to align preformed heterogeneous ceramic bricks, which are hot-pressed and infiltrated with an organic phase to generate a strong and tough composite that has a nacre-like brick-andmortar structure, interconnected with submicron interplatelet mineral bridges. The pioneering aspect of this study is the use of alumina platelets that are precoated with a ceramic layer that sinters at a lower temperature compared to the sintering temperature of the alumina platelets. Using precoated alumina platelets significantly minimize the processing time and material heterogeneity, which are commonly observed in fabrication processes that rely in co-sedimentation of particles exhibiting different size and density.@en

Porosity is an essential feature in a wide range of applications that combine light weight with high surface area and tunable density. Porous materials can be easily prepared with a vast variety of chemistries using the salt-leaching technique. However, this templating approach has so far been limited to the fabrication of structures with random porosity and relatively simple macroscopic shapes. Here, a technique is reported that combines the ease of salt leaching with the complex shaping possibilities given by additive manufacturing (AM). By tuning the composition of surfactant and solvent, the salt-based paste is rheologically engineered and printed via direct ink writing into grid-like structures displaying structured pores that span from the sub-millimeter to the macroscopic scale. As a proof of concept, dried and sintered NaCl templates are infiltrated with magnesium (Mg), which is typically highly challenging to process by conventional AM techniques due to its highly oxidative nature and high vapor pressure. Mg scaffolds with well-controlled, ordered porosity are obtained after salt removal. The tunable mechanical properties and the potential to be predictably bioresorbed by the human body make these Mg scaffolds attractive for biomedical implants and demonstrate the great potential of this additive technique.@en

Biological living materials, such as animal bones and plant stems, are able to self-heal, regenerate, adapt and make decisions under environmental pressures. Despite recent successful efforts to imbue synthetic materials with some of these remarkable functionalities, many emerging properties of complex adaptive systems found in biology remain unexplored in engineered living materials. Here, we describe a three-dimensional printing approach that harnesses the emerging properties of fungal mycelia to create living complex materials that self-repair, regenerate and adapt to the environment while fulfilling an engineering function. Hydrogels loaded with the fungus Ganoderma lucidum are three-dimensionally printed into lattice architectures to enable mycelial growth in a balanced exploration and exploitation pattern that simultaneously promotes colonization of the gel and bridging of air gaps. To illustrate the potential of such mycelium-based living complex materials, we three-dimensionally print a robotic skin that is mechanically robust, self-cleaning and able to autonomously regenerate after damage.@en

Porous materials are relevant for a broad range of technologies from catalysis and filtration, to tissue engineering and lightweight structures. Controlling the porosity of these materials over multiple length scales often leads to enticing new functionalities and higher efficiency but has been limited by manufacturing challenges and the poor understanding of the properties of hierarchical structures. Here, we report an experimental platform for the design and manufacturing of hierarchical porous materials via the stereolithographic printing of stable photo-curable Pickering emulsions. In the printing process, the micron-sized droplets of the emulsified resins work as soft templates for the incorporation of microscale porosity within sequentially photo-polymerized layers. The light patterns used to polymerize each layer on the building stage further generate controlled pores with bespoke three-dimensional geometries at the millimetre scale. Using this combined fabrication approach, we create architectured lattices with mechanical properties tuneable over several orders of magnitude and large complex-shaped inorganic objects with unprecedented porous designs.@en

Silica-based glasses can be shaped into complex geometries using a variety of additive manufacturing technologies. While the three-dimensional printing of glasses opens unprecedented design opportunities, the development of up-scaled, reliable manufacturing processes is crucial for the broader dissemination of this technology. Here, we design and study phase-separating resins that enable light-based 3D printing of oxide glasses with high-aspect-ratio features and enhanced manufacturing yields. The effect of the resin composition on the microstructure, mechanical properties and delamination resistance of parts printed by digital light processing is investigated with the help of printing experiments, compression tests and electron microscopy analysis. The chemical composition and microstructure of the cured resins were found to strongly affect the stiffness, delamination resistance, and calcination behavior of printed parts. These findings provide useful guidelines to enhance the reliability and yield of the DLP printing process of multicomponent silica-based glasses.@en

The digital fabrication of oxide glasses by three-dimensional (3D) printing represents a major paradigm shift in the way glasses are designed and manufactured, opening opportunities to explore functionalities inaccessible by current technologies. The few enticing examples of 3D printed glasses are limited in their chemical compositions and suffer from the low resolution achievable with particle-based or molten glass technologies. Here, we report a digital light-processing 3D printing platform that exploits the photopolymerization-induced phase separation of hybrid resins to create glass parts with complex shapes, high spatial resolutions and multi-oxide chemical compositions. Analogously to conventional porous glass fabrication methods, we exploit phase separation phenomena to fabricate complex glass parts displaying light-controlled multiscale porosity and dense multicomponent transparent glasses with arbitrary geometry using a desktop printer. Because most functional properties of glasses emerge from their transparency and multicomponent nature, this 3D printing platform may be useful for distinct technologies, sciences and arts.@en

Fibre-reinforced polymer structures are often used when stiff lightweight materials are required, such as in aircraft, vehicles and biomedical implants. Despite their very high stiffness and strength 1 , such lightweight materials require energy- and labour-intensive fabrication processes 2 , exhibit typically brittle fracture and are difficult to shape and recycle 3,4 . This is in stark contrast to lightweight biological materials such as bone, silk and wood, which form by directed self-assembly into complex, hierarchically structured shapes with outstanding mechanical properties 5–11 , and are circularly integrated into the environment. Here we demonstrate a three-dimensional (3D) printing approach to generate recyclable lightweight structures with hierarchical architectures, complex geometries and unprecedented stiffness and toughness. Their features arise from the self-assembly of liquid-crystal polymer molecules into highly oriented domains during extrusion of the molten feedstock material. By orienting the molecular domains with the print path, we are able to reinforce the polymer structure according to the expected mechanical stresses, leading to stiffness, strength and toughness that outperform state-of-the-art 3D-printed polymers by an order of magnitude and are comparable with the highest-performance lightweight composites 1,12 . The ability to combine the top-down shaping freedom of 3D printing with bottom-up molecular control over polymer orientation opens up the possibility to freely design and realize structures without the typical restrictions of current manufacturing processes. @en

Fibre-reinforced polymer structures are often used when stiff lightweight materials are required, such as in aircraft, vehicles and biomedical implants. Despite their very high stiffness and strength 1 , such lightweight materials require energy- and labour-intensive fabrication processes 2 , exhibit typically brittle fracture and are difficult to shape and recycle 3,4 . This is in stark contrast to lightweight biological materials such as bone, silk and wood, which form by directed self-assembly into complex, hierarchically structured shapes with outstanding mechanical properties 5–11 , and are circularly integrated into the environment. Here we demonstrate a three-dimensional (3D) printing approach to generate recyclable lightweight structures with hierarchical architectures, complex geometries and unprecedented stiffness and toughness. Their features arise from the self-assembly of liquid-crystal polymer molecules into highly oriented domains during extrusion of the molten feedstock material. By orienting the molecular domains with the print path, we are able to reinforce the polymer structure according to the expected mechanical stresses, leading to stiffness, strength and toughness that outperform state-of-the-art 3D-printed polymers by an order of magnitude and are comparable with the highest-performance lightweight composites 1,12 . The ability to combine the top-down shaping freedom of 3D printing with bottom-up molecular control over polymer orientation opens up the possibility to freely design and realize structures without the typical restrictions of current manufacturing processes. @en