Anisotropic materials formed by living organisms possess remarkable mechanical properties due to their intricate microstructure and directional freedom. In contrast, human-made materials face challenges in achieving similar levels of directionality due to material and manufacturability constraints. To overcome these limitations, an approach using 3D printing of self-assembling thermotropic liquid crystal polymers (LCPs) is presented. Their high stiffness and strength is granted by nematic domains aligning during the extrusion process. Here, a remarkably wide range of Young's modulus from 3 to 40 GPa is obtained during by utilizing directionality of the nematic flow during the printing process. By determining a relationship between stiffness, nozzle diameter, and line width, a design space where shaping and mechanical performance can be combined is identified. The ability to print LCPs with on-the-fly width changes to accommodate arbitrary spatially varying directions is demonstrated. This unlocks the possibility to manufacture exquisite patterns inspired by fluid dynamics with steep curvature variations. Utilizing the synergy between this path-planning method and LCPs, functional objects with stiffness and curvature gradients can be 3D-printed, offering potential applications in lightweight sustainable structures embedding crack-mitigation strategies. This method also opens avenues for studying and replicating intricate patterns observed in nature, such as wood or turbulent flow using 3D printing.

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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.

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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

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.

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DNA storage offers substantial information density^1–7 and exceptional half-life³. We devised a ‘DNA-of-things’ (DoT) storage architecture to produce materials with immutable memory. In a DoT framework, DNA molecules record the data, and these molecules are then encapsulated in nanometer silica beads⁸, which are fused into various materials that are used to print or cast objects in any shape. First, we applied DoT to three-dimensionally print a Stanford Bunny⁹ that contained a 45 kB digital DNA blueprint for its synthesis. We synthesized five generations of the bunny, each from the memory of the previous generation without additional DNA synthesis or degradation of information. To test the scalability of DoT, we stored a 1.4 MB video in DNA in plexiglass spectacle lenses and retrieved it by excising a tiny piece of the plexiglass and sequencing the embedded DNA. DoT could be applied to store electronic health records in medical implants, to hide data in everyday objects (steganography) and to manufacture objects containing their own blueprint. It may also facilitate the development of self-replicating machines.

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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

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.

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