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Lightweight electronic packaging that provides mechanical protection, cooling ability, and customizable electromagnetic interference (EMI) shielding effectiveness (SE) is needed for next-generation electronics. Although electronic packaging solutions with excellent EMI SE exist, there is limited research on how hierarchical design can modulate the EMI SE of an electronic packaging material on demand. In this study, the deliberate precise micro/macrostructure design of graphite-based materials using magnetically assisted 3D printing allows tuning of the EMI SE in the X band (8–12 GHz), leading to a maximum total shielding performance of 90 dB. Aligning high-density graphite microplatelets during 3D printing also remarkably amplified the total SE by 200%. Subsequently, rationally designing the oriented microstructure within a geometrical shape increases the reflection and improves the EMI SE from 40 to 60 dB in a specific direction. Our proof-of-concept samples demonstrate the potential of precise micro/macrostructure design for customizing and enhancing electronic packaging's EMI SE while achieving good heat dissipation and mechanical protection using a versatile 3D printing method. These advances pave the way for more reliable and safer electronic systems. Magnetically assisted 3D printing allows customizable electromagnetic interference (EMI) shielding effectiveness (SE). Aligning high-density graphite microplatelets during the 3D printing parallel or perpendicularly to incident waves leads to their tailored reflection and transmission. Designing the micro/macrostructure of materials allows customization and enhancement of electronic packaging's EMI SE while achieving good heat dissipation and mechanical protection. These advances pave the way for more reliable and safer electronic systems. [ABSTRACT FROM AUTHOR]

The Bouligand structure found in the dactyl club of mantis shrimps is known for its impact resistance. However, Bouligand-inspired reinforced composites with 3D shapes and impact resistance characteristics have not yet been demonstrated. Herein, direct ink writing was used to 3D print composites reinforced with glass microfibers assembled into Bouligand structures with controllable pitch angles. The energy absorption levels of the Bouligand composites under impact were found to surpass those of composites with unidirectional microfiber alignment. Additionally, the Bouligand composites with a pitch angle of 40° exhibited a maximum energy absorption of 2.4 kJ/m2, which was 140% higher than that of the unidirectional composites. Furthermore, the characterization of the topography of the fractured surface, supplemented with numerical simulations, revealed a combination of crack twisting and crack bridging mechanisms. Flexural tests conducted on the composites with a pitch angle of 40° revealed that these composites had the strongest properties, including a flexural strength of 36.9 MPa, a stiffness of 2.26 GPa, and energy absorption of 8 kJ/m2. These findings are promising for the microstructural design of engineered composites using direct ink writing for applications in aerospace, transportation, and defense. Inspired by Bouligand structure in the dactyl club of the mantis shrimp, direct ink writing is used to 3D print Bouligand composites reinforced with glass microfibres at controllable pitch angles. The Bouligand composites with a pitch angle of 40˚ exhibited a maximum energy absorption of 2.4 kJ/m2, which was 140 % higher than the unidirectional composites. The topography of the fractured surface supplemented with numerical simulations revealed the combination of crack twisting and crack bridging mechanisms. These findings have implications for the microstructural design of engineered composites using direct ink writing for applications in aerospace, transportation, defense, etc. [ABSTRACT FROM AUTHOR]

Natural strong and stiff composites exhibit complex microstructures that are responsible for their outstanding strength, stiffness, and toughness. Although horizontal nacre-like microstructures have demonstrated great potential in synthetic composites, they only demonstrate high performance along a specific loading direction. Here, we study how complex curved multilayered microstructures made of aluminum oxide microplatelets in a soft polymeric matrix can possess a combination of both stiffness and toughness. To do so, magnetically-assisted slip casting was used to direct the microplatelets into periodic orientations, as reported in previous studies, while the porous substrate used for the slip casting was designed with a raised step of different heights to control the shape of the oriented layers. The samples' microstructures achieved in-plane modulation of the microplatelet orientation, and the mechanical properties under compression were enhanced compared to samples with layers parallel to the horizontal plane. The microstructured design proposed here could be used to make more resilient bioinspired composites. [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]

Microstructured composites with hierarchically arranged fillers fabricated by three-dimensional (3D) printing show enhanced properties along the fillers' alignment direction. However, it is still challenging to achieve good control of the filler arrangement and high filler concentration simultaneously, which limits the printed material's properties. In this study, we develop a magnetically assisted drop-on-demand 3D printing technique (MDOD) to print aligned microplatelet reinforced composites. By performing drop-on-demand printing using aqueous slurry inks while applying an external magnetic field, MDOD can print composites with microplatelet fillers aligned at set angles with high filler concentrations up to 50 vol%. Moreover, MDOD allows multimaterial printing with voxelated control. We showcase the capabilities of MDOD by printing multimaterial piezoresistive sensors with tunable performances based on the local microstructure and composition. MDOD thus creates a large design space to enhance the mechanical and functional properties of 3D printed electronic or sensing devices using a wide range of materials. 3D printed composites with hierarchically arranged fillers have been challenging to fabricate. Here, the authors make use of magnetically assisted droplet-based printing to 3D print voxelated structures with high filler content, localized control of filler material, and orientation. [ABSTRACT FROM AUTHOR]

After more than 5 decades of research, the failure of bone implants is still poorly understood. The aging population makes it increasingly urgent to solve this issue. Among the reasons for failure, catastrophic brittle fracture can be directly related to the implant material and fabrication and deserves more attention. Indeed, clinically available implants do not sufficiently reproduce the hierarchical and heterogeneous microstructural organization of our natural bones, ultimately failing at replicating their mechanical strength and toughness. Nevertheless, recent advances in additive and advanced manufacturing have opened new horizons for the fabrication of biomimetic bone implants, challenging at the same time their characterization, testing, and modeling. This critical review covers selected recent achievements in bone implant research from a materials standpoint and aims at deciphering some of the most urgent issues in this multidisciplinary field. [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]

Materials combining optical transparency and mechanical strength are highly demanded for electronic displays, structural windows and in the arts, but the oxide-based glasses currently used in most of these applications suffer from brittle fracture and low crack tolerance. We report a simple approach to fabricate bulk transparent materials with a nacre-like architecture that can effectively arrest the propagation of cracks during fracture. Mechanical characterization shows that our glass-based composites exceed up to a factor of 3 the fracture toughness of common glasses, while keeping flexural strengths comparable to transparent polymers, silica- and soda-lime glasses. Due to the presence of stiff reinforcing platelets, the hardness of the obtained composites is an order of magnitude higher than that of transparent polymers. By implementing biological design principles into glass-based materials at the microscale, our approach opens a promising new avenue for the manufacturing of structural materials combining antagonistic functional properties. Transparent materials with high strength and hardness coupled with low crack tolerance remain challenging to manufacture. Here, the authors develop a process to fabricate transparent but tough glass composites with a nacre-like architecture that slows crack propagation. [ABSTRACT FROM AUTHOR]