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1. Dynamic Fluid‐Assisted Continuous Multimaterial 3D Printing for Seamless Gradient Structures

   https://doi.org/10.1002/admt.202500621  

   Wang, Wenbo; Liu, Siying; Liu, Luyang; Ma, Xukun; Nogueira, Cauê; Xu, Xin; Shefi, Orit; Lancaster, Jessica; Chen, Xiangfan (April 2025, Advanced Materials Technologies)

   Abstract Functionally gradient materials emulate nature's ability to seamlessly blend properties through variations in material composition, unlocking advanced engineering applications such as biomedical devices and high‐performance composites. Additive manufacturing, particularly stereolithography, enables sophisticated 3D geometries with diverse materials. However, current stereolithography‐based multi‐material 3D printing is constrained by time‐intensive material switching and compromised interfacial properties. To overcome these challenges, we present dynamic fluid‐assisted micro continuous liquid interface production (DF‐µCLIP), a high‐speed multi‐material 3D printing platform that integrates varying compositions in a fully continuous fashion. By utilizing the polymerization‐free “dead zone”, vliquid resins are seamlessly replenished within a resin bath equipped with dynamic fluidic channels and a synchronized material supply system. DF‐µCLIP achieves ultra‐fast printing speeds of 90 mm/hour with 7.4 µ m pixel‐1 resolution while enabling on‐the‐fly material transitions. This strategy enhances mechanical strength at multi‐material interface through entangled polymer networks and promotes seamless material transitions between distinct materials ilike fragile hydrogels and rigid polymers, addressing interfacial failure caused by mismatch of swelling behavior. Additionally, dynamic material replenishment with real‐time composition control enables continuous gradient printing instead of the conventional step‐wise controlled gradient. Demonstrations include polymers with gradient color transitions and gradient carbon nanotube (CNT) composites with seamlessly varying conductivity. 

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2. Enhancement of Relative Permittivity of Material with Metallic Inclusions – Experimental Verification

   https://doi.org/10.1109/SoutheastCon51012.2023.10115156  

   Saha, Arun Kumar; Pendleton, Walker (April 2023, IEEE)

   In this project, it was shown by simulation that the permittivity of a material could be enhanced by embedding metal inclusions in the host material. Later, a series of systematic experiments were carried out with free space material measurement equipment/system to demonstrate the enhancement of permittivity with circular metal patches printed periodically on a host material to validate the simulation results. 

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3. Additive Manufacturing of Polymer Matrix Composite Materials with Aligned or Organized Filler Material: A Review

   https://doi.org/10.1002/adem.202001002  

   Niendorf, Karl; Raeymaekers, Bart (January 2021, Advanced Engineering Materials)

   The ability to fabricate polymer matrix composite materials with continuous or discontinuous filler material, oriented in a user‐specified direction, enables implementing designer material properties, such as anisotropic mechanical, thermal, and electrical properties. Conventional fabrication methods rely on a mold, which limits specimen geometry and is difficult to implement. In contrast, additive manufacturing, including fused filament fabrication or fused deposition modeling, direct ink writing, or stereolithography, combined with a method to align filler material such as a mechanical force or an electric, magnetic, shear force, or ultrasound wave field, enables 3D printing polymer matrix composite material specimens with complex geometry and aligned filler material, without the need for a mold. Herein, we review the combinations of fabrication and filler material alignment methods used to fabricate polymer matrix composite materials, in terms of operating and design parameters including size, resolution, print speed, filler material alignment time, polymer matrix and filler material requirements, and filler manipulation requirements. The operating envelope of each fabrication method is described and their advantages, disadvantages, and limitations are discussed. Finally, different combinations of 3D printing and filler material alignment methods in the context of important engineering applications, such as structural materials, flexible electronics, and shape‐changing materials, are illustrated. 

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4. Scaling, Growth, and Size Effects on the Mechanical Behavior of a Topologically Interlocking Material Based on Tetrahedra Elements

   https://doi.org/10.1115/1.4044025  

   Short, M.; Siegmund, T. (November 2019, Journal of Applied Mechanics)

   Abstract The present study is concerned with the deformation response of an architectured material system, i.e., a 2D-material system created by the topological interlocking assembly of polyhedra. Following the analogy of granular crystals, the internal load transfer is considered along well-defined force networks, and internal equivalent truss structures are used to describe the deformation response. Closed-form relationships for stiffness, strength, and toughness of the topologically interlocked material system are presented. The model is validated relative to direct numerical simulation results. The topologically interlocked material system characteristics are compared with those of monolithic plates. The architectured material system outperforms equivalent size monolithic plates in terms of toughness for nearly all possible ratios of modulus to the strength of the material used to make the building blocks and plate, respectively. In addition, topologically interlocked material systems are shown to provide better strength characteristics than a monolithic system for low strength solids. 

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5. A facile multi-material direct laser writing strategy

   https://doi.org/10.1039/c9lc00398c  

   Lamont, Andrew C.; Restaino, Michael A.; Kim, Matthew J.; Sochol, Ryan D. (July 2019, Lab on a Chip)

   Direct laser writing (DLW) is a three-dimensional (3D) manufacturing technology that offers vast architectural control at submicron scales, yet remains limited in cases that demand microstructures comprising more than one material. Here we present an accessible microfluidic multi-material DLW (μFMM-DLW) strategy that enables 3D nanostructured components to be printed with average material registration accuracies of 100 ± 70 nm (Δ X ) and 190 ± 170 nm (Δ Y ) – a significant improvement versus conventional multi-material DLW methods. Results for printing 3D microstructures with up to five materials suggest that μFMM-DLW can be utilized in applications that demand geometrically complex, multi-material microsystems, such as for photonics, meta-materials, and 3D cell biology. 

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