The advancements in 3D printing systems together with medical imaging devices, including magnetic resonance imaging (MRI) and computed tomography (CT), have made it possible to fabricate customized implantable scaffolds from computer-aided designs (CAD), which can precisely fit to the affected region in body of patients. [1,2] Hydrogels are widely preferred scaffold materials for 3D printing since they can mimic the natural tissues due to their high water content, porosity, and flexibility. [1,3] Additionally, they can be easily functionalized with biochemical and biophysical cues, and have easy fabrication processes. [4,5] Deriving therapeutic benefits such as supporting cell adhesion, promoting cell proliferation, and providing mechanical support for the tissue remodeling are desired for hydrogels. Physical, chemical, or biochemical crosslinking of homopolymer or copolymer solutions is typically used to form the hydrogels. [6] Along with synthetic polymers, the natural polymeric hydrogels can provide a stable environment for cells to grow, migrate, proliferate, and/or differentiate. [1] Natural polymers can be extracted from natural products via physical or chemical techniques in order to form hydrogels. The natural polymeric hydrogels, such as gelatin, [7,8] alginate, [9] fibrinogen, [10] hyaluronic acid, [11] cellulose, [12] and chitosan, [13] can dissolve in biofriendly inorganic solvents including phosphate-buffered saline (PBS) and cell culture medium. [6] Besides the well-known biocompatibility and biodegradability of natural polymeric hydrogels, their mechanical characteristics, however, limit potential applications as bioinks for manufacturing of scaffolds through 3D printing process. [14] Collagen-based biomaterials, used in most of the previous studies due to their intrinsic cell-adhesion sites, have been reported to have poor printability and long crosslinking durations. [15] Likewise, sodium alginate, which is a block copolymer of consecutive and alternately arranged β-d-mannuronic acid and α-l-guluronic acid residues, is a broadly preferred material since it is easily crosslinked via ionotropic gelation with divalent cations (e.g., Ca 2+ , Zn 2+). [16] However, alginate hydrogels require additional bioactivation step to trigger cell adhesion. [17] Another 3D bioprinting of hydrogels has gained great attention due to its potential to manufacture intricate and customized scaffolds that provide favored conditions for cell proliferation. Nevertheless, plain natural hydrogels can be easily disintegrated, and their mechanical strengths are usually insufficient for printing process. Hence, composite hydrogels are developed for 3D printing. This study aims to develop a hydrogel ink for extrusion-based 3D printing which is entirely composed of natural polymers, gelatin, alginate, and cellulose. Physicochemical interactions between the components of the intertwined gelatin-cellulose-alginate network are studied via altering copolymer ratios. The structure of the materials and porosity are assessed using infr...

Recent advances in additive manufacturing made it feasible to fabricate products with desired shapes and features. Herein, a new, photocurable 3D printer ink mainly based on pentaerythritol triacrylate (PETA) is reported. To achieve rapid curing needed for 3D printing process, high performance water‐soluble photoinitiator, lithium phenyl‐2,4,6‐trimethylbenzoylphosphinate (LAP), was emulsified in PETA monomers and this suspension was evaluated for its polymerization kinetics by exposing to 395 nm UV‐light. The distinct influences of LAP and triethanolamine (TEA) concentrations on photo‐polymerization and printability were examined and an optimum concentration for extrusion‐based 3D printing was found to be 10 mM and 1.62 M for LAP and TEA, respectively. Synthesized PETA‐based 3D printer ink was functionalized by dispersing magnetic particles/flakes into the mixture, and consequently, a magneto responsive ink was obtained to be used in specialized applications. A ring‐shaped structure embedded with micron sized iron flakes was printed as a prototype. This study presents a versatile photo‐curable polymer formulation with possible translation to high performance 3D printing of customizable shapes that can be utilized in a wide range of areas such as micro‐robotics and medical science.

Fe16N2 is a compound with giant saturation magnetization approaching or exceeding that of rare‐earth‐based permanent magnets. The abundance of its elements and low‐cost synthesis of this compound has made it highly attractive to replace rare‐earth‐based permanent magnets that are becoming ever more expensive to utilize in applications. Herein, its synthesis from Fe flakes by surfactant‐assisted high energy ball milling is demonstrated. The synthesized Fe flakes are then reduced under forming gas (Ar/H2), followed by nitridation at low temperatures under ammonia (NH3) gas. The formation of Fe16N2 phase exceeding 50% by volumetric fraction is observed and confirmed by X‐ray diffraction and Mössbauer analysis. Following the Fe16N2 flake synthesis, extrusion‐based 3D printing is used to check the feasibility of incorporation of the flakes into functional polymer matrix composites. For this purpose, an ink of intermixed synthesized powder with photoresist SU8 is used. Using the prescribed method, a prototype Fe16N2 permanent magnet composite is successfully produced using an additive manufacturing approach. Such efficient production of Fe16N2 powders via routes already applicable to magnet production and the consolidation of the powders with 3D printing are expected to open up new possibilities for next‐generation permanent magnet applications.

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