Fabrication Of Structures Research Articles

Mechanical Behavior of 3D-Printed Zig-Zag Honeycomb Structures Made of BASF Ultrafuse 316L

The aim of this study is to determine the mechanical behavior of 2D honeycomb cellular structures with deformation initiators subject to quasi-static compression testing. Two different loading directions were studied: in-plane (IP) and out-of-plane (OP). The deformation initiators sought to stabilize the mechanical response by decreasing the initial peak force in the case of OP loading. The samples for testing were made using stainless steel 316L that was 3D-printed using material extrusion (MEX). The method enables fabrication of structures with high mechanical strength and ductility. The findings of the quasi-static compression testing showed that the additional deformation initiators were able to significantly reduce the orthotropy in the mechanical response of honeycomb cellular structures.

Fabrication of 3D Functional Nanocomposites Through Post-Doping of Two-Photon Microprinted Nanoporous Architectures.

Two-photon lithography (TPL) enables the fabrication of complex 3D structures with sub-micrometer precision. Incorporation of new functionalities into TPL-printed structures is key to advance their applications. A prevalent approach to achieve this is by directly adding functional nanomaterials into the photoresist (called "pre-doping"), which has several inherent challenges including material compatibility, light scattering, and nanoparticle agglomeration. Here, a conceptually different "post-doping" strategy is proposed, where the functionality of the TPL-printed architectures is achieved by impregnating functional materials into their nanoporous 3D mimics. Using the principle of polymerization-induced phase separation, TPL printing of complex microarchitectures with well-defined nanoporous structures having pores of ≈420nm is realized, which allows spontaneous impregnation of functional liquids via capillary effect. Importantly, unlike the "pre-doping" approach that requires printing optimization for each photoresist, this strategy is highly versatile in terms of functionalities possible. As a proof-of-concept, the impregnation of several functional liquids into TPL-printed porous microstructures is demonstrated: a fluorinated-lubricant, an ionic liquid, and three types of fluorescent liquids, conferring the microstructures with slippery, conductive, and localized fluorescence properties, respectively. Such versatility to fabricate complex microstructures with tailorable and localized functionalities is expected to open new possibilities in wide fields including bionics, electronics, and cell biology.

Resistance Element Welding (REW) of Steels with Non-Ferrous Materials: Potentials, Challenges, and Properties

Performance and functionality are two key factors in designing advanced components. One promising approach in manufacturing design is the fabrication of multi-material structures by joining dissimilar materials. Steels, known for their outstanding properties and cost-effective production, are widely used across several industries. However, their high density presents challenges when designing lightweight components. A solution lies in combining steels with lightweight, non-ferrous alloys to develop cost-effective multi-material parts. However, joining different materials is generally complex due to their different properties, making it sometimes challenging or even unfeasible. Resistance element welding (REW) offers a high-performance alternative to traditional methods, such as resistance spot welding, with a high potential in mass production industries like automotive manufacturing. This article comprehensively reviews the latest research on REW for dissimilar joining of steels and non-ferrous alloys. It focuses on the microstructural and mechanical properties of joints, innovations in the REW process, the influence of process parameters on joint quality, as well as simulation and numerical studies. In addition, REW is compared with traditional joining methods.

Peppermint extract-compound nanofiber production and characterization

PurposeAs a result of referee evaluation, the subject scope of the article has been expanded. Previously, only polycaprolactone (PCL) loaded with peppermint extract had been studied. As a result of peer review, nanostructure production was made with peppermint-loaded polylactic acid (PLA). Literature information about PLA polymer has been added to the Introduction section. Additionally, to analyze the presence of peppermint extract in Fourier transform infrared (FTIR) measurements, a comparison was made with 100% PCL, 100% PLA and 100% peppermint extract. In order to observe the effect of polymer type, evaluations were made between the produced peppermint-loaded nanostructures containing two different polymers. Mechanical, structural and morphological properties of the produced nanostructures were measured. The main purpose of the study is to analyze and evaluate peppermint-loaded nanostructures on different polymers.Design/methodology/approachNanofiber structures were produced by the electrospinning process due to their attractive properties such as low cost, flexibility, integrability and high efficiency. The production parameters of the nanofiber structure produced by the electrospinning process, mechanical measurements, fiber morphologies with scanning electron microscope (SEM) and structural characterization with FTIR measurement were analyzed, and its potential in possible usage areas was interpreted.FindingsIn this study, the production of nanostructures containing peppermint extract with PCL and PLA polymers, which are various biodegradable and biocompatible polymeric materials, was successfully achieved. In the studies carried out, nanofiber structures with positive properties such as low cost, easy accessibility, flexibility, integrability and sustainability were produced. When the two nanofiber structures produced were compared, it was observed that the peppermint extract nanofiber structure containing PCL provided better morphological and mechanical properties, such as higher strength, thinner fibers' diameter and a smooth and homogeneous surface, compared to the peppermint core nanofiber structure containing PLA. It has been observed that PCL polymer is more advantageous in obtaining nanofibers under the same environmental conditions and the same parameters. The addition of peppermint extract caused an approximately 25% loss in strength in nanostructures containing PCL polymer compared to nanostructures containing 100% PCL. The strength loss in PLA nanostructures containing peppermint extract is approximately 90% compared to nanostructures containing 100% PLA. This situation is associated with the regular arrangement of nanostructures containing PCL. In conclusion, incorporating peppermint extract into the nanofiber structures fabrication process offers several benefits, including enhanced antimicrobial properties and potential bioactive effects.Originality/valueIn the study, a uniform and suitable-for-use nanofiber structure with a smooth and partially beaded surface was obtained by an electrospinning method using peppermint extract and PCL and PLA polymers. Morphological evaluation was made with SEM images of the obtained nanofiber structure, and the presence of peppermint extract in the nanofiber structure was determined by the FTIR analysis. In the mechanical analysis, a decrease was observed in the elongation at break and tensile strength values of nanostructures loaded with mint extract, but this decrease did not prevent the production and use of the nanofiber structure.

Hybrid nanoparticle array fabricated using injection‐molded nanostructure

AbstractNow that well‐ordered nanoparticles can yield a promising performance in various fields, spatially regular arrangement of particles is a key requirement for nanoparticle‐embedded engineering materials and devices. Here, we demonstrate a feasible, robust method where nanoparticles can be regularly distributed and encapsulated. Polymeric substrates with different sized nanoholes were injection‐molded by controlling mold‐wall temperature in a spatial and temporal manner. A hybrid structure of nanoparticles was constructed by binding quantum dots with metal nanoparticles, and they were filled into the nanoholes using the knife coating process. The morphology of the nanostructure prepared via the molding process and the nanoparticle array was analyzed using a scanning electron microscope and a transmission electron microscope. Fluorescence emission of the hybrid nanostructure was measured. The finding showed that the strategic approach introduced in this study could allow fabrication of hybrid nanoparticle structures with good processability and productivity. © 2024 Society of Chemical Industry.

An induction curing technique for CFRP laminate via magnetic particle‐induced in situ heating

AbstractCuring high‐performance carbon fiber reinforced polymer (CFRP) structures with economical and energy‐efficient off‐oven techniques is important for the widespread application of the composite. In this work, we reported a magnetic particle‐induced in situ heating method to controllably cure CFRP laminates with stacking sequences of [0]8, [0/90]4s and [0/45/90/−45]2s. Results showed that all the laminates can undergo a consistent, layup‐independent two‐staged heating protocol via regulating the magnetic field intensity. Under the same curing protocol, the three stacking‐sequenced CFRP laminates can be cured more completely under induction heating than oven heating, in addition to a moderately improved tensile and flexural properties. However, the porosity of the laminates slightly increased under induction heating. The proposed new curing method provides a new avenue to the fabrication of advanced CFRP composite structures without oven or autoclave.Highlights A particle‐induced in situ heating method to controllably cure carbon fiber reinforced polymer (CFRP) laminates was proposed. This method was capable to cure CFRP laminates with different stacking sequences. Mechanical property of laminates was moderately improved under this method.

Structural, Magnetic, and Mössbauer Study on Nb and Heat Treatment of Fe-Si-B-P-Cu-Nb Ribbons

This study aims to enhance the amorphous formation ability and magnetic properties that are crucial for the production of high-quality nanocrystalline alloys. The structural, thermal, and magnetic characteristics of the alloy ribbons were analyzed through a systematic adjustment of Nb content, and, including Nb, significantly improved the amorphous formation ability and thermal stability of the alloy, which is vital for nanocrystalline production. By varying the Nb content within Fe85-xSi2B8P4Cu1Nbx (x = 0.0, 0.5, 1.0, and 1.5), we explored finer adjustments to achieve homogeneous amorphousness during the melt spinning process. Careful control over the Nb content facilitated the production of amorphous ribbons with consistent homogeneity, which was critical for the subsequent fabrication of nanocrystalline structures through heat treatment. As a result, the amorphous ribbon of Fe85.5Si2B8P4Cu1Nb0.5 showed a low coercivity of 7 A/m. The heat treatment showed a remarkably high saturation magnetic flux density of 1.94 T. Additionally, the grain size (D) decreased as the Nb content increased, with D values ranging from 25.09 nm to 24.29 nm, as calculated by the Scherrer formula. Mössbauer spectroscopy confirmed the formation of nanocrystalline and residual amorphous phases. The hyperfine magnetic field values (Beff) decreased from 25.7 T to 24.7 T in the amorphous samples and reached 33.0 T in the nanocrystalline phases. This study highlights Nb’s positive impact on thermal stability and amorphous formation capacity in Fe-Si-B-P-Cu alloys, culminating in the successful fabrication of nanocrystalline ribbons with superior structural and magnetic properties.

Tailoring thermal conductivity and printability in boron nitride/epoxy nano- and micro-composites for material extrusion 3D printing

This study explores the design and characterization of boron nitride (BN)/epoxy nano- and micro-composites, utilizing material extrusion 3D printing as a powerful technique to align filler particles within the matrix and produce effective thermally conductive and electrically insulating adhesive materials with possible applications in electronics. Investigating the uncharted correlation between filler morphology, including both boron nitride microplatelets (BNMP) and boron nitride nanosheets (BNNS), processability by additive manufacturing (AM), and ink functionalities, BNMP proves more effective in boosting thermal conductivity, with an enhancement of up to 400%. Fillers, that can be highly oriented through material extrusion, contribute to achieving high glass transition temperature (up to 137 °C) and thermal resistance, expanding the inks’ applicability. Optimized inks demonstrate exceptional shape fidelity, enabling the fabrication of complex structures. The findings emphasize the crucial role of ceramic filler content and morphology in optimizing multifunctional 3D-printed materials' performance and tailoring their properties, offering insights for future innovations in electronic materials and manufacturing methodologies for thermal management applications.

Material extrusion additive manufacturing of recycled discontinuous carbon fibre reinforced thermoplastic composites with high fibre efficiency

The study proposes a novel method, named angled feeding extrusion (AFE), for material extrusion additive manufacturing (MEX AM) of discontinuous recycled carbon fibre (rCF) reinforced thermoplastic composites with high fibre efficiency. The AFE system is also integrated with a 5-axis printer to enable the fabrication of complex structures. Characterisation of fibre morphology and structure is conducted using X-ray computed microtomography (μCT), and the mechanical properties of the AFE-manufactured rCF composites are investigated through mechanical testing. The results show that AFE demonstrates effectiveness in reducing the fabrication difficulty of rCF composites with high fibre efficiency, fibre efficiency encompasses factors such as fibre fraction, length, and orientation. Moreover, rCF composites additively manufactured by the AFE system achieve rCF lengths of up to 3.8mm and a fibre volume fraction of 30.3%. The tensile strength and modulus are 178MPa and 9.9GPa respectively. It exhibits a significant improvement of 90% and 254% in tensile strength and modulus compared to short fibre reinforced composites. Similarly, compressive tests of AFE-manufactured composite rings show an increase of 80% in ultimate compressive load.

Colloidal route towards sodium ionic conductor (NASICON) 3D complex solid electrolyte structures fabricated by Direct Ink Writing (DIW)

Progressing towards a sustainable energy model, safer new generation high-performance energy storage devices with large energy density and power are needed. In this sense, the improvement in terms of efficiency and sustainability has led to the interest in solid-state batteries (SSBs). Lately, sodium-ion batteries (SIBs) have become an emerging alternative due to the abundance of raw materials, low cost, and improvements in terms of fast sodium-ion conductor solid electrolytes (SCSEs). Among all the SCSEs, the sodium superionic conductor (NASICON) type electrolyte is one of the most well-known electrolytes, being widely developed in terms of synthesis and materials. However, the processing and manufacturing of these electrolytes have gone almost unnoticed, without considering that well-designed structures of electrodes/electrolytes are the bridge toward turning advanced energy materials into high-performance devices. This work presents the fabrication of 3D complex structures based on NASICON sodium solid electrolytes, obtained for the first time by direct ink writing (DIW). Through a colloidal route, fine NASICON phase powder with high pureness was prepared, enabling the manufacturing of intricate NASICON-printed electrolytes in a one-step fabrication process. By optimizing the ink, a dense electrolyte layer, acting as an ionic conductor and separator, was inserted between two complex porous pattern layers obtaining a device with a total height below 1.15 mm. Further, the densification of the 3D electrolyte was enhanced, reaching high ionic conductivities at room temperature (3.10-4 S·cm-1). Thus, a high-performance sodium ion conductor NASICON solid electrolyte with shorter diffusion pathways and larger interfacial surface areas between electrode/electrolyte was obtained, improving the overall electrochemical performance of the device by a 3D layer-by-layer design.

Advancing Mix Design Prediction in 3D Printed Concrete: Predicting Anisotropic Compressive Strength and Slump Flow

Introducing 3D-concrete printing has started a revolution in the construction industry, presenting unique opportunities alongside undeniable challenges. Among these, the major challenge is the iterative process associated with mix design formulation, which results in significant material and time consumption. This research uses machine learning (ML) techniques such as Extreme Gradient Boosting (XGBoost), Support Vector Machine (SVM), Decision Tree Regression (DTR), Gaussian Process Regression (GPR), and Artificial Neural Network (ANN) to overcome these challenges. A dataset containing 21 mix constituent features and 4 output properties (cast and printed compressive strength, and slump flow) was extracted from the literature to investigate the relationship between mix design and performance. The models were assessed using a range of evaluation metrics, including Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), Mean Squared Error (MSE), and R-squared value. Gaussian Process Regression (GPR) yielded more favorable results. In the case of cast strength, GPR achieved an R2 value of 0.9069, along with RMSE, MSE, and MAE values of 13.04, 170.12, and 9.40, respectively. A similar trend was observed for printed strengths in directions 1, 2, and 3. GPR achieved R-squared values exceeding 0.91 for all directions, accompanied by significantly lower RMSE values (below 4.1). The machine learning models were also validated using four unique mix designs. These mixes were 3D printed and tested for compressive strength and slump flow. GPR's average error was 10.55%, while SVM achieved a slightly lower average error of 9.38%. Overall, this work presents a novel approach for optimizing 3D-printed concrete by enabling the prediction of slump flow and compressive strength directly from the mix design. This approach can facilitate the design and fabrication of 3D-printed concrete structures that fulfill the necessary strength and printability requirements.

Fabrication and mechanical behaviors of recoverable thermoplastic sandwich structures with circular honeycomb cores based on the continuous approach

Fabrication and mechanical behaviors of recoverable thermoplastic sandwich structures with circular honeycomb cores based on the continuous approach

Cellulose-Based Acoustic Absorber with Macro-Controlled Properties

Cellulose-based materials are now commonly used, including in the field of acoustic comfort. Often presented as a less environmentally impactful alternative to traditional acoustic absorbents (such as melamine, glass wool, etc.), these cellulose-based materials are more frequently derived from recycling, undergoing, in most cases, a technical process that allows these cellulose fibers to be obtained, thus inheriting the acoustic properties of the latter, with limited or even non-existent control. This paper proposes a manufacturing process that allows for the production of cellulose foam with precise control over its porosity, pore size, and interconnections. In addition to exhibiting good sound absorption properties, this process also enables the fabrication of gradient-porous structures and other hybrid materials, which can result in remarkable sound absorption properties.

Enhanced Cu-Cu bonding for ultrahigh-density interconnection: Co passivation bonding with non-oxidation interfaces

Cu-based hybrid bonding, known for its high density and low latency, is widely applied in big data throughput scenarios. However, Cu joints are prone to oxidation and perform poorly at fine pitches, hindering signal transmission and leading to failures in integrated devices. One of the most promising approaches to overcome these challenges is applying a cobalt (Co) passivation layer on the Cu surface owing to its preferable electrical and anti-electromigration behavior in sub-micron scale. However, the high melting point (∼1500 °C) and inevitable oxidation of the Co film coated on Cu are scarcely evitable. In this work, a ternary plasma composed of Ar, NH3, and H2O is introduced to activate the surface of the Co-passivated Cu, facilitating bonding at a temperature of 200 °C. Significant surface and interface electrical resistivity reductions were observed, reduced to 67.5 % and less than 10 %, respectively. Additionally, tensile strength more than doubled with ternary plasma activation attributed to the continuous and tightly bonded Co-Co interface. The application of this Co-passivated Cu bonding structure is evaluated through signal integrity simulations for 3D interconnection with ultrafine pitch. In summary, this work provides guidelines for the future fabrication of high-performance interconnection structures.

Hydrogel impeller formation via vacuum degassing photopolymerization for micromixers

For effective mixing within microfluidic devices through the application of obstacle-based structures, a straightforward approach involves in-situ fabrication, such as the free-radical photopolymerization of hydrogel structures. However, oxygen inhibition presents a challenge for polydimethylsiloxane (PDMS)-based microfluidic chips. In this paper, we present a solution to the problem of hydrogel-structure formation hindered by oxygen inhibition at low light intensities and the photoinitiator concentration achieved using vacuum degassing. Furthermore, a kinetic model for photopolymerization under vacuum conditions was established and converted into an equation of light intensity and exposure time while keeping the other parameters constant. The exposure time range was successfully predicted by comparing the experimental data and analyzing scenarios. This method was used to fabricate an impeller for a passive micromixer. The impeller rotation was then analyzed. The results demonstrated that with an increased flow rate exceeding 6 mL/min, the mixing efficiency is significantly higher owing to the rotation of the impeller. The mixing efficiency was quantitatively assessed through experiments involving the mixing of three dyes, showing a three-fold increase compared to the chip without the impeller. Our research provides valuable insights into the fabrication of hydrogel structures in PDMS-based microfluidic chips under vacuum conditions.

Fabrication of Bioactive Helix aspersa Extract-Loaded Chitosan-Based Bilayer Wound Dressings for Skin Tissue Regeneration.

In recent years, there has been a notable shift toward exploring plant and animal extracts for the fabrication of tissue engineering structures that seamlessly integrate with the human body, providing both biological compatibility and physical reinforcement. In this particular investigation, we synthesized bilayer wound dressings by incorporating snail (Helix aspersa) secretions, comprising mucus and slime, into chitosan matrices via lyophilization and electrospinning methodologies. A nanofiber layer was integrated on top of the porous structure to mimic the epidermal layer for keratinocyte activity as well as acting as an antibacterial barrier against possible infection, whereas a porous structure was designed to mimic the dermal microenvironment for fibroblast activity. Comprehensive assessments encompassing physical characterization, antimicrobial efficacy, in vitro bioactivity, and wound healing potential were conducted on these bilayer dressings. Our findings revealed that the mucus and slime extract loading significantly altered the morphology in terms of nanofiber diameter and average pore size. Snail extracts loaded on a nanofiber layer of bilayer dressings showed slight antimicrobial activity against Staphylococcus epidermidis and Escherichia coli. An in vitro release study of slime extract loaded in the nanofiber layer indicated that both groups 1 and 2 showed a burst release up to 6 h, and a sustained release was observed up to 96 h for group 1, whereas slime extract release from group 2 continued up to 72 h. In vitro bioactivity assays unveiled the favorable impact of mucus and slime extracts on NIH/3T3 fibroblast and HS2 keratinocyte cell attachment, proliferation, and glycosaminoglycan synthesis. Furthermore, our investigations utilizing the in vitro scratch assay showcased the proliferative and migratory effects of mucus and slime extracts on skin cells. Collectively, our results underscore the promising prospects of bioactive snail secretion-loaded chitosan constructs for facilitating skin regeneration and advancing wound healing therapies.

Fabrication of 3D TPU microfiber structures with embedded dye probes for cyanide ion sensing via charge-reversed electro jet writing

An extremely organized sensing system that indicates the prompt indication of the cyanide ion in water was synthesized. The design of the sensing probe comprises the phenothiazine fluorophore system as an electron donor and tetramethyl-3H-indol-1-ium as an electron acceptor unit. A notable color change in daylight and UV light was observed in the probe when it comes in contact with the solution of cyanide ion. The probe interaction with the cyanide ion results in color change from purple to colorless and these changes occurs in the probe with the disconnection in the ICT process. The detection limit (LOD) 1.3 μM (UV–visible method) and 25 nM (Fluorescence method), denotes that the probe preferentially reacts with cyanide, which is less than the tolerable level of 1.9 μM. The probe reacts with cyanide ions via nucleophilic addition reaction mechanism and it is confirmed through the 1H NMR data. Furthermore, the HRMS value also confirms the same. For practical application of the probe a 3D structure composed of TPU microfiber containing probe molecule was fabricated by charge reversed electro jet writing (CREW) method by 3D printer has been efficiently sense cyanide ion. Also, for cyanide ion sensing probe successfully determines real resources, including cyanide containing various water samples. Besides, the developed PBI-encapsulated Polysulfone (PSF) capsule kit effectively sense cyanide ion in water. Moreover, the test strips, was also employed to detect the cyanide ion in presence of competing anions. Therefore, the synthesized probe displays an outstanding sensing ability towards the cyanide ion.

Multifunctional Biocomposite Materials from Chlorella vulgaris Microalgae.

Extrusion 3D-printing of biopolymers and natural fiber-based biocomposites enables the fabrication of complex structures, ranging from implants' scaffolds to eco-friendly structural materials. However, conventional polymer extrusion requires high energy consumption to reduce viscosity, and natural fiber reinforcement often requires harsh chemical treatments to improve adhesion. We address these challenges by introducing a sustainable framework to fabricate natural biocomposites using Chlorella vulgaris microalgae as the matrix. Through bioink optimization and process refinement, we produced lightweight, multifunctional materials with hierarchical architectures. Infrared spectroscopy analysis reveals that hydrogen bonding plays a critical role in the binding and reinforcement of Chlorella cells by hydroxyethyl cellulose (HEC). As water content decreases, the hydrogen bonding network evolves from water-mediated interactions to direct hydrogen bonds between HEC and Chlorella, enhancing the mechanical properties. A controlled dehydration process maintains continuous microalgae morphology, preventing cracking. The resulting biocomposites exhibit a bending stiffness of 1.6 GPa and isotropic heat transfer and thermal conductivity of 0.10 W/mK at room temperature, demonstrating effective thermal insulation. These characteristics make Chlorella biocomposites promising candidates for applications requiring both structural performance and thermal insulation, offering a sustainable alternative to conventional materials in response to growing environmental demands.

Magnetothermal Shape‐Morphing of Thermoset Structures

AbstractShape‐morphing of thermosets is challenging due to their permanently cross‐linked polymer network structure. Here, a magnetothermal shape‐morphing strategy is proposed for complex thermoset structures via reshaping, assembly, and shape memory. The thermoset composite is fabricated by adding magnetic nanoparticles into dynamically cross‐linked thermoset resin, which imparts magnetothermal effect and reprocessability under an alternating magnetic field. Epoxy composites are prepared with various weight fractions of Fe3O4 nanoparticles, and their magnetothermal and thermomechanical properties are studied. For a composite with 15 wt% Fe3O4 nanoparticles, the glass transition temperature Tg is 62 °C, and the topology freezing transition temperature Tv is 175 °C. An alternating magnetic field with a working power of 2000 W can generate a temperature of 156 °C, enabling bond exchange reactions and stress relaxation in the dynamically cross‐linked epoxy resin. Magnetothermal reshaping and bonding facilitate the assembly of complex‐shaped structures from simple units, while magnetothermal shape memory provides rapid actuation deformation responses within 60 s. Various examples of magnetothermal shape‐morphing of complex thermoset structures, including grasper, origami, and octopus‐inspired functional structures, are demonstrated. The results indicate that the present shape‐morphing strategy provides advantages such as remote control, high efficiency, flexible design, and straightforward structural fabrication.

Multi-Metal Additive Manufacturing by Extrusion-Based 3D Printing for Structural Applications: A Review

Additive manufacturing (AM) is a rapidly developing technical field that is becoming an irreplaceable tool to fabricate unique complex-shaped parts in aerospace, the automotive industry, medicine, and so on. One of the most promising directions for AM application is the design and production of multi-material components with different types of chemical, structural, and architectural gradients that also promote a breakthrough in bio-inspired approaches. At the moment there are a lot of different AM techniques involving various types of materials. This paper represents a review of extrusion-based AM techniques using metal-polymer composites for structural metal parts fabrication. These methods are significantly cheaper than powder bed fusion (PBF) and directed energy deposition (DED) techniques, though have a lower degree of part detail. Thus, they can be used for low-scale production of the parts that are not rentable to produce with PBF and DED. Multi-material structures application in machinery, main aspects of feedstock preparation, the subsequent steps of extrusion-based 3D printing, and the following treatment for manufacturing single-metallic and multi-metallic parts are considered. Main challenges and recommendations are also discussed. Multi-metallic extrusion-based 3D printing is just a nascent trend requiring further wide investigation, though even now it shows pretty interesting results.