In musculoskeletal tissue engineering, there is a need for bone implants that are biocompatible, resorbable, promote tissue regeneration, and degrade at a rate matching healing. Polycaprolactone (PCL), an FDA-approved biodegradable and bioinert polymer, can be functionalized with natural components without harsh crosslinking. This study presents the first demonstration of a homogeneous bulk polycaprolactone-gelatin (PCL-gelatin, PG) composite containing self-assembled gelatin nanoparticles that retain bioactivity despite thermal processing for 3D printing applications. PG composites with varying gelatin content (10%, 20%, and 30%) and β-tricalcium phosphate incorporation were fabricated through casting and melt processing into printable filaments at 110°C. Comprehensive characterization using mechanical testing, contact angle measurements, FTIR, TGA, EDS, and SEM confirmed homogeneous gelatin distribution as nanoscale particles throughout the PCL matrix, with systematic increases in hydrophilicity and enhanced mechanical properties proportional to gelatin content. Accelerated degradation studies revealed tunable degradation rates correlated with gelatin concentration, while invitro studies with human mesenchymal stem cells demonstrated enhanced proliferation and early osteogenic differentiation markers, particularly in PG30 compositions. Subcutaneous implantation in rats over 24 weeks showed biocompatibility comparable to PCL with minimal inflammatory response and biphasic degradation behavior characterized by initial swelling followed by controlled volume reduction. In critical-size femoral defects, PG30 exhibited superior early mechanical properties and increased preosteoblast density at bone interfaces compared to PCL and PCL-TCP controls at 4 weeks. This developed fabrication methodology enables precise spatial control through 3D printing while preserving gelatin bioactivity. This approach offers a promising advancement for tissue engineering applications requiring enhanced cellular interactions and controlled degradation.

Advancements in biochar-reinforced 3D printing filaments for material extrusion: A review on material performance, sustainability, and circular economy

Valorization of 3D printing filament waste into syngas via CO2-assisted pyrolysis.

Personalized oral drug delivery via FDM 3D printing: Polyvinyl alcohol capsules with tunable release profiles supported by in silico modeling.

Nanocomposite materials have garnered significant attention in advanced materials science due to their unique ability to exhibit multifunctional properties, particularly in the realm of magnetism and electromagnetic responsiveness. This study focuses on the development and characterization of acrylonitrile butadiene styrene (ABS) polymer matrix reinforced with ferromagnetic iron oxide (Fe3O4) nanoparticles. The primary objective was to investigate the electromagnetic properties of the nanocomposite and evaluate its potential for use in smart materials, sensors, and actuators via 4D printing. The nanocomposite was fabricated using a melt-mixing process, wherein Fe3O4 nanoparticles were incorporated into the ABS thermoplastic matrix at varying concentrations ranging from 10 to 20 wt. %. The mixture was then extruded into long, continuous 3D printing filaments and then to rectangular plates to facilitate testing and analysis. Its response to electromagnetic radiation was characterized by magnetic pull test using a 12 V DC Arduino-controller. An analytical model was developed and is validated using experiments. Experimental tests showed that the material exhibited significant magnetic receptiveness, by pulling and displacing the samples when subjected to applied magnetic field. The results indicated that increasing the concentration of Fe3O4 nanoparticles enhanced the material’s sensitivity, highlighting its potential for applications requiring precise control over magnetic interactions. Further, external magnetic field strength and sample dimensions are also shown to be significant parameters. In conclusion, this research underscores the potential of Fe3O4-reinforced polymer nanocomposites as a versatile and innovative material system for electromagnetic sensitivity.

A peanut-hull-PLA based 3D printing filament with antimicrobial effect

Abstract This study focuses on the development of three-dimensional (3D) printer filament made from post-consumer polypropylene utensils (PCP). A blend of injection-grade and extrusion-grade PCP was used to fabricate filament through extrusion process. The filament was then characterized based on diameter consistency, ovality, melt flow rate (MFR) and thermal properties followed by tensile testing of 3D printed specimens. The results showed that blending extrusion-grade PCP improved filament uniformity and reduced MFR, enhancing its suitability for fused filament fabrication (FFF). Among the prepared filament with injection-grade to extrusion-grade ratios of 100:0; 50:50 and 40:60, the 40:60 ratio was identified the starting ratio for producing filament with uniform diameter. Therefore, the 40:60 ratio was chosen for 3D printing tensile specimens for tensile testing. The tensile testing revealed that the tensile properties were influenced by printing layer height, with the 0.4 mm and 0.6 mm layers performing better than 0.8 mm due to better interlayer bonding. Comparative analysis with commercial poly(lactic acid) (PLA) filament at 0.6 mm layer height, while PLA outperformed PCP in tensile strength and elastic modulus, the PCP filament still demonstrated acceptable performance for non-structural 3D printed applications. Furthermore, the printing temperature used for this PCP blend was appropriate, as it did not exceed the onset thermal degradation temperature determined from thermal analysis. This project highlights the potential of upcycling the post-consumer polypropylene utensils in additive manufacturing.

This study investigates the functional groups of 3D printing material filaments made from biocomposites using polymers and natural fibers, analyzed through FTIR spectroscopy. The process of making 3D printing filament uses the extrusion method with a single extrusion machine. The integration of natural fibers into polymer matrices provides a sustainable alternative for 3D printing materials, improving mechanical properties while reducing environmental impact. FTIR analysis revealed significant interactions between polymer and fiber components, identifying key functional groups such as hydroxyl and carbonyl that are critical for performance. Functional groups such as hydroxyl (-OH) and carbonyl (C=O) significantly influence the quality of biocomposites through their impact on the material's mechanical, thermal, and interfacial properties. These findings provide insight into the structure-property relationship of these materials, demonstrating their potential for sustainable 3D printing applications.

Transforming date seed waste into sustainable 3D printing filament: A circular economy approach in UAE

In the past few years, many researchers have focused on using recycled or post-consumer materials in three-dimensional (3D) printing, which leads to better plastic waste management and sustainable practices. This study focuses on the fabrication of post-consumer polypropylene (rPP) filaments for use in the most common 3D printing method, fused filament fabrication (FFF). The rPP filaments were prepared by blending injection-grade rPP (i-rPP) and extrusion-grade rPP (e-rPP) at various ratios. The effect of different rPP grade ratios on filament diameter consistency, filament ovality, and melt flow index (MFI) was measured. The various ratios of i-rPP to e-rPP, such as 100:0, 40:60, 50:50, 60:40, and 0:100, were prepared. The 50:50 ratio was found as the starting point for achieving a consistent filament diameter. The MFI results showed that the MFI decreases when more e-rPP is incorporated in the blend. The tensile properties of 3D printed 50:50 rPP blend are also measured and compared with commercial PP. Overall, this research exhibits the potential of upcycling PP waste materials into functional filaments for sustainable 3D printing applications.

The paper is the second one of a series of papers regarding a simple method of PET plastic recycling that is desired to be implemented locally at an institution, meaning at Transilvania University of Brasov, the Faculty of Technological Engineering and Industrial Management. This paper presents a simple extrusion device for PET filament manufacturing, as low volume production for internal uses within the faculty. A brief study was made in order to find several constructive structures as a starting phase for the device design. The design stage started with a simplified 2D concept based on which the final 3D model of the filament extruder assembly was performed. The design stage generates the assembly components and their shapes and dimensions. The prototyping started with component manufacturing using cutting processes and also additive manufacturing. The final assembly was partially completed using those manufactured components and using standard parts for montage. The result is one of the simplest and cheapest to implement device in terms of attempts to manufacture PET recycled filament.

Nowadays, the modal analysis method is effectively employed in the design of low-noise, high-safety machines, the production of comfortable vehicles, and the development of structures resistant to dynamic loads, the establishment of safe operating conditions, and the determination of optimal operating parameters. In this study, modal analyses were conducted on spur gear models produced using four commonly utilized 3D printing filament materials (PLA, ABS, PET-G, and PC) each in four different thicknesses)3 mm, 5 mm, 7 mm, and 9 mm). The analyses were performed using a finite element analysis (FEA)-based simulation software. For each combination of material type and gear thickness, natural frequencies (Hz) and corresponding eigenvalues (1/s²) were obtained across six distinct vibration modes. The results indicate that both frequency and eigenvalue values vary significantly depending on the material type and gear thickness. It was observed that the thickness parameter has a substantial impact on the natural frequency in the lower modes. This comprehensive study graphically compares the vibrational behavior of different materials and thicknesses and provides a scientific basis for identifying the most suitable material–geometry combinations in terms of modal performance.

A 3D printing filament was fabricated from poly(lactic acid) (PLA), cassava pulp (CP), and epoxy using a twin-screw extruder. Several bio-composites were synthesized by varying the amount of epoxy (0.5, 1.0, 3.0, 5.0, and 10.0 wt.%). The size of the CP fibers significantly affected the surface quality, filament diameter, and mechanical properties of the final product. The smallest fiber size (45 µm) provided a smooth surface and consistent diameter. Incorporating 1 wt.% of epoxy into PLA/CP enhanced the tensile strength (56.6 MPa), elongation at break (6.2%), and hydrophobicity of the composite. The composite mechanical properties deteriorated at epoxy contents above 1 wt.% due to the amplified plasticizer effect of excessive epoxy. The optimized PLA/CP/epoxy formulation was used to generate the 3D filament. The resultant filament displayed a tensile strength of 64.6 MPa and elongation at break of 9.8%, attributed to the fine morphology achieved via thorough mixing provided by the twin-screw extruder. Epoxide-mediated crosslinking between PLA and CP enabled the development of a novel 3D printing filament with excellent mechanical properties. This research illustrates how agricultural residues can be upcycled into high-performance biomaterials with innovation in sustainable manufacturing, inclusive economic growth, reducing reliance on petroleum-based plastics and thus providing benefits regarding human health, climate change mitigation, plastic in the ocean, and environmental impacts.

This study investigates the mechanical behavior and energy absorption capacity of a novel metamortar composite, developed by embedding re-entrant auxetic cellular structures into a cementitious mortar matrix. Auxetic materials, which exhibit a negative Poisson's ratio, offer distinct advantages in impact resistance and stress dissipation. Despite their promising properties, their integration into cement-based systems remains limited. In this work, auxetic cells were fabricated using different 3D printing filaments and combined with mortar to form hybrid composites. The specimens were subjected to quasi-static compression tests to evaluate their Young's modulus, yield strength, and energy absorption capacity. Results indicate that the auxetic inclusions substantially improved the mechanical performance of the mortar, particularly in the case of PLA-based cells, which achieved the highest values across all tested parameters. The enhancements are attributed to the synergistic deformation mechanisms of the auxetic geometry and the surrounding matrix, promoting efficient load distribution and delayed crack propagation. These findings contribute to the advancement of cementitious metamaterials and establish a foundation for scaling toward metaconcrete systems with improved energy dissipation for use in protective, seismic, and infrastructure applications.

The rapid growth of 3D printing technology has opened up new avenues for innovation across various industries. However, the increasing use of non-biodegradable polymers in 3D printing has raised environmental concerns due to their contribution to plastic waste. This review paper examines sustainable approaches to 3D printing filament production, with a focus on recycling non-biodegradable waste, such as plastics, to create high-quality filaments. The paper explores current research on the development of recycling methods, material properties, economic viability, and the environmental impacts of using recycled polymers for 3D printing.

Abstract Additive manufacturing has incorporated renewable polymers, such as polylactic acid (PLA), but its low mechanical and thermal properties require the addition of 20% to 40% w/w of additives, which can reduce tensile strength by up to 60% and material degradation temperatures by 10 to 20 °C. This research seeks to reduce the use of commercial PLA additives by developing 3D printing filaments that incorporate a compatible plasticizer, polyethylene glycol (PEG), and synthesized PLA (PLA-R), in a lesser extent. The study presents the synthesis of filaments for fused filament fabrication (FFF) using a blend of commercial PLA, PLA-R obtained from 90% pure lactic acid, and PEG. The study focused on the evaluation of three blend ratios: these are pelletized and extruded using a single-screw extruder to produce filaments with a target diameter of 1.75 mm. Mechanical and thermal performance were evaluated using tensile testing and thermogravimetric analysis (TGA). The optimal formulation contains 80% commercial PLA, 15% PEG, and 5% PLA-R, resulting in a consistent filament diameter. This formulation was used to fabricate Dogbone samples on a desktop 3D printer using FFF. These samples were subsequently analyzed using tensile testing and scanning electron microscopy (SEM), demonstrating their improved properties and suitability for additive manufacturing. Graphical abstract Development of PLA-Based Filament for 3D Printing, Divided into Four Stages – (1) Ring Opening Polymerization of PLA-R; (2) Development of polymer blends; (3) Obtaining Filament by Extrusion; 4) 3D Printing by Fused Filament Fabrication Method.

The rapid growth of 3D printing in university makerspaces has created a new but often overlooked waste stream: discarded polylactic acid (PLA) filament from failed prints, support structures, and design errors. Although PLA is a bio-based and recyclable thermoplastic, most of this material currently ends up in landfills. This paper outlines a pilot project at NC State University to close this loop by collecting, processing, and re-extruding PLA waste into new 3D printing filaments. The system, developed through collaboration between the D.H. Hill Makerspace and Hodges Lab, employs a straightforward four-step process—collection, sorting, grinding, and extrusion—thereby achieving over 90% material efficiency. Besides demonstrating technical feasibility, the project emphasizes how campus-scale circular systems can reduce waste, lower costs, and serve as educational models for sustainable manufacturing. This initiative provides a replicable framework for universities and small-scale fabrication facilities seeking to incorporate circular economy principles into their operations.

Upcycling durian (Durio zibethinus) husk waste into PLA/activated carbon biocomposites for high-performance 3D printing filaments

3D-printed electrochemical devices have gained tremendousattentionrecently because they are highly customizable platforms for analysisand energy storage that can be produced using simple, inexpensivecomponents in a wide variety of settings. 3D-printed electrochemicalsensors, fabricated from carbon-loaded conductive thermoplastics,enable decentralized production of electrochemical devices that, ifoptimized, could be widely distributed. Achieving this goal requiresa comprehensive understanding of the electrochemical behavior of thesefilaments. Here, we investigated how the electrochemical behaviorof three commercial filaments was affected by alumina polishing, electrochemicalactivation in 0.5 M NaOH, and electrodepositing Au nanoparticles (NPs).The goal of this study is to characterize if/how these commonly usedpretreatments affect different filaments. The study is not an exhaustivecombination of all filaments and pretreatment options. We characterizedthe physical properties of each filament/pretreatment using thermogravimetricanalysis, scanning electron microscopy, and Raman microscopy measurements.We then benchmarked the background electrochemical processes (capacitanceand solvent window), the peak current response versus scan rate, andthe peak potential separation of two common outer-sphere redox species(ruthenium hexamine and ferrocene methanol) for each filament undereach pretreatment (i.e., nine total conditions).We subsequently investigated how the filaments responded to inner-sphereredox couples that were surface sensitive (ferrocyanide oxidation),dependent on surface adsorption (dopamine oxidation), and sensitiveto surface oxides (Fe2+ oxidation). The data collectivelyunderline the complexity of electrodes fabricated from conductive3D printing filaments and highlight several important considerationsthat should be addressed when interpreting the electrochemistry ofsuch materials. First, we present evidence that these materials behaveas partially blocked electrodes, which complicates interpretationsof electrochemical data. We also found that the outer-sphere electrochemicalreactivity on a given filament was largely consistent regardless ofpretreatment. The important variable for assessing outer-sphere electrontransfer was the uncompensated resistance (Ru), which varies depending on the filament material, electrodesize, and contact method. Finally, we observed that the selected filamentsdo not respond to pretreatments identically when tested against inner-sphereredox species, suggesting that a variety of treatments should be evaluatedwhen assessing conductive 3D-printed filament electrodes.

ABSTRACT The growing demand for sustainable materials in additive manufacturing highlights the need for biocomposites that are both environmentally friendly and industrially viable. However, most prior research on hemp fiber‐reinforced filaments has relied on chemically treated fibers and low fiber concentrations, limiting scalability, increasing production costs, and reducing industrial relevance. This study addresses that gap by developing 3D printing filaments using untreated hemp fibers combined with polylactic acid (PLA) and acrylonitrile styrene acrylate (ASA) polymer matrices, enhanced with bio‐based plasticizers. Filaments were produced via single‐screw extrusion and tested through fused deposition modeling (FDM) printing of ASTM D638 and D695‐compliant specimens. The results showed that incorporating 10% w/w hemp fiber with 2.5% w/w ESO in PLA led to a notable improvement in tensile strength and stiffness compared to the composition without plasticizer, while also enhancing printability. Excessive fiber or plasticizer content caused fabrication issues and performance degradation due to fiber agglomeration and poor interfacial bonding. In terms of plasticizers, ESO outperformed glycerin in mechanical reinforcement, though high ESO levels caused material buildup during extrusion. Importantly, when compared to some published data on chemically treated hemp composites, the developed untreated‐fiber formulations achieved comparable or superior mechanical performance, offering a more scalable and cost‐effective alternative for industrial applications. PLA‐based composites outperformed ASA‐based ones in mechanical metrics, but ASA composites offered better dimensional stability and surface finish. This study demonstrates a practical, scalable approach for producing biocomposite filaments without requiring fiber pretreatment, highlighting a cost‐effective pathway for sustainable 3D printing materials suitable for industrial‐scale use.