For Fused Filament Fabrication Research Articles

Uncertainty Quantification of Process- Property-Structure Linkage for Fused Filament Fabrication Parts

Uncertainty Quantification of Process- Property-Structure Linkage for Fused Filament Fabrication Parts

Additive manufacturing for sustainability, circularity and zero-waste: 3DP products from waste plastic bottles

Polymers and their composites are now widely used in several industrial sectors, owing to their flexibility in developing customized products. The significant surge in plastic usage has led to a severe challenge in managing end-of-life plastic waste. Millions of tons of plastic waste produced annually mainly end up in landfills, leaking into the environment and posing severe threats to ecosystems. Innovative solutions to reuse/recycle/repurpose plastic waste are desired to address these global challenges. Therefore, in this study, a sustainable route to converting plastic waste into additive manufacturing (AM) feedstock is presented, where waste plastic bottles (mainly Polyethylene Terephthalate, PET) are recycled using an in-house 3D-printed filament extrusion system to produce filaments for fused filament fabrication (FFF) process. In addition to the recycled PET (rPET), virgin carbon fiber reinforced polyamide-6 (PA6-CF) polymer composites were also used to produce hybrid feedstock filaments. The rPET and rPET/PA6-CF composite filaments were extruded using an in-house filament extruder setup. The produced rPET-based filaments were characterized for their chemical and thermal properties. Subsequently, mechanical characterization was performed on 3D-printed specimens. The mechanical analysis revealed better tensile strength for rPET/PA6-CF than rPET; however, the rPET demonstrated better failure strain and young modulus, demonstrating their potential as viable materials for industrial and consumer applications. The outcomes of this study revealed promising results to promote sustainable production and consumption, complementing the circular economy practices with a straightforward production route to convert plastic waste into AM feedstock.

How to Improve Sustainability in Fused Filament Fabrication (3D Printing) Research?

AbstractThis review aims to provide an overview of sustainable approaches that can be incorporated into well‐known procedures for the development of materials, pre‐ and post‐treatments, modifications, and applications of 3D‐printed objects, especially for fused filament fabrication (FFF). Different examples of conductive and non‐conductive bespoke filaments using renewable biopolymers, bioplasticizers, and recycled materials are presented and discussed. The main final characteristics of the polymeric materials achieved according to the feedstock, preparation, extrusion, and treatments are also covered. In addition to recycling and remanufacturing, this review also explores other alternative approaches that can be adopted to enhance the sustainability of methods, aiming to produce efficient and environmentally friendly 3D printed products. Adjusting printing parameters and miniaturizing systems are also highlighted in this regard. All these recommended strategies are employed to minimize environmental damage, while also enabling the production of high‐quality, economical materials and 3D printed systems. These efforts align with the principles of Green Chemistry, Sustainable Development Goals (SDGs), 3Rs (Reduce, Reuse, Recycle), and Circular Economy concepts.

Development of a Polypropylene-Based Material with Flame-Retardant Properties for 3D Printing.

In this study, a nanocomposite based on a heterophasic polypropylene copolymer containing 5 wt% of nanoclays and 3 wt% of compatibilizer was formulated via melt compounding to obtain a material suitable for Fused Filament Fabrication (FFF) processing with enhanced flame-retardant properties. From rheological analyses, the nanocomposite showed an important increase in the non-Newtonian behavior, and, therefore, improved FFF printability compared to the pristine PP COPO. A filament with suitable characteristics for FFF was produced using a single-screw extruder and subsequently 3D printed. Finally, cone calorimeter and UL94 tests were carried out on both 3D-printed and compression-molded specimens. The obtained results showed that the 3D-printed samples exhibited even better flame-retardant properties than the compression-molded ones, thus demonstrating not only the possibility of successfully developing and using functionalized PP-based filaments in 3D printing but also the possibility of obtaining enhanced flame-retardant properties compared to conventional compression molding.

Plastic waste recycling in additive manufacturing: Recovery of polypropylene from WEEE for the production of 3D printing filaments

The inefficient management of wastes recovered from electric and electronic apparatuses (the so-called WEEE or e-waste) has become a severe global concern in the last years, since the indiscriminate accumulation of wastes containing hazardous material poses serious risks for the environmental, as well as for the human health. Despite the continuous development of innovative and efficient technologies for the mechanical recycling of WEEE plastics, the effective re-utilization of these fractions is often limited by their poor value-added. In this work, we propose a strategy for the valorization of a typical WEEE plastic stream recovered from small appliances (mainly composed on polypropylene filled with talc particles) through the formulation of filaments suitable for Fused Filament Fabrication (FFF) 3D printing processes. Preliminary spectroscopic analyses on the WEEE plastics allowed separating the sample in two streams, according to the different content of talc. Both streams were first characterized from a rheological point of view, aiming at assessing their 3D printability. Then, the mechanical properties and the morphology of the filaments (obtained after a close optimization of the extrusion conditions) were evaluated; the obtained results indicated the achievement of a regular geometry and mechanical properties comparable to those of commercial filaments. Finally, 3D printed specimens showed a satisfactory quality in terms of resolution and definition, demonstrating the possibility of profitably enhancing the value-added of WEEE plastics, using them as feedstock to produce sustainable 3D printing filaments.

Bio-Composite Filaments Based on Poly(Lactic Acid) and Cocoa Bean Shell Waste for Fused Filament Fabrication (FFF): Production, Characterization and 3D Printing.

In this study, novel biocomposite filaments incorporating cocoa bean shell waste (CBSW) and poly(lactic acid) (PLA) were formulated for application in Fused Filament Fabrication (FFF) technology. CBSW, obtained from discarded chocolate processing remnants, was blended with PLA at concentrations of 5 and 10 wt.% to address the challenge of waste material disposal while offering eco-friendly composite biofilaments for FFF, thereby promoting resource conservation and supporting circular economy initiatives. A comprehensive analysis encompassing structural, morphological, thermal, and mechanical assessments of both raw materials and resultant products (filaments and 3D printed bars) was conducted. The findings reveal the presence of filler aggregates only in high concentrations of CBSW. However, no significant morphological or thermal changes were observed at either CBSW concentration (5 wt.% and 10 wt.%) and satisfactory printability was achieved. In addition, tensile tests on the 3D printed objects showed improved stiffness and load resistance in these samples at the highest CBSW concentrations. In addition, to demonstrate their practical application, several 3D prototypes (chocolate-shaped objects) were printed for presentation in the company's shop window as a chocolate alternative; while retaining the sensory properties of the original cocoa, the mechanical properties were improved compared to the base raw material. Future research will focus on evaluating indicators relevant to the preservation of the biocomposite's sensory properties and longevity.

Fabrication and Characterization of Electrically Conductive 3D Printable TPU/MWCNT Filaments for Strain Sensing in Large Deformation Conditions

AbstractThis study investigates the development of thermoplastic polyurethane (TPU) filaments incorporating multi‐walled carbon nanotubes (MWCNT) to enhance strain‐sensing capabilities. Various MWCNT reinforcement ratios are used to produce customized feedstock for fused filament fabrication (FFF) 3D printing. Mechanical properties and the piezoresistive response of samples printed with these multifunctional filaments are concurrently evaluated. Surface morphology and microstructural observations reveal that higher MWCNT weight percentages increase filament surface roughness and rigidity. The microstructural modifications directly influence the tensile strength and strain energy of the printed samples. The study identifies an apparent percolation threshold within the 10–12 wt.% MWCNT range, indicating the formation of a conductive network. At this threshold, higher gauge factors are achieved at lower strains. A newly introduced Electro‐Mechanical Sensitivity Ratio (ESR) parameter enables the classification of composite behaviors into two distinct zones, offering the ability to tailor self‐sensing structures with on‐demand properties. Finally, flexible structures with proven application in soft robotics and shape morphing are fabricated and tested at different loading conditions to demonstrate the potential applicability of the custom filaments produced. The results highlight a pronounced piezoresistive response and superior load‐bearing performance in the examined structures.

A Methodological Framework for Assessing the Influence of Process Parameters on Strand Stability and Functional Performance in Fused Filament Fabrication.

With an ever-increasing material and design space available for Fused Filament Fabrication (FFF) technology, fabrication of complex three-dimensional structures with functional performance offers unique opportunities for product customization and performance-driven design. However, ensuring the quality and functionality of FFF-printed parts remains a significant challenge, as material-, process-, and system-level factors introduce variability and potentially hinder the translation of bulk material properties in the respective FFF counterparts. To this end, the present study presents a methodological framework for assessing the influence of process parameters on FFF strand stability and functional performance through a systematic analysis of FFF structural elements (1D stacks of FFF strands and 3D blocks), in terms of dimensional deviation from nominal geometry and resistivity, corresponding to the printability and functionality attributes, respectively. The influence of printing parameters on strand stability was investigated in terms of dimensional accuracy and surface morphology, employing optical microscopy and micro-computed tomography (mCT) for dimensional deviation analysis. In parallel, electrical resistance measurements were carried out to assess the effect of different process parameter combinations and toolpath patterns on functional performance. In low-level structural elements, strand height (H) was found to induce the greatest influence on FFF strand dimensional accuracy and resistivity, with higher H values leading to a reduction in resistivity of up to 38% in comparison with filament feedstock; however, this occurred at the cost of increased dimensional deviation. At higher structural levels, the overall effect of process parameters was found to be less pronounced, indicating that the translation of 1D strand properties to 3D blocks is subject to a trade-off due to competing mechanisms that facilitate/hinder current flow. Overall, the proposed framework enables the quantification of the influence of process parameters on the selected response variables, contributing to the development of standard operating procedures and recommendations for selecting optimal process parameters to achieve the desired process stability and functional performance in FFF.

4D printed and multi-stimulus responsive shape memory polymer nanocomposites developed on hydrogen bonding–metal-phenolic sacrificial network: Application for hazardous chemical operations soft robots

Designing 4D printed shape memory polymers (SMPs) with mechanical robust and multi-stimulus responses applied in soft robot holds vast promise. While significant progress has been made in this area, implementing SMP composites with multi-stimulus response capabilities for fused filament fabrication (FFF) 4D printing typically sacrifices the inherent mechanical properties of the materials, limiting the requirements for robust and tough applications of SMP in soft robotics. In this work, Fe3O4 nanoparticles are employed as functional particles, and the "hydrogen bonding–metal-phenolic" sacrificial network in the nanoparticles and polymer is designed to achieve NIR light and magnetic stimulation response without sacrificing the maximum strength and toughness of the 4D printable SMP. The SMP nanocomposite developed from the sacrificial network has a tensile strength of 18.98 MPa and an elongation at break of 897 %, a 40 % increase in strength and 196 % increase in elongation at break compared to SMP nanocomposites with direct Fe3O4 addition. In addition, the shape-programmable soft robot with NIR light and magnetic stimulation response is developed based on 4D printing. The remote precision control and drugs release demonstrates the potential application of 4D printed soft robots in hazardous chemical operations.

Hazelnut shell carbon filled polylactic acid composite filaments for 3D printing photothermal structures

Low-cost, compostable, high-efficiency photothermal conversion materials with shaping freedom into complex geometrical structures have received considerable attention by the photothermal conversion technologies. In this study, a kind of bio-based filament with photothermal conversion function for fused filament fabrication (FFF) technology was prepared by adding hazelnut shell carbon (HSCs) in polylactic acid (PLA) matrix. The HSCs were obtained at 300, 500, 700, and 900 °C. The results revealed that the morphology, particle size, pore structure, surface functional groups, and degree of graphitization of HSCs varied with the pyrolysis temperature. Additionally, the three-dimensional (3D) printability of PLA-HSC composite filaments as well as the photothermal performance of the printed structures were affected by the pyrolysis temperature of HSCs. All PLA-HSC filaments were suitable for 3D printing besides HSC pyrolyzed at 300 °C. Furthermore, the fluidity of the composites increased with the pyrolysis temperature of HSCs. The rheology results demonstrated that the complex viscosity, storage modulus, and loss modulus decreased with the increase of pyrolysis temperature. However, the mechanical properties and the thermal stability of the PLA-HSC filaments showed opposite trend. At the wavelength range of 250–2500 nm, with HSCs pyrolyzed at 700 and 900 °C, the 3D printed PLA-HSC parts demonstrated excellent photothermal performance with a light absorption intensity of around 93 %. Overall, HSCs pyrolyzed at 700 °C is the most cost-effective candidates for the preparation of PLA-based filament for photothermal conversion components. In this work, a brine evaporation crystallizer was 3D printed to demonstrate the application of this filament.

Overview and Comparison of PLA Filaments Commercially Available in Europe for FFF Technology.

This study presents a comprehensive techno-economic analysis of PLA materials for fused filament fabrication (FFF) from eight European manufacturers. The comparison involved rigorous experimental assessments of the mechanical properties, dimensional accuracy, and print quality using standardized methods and equipment such as tensile and CT testing. What makes this study unique is the consistent methodology applied, considering factors such as material color, printing temperature, printing orientation, filament diameter, and printer selection, to ensure meaningful and reliable results. Contrary to the common belief that a higher price implies better quality, the study revealed that the second cheapest PLA material achieved the best overall performance within the methodology employed. The study also confirmed certain observations, such as the influence of printing orientation and geometry on dimensional accuracy and mechanical properties, as well as the significant disparities between manufacturer-provided values and actual measured mechanical properties, highlighting the importance of experimental verification. Hence, the findings of this study hold value not only for the scientific community but also for hobbyist printers and beginners in the 3D printing realm seeking guidance in material selection for their projects. Furthermore, the methodology employed in this research can be adapted for evaluating a broad range of other 3D printing materials.

Steering Potential for Printing Highly Aligned Discontinuous Fibre Composite Filament.

DcAFF (discontinuous aligned fibre filament) is a novel material for fused filament fabrication (FFF) 3D printing made of highly aligned discontinuous fibres produced using high performance discontinuous fibre (HiPerDiF) technology. It reinforces a thermoplastic matrix to provide high mechanical performance and formability. Accurate printing of DcAFF poses a challenge, especially for complex geometries, because: (i) there is a discrepancy between the path where the filament experiences the adhering pressure from the filleted nozzle and the nozzle path; and (ii) the rasters display poor adhesion to the build platform immediately after deposition, which causes the filament to be dragged when the printing direction changes. This paper explains the implication of these phenomena on steering capabilities and examines the techniques for improving DcAFF printing accuracy. In the first approach, the machine parameters were adjusted to improve the quality of the sharp turning angle without changing the desired path, but this showed insignificant effects in terms of precision improvements. In the second approach, a printing path modification with a compensation algorithm was introduced. The nature of the inaccuracy of the printing at the turning point was studied with a first-order lag relationship. Then the equation to describe the deposition raster inaccuracy was determined. A proportional-integral (PI) controller was added to the equation to calculate the nozzle movement in order to bring the raster back to the desired path. The applied compensation path is shown to give an accuracy improvement in curvilinear printing paths. This is particularly beneficial when printing larger circular diameter curvilinear printed parts. The developed printing approach can be applied with other fibre reinforced filaments to achieve complex geometries.

Assessing the capabilities of ChatGPT to improve additive manufacturing troubleshooting

This paper explores the potential of using Chat Generative Pre-trained Transformer (ChatGPT), a Large Language Model (LLM) developed by OpenAI, to address the main challenges and improve the efficiency of the Gcode generation process in Additive Manufacturing (AM), also known as 3D printing. The Gcode generation process, which controls the movements of the printer's extruder and the layer-by-layer build process, is a crucial step in the AM process and optimizing the Gcode is essential for ensuring the quality of the final product and reducing print time and waste. ChatGPT can be trained on existing Gcode data to generate optimized Gcode for specific polymeric materials, printers, and objects, as well as analyze and optimize the Gcode based on various printing parameters such as printing temperature, printing speed, bed temperature, fan speed, wipe distance, extrusion multiplier, layer thickness, and material flow. Here the capability of ChatGPT in performing complex tasks related to AM process optimization was demonstrated. In particular performance tests were conducted to evaluate ChatGPT's expertise in technical matters, focusing on the evaluation of printing parameters and bed detachment, warping, and stringing issues for Fused Filament Fabrication (FFF) methods using thermoplastic polyurethane polymer as feedstock material. This work provides effective feedback on the performance of ChatGPT and assesses its potential for use in the AM field. The use of ChatGPT for AM process optimization has the potential to revolutionize the industry by offering a user-friendly interface and utilizing machine learning algorithms to improve the efficiency and accuracy of the Gcode generation process and optimal printing parameters. Furthermore, the real-time optimization capabilities of ChatGPT can lead to significant time and material savings, making AM a more accessible and cost-effective solution for manufacturers and industry.

Influence of printing direction on 3D-printed vascular based self-healing cementitious composites

Compared with other self-healing mechanisms, embedding vascular networks in cementitious matrix enables repairing wider cracks and performing multiple healing cycles. For vascular-based self-healing cementitious composites, additive manufacturing (AM) allows fabricating vascular structures with complex geometry. For Fused Filament Fabrication (FFF), printing direction has great influences on the properties of the 3D-printed vascular network. To timely release the healing agent when cracks occur, selecting the proper printing direction for the vascular network in self-healing concretes is necessary. In this work, two commercial printing filaments, i.e., polylactic acid (PLA) and polyvinyl alcohol (PVA), are used to create the vascular structures. The influence of printing direction on the dissolution of 3D-printed PVA structure is investigated. Besides, the flexural strength and water tightness of samples with PLA vascular printed in different printing directions are compared. After the 4-point bending tests, epoxy resin is manually injected into the vascular networks to seal the cracks. It is found that the strength recovery and the permeability of the cracked specimens are influenced by the printing direction due to the different crack closure after unloading.

Degradation of microcystin algal toxin by 3D printable polymer immobilized photocatalytic TiO2

Novel and sustainable solutions are needed for surface water treatment. Photocatalytic TiO2 is studied but is not directly deployable into natural water bodies due to settling and poor recoverability. This research capitalizes on a convergence of the emerging technologies of 3D printing biocompatible polymer (polylactic acid, PLA) composites, nanotechnology, and advanced oxidative processes to immobilize TiO2 into customizable, high surface area, deployable, and retrievable structures with localized kinetic specificity for harmful algal blooms (HAB). PLA-TiO2 composites at varying loadings (3–34 %) were extruded as feedstock for fused filament fabrication (FFF) enabling low cost printing design freedom of photocatalyst structures (disks, lattices). Large surface area, 3D lattices were printed as PLA composites with highly loaded (34 % w/w) TiO2. Prior to HAB cyanotoxin experiments, the photocatalytic performance of the 3D printed PLA-TiO2 lattice composites (t1/2 = 0.8 h) under UV light were confirmed comparable to free TiO2 (t1/2 = 0.9 h). Under environmentally relevant solar simulation, photocatalysis by printed lattices successfully reduced microcystin (MC) cyanotoxin (t1/2 = 3 h) faster than photolysis alone (t1/2 = 36 h). Lattice mediated photocatalysis of MC in presence of cyanobacteria cells (t1/2 = 11 h) was faster than photolysis (t1/2 = 58 h) but slower than water-only treatment due to cell activity and light attenuation. PLA-TiO2 reduces local pH, promoting MC adsorption and degradation. This research is foundational to novel photocatalytic composite optimization for reactive surface area prototyping enabled by 3D printing and scale-up for sustainable water treatment structures, with applicability to traditional and emerging contaminants.

Additive manufacturing of polypropylene micro and nano composites through fused filament fabrication for automotive repair applications

AbstractThe emerging Additive manufacturing technologies are being adopted by different industries, which require developing new materials and procedures. Here we report the development of polypropylene (PP) based composite materials for fused filament fabrication (FFF) process with the aim of enabling fully automatic robotic repair application of plastic components in automotive industry. A key challenge in repair and joining of polyolefins, which are widely used in such applications, is understanding the interplay of microstructural features and the joining mechanisms employed to achieve a uniform and fully functional repaired components. Specifically, for components manufactured from polypropylene based material, we show that the addition of ethylene propylene diene monomer (EPDM), polyisobutylene (PIB) and carbon black (CB) successfully modifies its matrix and produces a composite material ideal for additively repairing of complex geometries found in the automotive applications. This was brought about by effective reduction of the crystallinity of the composite PP matrix from 46.2% to 34.4% and resulting in a net reduction in warpage of the FFF 3D printed samples. Further, the thermal stability of the developed composite was improved with the addition of a moderate amount of carbon filler, enabling an FFF process with higher hot‐end temperatures, which subsequently allowed for tuning of the raw material's viscosity, and hence ensuring consistent deposition of molten filaments for building successive layers. Mechanical properties' analysis revealed that the addition of 10 wt.% CB increased the true stiffness (storage modulus) by 20%, the impact strength by 62%, with the drop in ultimate tensile strength of 11%. The optimal elongation at break and toughness were achieved for the samples containing 2 wt.% CB increasing these key properties by 62% and 58%, respectively. In terms of the melt flow index (MFI), as a key rheological indicator, the measured value ranged between 12.5 and 19.0 for all compositions suitable for the FFF process. Morphological analysis of the extruded filaments and fracture surface of impact test samples showed a mesoscale interspersion of polymer phases and a proper filler dispersion in the matrix material with sizes ranging from hundreds of nanometers to hundreds of microns. The developed 3D‐printable PP composite filament was successfully used in a robotic cell to repair broken plastic lugs of a car headlight assembly.

The development and characterization of carbon nanofiber/polylactic acid filament for additively manufactured piezoresistive sensors

In this work, an investigation into the effects of manufacturing parameters on carbon nanofiber (CNF)/polylactic acid (PLA) filament for fused filament fabrication (FFF) additive manufacturing (AM)-produced strain sensors was conducted. A design of experiments (DOE) approach was undertaken to explore the impact of CNF weight fraction, extrusion temperature, and number of extrusions on sensor performance. The initial extrusion combined pulverized PLA material and CNFs via a dry melt-mixing process. Through the DOE process, it was found that extruding CNF/PLA material at 185 °C for two total extrusions yielded material with dramatic improvements in electrical properties compared to unmodified material. Using the optimal manufacturing procedure, piezoresistive dog-bone shaped sensors were manufactured via FFF with 5.0, 7.5, and 10.0 wt % CNF/PLA filament and three different sizes. Piezoresistive testing under monotonic and cyclic loading conditions revealed strong and repeatable behavior from the piezoresistive AM sensors produced with 7.5 and 10.0 wt % CNFs. In general, 7.5 wt % CNF/PLA sensors showed greater strain sensitivity than 10.0 wt % CNF/PLA sensors for monotonic loading. Additionally, sensor size appeared to contribute significantly to the performance of 7.5 wt % CNF/PLA sensors. However, the 10.0 wt % CNF/PLA sensors exhibited greater repeatability in their piezoresistive response, and sensor size had much less impact on strain sensing performance. The printed sensors also exhibited a strong response under cyclic loading, however, variability in their piezoresistive response was significantly higher than under monotonic loading conditions. The results of this study are an important step towards the realization of low-cost, easily produced, and highly customizable strain sensors produced via FFF technology.

Effects of a rotary shear field on the interlayer bond and mechanical properties of polylactide fabricated using fused filament fabrication

Polylactide (PLA) is a kind of distinct semicrystalline polymer and widely applied for fused filament fabrication (FFF), because of its low price and high mechanical properties. But the bad interface of FFF printed PLA parts and their high mechanical anisotropy limit their industrial application deeply. In this work, an innovative FFF 3D printer with a rotary shear head was developed to control the interface and crystallization of FFF printed PLA parts. Compared with traditional FFF, the tensile strength of specimen fabricated via the rotary shear field increases from 21.1 MPa to 59.3 MPa, and the degree of mechanical anisotropy decreases from 0.41 to 0.09. As indicated by the meso-structure morphologies, not only the triangular voids between adjacent strands were disappeared, but also the randomly-distributed shish-kebab structure crystals and fibrils were obtained by the rotary shear field treatment. And the DSC results showed a high crystallinity value of 26.1% of specimen with the rotary shear field treatment. Therefore, the good interface, randomly-distributed crystals and high crystallinity contribute the effort to increase the tensile strength and decrease the degree of mechanical anisotropy of FFF printed PLA parts.

Development and Processing of New Composite Materials Based on High-Performance Semicrystalline Polyimide for Fused Filament Fabrication (FFF) and Their Biocompatibility.

Samples of composite materials based on high-performance semicrystalline polyimide R-BAPB (based on the dianhydride R: 1,3-bis-(3′,4,-dicarboxyphenoxy)benzene and diamine BAPB: 4,4′-bis-(4″-aminophenoxy)diphenyl)) filled with carbon nanofibers and micron-sized discrete carbon fibers were obtained by FFF printing for the first time. The viscosity of melts of the composites based on R-BAPB, thermal, mechanical characteristics of the obtained composite samples, their internal structure, and biocompatibility were studied. Simultaneously with FFF printing, samples were obtained by injection molding. The optimal concentrations of carbon fillers in polyimide R-BAPB for their further use in FFF printing were determined. The effect of the incorporation of carbon fillers on the porosity of the printed samples was investigated. It was shown that the incorporation of carbon nanofibers reduces the porosity of the printed samples, which leads to an increase in deformation at break. Modification of polyimide with discrete carbon fibers increases the strength and Young’s modulus sufficiently but decreases the deformation at break. The cytotoxicity analysis showed that the obtained composite materials are bioinert.

The Effect of PCL Addition on 3D-Printable PLA/HA Composite Filaments for the Treatment of Bone Defects.

The still-growing field of additive manufacturing (AM), which includes 3D printing, has enabled manufacturing of patient-specific medical devices with high geometrical accuracy in a relatively quick manner. However, the development of materials with specific properties is still ongoing, including those for enhanced bone-repair applications. Such applications seek materials with tailored mechanical properties close to bone tissue and, importantly, that can serve as temporary supports, allowing for new bone ingrowth while the material is resorbed. Thus, controlling the resorption rate of materials for bone applications can support bone healing by balancing new tissue formation and implant resorption. In this regard, this work aimed to study the combination of polylactic acid (PLA), polycaprolactone (PCL) and hydroxyapatite (HA) to develop customized biocompatible and bioresorbable polymer-based composite filaments, through extrusion, for fused filament fabrication (FFF) printing. PLA and PCL were used as supporting polymer matrices while HA was added to enhance the biological activity. The materials were characterized in terms of mechanical properties, thermal stability, chemical composition and morphology. An accelerated degradation study was executed to investigate the impact of degradation on the above-mentioned properties. The results showed that the materials’ chemical compositions were not affected by the extrusion nor the printing process. All materials exhibited higher mechanical properties than human trabecular bone, even after degradation with a mass loss of around 30% for the polymer blends and 60% for the composites. It was also apparent that the mineral accelerated the polymer degradation significantly, which can be advantageous for a faster healing time, where support is required only for a shorter time period.