Commercial Filament Research Articles

Destructive and non-destructive testing of samples from PLA and PETG materials

This study deals with the properties of PLA and PETG materials, which are important for gaining knowledge in biomedical applications. The process of obtaining an ideal implant from a material with suitable mechanical and physical properties is a complex process considered to be one of the most difficult in tissue engineering. PLA and PETG material properties were determined based on performed non-destructive and destructive materials testing methods. Destructive testing was performed on Hegewald and Peschke equipment and non-destructive testing was performed on Carl Zeiss Metrotome 1500 (Germany). Commercial filaments from various companies were selected, from which type 5A dogbone samples were printed on a TRILAB printer. Subsequently, after carrying out the tests on dogbone samples, the results were evaluated and compared with the help of graphs and tables.

Current research in development of polycaprolactone filament for 3D bioprinting: a review

Three-dimensional printing (3DP) provides a fast and easy fabrication process without demanding post-processing. 3D-bioprinting is a special class in 3DP. Bio-printing is the process of accurately 3DP structural design using filament. 3D bio-printing technology is still in the development stage, its application in various engineering continues to increase, such as in tissue engineering. As a forming material in 3D printing, many types of commercial filaments have been developed. Filaments can be produced from either natural or synthetic biomaterials alone, or a combination of the two as a hybrid material. The ideal filament must have precise mechanical, rheological and biological properties. Polycaprolactone (PCL) is specifically developed and optimized for bio-printing of 3D structures. PCL is a strategy in 3D printing to better control interconnectivity and porosity spatially. Structural stability and less sensitive properties environmental conditions, such as temperature, humidity, etc make PCL as an ideal material for the FDM fabrication process. In this review, we provide an in-depth discussion of current research on PCL as a filament currently used for 3D bio-printing and outline some future perspectives in their further development.

Investigation on hot melt extrusion and prediction on 3D printability of pharmaceutical grade polymers

The development of printable filaments has been identified as a critical aspect for the processing of pharmaceutical grade polymers and the fabrication of oral solid dosage forms. In this study a range of plain and drug loaded polymers were investigated and assessed for their printability in comparison to commercial filaments. Physicochemical characterizations of the polymers included differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and rheology were studied prior to Hot Melt Extrusion processing for the filament fabrication. A texture analyser was used to study the filament mechanical properties in order to derive the maximum tensile strength, Young’s Modulus and elongation at break. Principal component analysis was used to compare the printability of the polymer and to identify the contribution of each mechanical property. The analysis showed that maximum tensile strength with a threshold between 15 and 20 MPa is the most critical property for the prediction of the printability. Furthermore, printable filaments were processed using Fusion Deposition Modelling technology and optimal printing parameters were identified. The study demonstrated that the prediction of filament printability is feasible by evaluating the mechanical properties.

Development of highly sensitive electrochemical sensor using new graphite/acrylonitrile butadiene styrene conductive composite and 3D printing-based alternative fabrication protocol

Here, a novel electrically conductive thermoplastic material composed of graphite/acrylonitrile butadiene styrene (G/ABS) is reported for the first time. This material was explored on the production of 3D printing-based electrochemical sensors with enhanced sensitivity using a novel fabrication approach. The developed G/ABS electrodes showed lower charge transfer resistance (157 vs. 3279 Ω), higher electroactive area (0.61 vs. 0.19 cm2) and peak currents ca. 69% higher when compared with electrodes fabricated using carbon black/polylactic acid (CB/PLA) commercial filament, which has been widely explored in recent literature. Moreover, the G/ABS sensor provided satisfactory repeatability, reproducibility and stability (relative standard deviations (RSDs) were 1.14%, 6.81% and 10.62%, respectively). This improved performance can be attributed to the fabrication protocol developed here, which allows the incorporation of greater amounts of conductive material in the polymeric matrix. The G/ABS electrode also required a simpler and quicker protocol for activation when compared to CB/PLA. As proof of concept, the G/ABS sensor was employed for electroanalytical quantification of paracetamol (PAR) in pharmaceutical products. The linear concentration range was observed from 0.20 to 30 μmol L−1 and the limit of detection achieved was 54 nmol L−1, much lower than several recent studies dealing with the same analyte. The sensitivity of the G/ABS electrode regarding PAR was also far better when compared to CB/PLA sensor (0.50 μA/μmol L−1 vs. 0.12 μA/μmol L−1). Analyses in commercial pill samples showed good accuracy (recoveries ca. 108%) and precision (RSDs < 5%), suggesting great potential for use of this novel conductive thermoplastic in electroanalytical applications based on 3D printing.

A Bending Passive RFID Tag as a Sensor for High-Temperature Exposure

This paper introduces a prototype of a low-energy high-temperature exposure sensor, which is a temperature-sensitive passive UHF RFID tag that bends forward when exposed to warm air. This “Bending Tag” design is based on a simple dipole antenna fabricated from an electro-textile material. The antenna has a 3D-printed substrate, which is constructed from a commercial Thermo Reactive Filament that gets soft when exposed to 50°C for 30 seconds, causing the tag to bend forward and curve. The sensor tag initially has a read range of more than 6 meters throughout the global UHF RFID frequency band. After bending, there is a significant decrease in the read range (to around 2–3 meters), which is caused by the changed backscattered power of the sensor tag. In an office environment, the backscattered power changes from −36 dBm to −43 dBm. The change in a sensor tag-reference tag system as dP% is approximately 70%. Based on these initial results, our bending tag can be further developed to work as a cost-effective low-energy sensor for monitoring high-temperature exposure.

Characterization of WEEE plastics and their potential valorisation through the production of 3D printing filaments

Plastic is probably the fraction of the waste of electrical and electronic equipment (WEEE) most challenging to manage and the market of recycled plastics from WEEE is limited to few cases. In this study, twenty WEEE plastic samples collected in two material recovery facilities (MRFs) from manually sorted housings and components and among some discarded devices stored in Casaccia Research Center were analysed through infrared identification and chemical-physical characterization. The analyses were carried out in order to select the suitable samples for mechanical recycling in 3D printer filaments. Eleven different polymers or blends were found in the WEEE samples and the majority of those collected in the MRFs resulted as mixtures of different plastics, although often of styrene-based nature. On the other hand, many WEEE samples showed a good similarity to the corresponding virgin polymers with a content of halogens and inorganic fillers less than 0.2 and 5 wt%, respectively. The thirteen selected WEEE plastic samples were washed, reduced to < 4 mm and extruded in filaments with the proper diameter. The polymeric heterogeneity and the presence of foreign materials in some samples were the main critical issues highlighted during the extrusion. The suitable filaments were used to print test objects with different geometries. The quality control of the scanned objects, through a structured-light 3D scanner, showed that specimens printed with WEEE plastic filaments had no significant higher deviation from the model design in comparison to the same object produced using the commercial filaments.

Study on attenuation of 3D printing commercial filaments on standard X-ray beams for dosimetry and tissue equivalence

3D printing techniques and materials have become widely available in the last couple of decades and remains an important topic of research as the equipments and supplements gets chipper. This study aims to evaluate the attenuation behaviour of several commercially available 3D printing filaments (ABS and PLA-based filaments and other polymers blends) over standard X-ray beams ranging from ~30 keV - to ~50 keV and comparing the experimental results with theoretical data of Cortical Bone, Soft Tissue and PMMA. It was used the transmission method to obtain experimental attenuation coefficients to all materials. HVL for the materials were also calculated. Results show that PLA-based printing filaments mixed with metals (Al, BRASS and Cu) has higher attenuation than pure PLA. Comparing the experimental data with theoretical cross section of Soft Tissue, Cortical Bone and PMMA, it was possible to observe that with the increase of beam energy, ABS-based and other blends’ attenuation behaviour agree with PMMA/Soft tissue. None of the studied materials showed agreement of attenuation with Cortical Bone. Some variations of PLA (SILK, Black and Bone) and some of the other blends of PETG and TPU showed good agreement with Soft Tissue/PMMA since about 30 keV and it can be concluded that these filaments can be used as substitute of PMMA for mimetizing soft tissue in 3D printed phantoms.

3D printed spherical mini-tablets: Geometry versus composition effects in controlling dissolution from personalised solid dosage forms

Oral dosage forms are by far the most common prescription and over-the-counter pharmaceutical dosage forms used worldwide. However, many patients suffer from adverse effects caused by their use of “one-size fits all” mass produced commercially available solid dosage forms, whereby they do not receive dedicated medication or dosage adjusted to their specific needs. The development of 3D printing paves the way for personalised medicine. This work focuses on personalised therapies for hypertensive patients using nifedipine as the model drug. 3D printed full solid and channelled spherical mini-tablets with enhanced surface area (1.6-fold higher) were printed using modified PVA commercial filaments loaded by passive diffusion (PD), and Kollidon VA64 (KVA) and ethylcellulose (EC) based filaments prepared by hot-melt extrusion (HME). Drug loading ranged from 3.7% to 60% based on the employed technique, with a 13-fold higher drug loading achieved with the HME compared to PD. Composition was found to have a more significant impact on drug dissolution than geometry and surface area. Both KVA and EC-based formulations exhibited a biphasic zero-order drug-release profile. Physicochemical characterization revealed that nifedipine was in the amorphous form in the KVA-based end-products which led to a greater dissolution control over a 24 h period compared to the EC-based formulations that exhibited low levels of crystallinity by PXRD. The proposed 3D printed spherical mini-tablets provide a versatile technology for personalised solid dosage forms with high drug loading and dissolution control, easily adaptable to patient and disease needs.

Fabrication of Drug-Eluting Nano-Hydroxylapatite Filled Polycaprolactone Nanocomposites Using Solution-Extrusion 3D Printing Technique

Polycaprolactone/nano-hydroxylapatite (PCL/nHA) nanocomposites have found use in tissue engineering and drug delivery owing to their good biocompatibility with these types of applications in addition to their mechanical characteristics. Three-dimensional (3D) printing of PCL/nHA nanocomposites persists as a defiance mostly because of the lack of commercial filaments for the conventional fused deposition modeling (FDM) method. In addition, as the composites are prepared using FDM for the purpose of delivering pharmaceuticals, thermal energy can destroy the embedded drugs and biomolecules. In this report, we investigated 3D printing of PCL/nHA using a lab-developed solution-extrusion printer, which consists of an extrusion feeder, a syringe with a dispensing nozzle, a collection table, and a command port. The effects of distinct printing variables on the mechanical properties of nanocomposites were investigated. Drug-eluting nanocomposite screws were also prepared using solution-extrusion 3D printing. The empirical outcomes suggest that the tensile properties of the 3D-printed PCL/nHA nanocomposites increased with the PCL/nHA-to-dichloromethane (DCM) ratio, fill density, and print orientation but decreased with an increase in the moving speed of the dispensing tip. Furthermore, printed drug-eluting PCL/nHA screws eluted high levels of antimicrobial vancomycin and ceftazidime over a 14-day period. Solution-extrusion 3D printing demonstrated excellent capabilities for fabricating drug-loaded implants for various medical applications.

Design and Full Characterization of a 3-D-Printed Hyperbolic Pyramidal Wideband Microwave Absorber

A fully 3-D-printed wideband metamaterial absorber, characterized by an absorptivity above 0.95 in the X and Ku-bands and with a fractional bandwidth of 0.71, is presented in this letter. A 250 mm × 250 mm sample, with a total thickness of 6.3 mm (0.26λ0), is fabricated exploiting the fused deposition modeling technique with commercial filaments. To achieve a wideband absorption, a hyperbolic metamaterial with a pyramidal shape is designed by vertically stacking multiple resonant cavities. Lossy filaments are used to increase the dissipative losses and cavities with tailored dimensions are designed to absorb equidistant frequencies to obtain a unitary and flat absorption. The measurements are performed for different azimuth and incident angles, for both vertical and horizontal polarizations in anechoic and nonanechoic chambers. For normal incidence, thanks to the symmetry of the structure, quasi-unitary absorption is obtained over a wide frequency range from 8.2 to 17.2 GHz for azimuthal rotations of 90°. For oblique incidence, the absorption behavior in vertical polarization is better than the one in horizontal polarization. Two cases at azimuth angles of 0° and 30°, corresponding to the best and the worst performances of the presented absorber, are demonstrated in this letter.

A Low-Cost Method to Prepare Biocompatible Filaments with Enhanced Physico-Mechanical Properties for FDM 3D Printing.

Fused Deposition Modelling (FDM) 3D printing has received much interest as a fabrication method in the medical and pharmaceutical industry due to its accessibility and cost-effectiveness. A low-cost method to produce biocompatible and biodegradable filaments can improve the usability of FDM 3D printing for biomedical applications. The feasibility of producing low-cost filaments suitable for FDM 3D printing via single screw and twin-screw hot melt extrusion was explored. A single-screw extruder and a twin-screw extruder were used to produce biocompatible filaments composed of varying concentrations of polyethylene glycol (PEG) at 10%, 20%, 30% w/w and polylactic acid (PLA) 90%, 80% and 70% w/w, respectively. DSC, TGA and FTIR were employed to investigate the effect of PEG on the PLA filaments. The presence of PEG lowered the processing temperature of the formulation compositions via melt-extrusion, making it suitable for pharmaceutical applications. The use of PEG can lower the melting point of the PLA polymer to 170°C, hence lowering the printing temperature. PEG can also improve the plasticity of the filaments, as the rupture strain of twin-screw extruded filaments increased up to 10-fold as compared to the commercial filaments. Advanced application of FTIR analysis confirmed the compatibility and miscibility of PEG with PLA. Twin-screw extrusion is more effective in producing a polymeric mixture of filaments as the mixing is more homogenous. The PEG/PLA filament is suitable to be used in 3D printing of medical or pharmaceutical applications such as medical implants, drug delivery systems, or personalised tablets.

Investigating Commercial Filaments for 3D Printing of Stiff and Elastic Constructs with Ligament-Like Mechanics.

The current gold standard technique for treatment of anterior cruciate ligament (ACL) injury is reconstruction with autograft. These treatments have a relatively high failure and re-tear rate. To overcome this, tissue engineering and additive manufacturing are being used to explore the potential of 3D scaffolds as autograft substitutes. However, mechanically optimal polymers for this have yet to be identified. Here, we use 3D printing technology and various materials with the aim of fabricating constructs better matching the mechanical properties of the native ACL. A fused deposition modeling (FDM) 3D printer was used to microfabricate dog bone-shaped specimens from six different polymers—PLA, PETG, Lay FOMM 60, NinjaFlex, NinjaFlex-SemiFlex, and FlexiFil—at three different raster angles. The tensile mechanical properties of these polymers were determined from stress–strain curves. Our results indicate that no single material came close enough to successfully match reported mechanical properties of the native ACL. However, PLA and PETG had similar ultimate tensile strengths. Lay FOMM 60 displayed a percentage strain at failure similar to reported values for native ACL. Furthermore, raster angle had a significant impact on some mechanical properties for all of the materials except for FlexiFil. We therefore conclude that while none of these materials alone is optimal for mimicking ACL mechanical properties, there may be potential for creating a 3D-printed composite constructs to match ACL mechanical properties. Further investigations involving co-printing of stiff and elastomeric materials must be explored.

Fabrication of Montelukast sodium loaded filaments and 3D printing transdermal patches onto packaging material.

The main objectives of this work were to develop and characterize new 3D printing filaments and print them directly onto a packaging material. Different blends of polymers were tested to achieve low-temperature printing filaments, which are flexible and durable to be wound onto spools. The mechanical properties of filaments were compared with commercial filaments and evaluated by bending tests. Kollidon 12PF, PEG 4000, and PEO 900k blends resulted in promising filaments that could be extruded at 70°C and had flexibility similar to commercial PLA filaments. Montelukast sodium (MS), which undergoes hepatic first-pass metabolism, was compounded into polymer blends, and drug-loaded filaments were extruded. All filaments were tested with a 3D printing pen prior to using with the 3D printer for transdermal patches. MS loaded filaments and patches showed similar flexibility with placebo. In vitro drug release studies showed 52% of MS was released in 24h. Printing on disposable packaging material is presented for the first time with this study. Build plate adhesion and cohesion of 3D printed layers were successfully achieved. This new technique could prevent cross-contamination, save time, and provide ease of use, which can take us one step closer to the production of personalized drugs in pharmacies.

Flash ablation metallization of conductive thermoplastics

Fused filament fabrication (FFF) is the most widely available 3D printing technology. Recently, a variety of conductive thermoplastic filaments have become commercially available, allowing printing of electronic structures using the technology. However, the contact interface and conductivity of these filaments after printing remains relatively poor, the latter of which is typically at least four orders of magnitude lower than bulk metal conductors. While several post-processing approaches exist to enhance conductivity, they are either user-intensive, time consuming, or cannot easily be integrated in-line with the rest of the printing process. In this work, we demonstrate that exposing conductive composite thermoplastic films (3D printed or solution-cast) to high-intensity pulsed light increases their conductance by up to two orders of magnitude in a manner that is fast, non-contact, and potentially in-line. This process, referred to as flash ablation metallization (FAM), is found to vaporize the thermoplastic matrix on the top surface of a composite film, leaving behind a metal-dense surface layer. The technique was found to be effective for a variety of commercial and custom-made conductive thermoplastic composites, with the largest response found in Electrifi, a commercial filament consisting of copper particle loading in a biodegradable polyester. 3D-printed circuit boards were constructed with and without FAM exposure, with exposed circuits exhibiting reduced operating voltages as well as improvements in reliability.

Thermal and rheological properties of self-fabricated polyethylene glycol-plasticized poly(lactic acid) filaments for fused deposition modeling

In this work, thermal and rheological properties of self-fabricated polylactic acid (PLA) filaments without and with 10-wt% polyethylene glycol (PLA/0PEG and PLA/10PEG, respectively) were investigated, and the properties were compared with a commercial PLA filament used for fused deposition modeling (FDM). The result showed that the melt flow index for self-fabricated filaments was comparable with commercial filaments at approximately 10 g/10 min at 190°C, suggesting suitability to be used as filament for FDM with well-wetted layers. Variation in thermal properties was found in PLA/10PEG with 20°C higher cold crystallization temperature ( T cc) after FDM in which disruption of the molecular arrangement reduced the ability for chain alignment and folding. The result also revealed that addition of PEG decreased the storage modulus ( G′), loss modulus ( G″), and complex viscosity ( η*), resulting in slow crystallization behavior, and however, the properties did not induce degradation of the filaments and printing products.

Commercial filament testing for use in 3D printed phantoms

There is a great demand for phantoms by many areas of knowledge to be used for teaching or daily work. However, commercial phantoms are expensive and hard to obtain, especially in countries going through development. As an alternative, 3D printing can be the way to produce less expensive and reliable 3D phantoms. The goal of this study is to evaluate 14 available commercial filaments, in order to find if and how they can be used in 3D printed phantoms in computed tomography. Each material was printed as a 2 cm edge cube with rectilinear pattern and 60, 80 and 100% infill. The 80% infill of five other patterns were also printed and compared. Each 100% infill cube was weighted and had its density calculated. After that, the cubes were scanned in a Philips CT Brilliance 6 with 120 kVp, 200 mA, 2 mm slices and standard reconstruction. At the center of each cube, a ~120 mm2 region of interest was set to measure the mean Hounsfield Unit (HU) and its standard deviation. The software Origin was used to plot HU results for rectilinear pattern, determine linear trends with its R2 and compare achieved values with HU tissue range from literature. To confirm the response of HU values of selected tested materials in CT imaging as a function of percentage infill, a phantom prototype of a finger was 3D printed. The HU of the tested materials ranged from −516.2 ± 7.3 to 329.8 ± 18.9. All human tissues could be mimicked making use of these materials, except cortical bone above ~350 HU and tooth parts. The most promising filament was PLA + Cu, due to the multiple infill configuration that allows the resulting HU range to represent from adipose and skin tissue to marrow bone.

Mechanical testing of hydroxyapatite filaments for tissue scaffolds preparation by fused deposition of ceramics

Composite filaments with diameter ∼1.75 mm suitable for fused deposition of ceramics were prepared from commercial hydroxyapatite powders (HAp-0, d50 ≤ 35 μm and HAp-1, d50 ≤ 16 μm) and thermoplastic polymer - polyvinyl alcohol. The filament printability in FDC applicable as specific bone-part replacements, is connected to its mechanical strength and slenderness ratio affecting the resistance to buckling. The HAp content in prepared composite filaments was at the level of ∼ 50 % and their mechanical properties were compared to commercial filament based on polylactic acid and ∼ 27 % of gypsite used as inorganic filler. The tensile strength of laboratory prepared filaments was about 3 times lower than strength found for commercial filament. The critical buckling pressure calculated from Euler buckling analysis using measured intrinsic Young´s modulus revealed underestimated critical pressure values ∼ 2.5–5.0 times if compared to values of maximal filament compressive pressure loads simulating buckling.

The mechanical performance of 3D printed hierarchical honeycombs using carbon fiber and carbon nanotube reinforced acrylonitrile butadiene styrene filaments

The aim of this paper is to design hierarchical honeycombs as well as manufacturing such structures with a commercial 3D Printer using Fused Filament Fabrication (FFF) technique. The materials under study are commercial filaments such as acrylonitrile butadiene styrene (ABS), acrylonitrile butadiene styrene/carbon fibers (ABS/CF) and acrylonitrile butadiene styrene/carbon nanotubes (ABS/CNTs). The fabricated hierarchical honeycombs were examined by compression tests in order to evaluate the mechanical behaviour of such honeycomb 3D printed structures. The compression behaviour of the hierarchical honeycombs was assessed also with finite element analysis (FEA) and at the end there was a comparison with the experimental findings. The results reveal that the 2nd order hierarchy presented an increase both in stiffness and strength in comparison with the 0th and the 1st hierarchies which make such designs a suitable for structures require such properties. Also, the results reveal that ABS/carbon fiber constructs outperform the other materials under study.

Polymer-derived SiOC replica of material extrusion-based 3-D printed plastics

A promising method for obtaining ceramic components with additive manufacturing (AM) is to use a two-step process of first printing the artifact in polymer and then converting it to ceramic using pyrolysis to form polymer derived ceramics (PDCs). AM of ceramic components using PDCs has been demonstrated with a number of high-cost techniques, but data is lacking for fused filament fabrication (FFF)-based 3-D printing. This study investigates the potential of lower-cost, more widespread and accessible FFF-based 3-D printing of PDCs. Low-cost FFF machines have a resolution limit set by the nozzle width, which is inferior to the resolutions obtained with expensive stereolithography or selective laser sintering AM systems. However, to match the performance a partial PDC conversion is used here, where only the outer surface of the printed polymer frame is converted to ceramic. Here the FFF-based 3-D printed sample is coated with a preceramic polymer and then it is converted into the corresponding PDC sample with a high temperature pyrolysis process. A screening experiment is performed on commercial filaments to obtain ceramic 3-D prints by surface coating both hard thermoplastics: poly lactic acid (PLA), polycarbonate (PC), nylon alloys, polypropylene (PP), polyethylene terephthalate glycol (PETG), polyethylene terephthalate (PET), and co-polyesters; and flexible materials including: flexible PLA, thermoplastic elastomer and thermoplastic polyurethane filaments. Mass and volume changes were quantified for the soaking and pyrolysis steps to form a hollow ceramic skin. All 3-D printing materials extruded at 250 microns successfully produced hollow ceramics skins of less than 100 microns. Details on the advantages and disadvantages of the different 3-D printing polymer precursors are discussed for this processing regime. The novel results developed here can be used to choose FFF-based polymers to use for PDC processing on a wide range of applications such as heat exchangers, heat sinks, scaffoldings for bone tissue growth, chemical/ gas filters and custom scientific hardware.

Additive manufacturing and characterization of a load cell with embedded strain gauges

In this paper we present the exploitation of Fused Filament Fabrication (FFF) to manufacture a load cell using double extrusion of conductive and non-conductive commercial materials in a single-step printing cycle. A load cell with four embedded strain gauges, manufactured with tailored process parameters and strategies, was used to deposit the conductive filament to obtain near equal electrical resistance values among the four strain gauges, aiming to connect them in a full Wheatstone bridge configuration. Subsequently, several tests were performed, firstly to understand the behavior of each strain gauge and then to characterize the load cell. The tests showed that the strain gauges are sensible to compressive and tensile deformation and that the load cell's voltage, obtained by connecting the four strain gauges in a full Wheatstone bridge, decreases as the force applied increases. This work demonstrates the potential of FFF technology in the sensor manufacturing field and that it is possible to integrate sensitive elements into non-sensitive elements without an additional assembly process by using low-cost commercial filaments and 3D printers.