Polymerization Of Filaments Research Articles

Development of 3D-Printed Bicompartmental Devices by Dual-Nozzle Fused Deposition Modeling (FDM) for Colon-Specific Drug Delivery.

Dual-nozzle fused deposition modeling (FDM) is a 3D printing technique that allows for the simultaneous printing of two polymeric filaments and the design of complex geometries. Hence, hybrid formulations and structurally different sections can be combined into the same dosage form to achieve customized drug release kinetics. The objective of this study was to develop a novel bicompartmental device by dual-nozzle FDM for colon-specific drug delivery. Hydroxypropylmethylcellulose acetate succinate (HPMCAS) and polyvinyl alcohol (PVA) were selected as matrix-forming polymers of the outer pH-dependent and the inner water-soluble compartments, respectively. 5-Aminosalicylic acid (5-ASA) was selected as the model drug. Drug-free HPMCAS and drug-loaded PVA filaments suitable for FDM were extruded, and their properties were assessed by thermal, X-ray diffraction, microscopy, and texture analysis techniques. 5-ASA (20% w/w) remained mostly crystalline in the PVA matrix. Filaments were successfully printed into bicompartmental devices combining an outer cylindrical compartment and an inner spiral-shaped compartment that communicates with the external media through an opening. Scanning electron microscopy and X-ray tomography analysis were performed to guarantee the quality of the 3D-printed devices. In vitro drug release tests demonstrated a pH-responsive biphasic release pattern: a slow and sustained release period (pH values of 1.2 and 6.8) controlled by drug diffusion followed by a faster drug release phase (pH 7.4) governed by polymer relaxation/erosion. Overall, this research demonstrates the feasibility of the dual-nozzle FDM technique to obtain an innovative 3D-printed bicompartmental device for targeting 5-ASA to the colon.

Mesoscopic analysis and intra-layer progressive failure model of fused filament fabrication 3D printing GFRP

The deficiency of failure analysis methods severely hinders the civil engineering application of Fused Filament Fabrication (FFF) 3D printing composites. In order to comprehensively investigate the failure process, this paper innovatively proposes the concept of continuous printing filament hypothesis based on mesoscopic analysis. This hypothesis serves to characterize the interconnection status between glass fiber reinforced polymer (GFRP) filaments during FFF 3D printing. Building upon this hypothesis, a progressive failure model is established, which can predict the intra-layer failure process under axial quasi-static load accurately. In the failure model, both Mode-2D and Mode-3D failure criteria are employed to pinpoint intra-layer damage initiation, while damage evolution is depicted using a stiffness reduction mode based on the fracture energy criterion. Simultaneously, the fundamental orthotropic mechanical parameters are examined, and 24 variations of printing laminates are meticulously designed. The ultimate tensile strengths (UTS), encompassing both cross-stacking (2/8, 4/6, 5/5) and angle-stacking (30°, 45°, 60°), are tested and simulated using the progressive failure method established during this study. Experimental results show that the lower layers of composites exhibit stronger ultimate resistance due to their layer-by-layer characteristics. Compared to the experimental results, all the relative errors of UTS predicted by Mode-3D are less than 15%. Therefore, the accuracy and predictive capacity of the progressive failure model are affirmed by the experimental data.

3D printed PLGA implants: How the filling density affects drug release

Different types of ibuprofen-loaded, poly (D,L lactic-co-glycolic acid) (PLGA)-based implants were prepared by 3D printing (Droplet Deposition Modeling). The theoretical filling density of the mesh-shaped implants was varied from 10 to 100%. Drug release was measured in agarose gels and in well agitated phosphate buffer pH 7.4. The key properties of the implants (and dynamic changes thereof upon exposure to the release media) were monitored using gravimetric measurements, optical microscopy, Differential Scanning Calorimetry, Gel Permeation Chromatography, and Scanning Electron Microscopy. Interestingly, drug release was similar for implants with 10 and 30% filling density, irrespective of the experimental set-up. In contrast, implants with 100% filling density showed slower release kinetics, and the shape of the release curve was altered in agarose gels. These observations could be explained by the existence (or absence) of a continuous aqueous phase between the polymeric filaments and the “orchestrating role” of substantial system swelling for the control of drug release. At lower filling densities, it is sufficient for the drug to be released from a single filament. In contrast, at high filling densities, the ensemble of filaments acts as a much larger (more or less homogeneous) polymeric matrix, and the average diffusion pathway to be overcome by the drug is much longer. Agarose gel (mimicking living tissue) hinders substantial PLGA swelling and delays the onset of the final rapid drug release phase. This improved mechanistic understanding of the control of drug release from PLGA-based 3D printed implants can help to facilitate the optimization of this type of advanced drug delivery systems.

3D printing of wrist splint using low-temperature thermoplastic (LTTP) based polycaprolactone (PCL) material

ABSTRACT Fused Deposition Modelling (FDM) is a 3D printing process that allows layer-wise fabrication of a component by depositing thermoplastic material from a heated nozzle. The splints fabricated using the FDM technique should be mouldable so that they can easily be fitted on the body part. However, for some of the biomedical devices where remoulding is required, it cannot be fulfilled by the traditional polymer filaments used in the FDM process. Therefore, Low-Temperature Thermoplastic (LTTP) materials, having lower activation temperatures, can be used for such applications. Polycaprolactone (PCL) is a biocompatible LTTP material used in the FDM process that can be easily mouldable. In the present work, a wrist splint is fabricated using PCL filament by the FDM process. A detailed study of the influence of three FDM processing conditions viz. infill density, layer height and raster angle on the compressive properties is carried out to get the optimised values of the FDM processing parameters. The wrist splint has been fabricated using the optimised values of FDM parameters. The 3D printed wrist splint is found to fit comfortably with the user and it provides a suitable fit to immobilise an injured arm.

Simple Determination of the Melt Flow Index of Composite Polymer Filaments Used in Material Extrusion Additive Manufacturing

The mechanical properties improving filler introduction into polymer filaments often lead to the formation of defects in 3D-printed products. Studying the bulk modification of polyethylene terephthalate glycol (PETG) filaments with 0.5–1.5 wt% of natural shungite and molybdenum disulfide, we found the melt flow index (MFI) value reduced by 18%–30%. We investigate the effect of bulk modification on the filaments’ rheological properties, develop a technique that eliminates typical additive prototyping defects by regulation of the extrusion parameters in Cura slicing software, and propose an effective method for the MFI-measurement of the 3D-printed filaments that does not require special laboratory equipment (plastometers).

Dual-light emitting 3D encryption with printable fluorescent-phosphorescent metal-organic frameworks

Optical encryption technologies based on room-temperature light-emitting materials are of considerable interest. Herein, we present three-dimensional (3D) printable dual-light-emitting materials for high-performance optical pattern encryption. These are based on fluorescent perovskite nanocrystals (NCs) embedded in metal-organic frameworks (MOFs) designed for phosphorescent host-guest interactions. Notably, perovskite-containing MOFs emit a highly efficient blue phosphorescence, and perovskite NCs embedded in the MOFs emit characteristic green or red fluorescence under ultraviolet (UV) irradiation. Such dual-light-emitting MOFs with independent fluorescence and phosphorescence emissions are employed in pochoir pattern encryption, wherein actual information with transient phosphorescence is efficiently concealed behind fake information with fluorescence under UV exposure. Moreover, a 3D cubic skeleton is developed with the dual-light-emitting MOF powder dispersed in 3D-printable polymer filaments for 3D dual-pattern encryption. This article outlines a universal principle for developing MOF-based room-temperature multi-light-emitting materials and a strategy for multidimensional information encryption with enhanced capacity and security.

Experimental and Statistical Modeling for Effect of Nozzle Diameter, Filling Pattern, and Layer Height of FDM-Printed Ceramic–Polymer Green Body on Biaxial Flexural Strength of Sintered Alumina Ceramic

This paper deals with the application of statistical analysis in the study of the dependence of the flexural strength of sintered alumina (Al2O3) disks on the parameters (nozzle diameter of the printer print head, layer height, and filling pattern) of the fused deposition method (FDM) printing of ceramic–polymer filament containing 60 vol.% alumina and 40 vol.% polylactide. By means of a correlation analysis applied to the results of flexural tests, a linear relationship was found between the thickness of the printed layer and the strength of the sintered specimens. A statistically significant linear relationship was found between the geometric parameters and the weight of both printed ceramic–polymer and sintered ceramic samples, as well as the diameter of the nozzle used in the printing of the workpiece. It was found that the highest strength is achieved with a layer thickness equal to 0.4 mm, and the smallest scatter of mass values and geometric dimensions of ceramic samples is achieved using a nozzle diameter of 0.6 mm. As a result of the conducted research, linear equations allowing the prediction of changes in the geometry and mass of samples after sintering, as well as the strength properties of sintered samples, taking into account the geometry and mass of FDMed samples, were obtained.

Nascent adhesions shorten the period of lamellipodium protrusion through the Brownian ratchet mechanism.

Directional cell migration is driven by the conversion of oscillating edge motion into lasting periods of leading edge protrusion. Actin polymerization against the membrane and adhesions control edge motion, but the exact mechanisms that determine protrusion period remain elusive. We addressed this by developing a computational model in which polymerization of actin filaments against a deformable membrane and variable adhesion dynamics support edge motion. Consistent with previous reports, our model showed that actin polymerization and adhesion lifetime power protrusion velocity. However, increasing adhesion lifetime decreased the protrusion period. Measurements of adhesion lifetime and edge motion in migrating cells confirmed that adhesion lifetime is associated with and promotes protrusion velocity, but decreased duration. Our model showed that adhesions' control of protrusion persistence originates from the Brownian ratchet mechanism for actin filament polymerization. With longer adhesion lifetime or increased-adhesion density, the proportion of actin filaments tethered to the substrate increased, maintaining filaments against the cell membrane. The reduced filament-membrane distance generated pushing force for high edge velocity, but limited further polymerization needed for protrusion duration. We propose a mechanism for cell edge protrusion in which adhesion strength regulates actin filament polymerization to control the periods of leading edge protrusion.

E-cigarette vapor renders neutrophils dysfunctional due to filamentous actin accumulation

Electronic cigarette (e-cigarette) use continues to rise despite concerns of long-term effects, especially the risk of developing lung diseases such as chronic obstructive pulmonary disease. Neutrophils are central to the pathogenesis of chronic obstructive pulmonary disease, with changes in phenotype and function implicated in tissue damage. We sought to measure the impact of direct exposure to nicotine-containing and nicotine-free e-cigarette vapor on human neutrophil function and phenotype. Neutrophils were isolated from the whole blood of self-reported nonsmoking, nonvaping healthy volunteers. Neutrophils were exposed to 40 puffs of e-cigarette vapor generated from e-cigarette devices using flavorless e-cigarette liquids with and without nicotine before functions, deformability, and phenotype were assessed. Neutrophil surface marker expression was altered, with CD62L and CXCR2 expression significantly reduced in neutrophils treated with e-cigarette vapor containing nicotine. Neutrophil migration to IL-8, phagocytosis of Escherichia coli and Staphylococcus aureus pHrodo bioparticles, oxidative burst response, and phorbol 12-myristate 13-acetate-stimulated neutrophil extracellular trap formation were all significantly reduced by e-cigarette vapor treatments, independent of nicotine content. E-cigarette vapor induced increased levels of baseline polymerized filamentous actin levels in the cytoplasm, compared with untreated controls. The significant reduction in effector neutrophil functions after exposure to high-power e-cigarette devices, even in the absence of nicotine, is associated with excessive filamentous actin polymerization. This highlights the potentially damaging impact of vaping on respiratory health and reinforces the urgency of research to uncover the long-term health implications of e-cigarettes.

Rheological Model of a Polymer Filament with Hidden Degrees of Freedom

Rheological Model of a Polymer Filament with Hidden Degrees of Freedom

Long-length 3D printed hollow-core polymer optical fiber for wideband light guidance

A hollow-core microstructured polymer optical fiber containing a six-pointed star cladding design is directly drawn from a 3D printed preform for wideband light guidance. Fabrication of a complex geometry-based preform is enabled using commercially available translucent polymer filaments in a 3D printer. Light guidance from visible to infrared regions through the core of 57.8 cm long fiber is achieved with a minimum loss of 0.11 dB/cm in the near-infrared spectrum. The bending loss of the proposed design is also investigated to determine the light guidance under a mechanical effect. The modified fabrication process of the polymer optical fiber with novel design could be an alternative to conventional optical fibers for visible and infrared light guidance.

Circular Economy Advancements in Additive Manufacturing and Polymer Waste Recycling: Reshaping Sustainability

Abstract: Additive manufacturing is an exponentially growing sector that utilizes a lesser number of materials to create numerous products with the aid of Computer-Aided Design (CAD). Over the years, the adoption rate of polymer filaments in 3D printing has radically increased due to their user-friendliness and molecular properties. However, there are still different ways in which waste can be generated from 3D printing. This paper explores different aspects of ongoing studies to discuss efficacious solutions for closed-loop recycling systems in Distributed Recycling and Additive Manufacturing (DRAM). Concurrently, it probes for different additives that can reinforce the molecular structure of polymers, promoting repeated recycling. On the contrary, the existing papers have only explored the basic phases of the DRAM process. The implementation of closed-loop recycling can revolutionize the manufacturing sector by reducing overall Bourne costs and labor. Moreover, the proposal of compatibility of the DRAM process with different printing technologies, along with the effective implementation of additives, can provide integral benefits. Furthermore, the comparison of pure filaments and recycled filaments used for AM has helped us analyze the economic feasibility and energy recycling elements deployed for polymer wastes. Hence, the contemplation of the pyrolysis process has pontificated the necessity of various catalysts to increase the gasoline and diesel percentage in polymer waste recycling.

Implication of machining characteristics of PLA/BRONZE intermixture synthesized by additive manufacturing

This study focused on the drilling characteristics of polymeric composite filaments containing 12% bronze and are hot extruded under FDM conditions. The bronze 90 nm particle size was added with PLA matrix and extruded at 65°C to form a 1.25 mm diameter 3D filament mix and it was printed. A CNC micro drilling machining operation was carried out using tungsten carbide tooling with 45° flute angle by varying the diameter by 0.4, 0.6, and 0.8 mm respectively. Micro hole characteristics of printed blends were measured using an L27 orthogonal array, and the characteristics of the hole after drilling was measured using a scanning electron microscope. Experiments have shown that the delamination zone is affected by cutting speed and feed when measuring composite samples, and the hole.

Cytochalasans and Their Impact on Actin Filament Remodeling.

The eukaryotic actin cytoskeleton comprises the protein itself in its monomeric and filamentous forms, G- and F-actin, as well as multiple interaction partners (actin-binding proteins, ABPs). This gives rise to a temporally and spatially controlled, dynamic network, eliciting a plethora of motility-associated processes. To interfere with the complex inter- and intracellular interactions the actin cytoskeleton confers, small molecular inhibitors have been used, foremost of all to study the relevance of actin filaments and their turnover for various cellular processes. The most prominent inhibitors act by, e.g., sequestering monomers or by interfering with the polymerization of new filaments and the elongation of existing filaments. Among these inhibitors used as tool compounds are the cytochalasans, fungal secondary metabolites known for decades and exploited for their F-actin polymerization inhibitory capabilities. In spite of their application as tool compounds for decades, comprehensive data are lacking that explain (i) how the structural deviances of the more than 400 cytochalasans described to date influence their bioactivity mechanistically and (ii) how the intricate network of ABPs reacts (or adapts) to cytochalasan binding. This review thus aims to summarize the information available concerning the structural features of cytochalasans and their influence on the described activities on cell morphology and actin cytoskeleton organization in eukaryotic cells.

Basally distributed actin array drives embryonic hypocotyl elongation during the seed-to-seedling transition in Arabidopsis.

Seed germination is a vital developmental transition for the production of progeny by sexual reproduction in spermatophytes. The seed-to-seedling transition is predominately driven by hypocotyl cell elongation. However, the mechanism that underlies hypocotyl growth remains largely unknown. In this study, we characterized the actin array reorganization in embryonic hypocotyl epidermal cells. Live-cell imaging revealed a basally organized actin array formed during hypocotyl cell elongation. This polarized actin assembly is a barrel-shaped network, which comprises a backbone of longitudinally aligned actin cables and a fine actin cap linking these cables. We provide genetic evidence that the basal actin array formation requires formin-mediated actin polymerization and directional movement of actin filaments powered by myosin XIs. In fh1-1 and xi3ko mutants, actin filaments failed to reorganize into the basal actin array, and the hypocotyl cell elongation was inhibited compared with wild-type plants. Collectively, our work uncovers the molecular mechanisms for basal actin array assembly and demonstrates the connection between actin polarization and hypocotyl elongation during seed-to-seedling transition.

Experimental Investigations of the Influence of 3D Printing at 100% Filling on the Elastic Properties of PLA Polymer Filament Samples

Experimental Investigations of the Influence of 3D Printing at 100% Filling on the Elastic Properties of PLA Polymer Filament Samples

Development of Diclofenac Sodium 3D Printed Cylindrical and Tubular-Shaped Tablets through Hot Melt Extrusion and Fused Deposition Modelling Techniques.

The present study aimed to develop 3D printed dosage forms, using custom-made filaments loaded with diclofenac sodium (DS). The printed tablets were developed by implementing a quality by design (QbD) approach. Filaments with adequate FDM 3D printing characteristics were produced via hot melt extrusion (HME). Their formulation included DS as active substance, polyvinyl alcohol (PVA) as a polymer, different types of plasticisers (mannitol, erythritol, isomalt, maltodextrin and PEG) and superdisintegrants (crospovidone and croscarmellose sodium). The physicochemical and mechanical properties of the extruded filaments were investigated through differential scanning calorimetry (DSC), X-ray diffraction (XRD) and tensile measurements. In addition, cylindrical-shaped and tubular-shaped 3D dosage forms were printed, and their dissolution behaviour was assessed via various drug release kinetic models. DSC and XRD results demonstrated the amorphous dispersion of DS into the polymeric filaments. Moreover, the 3D printed tablets, regardless of their composition, exhibited a DS release of nearly 90% after 45 min at pH 6.8, while their release behaviour was effectively described by the Korsmeyer-Peppas model. Notably, the novel tube design, which was anticipated to increase the drug release rate, proved the opposite based on the in vitro dissolution study results. Additionally, the use of crospovidone increased DS release rate, whereas croscarmellose sodium decreased it.

Effect of printing parameters on extrusion-based additive manufacturing using highly filled CuSn12 filament

Typical additive manufacturing (AM) processes for producing metal and ceramic parts are highly energy-consuming and expensive to install and maintain. On the other hand, material extrusion AM (MEAM) technologies are conventionally used to produce polymeric parts but only marginally to process metallic materials. A feasible alternative is to process polymeric filaments loaded with metal particles. Debinding and sintering processes are then required to join the metal particles and obtain the final parts. In recent years, highly filled metal filaments consisting of a polymer loaded with a high concentration of metal powder have been commercialized for this purpose. In this study, the printability of a commercial CuSn12 filament was investigated by evaluating the influence of the process parameters on the density, shrinkage, porosity, and mechanical properties of the additively manufactured samples using a low-cost desktop 3D printer. Parameters such as the flow rate and ironing had the greatest influence on the density of the green samples. The correct selection of these parameters may reduce shrinkage after sintering. Furthermore, the obtained bronze had a notable ultimate tensile strength (mean value of 107 MPa), high stiffness (E values range from 38 to 50 GPa), and a greater elongation at break (mean value of 13%) than that of cast bronze of the same CuSn12 type. In this case, the extrusion pattern and ironing had the most significant influence on the final mechanical performance. The study provides insights into the use of highly filled bronze filaments combined with MEAM to produce functional parts for engineering applications.

Property enhancement of 3D printed of timber waste/PLA composite by surface coating

Poly Lactic Acid (PLA) is a biodegradable polymer that is both biocompatible and biodegradable. It is one of the bio-driven polymers. Additive manufacturing has opened up a plethora of new product types and application possibilities. In order to print components and parts, the fused deposition modeling technique makes use of polymer filaments. An experimental investigation was carried out to determine the effects of layer thickness and epoxy resin coating on the mechanical and water absorption capabilities of 3D printed timber waste/PLA composites. The results of the investigation are presented in this paper. The specimens were printed using a commercial Fused Deposition Modelling (FDM) method with layer thicknesses of 0.15 mm, 0.20 mm, and 0.25 mm. The specimens were made of wood waste and PLA composite. It was decided to cover the specimens with Araldite LY556 epoxy resin, with Aradur HY 591 serving as a hardener. Standard ASTM testing procedures were used to evaluate the tensile, impact, and water absorption capabilities of the material. Layer thicknesses of 0.15 mm yield the greatest results in terms of tensile strength and impact resistance. The samples with 0.15 mm layer thicknees provided the best tensile strength of 14.647 MPa, impact strength of 4.952 KJ/mm and 1.813 Wt. % of water absoption. The Araldite LY556 epoxy coating improved the tensile and impact strength of 3D printed specimens of different layer thicknesses and also reduced the water absorption to an appreciable amount. The coating improved the average tensile strength by 25.66% and impact strength by 33.16% and also reduced the water absorption by 89.96%.

Nanomaterials Reinforced Polymer Filament for Fused Deposition Modeling: A State-of-the-Art Review.

For the past years, fused deposition modeling (FDM) technology has received increased attention in the applications of industrial manufacturing fields, particularly for rapid prototyping, small batch production and highly customized products, owing to the merits of low-cost, user-friendliness and high design freedom. To further expand the application potential and promote the performance of the as-manufactured products, many efforts have been spent on the development of suitable materials for FDM applications. In recent years, the involvement of nanomaterials in the FDM-based polymer matrix, which has been demonstrated with great opportunities to enhance the performance and versatility of FDM printed objects, has attracted more and more research interest and the trend is expected to be more pronounced in the next few years. This paper attempts to provide a timely review regarding the current research advances in the use of nanomaterials to reinforce polymer filaments for the FDM technique. Polymer composite filaments based on nanomaterials such as carbon nanotubes, nanoclay, carbon fibers, graphene, metal nanoparticles and oxides are discussed in detail regarding their properties and applications. We also summarized the current research challenges and outlooked the future research trends in this field. This paper aims at providing a useful reference and guidance for skilled researchers and also beginners in related fields. Hopefully, more research advances can be stimulated in the coming years.