Prospects for SLS 3D printing of PA12/bentonite/kaolinite composite membrane

Assessment of mechanical properties and microstructure of Co-Cr dental alloys manufactured by casting, milling, and 3D printing.

Introduction: With the advent of digital dentistry, modern fabrication techniques, such as three-dimensional (3D) printing and computer-aided design/computer-aided manufacturing (CAD/CAM) milling, might offer promising alternatives to conventional heat-cured methods. This study aimed to compare the flexural and impact strengths of polymethyl methacrylate (PMMA) denture base resins fabricated using 3D printing, CAD/CAM milling, and conventional heat polymerization.Materials and methods: An in vitro experimental design was employed to fabricate denture base resin specimens using three different techniques. Group 1 (n = 40) consisted of heat-polymerized PMMA specimens, Group 2 (n = 40) comprised CAD/CAM-milled PMMA disks, and Group 3 (n = 40) included specimens fabricated with 3D-printed PMMA resin. Standardized rectangular samples were prepared for each group and subjected to thermocycling and artificial saliva immersion to simulate oral conditions. The flexural strength was tested using a three-point bend method on a universal testing machine, while the impact strength was evaluated using an Izod-type impact testing machine. Each group consisted of 20 specimens for flexural strength testing and 20 specimens for impact strength testing. Statistical analysis was conducted using one-way analysis of variance (ANOVA) and Tukey’s post hoc test, with a significance level set at p < 0.05.Results: Flexural strength analysis revealed that the CAD/CAM-milled specimens exhibited the highest mean strength, followed by the 3D-printed and conventional groups. Significant differences were found between the CAD/CAM and the other two groups (p < 0.05), while the 3D-printed and conventional groups showed no significant difference (p > 0.05). Impact strength testing showed that the 3D-printed specimens had the highest mean values, followed by the CAD/CAM and conventional groups. All pairwise comparisons for impact strength were statistically significant, indicating superior energy absorption in the 3D-printed specimens (p < 0.05).Conclusion: This study demonstrated that CAD/CAM milling resulted in the highest flexural strength, making it favorable for resisting functional stress. However, the 3D-printed resins exhibited superior impact strength, suggesting enhanced resistance to sudden forces.

The field of three-dimensional (3D) printing has witnessed significant advancements in recent years, and its potential for revolutionizing medical applications is rapidly emerging. This review aims to provide an overview of the current state and scope of 3D printing in the medical field. The review begins by highlighting the various 3D printing technologies currently employed in healthcare settings, including stereolithography, selective laser sintering, fused deposition modeling, and inkjet printing. Each technology's advantages and limitations are discussed, shedding light on their suitability for different medical applications. Next, the review delves into the diverse range of medical applications where 3D printing has shown promise. These applications include the fabrication of patient-specific anatomical models for preoperative planning, surgical guides and tools, customized implants and prosthetics, tissue engineering scaffolds, and drug delivery systems. The potential benefits of using 3D printing in these areas, such as enhanced surgical accuracy, improved patient outcomes, reduced surgery time, and personalized medicine, are explored. Furthermore, the review addresses the challenges and limitations associated with implementing 3D printing in medical settings. These challenges include regulatory concerns, standardization of processes, material biocompatibility, cost-effectiveness, and scalability. The ongoing efforts to overcome these barriers and the future directions of 3D printing in medicine are also discussed. In conclusion, 3D printing holds immense potential for transforming various aspects of medical practice. While considerable progress has been made, there are still challenges to be addressed before widespread adoption can be achieved. With continued research and development, coupled with regulatory support and collaboration between academia, industry, and healthcare professionals, 3D printing is poised to International Journal of Scientific Research in Engineering and Management (IJSREM) Volume: 07 Issue: 07 | July - 2023 SJIF Rating: 8.176 ISSN: 2582-3930 © 2023, IJSREM | www.ijsrem.com DOI: 10.55041/IJSREM24845 | Page 2 make a substantial impact in the field of medicine, improving patient care and treatment outcomes. Key words: Additive manufacturing (AM); Bio-medical; Fused Deposition Modelling (FDM); Selective Laser Sintering (SLS); Stereolithography (SLA); Digital Light Processing (DLP); Binder Jetting; Material Jetting; Direct Energy Deposition (DED).

PurposeThe range of applications of the currently available biomass selective laser sintering (SLS) parts is limited and low-quality. This study aims to demonstrate the effects of the various processing parameters on the dimensional accuracy, bending strength, tensile strength, density and impact strength of the Prosopis chilensis/polyethersulfone (PES) composites (PCPCs) that were produced by SLS. The various processing parameters are laser power, scan speed, preheating temperature, scan spacing and layer thickness. In addition, the authors’ studied the effects of PCP particle size on the mechanical properties of the PCPCs.Design/methodology/approachThe PCPC specimens were printed using an AFS SLS machine (additive manufacturing). The bending, tensile and impact strengths of the specimens were measured using a universal tensile tester. The dimensional accuracy of the bending specimens was determined by a Vernier caliper. The formability of the PCPC at various mixing ratios of the raw materials was earlier investigated by single-layer sintering experiments (Idriss et al., 2020b). The microstructure and particle distribution of the various PCPC specimens were analyzed by scanning electron microscopy (SEM).FindingsThe mechanical strengths (bending, tensile and impact strengths and density) and the dimensional accuracy of the PCPC SLS parts were directly and inversely proportional, respectively, to the laser power and preheating temperature. Furthermore, the mechanical strengths and dimensional accuracy of the PCPC SLS parts were inversely and directly proportional, respectively, to the scanning speed, scan spacing and layer thickness.Practical implicationsPCPC is an inexpensive, energy-efficient material that can address the drawbacks of the existing SLS parts. It is also eco-friendly because it lowers the pollution and CO2 emissions that are associated with waste disposal and SLS, respectively. The optimization of the processing parameters of SLS in this study produced high-quality PCPC parts with high mechanical strengths and dimensional accuracy that could be used for the manufacture of the roof and wooden floors, construction components and furniture manufacturing.Originality/valueTo the best of the authors’ knowledge, this study is among the first to elucidate the impact of the various SLS processing parameters on the mechanical properties and dimensional accuracy of the sintered parts. Furthermore, novel PCPC parts were produced in this study by SLS.

Fabrication of Si3N4–SiC/SiO2 composites using 3D printing and infiltration processing

Morphology, microstructure, and phase states in selective laser sintered lithium ion battery cathodes

With the rapid development of 3D printing technology, the requirement of coated sand for Selective Laser Sintering (SLS) is becoming higher in terms of performance and volume. As a molding material with higher performance requirement and much more expensive than common shell molding sand, the emissions of one-time used SLS coated sand could lead to not only environmental pollution but also waste of resources. In this paper, the regeneration processes of coated sand for SLS was studied to discover the best parameters for the regeneration technology. Subsequently, the regenerated sand was coated. The samples for tensile strength and bending strength testing were sintered using HRPS-VI SLS equipment. Afterwards, the original sand for SLS and the regenerated sand was analyzed and compared in terms of sand microstructure, tensile strength, bending strength and cauterant decrease are analyzed and compared between original SLS sand and generated sand. The primary results show that: The morphology of regenerated sand is approximately close to spherical; the tensile strength and bending strength of the samples sintered using SLS coated regenerated sand are almost the same of the original SLS coated sand.

Chapter 2 - 3D printing and nanotechnology

3D Printing, sometimes referred to as additive manufacturing, has made the concept of personalized medicine a reality. The primary objective of 3D and 4D printing is to produce intricate, customized pharmaceuticals at a reasonable cost. With improvements in materials, resolution, and speed, 3D printing technology is quickly developing. It includes faster construction, cost efficiency through reduced waste, design flexibility for complex structures, and sustainability through optimized material usage. An extensive literature survey was done on 3D and 4D printing of pharmaceuticals using PubMed, Elsevier, ScienceDirect, and Springer. The results were then filtered based on the titles, abstracts, and accessibility of the complete texts. The search engine Google Scholar was accessed for literature data mining. From the data mining, it was found that from the year 2009 to 2024 the number of research publications surged more than 200 times on the current topic. Even though 3-D and 4-D printing technologies have advanced significantly in a short amount of time, the most often used ones are still stereolithography, nozzle-based deposition, inkjet, and selective laser sintering. Their use has been modified for the production of nanoparticles, polypills, tablets, and implants, etc. Pharma's aspirations for tailored medications are being revolutionized by 3D printing, but cost, flexibility, and bioequivalence still need to be investigated. The present review offers a thorough analysis of various 3D and 4D printing methods and emphasizes the major advantages and disadvantages and major key challenges of 3D and 4D printing related to pharmaceuticals. Compared to 3D Printing, 4D printing offers better quality, efficacy, and functionality.

3D printing is a new emerging technology in the pharmaceutical manufacturing landscape. Its potential advantages for personalized medicine have been widely explored and commented on in the literature over recent years. More recently, the selective laser sintering (SLS) technique has been investigated for oral drug-delivery applications. Thus, this article reviews the work that has been conducted on SLS 3D printing for the preparation of solid oral forms (SOFs) from 2017 to 2020 and discusses the opportunities and challenges for this state-of-the-art technology in precision medicine. Overall, the 14 research articles reviewed report the use of SLS printers equipped with a blue diode laser (445–450 nm). The review highlights that the printability of pharmaceutical materials, although an important aspect for understanding the sintering process has only been properly explored in one article. The modulation of the porosity of printed materials appears to be the most interesting outcome of this technology for pharmaceutical applications. Generally, SLS shows great potential to improve compliance within fragile populations. The inclusion of “Quality by Design” tools in studies could facilitate the deployment of SLS in clinical practice, particularly where Good Manufacturing Practices (GMPs) for 3D-printing processes do not currently exist. Nevertheless, drug stability and powder recycling remain particularly challenging in SLS. These hurdles could be overcome by collaboration between pharmaceutical industries and compounding pharmacies.

This research demonstrates the influence of laser speed and the drug particle size on the manufacturing of amorphous solid dispersions (ASD) and dosage forms thereof using selective laser sintering 3-dimensional (3D) printing. One-step manufacturing of ASD is possible using selective laser sintering 3D printing processes, however, the mechanism of ASD formation by this process is not completely understood and it requires further investigation. We hypothesize that the mechanism of ASD formation is the diffusion and dissolution of the drug in the polymeric carrier during the selective laser sintering (SLS) process and the drug particle size plays a critical role in the formation of said ASDs as there is no mixing involved in the sintering process. Herein, indomethacin was used as a model drug and introduced into the feedstock (Kollidon® VA64 and Candurin® blend) as either unprocessed drug crystals (particle size > 50 µm) or processed hot-melt extruded granules (DosePlus) with reduced drug particle size (<5 µm). These feedstocks were processed at 50, 75, and 100 mm/s scan speed using SLS 3D printing process. Characterization and performance testing were conducted on these tablets which revealed the amorphous conversion of the drug. Both MANOVA and ANOVA analyses depicted that the laser speed and drug particle size significantly impact the drug’s apparent solubility and drug release. This significant difference in performance between formulations is attributed to the difference in the extent of dissolution of the drug in the polymeric matrix, leading to residual crystallinity, which is detrimental to ASD’s performance. These results demonstrate the influence of drug particle size on solid-state and performance of 3D printed solid dispersions, and, hence, provide a better understanding of the mechanism and limitations of SLS 3D printing of ASDs and its dosage forms.

ObjectivesThe aim of this systematic review and network meta-analysis was to compare the flexural strength of provisional fixed dental prostheses (PFDPs) fabricated using different 3D printing technologies, including digital light processing (DLP), stereolithography (SLA), liquid crystal display (LCD), selective laser sintering (SLS), Digital Light Synthesis (DLS), and fused deposition modeling (FDM).Materials and methodsA comprehensive literature search was conducted in databases including PubMed, Web of Science, Scopus, and Open Grey up to September 2024. Studies evaluating the flexural strength of PFDPs fabricated by 3D printing systems were included. A network meta-analysis was performed, using standardized mean differences (SMDs) and 95% confidence intervals (CIs) to assess the effects of each system on flexural strength.ResultsA total of 11 in vitro studies were included, with 9 studies contributing to the network meta-analysis. SLS (77.70%) and SLA (63.82%) systems ranked the highest in terms of flexural strength, while DLP ranked the lowest (23.40%). Significant differences were observed between SLS and multiple other systems, including DLP (-14.58, CI: -22.67 to -6.48), LCD (-14.65, CI: -25.54 to -3.59), FDM (-12.87, CI: -23.30 to -2.52), SLA (-11.41, CI: -18.74 to -4.01), and DLS (-10.89, CI: -21.23 to -0.67). Direct comparisons were limited, with DLP vs. SLA having the most data. Other comparisons were predominantly indirect.ConclusionsSLS and SLA systems exhibited superior flexural strength compared to other systems. However, the limited number of direct comparisons and reliance on indirect evidence suggest that further research is necessary to confirm these findings.

Graphene is an important nanocarbon nanofiller for polymeric matrices. The polymer–graphene nanocomposites, obtained through facile fabrication methods, possess significant electrical–thermal–mechanical and physical properties for technical purposes. To overcome challenges of polymer–graphene nanocomposite processing and high performance, advanced fabrication strategies have been applied to design the next-generation materials–devices. This revolutionary review basically offers a fundamental sketch of graphene, polymer–graphene nanocomposite and three-dimensional (3D) and four-dimensional (4D) printing techniques. The main focus of the article is to portray the impact of 3D and 4D printing techniques in the field of polymer–graphene nanocomposites. Polymeric matrices, such as polyamide, polycaprolactone, polyethylene, poly(lactic acid), etc. with graphene, have been processed using 3D or 4D printing technologies. The 3D and 4D printing employ various cutting-edge processes and offer engineering opportunities to meet the manufacturing demands of the nanomaterials. The 3D printing methods used for graphene nanocomposites include direct ink writing, selective laser sintering, stereolithography, fused deposition modeling and other approaches. Thermally stable poly(lactic acid)–graphene oxide nanocomposites have been processed using a direct ink printing technique. The 3D-printed poly(methyl methacrylate)–graphene have been printed using stereolithography and additive manufacturing techniques. The printed poly(methyl methacrylate)–graphene nanocomposites revealed enhanced morphological, mechanical and biological properties. The polyethylene–graphene nanocomposites processed by fused diffusion modeling have superior thermal conductivity, strength, modulus and radiation- shielding features. The poly(lactic acid)–graphene nanocomposites have been processed using a number of 3D printing approaches, including fused deposition modeling, stereolithography, etc., resulting in unique honeycomb morphology, high surface temperature, surface resistivity, glass transition temperature and linear thermal coefficient. The 4D printing has been applied on acrylonitrile-butadiene-styrene, poly(lactic acid) and thermosetting matrices with graphene nanofiller. Stereolithography-based 4D-printed polymer–graphene nanomaterials have revealed complex shape-changing nanostructures having high resolution. These materials have high temperature stability and high performance for technical applications. Consequently, the 3D- or 4D-printed polymer–graphene nanocomposites revealed technical applications in high temperature relevance, photovoltaics, sensing, energy storage and other technical fields. In short, this paper has reviewed the background of 3D and 4D printing, graphene-based nanocomposite fabrication using 3D–4D printing, development in printing technologies and applications of 3D–4D printing.

Selective Laser Sintering (SLS) is a manufacturing process that can build arbitrarily shaped parts without part specific tooling. Its advantages have been employed in many different fields, one of these being medical surgery. Currently, SLS is limited in medical applications as a pre-operative modeling tool. For SLS manufacturing to progress in areas like compliant surgical tooling and patient specific bone matrices, concurrent work is needed to investigate the effects of medical sterilization on SLS materials. This paper presents the results of sterilization experiments on SLS parts built from nylon 11. To simulate the process of introducing tools into a sterile environment, these specimens were subjected to multiple rounds of dry heat sterilization. Changes to the dimensions, tensile strength and flexibility were recorded and analyzed. It was found that the specimens’ dimensions remained relatively constant. Both the tensile modulus and the flexural modulus decreased as the sterilization cycles progressed. The tensile modulus decreased by 25% and the flexure modulus decreased by 19% after ten rounds of sterilization.

Thermoplastic materials such as PA12 and PA6 have been extensively employed in Selective Laser Sintering (SLS) 3D printing applications due to their printability, processability, and crystalline structure. However, thermoplastic-based materials lack polymer inter-chain bonding, resulting in inferior mechanical and thermal properties and relatively low fatigue behavior. Therefore, 3D printing of high-performance crosslinked thermosets using SLS technology is paramount to pursue as an alternative to thermoplastics. In this work, a thermoset resin was successfully 3D printed using SLS, and its thermal stability of printed parts after a multi-step post-curing process was investigated. Dimensionally stable and high glass transition temperature (Tg: ~300 °C) thermoset parts were fabricated using SLS. The polymer crosslinking mechanism during the printing and curing process was investigated through FTIR spectra, while the mechanical stability of the SLS 3D-printed thermoset was characterized through compression tests. It is found that 100% crosslinked thermoset can be 3D printed with 900% higher compressive strength than printed green parts.