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Öğe Biomimetic design and fabrication of thermally induced radial gradient shape memory scaffolds using fused deposition modeling (FDM) for bone tissue engineering(Sage Publications Ltd, 2025) Eryildiz, MeltemBone defects pose a significant challenge, often exceeding natural healing capabilities. This study explores the potential of thermally induced radial gradient shape memory (RGSM) scaffolds for minimally invasive bone repair. Inspired by the natural porosity gradient of bone, these scaffolds feature a high-porosity inner zone that mimics cancellous bone and a low-porosity outer zone that resembles cortical bone. When the relationship between porosity and key properties was investigated, it was found that lower-porosity RGSM scaffolds exhibited higher compressive strength but experienced higher residual strain and lower shape recovery ratio compared to their higher-porosity counterparts. Despite this trade-off, the gradient design successfully mimicked the natural bone structure, potentially enhancing osseointegration and bone regeneration. These results demonstrate the feasibility of RGSM scaffolds for bone tissue engineering. This holds promise for advancing minimally invasive surgical techniques and improving the treatment of bone defects.Öğe Comparison of notch fabrication methods on the impact strength of FDM-3D-printed PLA specimens(Walter De Gruyter Gmbh, 2023) Eryildiz, MeltemIn this study, the effect of the notch fabrication method (printing the notch on the part, and machining the notch) on the impact results of 3D-printed polylactic acid (PLA) was investigated. Sensitivity to build orientation was also noted in both test situations. The impact test specimens were printed using an FDM-based printer with or without a notch at various build and print orientations. Un-notched specimens were then machined to create notches. To simulate the impact effects, Ansys software was employed to create a finite element model, and the results of the finite element analysis were consistent with the experimental results. According to the findings, the impact strength of the specimens with 3D-printed notches increased by 11-38% compared to specimens whose notch was machined after the rectangular bars were 3D printed. In addition, it has been observed that the build and print orientations affect the impact strength.Öğe Determination of the Effective Fused Deposition Modeling Process Parameters on the Mechanical Properties of Carbon Fiber-Reinforced Polypropylene Parts(Amer Soc Testing Materials, 2024) Eryildiz, Meltem; Kosa, Ergin; Yavuzer, Bekir; Akgun, Ismail CemAdditive manufacturing is gaining popularity for producing components in industries such as automotive, aerospace, and medicine due to its potential to minimize material waste. Because the strength of the 3-D-printed part is so important, it's crucial to do research and optimize process parameters to make the printed parts as strong as possible. This work focuses on the experimental investigation and discussion of the tensile and impact strength of parts made from carbon fiber-reinforced polypropylene (PP-CF) using the fused deposition modeling (FDM) technique. Various process parameters, including infill pattern, infill density, layer thickness, and build orientation, are examined on three different levels to determine their influence on the tensile and impact strength of the printed part. The outcomes of the analysis of variance (ANOVA) analysis reveal that infill density primarily affects impact strength, whereas layer thickness significantly influences tensile strength. The optimal combination of parameters leading to the maximum tensile and impact strength consists of a grid infill pattern, 60 % infill density, 0.36-mm layer thickness, and a 45 degrees build orientation. Furthermore, fracture surface analysis is consistent with mechanical test results.Öğe Development and Characterization of PLA/PCL Blend Filaments and 3D Printed Scaffolds(Springer, 2024) Eryildiz, Meltem; Karakus, Aleyna; Altan Eksi, MihrigulThis study investigates the manufacturing and characterization of polylactic acid (PLA)/polycaprolactone (PCL) blend filaments and 3D printed scaffolds for tissue engineering applications. This research provides a comprehensive investigation into both the PLA/PCL filament fabrication process and the subsequent 3D printing of PLA/PCL scaffolds. PLA/PCL blends have been prepared with a twin-screw extruder, followed by filament fabrication and 3D printing. The resulting samples underwent thorough characterization through mechanical, thermal, chemical, morphological, and rheological analyses, all tailored toward their application in tissue engineering. Results revealed that the addition of 20 wt. % PCL resulted in PLA/PCL blend scaffolds with improved mechanical and thermal properties, showing promise for future tissue engineering applications. This study provides novel insights into the fabrication and properties of PLA/PCL scaffolds, advancing the understanding of their potential in tissue engineering and offering valuable guidance for future research efforts in this domain. © ASM International 2024.Öğe Enhancing 3D-Printed PP-CF parts: A novel resin-filling technique for mechanical property optimization(Sage Publications Ltd, 2025) Eryildiz, Meltem; Kosa, Ergin; Akgun, Ismail Cem; Yavuzer, BekirThis study investigates a novel post-processing technique aimed at enhancing the mechanical properties of 3D-printed polypropylene-carbon fiber (PP-CF) composite parts. The method involves printing components with internal voids to reduce weight and printing time, subsequently filling these voids with a low-cost resin known for its superior mechanical properties. Through systematic experimentation varying infill density and pattern, key quantitative findings were obtained. Tensile strength generally increased with higher infill density, reaching a maximum of 55.664 MPa for the resin-filled triangle infill pattern with 60% infill density. Impact energy showed a decreasing trend with increasing infill density, with the highest impact energy of 0.5 J recorded for the resin-filled triangle infill pattern with 60% infill density. Microstructural analysis revealed that the triangle infill pattern at 60% infill density exhibited the most effective resin penetration, contributing to superior mechanical performance. These findings emphasize the importance of infill pattern selection in resin distribution and mechanical enhancement in 3D-printed composite materials.Öğe Experimental investigation and simulation of 3D printed sandwich structures with novel core topologies under bending loads(Walter De Gruyter Gmbh, 2023) Eryildiz, MeltemIn a range of applications, such as the automotive, aerospace, and shipbuilding sectors, where weight reduction is essential, sandwich structures are getting more popular. The performance of sandwich structures in bending can be enhanced by using lightweight core topologies. In this study, six different novel and new core topologies were designed with CATIA V5. Polylactic acid (PLA) sandwich structures with new core designs were produced using the fused deposition modeling (FDM) additive manufacturing method. In order to determine the mechanical characteristics of these six designed core topologies, three-point bending tests on sandwich structures were performed. The influence of core topology on the flexural characteristics of lightweight sandwich structures was investigated to appropriately choose and design the core topology of the sandwich structures to meet desired structural requirements. To evaluate the flexural behavior of sandwich structures, finite element simulation using ANSYS Workbench 2021 R2 was also performed. Both the experimental data and simulation were in good agreement and clearly showed that the sandwich structure with the triple bow core exhibited the highest mechanical properties. These results provide new perspectives on the investigation of the mechanical response of sandwich structures, which can be beneficial for many other industries and applications.Öğe Fabrication of a Microfluidic Test Device with a 3D Printer and Its Combination with the Loop Mediated Isothermal Amplification Method to Detect Streptococcus pyogenes(MDPI, 2024) Uysal, Hayriye Kirkoyun; Eryildiz, Meltem; Demirci, MehmetNew rapid, reliable, and cost-effective alternative systems are needed for the rapid diagnosis of Streptococcus pyogenes. The aim of this study was to fabricate a microfluidic test device to detect Streptococcus pyogenes by combining the Loop-mediated isothermal amplification method via a 3D printer. Microfluidic test devices were designed in CATIA V5 Release 16 software, and data were directly transferred to a 3D printer and produced using the FDM method with biocompatible PLA filament. The S. pyogenes ATCC 19615 and different ATCC strains was used. Following identification by classical culture methods, a 0.5 McFarland suspension was prepared from the colonies, and DNA isolation was performed from this liquid by a boiling method. S. pyogenes specific speB gene was used to desing LAMP primer sets in PrimerExplorer V5 software and tested on a microfluidic device. LAMP reactions were performed on microfluidic device and on a microcentrifuge tube separately. Both results were analyzed using the culture method as the standard method to diagnostic values. Melting curve analysis of the amplicons of the LAMP reactions performed on a LightCycler 480 system to detect amplification. Among the 50 positive and 100 negative samples, only four samples were found to be false negative by LAMP reaction in a microcentrifuge tube, while eight samples were found to be false negative by LAMP reaction on a microfluidic device. Six samples were found to be false positive by the LAMP reaction in the microcentrifuge tube, while ten samples were found to be false positive by the LAMP reaction on a microfluidic chip. The sensitivity, specificity, positive predictive value, and negative predictive value of the LAMP reactions performed in the microcentrifuge tube and on the microfluidic device were 92-84%, 94-90%, 88.46-80.77%, and 95.92-91.84%, respectively. The limit of detection (LOD) was found to be the same as 1.5 x 10(2) CFU/mL and the limit of quantification (LOQ) values of the LAMP reactions were performed on the microcentrifuge tube and on the microfluidic device were 2.46 x 102-7.4 x 10(2) CFU/mL, respectively. Cohen's kappa (kappa) values of the LAMP reactions were performed on the microcentrifuge tube and on the microfluidic device were 0.620-0.705, respectively. In conclusion, our data showed that the LAMP method can be combined with microfluidic test device to detect S. pyogenes, this microfluidic device can be manufactured using 3D printers and results are close to gold standard methods. These devices can be combined with LAMP reactions to detect different pathogens where resources are limited and rapid results are required.Öğe Fabrication of Drug-Loaded 3D-Printed Bone Scaffolds with Radial Gradient Porosity(Springer, 2023) Eryildiz, MeltemAs a result of the combination of better mechanical and biological properties, gradient porous scaffolds are becoming more and more interesting alternatives for bioengineering and medical implants. In this study, drug-loaded functionally radial gradient scaffolds were investigated. Drug-loaded polylactic acid scaffolds with radial gradient porosities with different infill zones that mimic the heterogeneous bone structure were designed and manufactured. The PLA scaffolds with radial gradients were produced using the fused deposition modeling (FDM) method with gyroid infill Homogeneous porosity scaffolds were also tested to compare the results. The porosity, cell proliferation, drug release, and compressive strength of the fabricated 3D printed scaffolds were all tested in vitro. According to findings, the scaffolds with radial gradients contained the highest cell proliferation and drug release results but exhibited decreased mechanical strength because of the increased porosity. The drug-loaded radial gradient scaffolds fabricated in this work could be used as bone scaffolds to supply antibiotics, and they have compressive strength and cell proliferation levels that are comparable to real bones. [GRAPHICS] .Öğe Influence of Process Parameters on the Shape Recovery Properties of 4D-Printed Polylactic Acid Parts Produced by Fused Deposition Modeling(Springer, 2023) Eryildiz, MeltemFour-dimensional (4D) printing technology allows printed parts to further alter their shapes or functions in response to external stimulus. 4D printing has been suggested for several potential applications in a range of industries, such as smart actuators, soft robotics, biomedical, and electronics. Shape memory polymers (SMP), which have the ability to change shape when heated, are programmable and deformable materials that are particularly well-suited for 4D printing. This study investigated the effect of 4D printing process parameters on the percentage of shape recovery. The selection of the appropriate process parameters is crucial to the success of 4D printing. Despite the large number of studies on the use of SMP, there is currently insufficient information on the relationship between the process parameters of the 4D printing process. The shape memory effect of the samples was examined by adjusting the sample thickness, nozzle temperature, deformation temperature, and holding time to achieve maximum percentage recovery for polylactic acid (PLA) using Taguchi's L16 orthogonal array. ANOVA was used to examine the impact of the process parameters taken into consideration. The results of the experiment showed that the sample thickness had the greatest influence. According to the results, the shape recovery percentage of the printed structures was enhanced by increasing the deformation temperature, holding temperature, and nozzle temperature while increasing the total thickness of the sample had a negative impact on shape recovery. A regression model on the recovery percentage against the process parameters is developed. This study has the feature of being a reference for future 4D printing studies.Öğe Scaffold fabrication from drug loaded HNT reinforced polylactic acid by FDM for biomedical applications(Wiley, 2023) Kokcu, Ilknur; Eryildiz, Meltem; Altan, Mirigul; Ertugrul, Melek Ipek; Odabas, SedatIn this study, multifunctional polymer nanocomposite scaffolds were fabricated by the fused deposition method (FDM) for biomedical applications. First, halloysite nanotube reinforced (1-5 wt%) polylactic acid filaments were prepared by melt mixing process. For the selected compositions, HNT was loaded with metformin (MET) by electrostatic interactions. The characterization of the scaffolds was observed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The morphology of the nanocomposite scaffolds was investigated by scanning electron microscope. Mechanical behavior of the scaffolds was determined by tensile, compression, and three-point flexural tests. It has been seen that 3%wt of HNT loading showed 124%, 145%, and 41% increments in tensile, compression, and three-point flexural strength of the scaffolds, respectively. In-vitro drug release and cell viability of the scaffolds were also examined. According to the cell viability result, a better cell proliferation regimen was achieved in all HNT-containing groups without any cytotoxicity effect. Also, approximately 50% of the total drug was released from the scaffolds at the end of 120 h. Finally, it has been seen that the developed scaffolds show promise for bone regeneration and replacement of bone.Öğe Tailoring mechanical properties of FDM-3D-printed parts through titanium dioxide-reinforced resin filling technique(Sage Publications Ltd, 2024) Eryildiz, MeltemFused deposition modeling (FDM) is a type of additive manufacturing that falls under the category of material extrusion. Building an object using FDM involves layer-by-layer selective deposition of melted material along a predetermined path. However, FDM parts are inherently anisotropic, meaning their mechanical properties vary depending on the direction of loading, which makes them prone to failure under transverse loads. This study introduces a novel post-processing technique to enhance the mechanical properties of FDM parts. Unlike conventional FDM printing, this study explores a post-processing technique where TiO2-infused resin is injected into the internal voids of printed parts to reinforce their structure. Compared to unfilled counterparts, resin filled structures exhibited significant improvements in tensile strength (up to 40%) and impact energy (up to 28%). A 20% infill density was found to offer a cost-effective balance between material usage and performance, while 2% wt. TiO2 achieved the optimal balance between reinforcement and dispersion, exceeding the performance gains of other concentrations. SEM analysis confirmed effective TiO2 dispersion at lower concentrations, leading to smoother surfaces and potentially improved mechanical properties. This technique presents a promising approach for fabricating high-performance FDM parts with enhanced strength and toughness.
