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Publication Metadata only A review of bioresorbable implantable medical devices: materials, fabrication, and implementation(Wiley, 2020) N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Singh, Rahul; Bathaei, Mohammad Javad; İstif, Emin; Beker, Levent; PhD Student; PhD Student; Researcher; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 354990; 308798Implantable medical devices (IMDs) are designed to sense specific parameters or stimulate organs and have been actively used for treatment and diagnosis of various diseases. IMDs are used for long-term disease screening or treatments and cannot be considered for short-term applications since patients need to go through a surgery for retrieval of the IMD. Advances in bioresorbable materials has led to the development of transient IMDs that can be resorbed by bodily fluids and disappear after a certain period. These devices are designed to be implanted in the adjacent of the targeted tissue for predetermined times with the aim of measurement of pressure, strain, or temperature, while the bioelectronic devices stimulate certain tissues. They enable opportunities for monitoring and treatment of acute diseases. To realize such transient and miniaturized devices, researchers utilize a variety of materials, novel fabrication methods, and device design strategies. This review discusses potential bioresorbable materials for each component in an IMD followed by programmable degradation and safety standards. Then, common fabrication methods for bioresorbable materials are introduced, along with challenges. The final section provides representative examples of bioresorbable IMDs for various applications with an emphasis on materials, device functionality, and fabrication methods.Publication Metadata only An exploration of plastic deformation dependence of cell viability and adhesion in metallic implant materials(Elsevier, 2016) Gerstein, G.; Maier, H. J.; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Uzer, Benay; Toker, Sıdıka Mine; Cingöz, Ahmet; Önder, Tuğba Bağcı; Canadinç, Demircan; Researcher; PhD Student; Researcher; Faculty Member; Faculty Member; Department of Mechanical Engineering; N/A; Graduate School of Sciences and Engineering; Graduate School of Health Sciences; School of Medicine; College of Engineering; N/A; 255504; N/A; 184359; 23433The relationship between cell viability and adhesion behavior, and micro-deformation mechanisms was investigated on austenitic 316L stainless steel samples, which were subjected to different amounts of plastic strains (5%, 15%, 25%, 35% and 60%) to promote a variety in the slip and twin activities in the microstructure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) revealed that cells most favored the samples with the largest plastic deformation, such that they spread more and formed significant filopodial extensions. Specifically, brain tumor cells seeded on the 35% deformed samples exhibited the best adhesion performance, where a significant slip activity was prevalent, accompanied by considerable slip-twin interactions. Furthermore, maximum viability was exhibited by the cells seeded on the 60% deformed samples, which were particularly designed in a specific geometry that could endure greater strain values. Overall, the current findings open a new venue for the production of metallic implants with enhanced biocompatibility, such that the adhesion and viability of the cells surrounding an implant can be optimized by tailoring the surface relief of the material, which is dictated by the micro-deformation mechanism activities facilitated by plastic deformation imposed by machining.Publication Metadata only Application of the finite element method in spinal implant design and manufacture(Woodhead Publ Ltd, 2012) N/A; Department of Mechanical Engineering; Zafarparandeh, Iman; Lazoğlu, İsmail; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391This chapter reviews the application of the finite element (FE) method in designing and manufacturing spinal implants. The structure of the chapter is built upon the procedure of creating the FE model for the human spine, which consists of establishing the FE model for each component of the spine, including mesh generation and material property, verification, validation and, finally, implant design process. Each part of the spine FE model is discussed from the simulation point of view and available models are introduced. For the implant design, some examples are chosen from the literature, which are also being used widely in the medical industry.Publication Metadata only Electro-conductive silica nanoparticles-incorporated hydrogel based on alginate as a biomimetic scaffold for bone tissue engineering application(Taylor and Francis Ltd., 2023) Derakhshankhah, Hossein; Eskandani, Morteza; Vandghanooni, Somayeh; Jaymand, Mehdi; Department of Mechanical Engineering; N/A; Taşoğlu, Savaş; Nakhjavani, Sattar Akbar; Faculty Member; Researcher; Department of Mechanical Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Engineering; N/A; 291971; N/AAn innovative electrically conductive hydrogel was fabricated through the incorporation of silica nanoparticles (SiO2 NPs) and poly(aniline-co-dopamine) (PANI-co-PDA) into oxidized alginate (OAlg) as a biomimetic scaffold for bone tissue engineering application. The developed self-healing chemical hydrogel was characterized by FTIR, SEM, TEM, XRD, and TGA. The electrical conductivity and swelling ratio of the hydrogel were obtained as 1.7 × 10−3 S cm−1 and 130%, respectively. Cytocompatibility and cell proliferation potential of the developed scaffold were approved by MTT assay using MG-63 cells. FE-SEM imaging approved the potential of the fabricated scaffold for hydroxyapatite (HA) formation and bioactivity induction through immersing in SBF solution.Publication Metadata only Evaluation of passive oxide layer formation–biocompatibility relationship in NiTi shape memory alloys: geometry and body location dependency(Elsevier, 2014) Maier, H. J.; N/A; Department of Mechanical Engineering; N/A; Toker, Sıdıka Mine; Canadinç, Demircan; Birer, Özgür; PhD Student; Faculty Member; Researcher; Department of Mechanical Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; N/A; 255504; 23433; N/AA systematic set of ex-situ experiments were carried out on Nickel-Titanium (NiTi) shape memory alloy (SMA) in order to identify the dependence of its biocompatibility on sample geometry and body location. NiTi samples with three different geometries were immersed into three different fluids simulating different body parts. The changes observed in alloy surface and chemical content of fluids upon immersion experiments designed for four different time periods were analyzed in terms of ion release, oxide layer formation, and chemical composition of the surface layer. The results indicate that both sample geometry and immersion fluid significantly affect the alloy biocompatibility, as evidenced by the passive oxide layer formation on the alloy surface and ion release from the samples. Upon a 30 day immersion period, all three types of NiTi samples exhibited lower ion release than the critical value for clinic applications. However; a significant amount of ion release was detected in the case of gastric fluid, warranting a thorough investigation prior to utility of NiTi in gastrointestinal treatments involving long-time contact with tissue. Furthermore, certain geometries appear to be safer than the others for each fluid, providing a new set of guidelines to follow while designing implants making use of NiTi SMAs to be employed in treatments targeting specific body parts.Publication Metadata only In silico analysis of modular bone plates(Elsevier, 2021) N/A; N/A; Department of Mechanical Engineering; N/A; Department of Mechanical Engineering; Subaşı, Ömer; Oral, Atacan; Noyan, Sinan; Tunçözgür, Orçun; Lazoğlu, İsmail; PhD Student; PhD Student; Undergraduate Student; Master Student; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; 179391Background: Inventory management or immediate availability of fracture plates can be problematic since for each surgical intervention a specific plate of varying size and functionality must be ordered. Modularization of the standard monolithic plate is proposed to address this issue. Methods: The effects of four different unit module design parameters (type, degree of modularization, connector screw diameter, sandwich ratio) on the plate bending stiffness and failure are investigated in a finite element four-point-bending analysis. A chosen, best-performing modular plate is then tested in silico for a simple diaphyseal tibial fracture scenario under anatomical compressional, torsional, and bending loads . Results: A modularization strategy is proposed to match the monolithic plate bending properties as closely as possible. With the best combination of design parameters, a fully modularized equivalent length plate with a 42.3% decrease in stiffness and 46.2% decrease in strength could be assembled. The chosen modular plate also displayed sufficient mechanical performance under the fracture fixation scenarios for a potentially successful osteosynthesis. Conclusions: Via computational methods, the viability of the modularization strategy as an alternate to the traditional monolithic plate is demonstrated. As a further realized advantage, the modular plates can alleviate stress shielding thanks to the reduced stiffness.Publication Metadata only In silico analysis of superelastic nitinol staples for trans-sternal closure(Elsevier, 2020) N/A; N/A; Department of Mechanical Engineering; Subaşı, Ömer; Torabnia, Shams; Lazoğlu, İsmail; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 179391Background: Superelastic Nitinol staples, utilized routinely in foot surgeries, are proposed to be used for sternal closure application in this study. It is hypothesized that the shape memory induced superelasticity will allow multiple staples placed along the sternum to promote fast and safe recovery by maintaining constant clamping pressure at the sternotomy midline. Methods: Two different Nitinol staples of different alloying compositions, one representing the metal formed wire geometry and, the other, powder metallurgy manufactured rectangular geometry, are chosen from the literature. Austenite finish temperatures of both materials are confirmed to be appropriately below the body temperature for superelastic shape memory activation. The adopted finite element superelasticity model is first validated and, via design optimization of parametrized dimensions, the staple geometries for producing maximal clamping forces are identified. The performances of the optimized staples for full trans-sternal closure (seven staples for each) are then tested under lateral sternal loading in separate computational models. Results: The optimized metal formed staple exerts 70.2 N and the optimized powder metallurgy manufactured staple exerts 245 N clamping force, while keeping the maximum localized stresses under the yield threshold for 90 degrees leg bending. Testing the staple-sternum constructs under lateral sternal loading revealed that the former staple can be utilized for small-chested patients with lower expected physiological loading, while the latter staple can be used for high-risk patients, for which high magnitude valsalva maneuver is expected. Conclusion: Computational results prove that superelastic Nitinol staples are promising candidates as alternatives to routinely performed techniques for sternal closure.Publication Metadata only The effect of plastic deformation on the cell viability and adhesion behavior in metallic implant materials(Wiley, 2018) N/A; Department of Mechanical Engineering; Uzer, Benay; Canadinç, Demircan; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 23433This chapter examines the relation between the plastic deformation and cell response on the austenitic 316L stainless steel samples, which were deformed by tensile loading up to 5 different strains: 5, 15, 25, 35 and 60% in an experiment. The specimens were ground with 400, 800, 1200 and 2500 grit SiC papers, and polished with the diamond abrasives with varied particle sizes. After completing the surface analyses, the steel samples were sterilized with an autoclave and each sample was placed into one well in a 24-well tissue culture plate (Costar). Then brain tumor and fibroblast cells were seeded on each well containing 1 ml growth medium and were incubated. The microscopy investigations of the implant surface in parallel with the cell response showed that the plastic deformation induced micro-deformation mechanisms improved the cell viability, attachment and spreading of the brain tumor cells, particularly by distorting the surface topography and enhancing the surface roughness. Surface characterization and microscopy analyses showed that increasing plastic deformation significantly altered surface topography by the formation of surface extrusions and grooves, which increased the surface roughness.Publication Metadata only Three-dimensional neurovascular co-culture inside a microfluidic invasion chemotaxis chip(Mary Ann Liebert, Inc, 2022) Cücük, Levent; Polat, İrem; N/A; Department of Mechanical Engineering; Sokullu, Emel; Taşoğlu, Savaş; Faculty Member; Faculty Member; Department of Mechanical Engineering; School of Medicine; College of Engineering; 163024; 291971N/A