Researcher:
Uzer, Benay

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PhD Student

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Benay

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Uzer

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Uzer, Benay

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2016 - 20187

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Researcher Of Publications: search.filters.isAuthorOfPublication.8213ca92-e515-41bb-b2f7-fafa0ff02327

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Now showing 1 - 7 of 7
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    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; 23433
    The 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.
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    Nanotwin formation in high-manganese austenitic steels under explosive shock loading
    (Springer, 2018) Elmadagli, M.; Guner, F.; Department of Mechanical Engineering; N/A; Canadinç, Demircan; Uzer, Benay; Faculty Member; PhD Student; Department of Mechanical Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Engineering; Graduate School of Sciences and Engineering; 23433; N/A
    The micro-deformation mechanisms active in a high-manganese austenitic steel were investigated upon explosive shock loading. Single system of nanotwins forming within primary twins were shown to govern the deformation despite the elevated temperatures attained during testing. The benefits of nanotwin formation for potential armor materials were demonstrated.
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    The influence of plastic deformation mechanisms on the adhesion behavior and collagen formation in osteoblast cells
    (Springer, 2018) Monte F.; Awad, Kamal R.; Aswath, Pranesh B.; Varanasi, Venu G.; 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; 23433
    In many of biomedical applications, the implant might get in direct contact with the bone tissue where the osteogenesis needs to be stimulated. If osteoblasts can not successfully attach on the implant surface, the bone might resorb and implant can fail. In the current study MC3T3 cells were cultured on the 316L stainless steel samples which were deformed up to four different strain levels (5, 15, 25 and 35%) to activate plastic deformation mechanisms (slip and twinning) in different volume fractions. Scanning electron microscopy (SEM) images showed that cells adhered and spread significantly on the 25 and 35% deformed samples owing to the greater surface roughness and energy provided by the increased density of micro-deformation mechanisms which promoted the formation of focal contacts. In addition, significant amount of collagen formation was observed on the sample deformed up to 25% of strain which can be due to the ideal match of the surface roughness and collagen molecules. Overall these results show that material’s microstructure can be manipulated through plastic deformation mechanisms in order to enhance the cell response and collagen deposition. As a result long lasting implants could be obtained which would eliminate additional surgical interventions and provide a successful treatment.
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    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; 23433
    This 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.
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    PublicationOpen Access
    A critical approach to the biocompatibility testing of NiTi orthodontic archwires
    (Vibgyor Online Publishers, 2016) Şahbazoğlu, D.; Toker, S. M.; Saher, D.; Department of Mechanical Engineering; Canadinç, Demircan; Gümüş, Berkay; Uzer, Benay; Yıldırım, Cansu; Polat-Altıntaş, Sevgi; Faculty Member; Department of Mechanical Engineering; College of Engineering; 23433; N/A; N/A; N/A; N/A
    The biocompatibility of Nickel-Titanium (NiTi) archwires was investigated by simulating actual contact state of archwires around brackets, which enabled incorporation of realistic mechanical conditions into ex situ experiments. Specifically, archwires (undeformed, and bound to brackets on acrylic dental molds) were statically immersed in artificial saliva (AS) for 31 days. Following the immersion, the archwires and the immersion solutions were analyzed with the aid of variouselectron-optical techniques, and it was observed that carbon-rich corrosion products formed on both archwire sets upon immersion. The corrosion products preferentially formed at the archwire–bracket contact zones, which is promoted by the high energy of these regions and the micro-cracks brought about by stress assisted corrosion. Moreover, it is suggested that these corrosion products prevented significant Ni or Ti ion release by blocking the micro-cracks, which, otherwise, would have led to enhanced ion release during immersion. The current findings demonstrate the need for incorporating both realistic chemical and mechanical conditions into the ex situ biocompatibility experiments of orthodontic archwires, including the archwire-bracket contact.
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    PublicationOpen Access
    On the mechanical response and microstructure evolution of NiCoCr single crystalline medium entropy alloys
    (Taylor _ Francis, 2018) Picak, S.; Liu, J.; Jozaghi, T.; Karaman, I.; Chumlyakov, Y. I.; Kireeva, I.; Department of Mechanical Engineering; Uzer, Benay; Canadinç, Demircan; Faculty Member; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; N/A; 23433
    Unusual strain hardening response and ductility of NiCoCr equiatomic alloy were investigated through microstructural analysis of [111], [110] and [123] single crystals deformed under tension. Nano-twinning prevailed at, as early as, 4% strain along the [110] orientation, providing a steady work hardening, and thereby a significant ductility. While single slip dominated in the [123] orientation at the early stages of deformation, multiple slip and nanotwinning was prominent in the [111] orientation. Significant dislocation storage capability and resistance to necking due to nanotwinning provided unprecedented ductility to NiCoCr medium entropy alloys, making it superior than quinary variants, and conventional low and medium stacking fault energy steels.
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    PublicationOpen Access
    Investigation of the dissolution-reformation cycle of the passive oxide layer on NiTi orthodontic archwires
    (Springer, 2017) Department of Chemistry; Department of Mechanical Engineering; Uzer, Benay; Birer, Özgür; Canadinç, Demircan; Researcher; Faculty Member; Department of Chemistry; 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; N/A; N/A; 23433
    Dissolution-reformation cycle of the passive oxide layer on the nickel-titanium (NiTi) orthodontic archwires was investigated, which has recently been recognized as one of the key parameters dictating the biocompatibility of archwires. Specifically, commercially available NiTi orthodontic archwires were immersed in artificial saliva solutions of different pH values (2.3, 3.3, and 4.3) for four different immersion periods: 1, 7, 14, and 30 days. Characterization of the virgin and tested samples revealed that the titanium oxide layer on the NiTi archwire surfaces exhibit a dissolution-reformation cycle within the first 14 days of the immersion period: the largest amount of Ni ion release occurred within the first week of immersion, while it significantly decreased during the reformation period from day 7 to day 14. Furthermore, the oxide layer reformation was catalyzed on the grooves within the peaks and valleys due to relatively larger surface energy of these regions, which eventually decreased the surface roughness significantly within the reformation period. Overall, the current results clearly demonstrate that the analyses of dissolution-reformation cycle of the oxide layer in orthodontic archwires, surface roughness, and ion release behavior constitute utmost importance in order to ensure both the highest degree of biocompatibility and an efficient medical treatment.