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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Item Metadata only 3D-printed microrobots: translational challenges(MDPI, 2023) 0000-0003-4604-217X; 0000-0002-5295-5701; 0000-0003-0519-4513; Yetisen, Ali K.; Department of Mechanical Engineering; N/A; N/A; Taşoğlu, Savaş; Sarabi, Misagh Rezapour; Karagöz, Ahmet Agah; Faculty Member; PhD Student; PhD Student; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Koç Üniversitesi İş Bankası Yapay Zeka Uygulama ve Araştırma Merkezi (KUIS AI)/ Koç University İş Bank Artificial Intelligence Center (KUIS AI); College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 291971; N/A; N/AThe science of microrobots is accelerating towards the creation of new functionalities for biomedical applications such as targeted delivery of agents, surgical procedures, tracking and imaging, and sensing. Using magnetic properties to control the motion of microrobots for these applications is emerging. Here, 3D printing methods are introduced for the fabrication of microrobots and their future perspectives are discussed to elucidate the path for enabling their clinical translation.Item Metadata only In situ design of a nanostructured ınterface between NiMo and CuO derived from metal-organic framework for enhanced hydrogen evolution in alkaline solutions(Amer Chemical Soc, 2024) 0000-0003-1164-1973; 0000-0002-2991-5488; N/A; 0000-0003-0832-0546; Yildirim, Ipek Deniz; Erdem, Emre; Department of Chemistry; N/A; N/A; N/A; Aydemir, Umut; Peighambardoust, Naeimeh Sadat; Chamani, Sanaz; Sadeghi, Ebrahim; Faculty Member; Researcher; Researcher; PhD Student; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); College of Sciences; N/A; N/A; Graduate School of Sciences and Engineering; 58403; N/A; N/A; N/AHydrogen shows great promise as a carbon-neutral energy carrier that can significantly mitigate global energy challenges, offering a sustainable solution. Exploring catalysts that are highly efficient, cost-effective, and stable for the hydrogen evolution reaction (HER) holds crucial importance. For this, metal-organic framework (MOF) materials have demonstrated extensive applicability as either a heterogeneous catalyst or catalyst precursor. Herein, a nanostructured interface between NiMo/CuO@C derived from Cu-MOF was designed and developed on nickel foam (NF) as a competent HER electrocatalyst in alkaline media. The catalyst exhibited a low overpotential of 85 mV at 10 mA cm(-2) that rivals that of Pt/C (83 mV @ 10 mA cm(-2)). Moreover, the catalyst's durability was measured through chronopotentiometry at a constant current density of -30, -100, and -200 mA cm(-2) for 50 h each in 1.0 M KOH. Such enhanced electrocatalytic performance could be ascribed to the presence of highly conductive C and Cu species, the facilitated electron transfer between the components because of the nanostructured interface, and abundant active sites as a result of multiple oxidation states. The existence of an ionized oxygen vacancy (O-v) signal was confirmed in all heat-treated samples through electron paramagnetic resonance (EPR) analysis. This revelation sheds light on the entrapment of electrons in various environments, primarily associated with the underlying defect structures, particularly vacancies. These trapped electrons play a crucial role in augmenting electron conductivity, thereby contributing to an elevated HER performance.Item Metadata only Ti3C2MXene/polyaniline/montmorillonite nanostructures toward solvent-free powder coatings with enhanced corrosion resistance and mechanical properties(Amer Chemical Soc, 2023) 0000-0003-1164-1973; 0000-0003-3243-6442; Hosseini, Seyyedeh Fatemeh; Dorraji, Mir Saeed Seyed; Rasoulifard, Mohammad Hossein; Department of Chemistry; N/A; Aydemir, Umut; Nazarlou, Ziba; Faculty Member; PhD Student; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); College of Sciences; Graduate School of Sciences and Engineering; 58403; N/ASolvent-free powdercoatings have become very popular in the coatingindustry in replacing conventional liquid coatings for the last decades.However, poor adhesion of powder coatings to the substrate and microporesinevitably created during the curing process of coatings lead to localizedcorrosion and reduced mechanical resistance. For this purpose, Ti3C2 MXene/polyaniline (PANI)/montmorillonite (MMT)nanocomposites with superior conductivity and adhesion capabilitieswere incorporated into the eco-friendly powder coating. The as-synthesizednanocomposites were analyzed using various techniques such as Fouriertransform infrared spectroscopy, X-ray diffraction, X-ray photoelectronspectroscopy, high-resolution transmission electron microscopy, field-emissionscanning electron microscopy, and Raman spectroscopy. To evaluatethe effectiveness of the powder coating in preventing corrosion ona mild steel substrate, two methods were employed: potentiodynamicpolarization and electrochemical impedance spectroscopy. The electrochemicaltests revealed that an excellent dispersion of 1.5 wt % Ti3C2 MXene/PANI/MMT nanosheets in a polyester/epoxy powdercoating resulted in superior anti-corrosion performance (4.8 x10(6) omega) after 42 days of immersion in 3.5 wt % NaClas compared to blank samples (7.2 x 10(2) omega).According to Tafel analysis, the corrosion potential of the optimalsample is -0.062 V, which is more positive than that of thepristine powder coating (-0.83 V). The polarization resistance(R (p)) and corrosion current (i (corr)) of the optimal sample are determined to be 3.39x 10(6) omega center dot cm(2) and 7.69 x10(-9) A center dot cm(-2), respectively.Moreover, the optimal sample marginally increased the hardness (229.42MPa) compared to the pure sample (152.68 MPa) due to the synergisticeffect of Ti3C2 MXene and flake-like MMT nanoparticles,which results in an improvement in the mechanical strength of powdercoatings. Additionally, the presence of PANI caused further crosslinkingand modulation of the electrical conductivity of the produced nanocomposites.The present study proposes a practical method to enhance the mechanicaland shielding properties of solvent-free powder coatings, making themsuitable for use in various real-world applications, including commercial,medical, and household sectors.Item Metadata only Nanomechanical properties of Al-Tb marginal metallic glass(Elsevier Science Sa, 2023) 0000-0001-6753-9316; Okuyucu, Can; Ulucan, Tolga Han; Abboud, Mohammad; Motallebzadeh, Amir; Ozerinc, Sezer; Kalay, Ilkay; Kalay, Yunus Eren; N/A; Motallebzadeh, Amir; Researcher; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/AAl-Rare Earth (RE) metallic glasses provide an effective model system to study the effect of nanocrystallites in an amorphous matrix on nanomechanical behavior. In this work, we achieved a series of Al-Tb metallic glasscrystalline composites with systematically varying crystalline content through annealing. The nanomechanical properties were characterized using micropillar compression tests and nanoindentation for as-quenched amorphous and annealed amorphous/nanocrystalline composite specimens. The promising hardness increases after annealing from 3.0 GPa to 4.6 GPa and elastic modulus increment from 68 GPa to 92 GPa were discussed in detail, considering the structural features of Al-RE marginal metallic glass formers. The increase in elastic modulus is associated with the nucleated fcc-Al nanocrystals that divide the amorphous matrix, leading to the branching of the shear bands. The correlation between the fcc-Al nanocrystals and the behavior of shear bands was discussed in detail.Item Metadata only Genetically encoded fluorescent probe for detection of heme-induced conformational changes in cytochrome C(MDPI, 2023) Genceroglu, Mehmet Yunus; Cavdar, Cansu; Manioglu, Selen; Bayraktar, Halil; N/A; Manioğlu, Selen; Master Student; Graduate School of Sciences and EngineeringCytochrome c (Cytc) is a key redox protein for energy metabolism and apoptosis in cells. The activation of Cytc is composed of several steps, including its transfer to the mitochondrial membrane, binding to cytochrome c heme lyase (CCHL) and covalent attachment to heme. The spectroscopic methods are often applied to study the structural changes of Cytc. However, they require the isolation of Cytc from cells and have limited availability under physiological conditions. Despite recent studies to elucidate the tightly regulated folding mechanism of Cytc, the role of these events and their association with different conformational states remain elusive. Here, we provide a genetically encoded fluorescence method that allows monitoring of the conformational changes of Cytc upon binding to heme and CCHL. Cerulean and Venus fluorescent proteins attached at the N and C terminals of Cytc can be used to determine its unfolded, intermediate, and native states by measuring FRET amplitude. We found that the noncovalent interaction of heme in the absence of CCHL induced a shift in the FRET signal, indicating the formation of a partially folded state. The higher concentration of heme and coexpression of CCHL gave rise to the recovery of Cytc native structure. We also found that Cytc was weakly associated with CCHL in the absence of heme. As a result, a FRET-based fluorescence approach was demonstrated to elucidate the mechanism of heme-induced Cytc conformational changes with spatiotemporal resolution and can be applied to study its interaction with small molecules and other protein partners in living cells.Item Metadata only MNO2 nanoflower integrated optoelectronic biointerfaces for photostimulation of neurons(Wiley, 2023) 0000-0003-0394-5790; 0000-0002-7669-9589; 0000-0003-3682-6042; 0000-0002-4355-7592; 0000-0001-9885-5653; 0009-0002-2549-3983; 0000-0001-7789-8152; Vanalakar, Sharadrao Anandrao; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; N/A; N/A; N/A; Nizamoğlu, Sedat; Karatüm, Onuralp; Önal, Asım; Kaleli, Humeyra Nur; Hasanreisoğlu, Murat; Balamur, Rıdvan; Kaya, Lokman; Faculty Member; PhD Student; PhD Student; PhD Student; Faculty Member; PhD Student; Master Student; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Health Sciences; School of Medicine; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 130295; N/A; N/A; N/A; 182001; N/A; N/AOptoelectronic biointerfaces have gained significant interest for wireless and electrical control of neurons. Three-dimentional (3D) pseudocapacitive nanomaterials with large surface areas and interconnected porous structures have great potential for optoelectronic biointerfaces that can fulfill the requirement of high electrode-electrolyte capacitance to effectively transduce light into stimulating ionic currents. In this study, the integration of 3D manganese dioxide (MnO2) nanoflowers into flexible optoelectronic biointerfaces for safe and efficient photostimulation of neurons is demonstrated. MnO2 nanoflowers are grown via chemical bath deposition on the return electrode, which has a MnO2 seed layer deposited via cyclic voltammetry. They facilitate a high interfacial capacitance (larger than 10 mF cm(-2)) and photogenerated charge density (over 20 & mu;C cm(-2)) under low light intensity (1 mW mm(-2)). MnO2 nanoflowers induce safe capacitive currents with reversible Faradaic reactions and do not cause any toxicity on hippocampal neurons in vitro, making them a promising material for biointerfacing with electrogenic cells. Patch-clamp electrophysiology is recorded in the whole-cell configuration of hippocampal neurons, and the optoelectronic biointerfaces trigger repetitive and rapid firing of action potentials in response to light pulse trains. This study points out the potential of electrochemically-deposited 3D pseudocapacitive nanomaterials as a robust building block for optoelectronic control of neurons.Publication Metadata only Biomedical optical fibers(Royal Soc Chemistry, 2021) Jiang, Nan; Yetişen, Ali K.; N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Sarabi, Misagh Rezapour; Öztürk, Ece; Taşoğlu, Savaş; PhD Student; Faculty Member; Faculty Member; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; N/A; 326940; 291971Optical fibers with the ability to propagate and transfer data via optical signals have been used for decades in medicine. Biomaterials featuring the properties of softness, biocompatibility, and biodegradability enable the introduction of optical fibers' uses in biomedical engineering applications such as medical implants and health monitoring systems. Here, we review the emerging medical and health-field applications of optical fibers, illustrating the new wave for the fabrication of implantable devices, wearable sensors, and photodetection and therapy setups. A glimpse of fabrication methods is also provided, with the introduction of 3D printing as an emerging fabrication technology. The use of artificial intelligence for solving issues such as data analysis and outcome prediction is also discussed, paving the way for the new optical treatments for human health.Publication Metadata only Silk as a biodegradable resist for field-emission scanning probe lithography(Institute of Physics (IOP) Publishing, 2020) Sadeghi, Sadra; Rangelow, Ivo W.; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; N/A; N/A; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Alaca, Burhanettin Erdem; Kumar, Baskaran Ganesh; Melikov, Rustamzhon; Doğru-Yüksel, Itır Bakış; Nizamoğlu, Sedat; Faculty Member; Other; PhD Student; PhD Student; Faculty Member; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştirmalari Merkezi (KUYTAM); N/A; N/A; N/A; N/A; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 115108; N/A; N/A; N/A; 130295The patterning of silk allows for manufacturing various structures with advanced functionalities for optical and tissue engineering and drug delivery applications. Here, we propose a high-resolution nanoscale patterning method based on field-emission scanning probe lithography (FE-SPL) that crosslinks the biomaterial silk on conductive indium tin oxide (ITO) promoting the use of a biodegradable material as resist and water as a developer. During the lithographic process, Fowler-Nordheim electron emission from a sharp tip was used to manipulate the structure of silk fibroin from random coil to beta sheet and the emission formed nanoscale latent patterns with a critical dimension (CD) of similar to 50 nm. To demonstrate the versatility of the method, we patterned standard and complex shapes. This method is particularly attractive due to its ease of operation without relying on a vacuum or a special gaseous environment and without any need for complex electronics or optics. Therefore, this study paves a practical and cost-effective way toward patterning biopolymers at ultra-high level resolution.Publication Metadata only Structural changes in a Schiff base molecular assembly initiated by scanning tunneling microscopy tip(Institute of Physics (IOP) Publishing, 2016) Tomak, A.; Bacaksiz, C.; Mendirek, G.; Sahin, H.; Hur, D.; Gorgun, K.; Senger, R. T.; Peeters, F. M.; Zareie, H. M.; N/A; Birer, Özgür; Researcher; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/AWe report the controlled self-organization and switching of newly designed Schiff base (E)-4-((4-(phenylethynyl) benzylidene) amino) benzenethiol (EPBB) molecules on a Au (111) surface at room temperature. Scanning tunneling microscopy and spectroscopy (STM/STS) were used to image and analyze the conformational changes of the EPBB molecules. The conformational change of the molecules was induced by using the STM tip while increasing the tunneling current. The switching of a domain or island of molecules was shown to be induced by the STM tip during scanning. Unambiguous fingerprints of the switching mechanism were observed via STM/STS measurements. Surface-enhanced Raman scattering was employed, to control and identify quantitatively the switching mechanism of molecules in a monolayer. Density functional theory calculations were also performed in order to understand the microscopic details of the switching mechanism. These calculations revealed that the molecular switching behavior stemmed from the strong interaction of the EPBB molecules with the STM tip. Our approach to controlling intermolecular mechanics provides a path towards the bottom-up assembly of more sophisticated molecular machines.Publication Metadata only Multiscale coupling based on quasicontinuum method in nanowires at finite temperatures(IEEE, 2015) Sonne, Mads Rostgaard; Hattel, Jesper Henri; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Esfahani, Mohammad Nasr; Alaca, Burhanettin Erdem; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 115108Nanoelectromechanical systems have been developed for ultra-high frequency oscillators because of their small size and excellent material properties. Using flexural modes and electrothermal features in nanowires for frequency tuning necessitates a sound modeling approach. The quasicontinuum method was developed to link atomistic models with the continuum finite element method in order to study the material behavior across multiple length scales. These significant efforts to develop a continuum theory based on atomistic models have so far been limited to zero temperature. The purpose of this work is to develop the theoretical framework needed to study the mechanical response in nanoscale components such as nanowires at finite temperatures. This is achieved up to a temperature of 1000 K by integrating Engineering Molecular Mechanics and the Cauchy-Born hypothesis. The proposed method is verified with Molecular Dynamics and Molecular Mechanics simulations reported in literature. Bending properties of nanowires at finite temperatures were studied with the proposed method. Thermomechanical properties were investigated by including surface effects.