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Permanent URI for this communityhttps://hdl.handle.net/20.500.14288/2
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Publication Open Access 3D printing of elastomeric bioinspired complex adhesive microstructures(Wiley, 2021) Dayan, Cem Balda; Chun, Sungwoo; Krishna Subbaiah, Nagaraj; Drotlef, Dirk Michael; Akolpoğlu, Mükrime Birgül; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; Department of Mechanical Engineering; College of Engineering; School of Medicine; 297104Bioinspired elastomeric structural adhesives can provide reversible and controllable adhesion on dry/wet and synthetic/biological surfaces for a broad range of commercial applications. Shape complexity and performance of the existing structural adhesives are limited by the used specific fabrication technique, such as molding. To overcome these limitations by proposing complex 3D microstructured adhesive designs, a 3D elastomeric microstructure fabrication approach is implemented using two-photon-polymerization-based 3D printing. A custom aliphatic urethane-acrylate-based elastomer is used as the 3D printing material. Two designs are demonstrated with two combined biological inspirations to show the advanced capabilities enabled by the proposed fabrication approach and custom elastomer. The first design focuses on springtail- and gecko-inspired hybrid microfiber adhesive, which has the multifunctionalities of side-surface liquid super-repellency, top-surface liquid super-repellency, and strong reversible adhesion features in a single fiber array. The second design primarily centers on octopus- and gecko-inspired hybrid adhesive, which exhibits the benefits of both octopus- and gecko-inspired microstructured adhesives for strong reversible adhesion on both wet and dry surfaces, such as skin. This fabrication approach could be used to produce many other 3D complex elastomeric structural adhesives for future real-world applications.Publication Open Access Adaptive self-sealing suction-based soft robotic gripper(Wiley, 2021) Song, Sukho; Drotlef, Dirk-Michael; Son, Donghoon; Koivikko, Anastasia; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; Department of Mechanical Engineering; School of Medicine; College of Engineering; 297104While suction cups prevail as common gripping tools for a wide range of real-world parts and surfaces, they often fail to seal the contact interface when engaging with irregular shapes and textured surfaces. In this work, the authors propose a suction-based soft robotic gripper where suction is created inside a self-sealing, highly conformable and thin flat elastic membrane contacting a given part surface. Such soft gripper can self-adapt the size of its effective suction area with respect to the applied load. The elastomeric membrane covering edge of the soft gripper can develop an air-tight self-sealing with parts even smaller than the gripper diameter. Such gripper shows 4 times higher adhesion than the one without the membrane on various textured surfaces. The two major advantages, underactuated self-adaptability and enhanced suction performance, allow the membrane-based suction mechanism to grip various three-dimensional (3D) geometries and delicate parts, such as egg, lime, apple, and even hydrogels without noticeable damage, which can have not been gripped with the previous adhesive microstructures-based and active suction-based soft grippers. The structural and material simplicity of the proposed soft gripper design can have a broad use in diverse fields, such as digital manufacturing, robotic manipulation, transfer printing, and medical gripping.Publication Open Access Design and adoption of low-cost point-of-care diagnostic devices: Syrian case(Multidisciplinary Digital Publishing Institute (MDPI), 2021) Alseed, M. Munzer; Yetişen, Ali K.; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Syed, Hamzah; Taşoğlu, Savaş; Onbaşlı, Mehmet Cengiz; Faculty Member; Faculty Member; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; 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); School of Medicine; College of Engineering; 318138; 291971; 258783Civil wars produce immense humanitarian crises, causing millions of individuals to seek refuge in other countries. The rate of disease prevalence has inclined among the refugees, increasing the cost of healthcare. Complex medical conditions and high numbers of patients at healthcare centers overwhelm the healthcare system and delay diagnosis and treatment. Point-of-care (PoC) testing can provide efficient solutions to high equipment cost, late diagnosis, and low accessibility of healthcare services. However, the development of PoC devices in developing countries is challenged by several barriers. Such PoC devices may not be adopted due to prejudices about new technologies and the need for special training to use some of these devices. Here, we investigated the concerns of end users regarding PoC devices by surveying healthcare workers and doctors. The tendency to adopt PoC device changes is based on demographic factors such as work sector, education, and technology experience. The most apparent concern about PoC devices was issues regarding low accuracy, according to the surveyed clinicians.Publication Restricted Fast analysis of nanomechanical resonant sensing systems based on canonical models(Koç University, 2022) Kargıoğlu, Tarık; Demir, Alper; 0000-0002-1927-3960; Koç University Graduate School of Sciences and Engineering; Electrical and Electronics Engineering; 3756Publication Open Access Molecular dynamics study of orientation-dependent tensile properties of Si nanowires with native oxide: surface stress and surface energy effects(Institute of Electrical and Electronics Engineers (IEEE), 2021) Esfahani, Mohammad Nasr; Department of Mechanical Engineering; Alaca, Burhanettin Erdem; Zarepakzad, Sina; Faculty Member; 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; 115108; N/AMolecular dynamics (MD) simulations are employed to investigate the influence of native oxide layer on the mechanical properties of Si nanowires (NWs) through analyzing surface stress and surface energy effect. This work studies the tensile response of Si NWs along <100> and <110> crystal orientations. MD results are compared with the traditional core-shell model on the estimation of the modulus of elasticity of Si NWs with a native oxide layer. Density functional theory (DFT) methods are used to verify MD results on the surface energy calculations. Surface stress and surface elastic constants are studied for native oxide surface using MD simulations and compared with unreconstructed surfaces. In this work, the role of native oxide is addressed to understand the difference between experimental and computational findings on the modulus of elasticity of Si NWs.Publication Open Access Remote modular electronics for wireless magnetic devices(Wiley, 2021) Boyvat, Mustafa; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; Department of Mechanical Engineering; School of Medicine; College of Engineering; 297104Small-scale wireless magnetic robots and devices offer an effective solution to operations in hard-to-reach and high-risk enclosed places, such as inside the human body, nuclear plants, and vehicle infrastructure. In order to obtain functionalities beyond the capability of magnetic forces and torques exerted on magnetic materials used in these robotic devices, electronics need to be also integrated into them. However, their capabilities and power sources are still very limited compared to their larger-scale counterparts due to their much smaller sizes. Here, groups of milli/centimeter-scale wireless magnetic modules are shown to enable on-site electronic circuit construction and operation of highly demanding wireless electrical devices with no batteries, that is, with wireless power. Moreover, the mobility of the modular components brings remote modification and reconfiguration capabilities. When these small-scale robotic modules are remotely assembled into specific geometries, they can achieve, if not impossible, challenging electrical tasks for individual modules. Using such a method, several wireless and battery-free robotic devices are demonstrated using milli/centimeter-scale robotic modules, such as a wireless circuit to power light-emitting diodes with lower external fields, a device to actuate relatively high force-output shape memory alloy actuators, and a wireless force sensor, all of which can be modified on-site.Publication Open Access RGDS-functionalized polyethylene glycol hydrogel-coated magnetic iron oxide nanoparticles enhance specific intracellular uptake by HeLa cells(Dove Medical Press, 2012) N/A; Department of Chemical and Biological Engineering; Department of Chemistry; Nazlı, Caner; Ergenç, Tuğba İpek; Yar, Yasemin; Acar, Havva Funda Yağcı; Kızılel, Seda; PhD Student; Undergraduate Student; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 178902; 28376The objective of this study was to develop thin, biocompatible, and biofunctional hydrogel-coated small-sized nanoparticles that exhibit favorable stability, viability, and specific cellular uptake. This article reports the coating of magnetic iron oxide nanoparticles (MIONPs) with covalently cross-linked biofunctional polyethylene glycol (PEG) hydrogel. Silanized MIONPs were derivatized with eosin Y, and the covalently cross-linked biofunctional PEG hydrogel coating was achieved via surface-initiated photopolymerization of PEG diacrylate in aqueous solution. The thickness of the PEG hydrogel coating, between 23 and 126 nm, was tuned with laser exposure time. PEG hydrogel-coated MIONPs were further functionalized with the fibronectin-derived arginine-glycine-aspartic acid-serine (RGDS) sequence, in order to achieve a biofunctional PEG hydrogel layer around the nanoparticles. RGDS-bound PEG hydrogel-coated MIONPs showed a 17-fold higher uptake by the human cervical cancer HeLa cell line than that of amine-coated MIONPs. This novel method allows for the coating of MIONPs with nano-thin biofunctional hydrogel layers that may prevent undesirable cell and protein adhesion and may allow for cellular uptake in target tissues in a specific manner. These findings indicate that the further biofunctional PEG hydrogel coating of MIONPs is a promising platform for enhanced specific cell targeting in biomedical imaging and cancer therapy.Publication Restricted Synthesis and characterization of Fe3+ doped PbTiO3 nanopowders(Koç University, 2009) Kiraz, Kamil; Somer, Mehmet Suat; 0000-0001-5606-9101; Koç University Graduate School of Sciences and Engineering; Materials Science and Engineering; 178882Publication Restricted Toward efficient electrochemical reduction of CO2 to CO : decorating ZnO nanorods with CuxO(Koç University, 2023) Yusufoğlu, Muhammed; Kaya, Sarp; 0000-0002-2591-5843; Koç University Graduate School of Sciences and Engineering; Materials Science and Engineering; 116541Publication Open Access Zr-MOFs for CF4/CH4, CH4/H-2, and CH4/N-2 separation: towards the goal of discovering stable and effective adsorbents(Royal Society of Chemistry (RSC), 2021) Department of Chemical and Biological Engineering; Demir, Hakan; Keskin, Seda; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; N/A; 40548Zirconium metal-organic frameworks (MOFs) can be promising adsorbents for various applications as they are highly stable in different chemical environments. In this work, a collection of Zr-MOFs comprised of more than 100 materials is screened for CF4/CH4, CH4/H-2, and CH4/N-2 separations using atomistic-level simulations. The top three MOFs for the CF4/CH4 separation are identified as PCN-700-BPDC-TPDC, LIFM-90, and BUT-67 exhibiting CF4/CH4 adsorption selectivities of 4.8, 4.6, and 4.7, CF4 working capacities of 2.0, 2.0, and 2.1 mol kg(-1), and regenerabilities of 85.1, 84.2, and 75.7%, respectively. For the CH4/H-2 separation, MOF-812, BUT-67, and BUT-66 are determined to be the top performing MOFs demonstrating CH4/H-2 selectivities of 61.6, 36.7, and 46.2, CH4 working capacities of 3.0, 4.1, and 3.4 mol kg(-1), and CH4 regenerabilities of 70.7, 82.7, and 74.7%, respectively. Regarding the CH4/N-2 separation, BUT-67, Zr-AbBA, and PCN-702 achieving CH4/N-2 selectivities of 4.5, 3.4, and 3.8, CH4 working capacities of 3.6, 3.9, and 3.5 mol kg(-1), and CH4 regenerabilities of 81.1, 84.0, and 84.5%, in successive order, show the best overall separation performances. To further elucidate the adsorption in top performing adsorbents, the adsorption sites in these materials are analyzed using radial distribution functions and adsorbate density profiles. Finally, the water affinities of Zr-MOFs are explored to comment on their practical use in real gas separation applications. Our findings may inspire future studies probing the adsorption/separation mechanisms and performances of Zr-MOFs for different gases.