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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access Thiophene-based trimers for in vivo electronic functionalization of tissues(American Chemical Society (ACS), 2020) Mantione, Daniele; Dufil, Gwennael; Vallan, Lorenzo; Parker, Daniela; Brochon, Cyril; Cloutet, Eric; Hadziioannou, Georges; Berggren, Magnus; Stavrinidou, Eleni; Pavlopoulou, Eleni; Department of Mechanical Engineering; İstif, Emin; Faculty Member; Master Student; Department of Mechanical Engineering; College of EngineeringElectronic materials that can self-organize in vivo and form functional components along the tissue of interest can result in a seamless integration of the bioelectronic interface. Previously, we presented in vivo polymerization of the conjugated oligomer ETE-S in plants, forming conductors along the plant structure. The EDOT-thiophene-EDOT trimer with a sulfonate side group polymerized due to the native enzymatic activity of the plant and integrated within the plant cell wall. Here, we present the synthesis of three different conjugated trimers based on thiophene and EDOT or purely EDOT trimers that are able to polymerize enzymatically in physiological pH in vitro as well as in vivo along the roots of living plants. We show that by modulating the backbone and the side chain, we can tune the electronic properties of the resulting polymers as well as their localization and penetration within the root. Our work paves the way for the rational design of electronic materials that can self-organize in vivo for spatially controlled electronic functionalization of living tissue.Publication Open Access Finger-actuated microneedle array for sampling body fluids(Multidisciplinary Digital Publishing Institute (MDPI), 2021) Ahmadpour, Abdollah; Yetişen, Ali K.; Department of Mechanical Engineering; Taşoğlu, Savaş; Sarabi, Misagh Rezapour; Faculty Member; Department of Mechanical Engineering; 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); College of Engineering; Graduate School of Sciences and Engineering; 291971; N/AThe application of microneedles (MNs) for minimally invasive biological fluid sampling is rapidly emerging, offering a user-friendly approach with decreased insertion pain and less harm to the tissues compared to conventional needles. Here, a finger-powered microneedle array (MNA) integrated with a microfluidic chip was conceptualized to extract body fluid samples. Actuated by finger pressure, the microfluidic device enables an efficient approach for the user to collect their own body fluids in a simple and fast manner without the requirement for a healthcare worker. The processes for extracting human blood and interstitial fluid (ISF) from the body and the flow across the device, estimating the amount of the extracted fluid, were simulated. The design in this work can be utilized for the minimally invasive personalized medical equipment offering a simple usage procedure.Publication 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 3D-printed contact lenses: challenges towards translation and commercialization(Future Medicine, 2022) Yetişen, Ali K.; Department of Mechanical Engineering; Taşoğlu, Savaş; Özdalgıç, Berin; Faculty Member; PhD Student; Department of Mechanical Engineering; 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); College of Engineering; Graduate School of Sciences and Engineering; 291971; 323683NAPublication Open Access Special issue “hybrid rocket (volume II)”(Multidisciplinary Digital Publishing Institute (MDPI), 2022) Shimada, T.; Carmicino, C.; Department of Mechanical Engineering; Karabeyoğlu, Mustafa Arif; Faculty Member; Department of Mechanical Engineering; College of EngineeringPublication Open Access Mechanics of a pressure-controlled adhesive membrane for soft robotic gripping on curved surfaces(Elsevier, 2019) Song, Sukho; Drotlef, Dirk-M; PaIk, Jamie; Majidi, Carmel; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; Department of Mechanical Engineering; College of EngineeringThis paper aims at understanding the adhesion mechanics of a pressure-controlled adhesive thin elastomeric membrane for soft robotic gripping on non-planar, curved surfaces. The adhesive elastic membrane is lined with gecko-inspired microfiber arrays and can be inflated or deflated by controlled internal air pressure. Previous studies with the soft robotic grippers using dry adhesives showed repeatable adhesion and transfer printing of various non-planar objects with high reliability. In this study, we perform experimental characterization and theoretical analysis to better understand the influence of size and shape of the adhering curved objects on the range of internal air pressures as well as the force profile. In addition, decrease in the internal air pressure results in an increased pull-off force associated with a change in the range of gripper retraction for pulling off the membrane on various curved surfaces. An approximate analytical model dealing with the complex boundary conditions presented in this paper can provide quantitative estimates of pull-off forces for a wide variety of surface curvatures and internal air pressures, as well as qualitative understanding of how force profiles change under moderate pressure differentials.Publication Open Access Effects of interphase boundary anisotropy on the three-phase growth dynamics in the β(In) - In2Bi - γ(Sn) ternary-eutectic system(Institute of Physics (IOP) Publishing, 2019) Hecht, U.; Bottin-Rousseau, S.; Akamatsu, S.; Faivre, G.; Department of Mechanical Engineering; Mohagheghi, Samira; Şerefoğlu, Melis; PhD Student; Researcher; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; N/A; 44888We present an experimental investigation on the effects of the interphase energy anisotropy on the formation of three-phase growth microstructures during directional solidification (DS) of the β(In)-In2Bi-γ(Sn) ternary-eutectic system. Standard DS and rotating directional solidification (RDS) experiments were performed using thin alloy samples with real-time observation. We identified two main types of eutectic grains (EGs): (i) quasi-isotropic EGs within which the solidification dynamics do not exhibit any substantial anisotropy effect, and (ii) anisotropic EGs, within which RDS microstructures exhibit an alternation of locked and unlocked microstructures. EBSD analyses revealed (i) a strong tendency to an alignment of the In2Bi and γ(Sn) crystals (both hexagonal) with respect to the thin-sample walls, and (ii) the existence of special crystal orientation relationships (ORs) between the three solid phases in both quasi-isotropic and anisotropic EGs. We initiate a discussion on the dominating locking effect of the In2Bi-β(In) interphase boundary during quasi steady-state solidification, and the existence of strong crystal selection mechanisms during early nucleation and growth stages.Publication Open Access Flexural wave-based soft attractor walls for trapping microparticles and cells(Royal Society of Chemistry (RSC), 2021) Aghakhani, Amirreza; Çetin, Hakan; Erkoç, Pelin; Tombak, Güney Işık; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; Department of Mechanical Engineering; College of Engineering; School of MedicineAcoustic manipulation of microparticles and cells, called acoustophoresis, inside microfluidic systems has significant potential in biomedical applications. In particular, using acoustic radiation force to push microscopic objects toward the wall surfaces has an important role in enhancing immunoassays, particle sensors, and recently microrobotics. In this paper, we report a flexural-wave based acoustofluidic system for trapping micron-sized particles and cells at the soft wall boundaries. By exciting a standard microscope glass slide (1 mm thick) at its resonance frequencies <200 kHz, we show the wall-trapping action in sub-millimeter-size rectangular and circular cross-sectional channels. For such low-frequency excitation, the acoustic wavelength can range from 10–150 times the microchannel width, enabling a wide design space for choosing the channel width and position on the substrate. Using the system-level acousto-structural simulations, we confirm the acoustophoretic motion of particles near the walls, which is governed by the competing acoustic radiation and streaming forces. Finally, we investigate the performance of the wall-trapping acoustofluidic setup in attracting the motile cells, such as Chlamydomonas reinhardtii microalgae, toward the soft boundaries. Furthermore, the rotation of microalgae at the sidewalls and trap-escape events under pulsed ultrasound are demonstrated. The flexural-wave driven acoustofluidic system described here provides a biocompatible, versatile, and label-free approach to attract particles and cells toward the soft walls.Publication Open Access Multiple piezo-patch energy harvesters on a thin plate with respective AC-DC conversion(Society of Photo-optical Instrumentation Engineers (SPIE), 2018) Department of Mechanical Engineering; Aghakhani, Amirreza; Başdoğan, İpek; PhD Student; Department of Mechanical Engineering; College of Engineering; N/A; 179940Piezoelectric patch energy harvesters can be directly integrated to plate-like structures which are widely used in automotive, marine and aerospace applications, to convert vibrational energy to electrical energy. This paper presents two different AC-DC conversion techniques for multiple patch harvesters, namely single rectifier and respective rectifiers. The first case considers all the piezo-patches are connected in parallel to a single rectifier, whereas in the second case, each harvester is respectively rectified and then connected in parallel to a smoothing capacitor and a resistive load. The latter configuration of AC-DC conversion helps to avoid the electrical charge cancellation which is a problem with the multiple harvesters attached to different locations of the host plate surface. Equivalent circuit model of the multiple piezo-patch harvesters is developed in the SPICE software to simulate the electrical response. The system parameters are obtained from the modal analysis solution of the plate. Simulations of the voltage frequency response functions (FRFs) for the standard AC input - AC output case are conducted and validated by experimental data. Finally, for the AC input - DC output case, numerical simulation and experimental results of the power outputs of multiple piezo-patch harvesters with multiple AC-DC converters are obtained for a wide range of resistive loads and compared with the same array of harvesters connected to a single AC-DC converter.Publication Open Access Three-dimensional-bioprinted liver chips and challenges(Multidisciplinary Digital Publishing Institute (MDPI), 2022) Özdalgıç, B.; Mustafaoğlu, N.; Department of Mechanical Engineering; Taşoğlu, Savaş; Dabbagh, Sajjad Rahmani; Faculty Member; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; 291971; N/ADrug testing, either on animals or on 2D cell cultures, has its limitations due to inaccurate mimicking of human pathophysiology. The liver, as one of the key organs that filters and detoxifies the blood, is susceptible to drug-induced injuries. Integrating 3D bioprinting with microfluidic chips to fabricate organ-on-chip platforms for 3D liver cell cultures with continuous perfusion can offer a more physiologically relevant liver-mimetic platform for screening drugs and studying liver function. The development of organ-on-chip platforms may ultimately contribute to personalized medicine as well as body-on-chip technology that can test drug responses and organ-organ interactions on a single or linked chip model.