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Department: search.filters.department.Department of Mechanical EngineeringSubject: search.filters.subject.Applied physics

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Now showing 1 - 10 of 26
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    PublicationOpen Access
    3D printed microneedles for point of care biosensing applications
    (Multidisciplinary Digital Publishing Institute (MDPI), 2022) Department of Mechanical Engineering; Sarabi, Misagh Rezapour; Nakhjavani, Sattar Akbar; Taşoğlu, Savaş; Faculty Member; Department of Mechanical 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); Koç Üniversitesi İş Bankası Yapay Zeka Uygulama ve Araştırma Merkezi (KUIS AI)/ Koç University İş Bank Artificial Intelligence Center (KUIS AI); Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 291971
    Microneedles (MNs) are an emerging technology for user-friendly and minimally invasive injection, offering less pain and lower tissue damage in comparison to conventional needles. With their ability to extract body fluids, MNs are among the convenient candidates for developing biosensing setups, where target molecules/biomarkers are detected by the biosensor using the sample collected with the MNs. Herein, we discuss the 3D printing of microneedle arrays (MNAs) toward enabling point-of-care (POC) biosensing applications.
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    A deformation-based approach to tuning of magnetic micromechanical resonators
    (2018) Yalçınkaya, Arda D.; Department of Mechanical Engineering; N/A; Department of Mechanical Engineering; Biçer, Mahmut; Esfahani, Mohammad Nasr; Alaca, Burhanettin Erdem; Researcher; PhD Student; 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; College of Engineering; N/A; N/A; 115108
    Resonance frequency tuning in magnetic micromechanical resonators remains a primary field of study for frequency reference applications. The use of magnetic micromechanical resonators for innovative timing, oscillator and sensing applications necessitates a platform for the precise control of the resonance frequency. The present work addresses a deformation based technique for tuning the resonance frequency of nickel micromechanical resonators. Frequency response is measured through magnetic actuation and optical readout. The tuning approach is based on a combination of flexural deformation and uniaxial strain. The bending deformation is achieved by using a DC current through the microbeam. This magnetomotive mechanism reduces the resonance frequency by about 13% for a maximum DC current of 80 mA. A substrate bending method is used for applying uniaxial strain to increase the resonance frequency by about 8%. A bidirectional frequency modulation is thus demonstrated by utilizing both deformation techniques. The interpretation of results is carried out by finite element analysis and electromechanical analogy in an equivalent circuit. Using deformation techniques, this study provides a rigorous approach to control the resonance frequency of magnetic micromechanical resonators.
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    A magnetically actuated resonant mass sensor with integrated optical readout
    (Ieee-Inst Electrical Electronics Engineers Inc, 2008) N/A; N/A; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Öztürk, Alibey; Ocaklı, Hüseyin İlker; Özber, Natali; Ürey, Hakan; Kavaklı, İbrahim Halil; Alaca, Burhanettin Erdem; Master Student; Researcher; Master Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; 8579; 40319; 115108
    Nickel cantilevers with integrated diffraction gratings are used as resonant mass sensors with a resolution of 500 femtograms. Their applicability to biosensing is demonstrated with human opioid receptors. The device is fabricated through a single-mask lithographic process. The microoptical readout provides a simple measurement platform with one external photodiode. Thanks to its ac operation principle, the device is immune to environmental noise and entails a high tolerance to fabrication defects. Obtained signal-to-noise ratio is comparable to that of a high-end Doppler vibrometer. The device with these aspects for systems integration and microarray technology is a candidate for low-cost portable sensors.
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    A monolithic approach to downscaling silicon piezoresistive sensors
    (Ieee-Inst Electrical Electronics Engineers Inc, 2017) Leblebici, Yusuf; N/A; Department of Mechanical Engineering; Esfahani, Mohammad Nasr; Alaca, Burhanettin Erdem; PhD Student; Faculty Member; 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; 115108
    Multi-scale integration remains the primary challenge in the fabrication of miniature piezoresistive sensors, as the co-fabrication of a silicon nanowire along with a microscale shuttle is the main architecture facilitating high-sensitivity transduction. The efforts in this field are marred by the lack of batch techniques compatible with semiconductor manufacturing. A technology is introduced here that leads to the fabrication of a piezoresistive silicon nanowire sharing the same single-crystalline device layer of a thick silicon-on-insulator wafer as the microscale component. The approach is based on a combination of high-resolution lithography with a two-stage etching process. The demonstration is carried out by spanning an electrostatic comb-drive actuator and a micromechanical amplifier by a single nanowire. A gage factor range of 135-145 is obtained, corresponding to an almost 20% resistance change for a nanowire strain of 1.26 x 10(-3). The technique is shown to generate a two-order-of-magnitude scale difference within the same silicon crystal. It also provides ease of electrical access to the nanowire, as the nanowire does not remain buried underneath the thick micromechanical system. With the associated lack of high-temperature processes and its CMOS-compatibility, the technique is a promising enabler for future miniaturized piezoresistive sensors. [2017-0007]
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    PublicationOpen Access
    A new consistent hybrid algorithm for solution of the PDF equations of turbulent reactive flow
    (American Institute of Physics (AIP) Publishing, 2013) Department of Mechanical Engineering; Sheikhsarmast, Reza Mokhtarpoor; Inmas, Shabrina Virta; Muradoğlu, Metin; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 46561
    This paper presents a newly developed consistent hybrid finite-volume (FV)/particle algorithm for solution of joint PDF (JPDF) model equation of turbulent reacting flows. In this approach, the open source FV package of OpenFOAM is employed to solve the Favre-averaged mean mass and momentum equations using pressure-based PISO algorithm while a particle-based Monte Carlo algorithm is used to solve the fluctuating velocity-turbulence frequency-compositions JPDF transport equation. In the earlier hybrid method [2, 3], a density-based FV algorithm was used to solve the mean flow equations but it has been found to be too dissipative and yet not very robust for incompressible or nearly incompressible flows mainly due to stiffness of the compressible flow equations in the low Mach number limit. In the this work, the density-based FV algorithm is first replaced with a pressure-based PISO algorithm to tackle this problem and then applied for simulation of the Sydney swirl stabilized bluff-body flame SM1. All the equations solved by the FV and particle algorithms are directly derived from the modeled JPDF transport equation so the present method is completely consistent at the level of governing equations. The position and velocity correction algorithms [3] are used to enforce full constancy at the numerical solution level. The results are found to be in a good agreement with the available experimental data and the recent computational results of De Meester et al. [1].
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    PublicationOpen Access
    Adaptive Q control for tapping-mode nanoscanning using a piezoactuated bimorph probe
    (American Institute of Physics (AIP) Publishing, 2007) Department of Mechanical Engineering; Günev, İhsan; Varol, Aydın; Karaman, Sertaç; Başdoğan, Çağatay; Master Student; Faculty Member; Department of Mechanical Engineering; College of Engineering; N/A; N/A; N/A; 125489
    A new approach, called adaptive Q control, for tapping-mode atomic force microscopy (AFM) is introduced and implemented on a homemade AFM setup utilizing a laser Doppler vibrometer and a piezoactuated bimorph probe. In standard Q control, the effective Q factor of the scanning probe is adjusted prior to the scanning depending on the application. However, there is a trade-off in setting the effective Q factor of an AFM probe. The Q factor is either increased to reduce the tapping forces or decreased to increase the maximum achievable scan speed. Realizing these two benefits simultaneously using standard Q control is not possible. In adaptive Q control, the Q factor of the probe is set to an initial value as in standard Q control, but then modified on the fly during scanning when necessary to achieve this goal. In this article, we present the basic theory behind adaptive Q control, the electronics enabling the online modification of the probe's effective Q factor, and the results of the experiments comparing three different methods: scanning (a) without Q control, (b) with standard Q control, and (c) with adaptive Q control. The results show that the performance of adaptive Q control is superior to the other two methods.
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    An electrochemical gelation method for patterning conductive PEDOT:PSS hydrogels
    (2019) Feig, Vivian Rachel; Tran, Helen; Lee, Minah; Liu, Kathy; Huang, Zhuojun; Mackanic, David G.; Bao, Zhenan; Department of Mechanical Engineering; Beker, Levent; Faculty Member; Department of Mechanical Engineering; College of Engineering; 308798
    Due to their high water content and macroscopic connectivity, hydrogels made from the conducting polymer PEDOT:PSS are a promising platform from which to fabricate a wide range of porous conductive materials that are increasingly of interest in applications as varied as bioelectronics, regen-erative medicine, and energy storage. Despite the promising properties of PEDOT:PSS-based porous materials, the ability to pattern PEDOT:PSS hydrogels is still required to enable their integration with multifunctional and multichannel electronic devices. In this work, a novel electrochemical gelation (“electrogelation”) method is presented for rapidly patterning PEDOT:PSS hydrogels on any conductive template, including curved and 3D surfaces. High spatial resolution is achieved through use of a sacrificial metal layer to generate the hydrogel pattern, thereby enabling high-performance conducting hydrogels and aerogels with desirable material properties to be introduced into increasingly complex device architectures
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    Application of proportional velocity feedback control to attenuate the vibrations of a flexible plate using piezoceramic patch actuators
    (Springer-Verlag Berlin, 2011) N/A; N/A; N/A; Department of Mechanical Engineering; Külah, Serkan; Boz, Utku; Başdoğan, İpek; Master Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 179940
    This paper presents a theoretical and experimental study on the control performance of proportional velocity feedback control with rectangular piezoceramic patch actuators to attenuate the vibrations of a thin flexible plate. For this purpose, first, frequency response funciton of the plate is obtained based on the experimental frequency sweep data. Then, a state space model was fitted to the measured frequency response to be used in the simulations to represent the plant dynamics. The controlled response of the plate is investigated via simulations using MATLAB/SIMULINK. Control performance of the controller is investigated and discussed for various feedback gains.
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    PublicationOpen Access
    Broadband and band-limited random vibration energy harvesting using a piezoelectric patch on a thin plate
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2014) Erturk, Alper; Department of Mechanical Engineering; Arıdoğan, Mustafa Uğur; Başdoğan, İpek; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179940
    This paper presents analytical modeling and case studies of broadband and band-limited random vibration energy harvesting using a piezoceramic patch attached on a thin plate. The literature of vibration-based energy harvesting has been mostly focused on resonant cantilevered structures. However, cantilevered beam-type harvesters have limited broadband vibration energy harvesting capabilities unless they are combined with a nonlinear component. Moreover, cantilever arrangements cannot always be mounted on thin structures (which are basic components of marine, aerospace, and ground transportation systems) without significantly affecting the host system's design and overall dynamics. A patch-based piezoelectric energy harvester structurally integrated to a thin plate can be a proper alternative to using resonant cantilevers for harvesting energy from thin structures. Besides, plate-like structures have more number of vibration modes compared to beam structures, offering better broadband performance characteristics. In this paper, we present analytical modelling of patch-based piezoelectric energy harvester attached on a thin plate for random vibrations. The analytical model is based on electromechanically-coupled distributed-parameter formulation and validated by comparing the electromechanical frequency response functions (FRFs) with experimental results. Example case studies are then presented to investigate the expected power output of a piezoceramic patch attached on an aluminum plate for the case of random force excitations. The effect of bandwidth of random excitation on the mean power and shunted mean-square vibration response are explored with a focus on the number of vibration modes covered in the frequency range of input power spectral density (PSD).
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    Dynamics of spacing adjustment and recovery mechanisms of ABAC-type growth pattern in ternary eutectic systems
    (Elsevier, 2017) N/A; N/A; Department of Mechanical Engineering; Mohagheghi, Samira; Şerefoğlu, Melis; PhD Student; Researcher; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; 329277; 44888
    In directionally solidified 2D samples at ternary eutectic compositions, the stable three-phase pattern is established to be lamellar structure with ABAC stacking, where A, B, and C are crystalline phases. Beyond the stability limits of the ABAC pattern, the system uses various spacing adjustment mechanisms to revert to the stable regime. In this study, the dynamics of spacing adjustment and recovery mechanisms of isotropic ABAC patterns were investigated using three-phase In-Bi-Sn alloy. Unidirectional solidification experiments were performed on 23.0 and 62.7 mu m-thick samples, where solidification front was monitored in real-time from both sides of the sample using a particular microscopy system. At these thicknesses, the pattern was found to be 2D during steady-state growth, i.e. both top and bottom microstructures were the same. However, during spacing adjustment and recovery mechanisms, 3D features were observed. Dynamics of two major instabilities, lamellae branching and elimination, were quantified. After these instabilities, two key ABAC pattern recovery mechanisms, namely, phase invasion and phase exchange processes, were identified and analyzed. After elimination, ABAC pattern is recovered by either continuous eliminations of all phases or by phase exchange. After branching, the recovery mechanisms are established to be phase invasion and phase exchange.