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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Batch fabrication of self-assembled nickel-iron nanowires by electrodeposition(IEEE, 2006) N/A; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Şardan, Özlem; Yalçınkaya, Arda Deniz; Alaca, Burhanettin Erdem; Master Student; Researcher; Faculty Member; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 144523; 115108Lack of batch-compatible fabrication techniques can be considered as the most important challenge in the integration of nanostructures with microelectromechanical systems (MEMS). a solution to the micro-nano integration problem is offered by introducing a batch-compatible nanowire fabrication technique based on basic lithographic techniques and guided self-assembly. the basic principle is obtaining cracks at predetermined locations in a sacrificial SiO2 layer on Si and filling these cracks with a suitable metal by electrodeposition. the technique is demonstrated by using Nickel-Iron as the deposition material and verifying the magnetic behavior of resulting nanowires.Publication Metadata only Two-axis MENIS scanner for display and imaging applications(IEEE-Inst Electrical Electronics Engineers Inc, 2005) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; Department of Mechanical Engineering; Ürey, Hakan; Yalçınkaya, Arda Deniz; Brown, Dean; Anaç, Ozan; Ataman, Çağlar; Başdoğan, İpek; Faculty Member; Researcher; Researcher; N/A; N/A; Master Student; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 8579; 144523; N/A; N/A; N/A; N/A; N/A; 179940Two-axis gimbaled scanner used in an SVGa display product with 58deg optical scan angle, 1.5mm mirror size, and 21.KHz resonant frequency is reported Scanner is actuated electromagnetically using a single coil on the outer frame and by mechanical coupling of outer frame motion into the inner mirrorframe.Publication Metadata only Modeling miniaturized piezoelectric ultrasound transducers: comparison of lumped and finite element models(IEEE, 2020) Department of Mechanical Engineering; Kullukçu, Berkay; Beker, Levent; PhD Student; Master Student; Faculty Member; Department of Mechanical Engineering; College of Engineering; N/A; N/A; 308798In the quest to develop wirelessly-powered implantable medical devices (IMD), ultrasonic power transfer has received significant attention due to its distinct advantages (sub-mm wavelength, lower attenuation, higher allowed power intensity by the FDA) compared to other alternatives such as radio frequency-based approaches. A typical power link structure for US-based IMDs consists of a piezoelectric cube (PC) and an easy to use modeling technique would provide value insights for design of such wireless power systems. Equivalent circuit modeling (ECM) is the most common method utilized to model piezoelectric acoustic devices. In this work, a detailed analysis of two commonly used ECM models, KLM and Leach are developed specifically for a PC resonator. Then, a 3D finite element model is developed and the results of the developed ECM are compared with the finite element model results for a PC as well as other aspect ratios of the transducer. The two ECM models yielded similar results with a difference of less than 0.5%. The Leach model does not utilize frequency-dependent elements, its implementation in conventional circuit analysis software is more straightforward. Through ECM, the effect of each design parameter on transducer characteristics could be determined. However, to achieve more accurate results as the aspect ratio converges to one, the use FEM or experimental data to perform modification on ECM is necessary.Publication Metadata only Tactile perception of change in friction on an ultrasonically actuated glass surface(Institute of Electrical and Electronics Engineers (IEEE), 2017) Yılmaz, Çetin; N/A; Department of Mechanical Engineering; Saleem, Muhammad Khurram; Başdoğan, Çağatay; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489We conducted psychophysical experiments to investigate human haptic perception when they experience a step change in friction on an ultrasonically actuated glass surface under two experimental conditions; sliding finger and stationary finger pressed on the surface. During the experiments, the forces acting on the subjects' finger and the out of plane vibrations of the touch surface were measured by a force and a piezoelectric sensor, respectively. The results showed that stationary finger more easily detected falling friction, whereas, sliding finger was more sensitive to rising friction at higher actuation levels. Moreover, sliding finger was twice more sensitive to changes in friction than stationary finger. Finally, we found that the rate of change of contact forces were best correlated with the subjects' perception of change in friction under both experimental conditions.Publication Metadata only A novel triaxial optoelectronic based dynamometer for machining processes(Elsevier Science Sa, 2018) N/A; N/A; Department of Mechanical Engineering; Subaşı, Ömer; Yazgı, Sertaç Güneri; Lazoğlu, İsmail; PhD Student; Master Student; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 179391A compact triaxial dynamometer for detecting the cutting forces in machining is developed. force measurements are performed using photo-interrupters. Structural parameters of a monolithic flexural component are chosen through parametric analysis for coupling the exerted forces with the optical sensors. a prototype of the dynamometer is manufactured, and the calibration tests are conducted in three orthogonal directions to determine the linearity, hysteresis, repeatability and resolution. force measurements are also compared with a reference dynamometer (Kistler 9256C1). Modal analysis and milling tests are performed to observe the dynamic properties and operability of the force sensor for machining applications. Results of the experimental studies validate that the proposed sensor is a feasible low-cost solution for force measurement in machining without compromising reliability and accuracy.Publication Metadata only Dynamic characterization and modification of dynamic properties of a micro scanner(Springer Heidelberg, 2010) N/A; Department of Mechanical Engineering; Veryeri, Ilgar; Başdoğan, İpek; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179940Micro electro mechanical systems (MEMS) are used in many application areas in different disciplines and took their place among the most promising technologies. The performance of such systems is primarily related to their dynamical characteristics. This study presents the dynamic characterization techniques that are used to identify the modal parameters of a MEMS device and the methods that can be implemented to change its dynamic response. An electrostatic scanner is chosen as the case study to demonstrate the developed methodologies. Initially, the micro scanner is characterized using experimental modal analysis techniques to obtain frequency response function, modal damping, resonance frequencies, and mode shapes. Then, velocity and position feedback control loops are implemented to the scanner system to alter the damping and stiffness characteristics. A closed-loop Simulink model of the scanner is developed to verify the experimental measurements. Several curve fitting methods are used in order to have an accurate representation of the scanner system. Using the model, the influence of both position and velocity feedback on the effective damping, resonance frequency and the transient behavior of the scanner is investigated. The stability limits of the scanner under velocity feedback are also studied via numerical simulations. Based on the experimental and simulation results, the methodology developed in this study proves itself to be very efficient to alter the dynamical characteristics of the MEMS structures and it can be easily adapted to other MEMS applications.Publication Metadata only Modeling miniaturized piezoelectric ultrasound transducers: comparison of lumped and finite element models(Ieee, 2020) Department of Mechanical Engineering; N/A; N/A; Department of Mechanical Engineering; Ziarati, Pouriya Torkinejad; Kullukçu, Berkay; Beker, Levent; N/A; Master Student; Faculty Member; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 308798In the quest to develop wirelessly-powered implantable medical devices (IMD), ultrasonic power transfer has received significant attention due to its distinct advantages (sub-mm wavelength, lower attenuation, higher allowed power intensity by the FDA) compared to other alternatives such as radio frequency-based approaches. A typical power link structure for US-based IMDs consists of a piezoelectric cube (PC) and an easy to use modeling technique would provide value insights for design of such wireless power systems. Equivalent circuit modeling (ECM) is the most common method utilized to model piezoelectric acoustic devices. In this work, a detailed analysis of two commonly used ECM models, KLM and Leach are developed specifically for a PC resonator. Then, a 3D finite element model is developed and the results of the developed ECM are compared with the finite element model results for a PC as well as other aspect ratios of the transducer. The two ECM models yielded similar results with a difference of less than 0.5%. The Leach model does not utilize frequency-dependent elements, its implementation in conventional circuit analysis software is more straightforward. Through ECM, the effect of each design parameter on transducer characteristics could be determined. However, to achieve more accurate results as the aspect ratio converges to one, the use FEM or experimental data to perform modification on ECM is necessary.Publication Metadata only Roughness perception of virtual textures displayed by electrovibration on touch screens(IEEE, 2017) N/A; N/A; N/A; Department of Mechanical Engineering; Vardar, Yasemin; İşleyen, Aykut; Saleem, Muhammad Khurram; Başdoğan, Çağatay; PhD Student; Master Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 125489In this study, we have investigated the human roughness perception of periodical textures on an electrostatic display by conducting psychophysical experiments with 10 subjects. To generate virtual textures, we used low frequency unipolar pulse waves in different waveform (sinusoidal, square, saw-tooth, triangle), and spacing. We modulated these waves with a 3kHz high frequency sinusoidal carrier signal to minimize perceptional differences due to the electrical filtering of human finger and eliminate low-frequency distortions. The subjects were asked to rate 40 different macro textures on a Likert scale of 1-7. We also collected the normal and tangential forces acting on the fingers of subjects during the experiment. The results of our user study showed that subjects perceived the square wave as the roughest while they perceived the other waveforms equally rough. The perceived roughness followed an inverted U-shaped curve as a function of groove width, but the peak point shifted to the left compared to the results of the earlier studies. Moreover, we found that the roughness perception of subjects is best correlated with the rate of change of the contact forces rather than themselves.Publication Metadata only Monolithic fabrication of silicon nanowires bridging thick silicon structures(IEEE-Inst Electrical Electronics Engineers Inc, 2018) Peric, Oliver; Sacchetto, Davide; Fantner, Georg Ernest; Leblebici, Yusuf; N/A; Department of Mechanical Engineering; Taşdemir, Zuhal; 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; 115108A monolithic process is developed for the fabrication of Si nanowires within thick Si substrates. A combination of anisotropic etch and sidewall passivation is utilized to protect and release Si lines during the subsequent deep etch. An etch depth of 10 mu m is demonstrated with a future prospect for 50 mu m opening up new possibilities for the deterministic integration of nanowires with microsystems. Nanowires with in-plane dimensions as low as 20 nm and aspect ratios up to 150 are obtained. Nanomechanical characterization through bending tests further confirms structural integrity of the connection between nanowires and anchoring Si microstructures.Publication Metadata only Monolithic integration of Si nanowires with metallic electrodes: NEMS resonator and switch applications(Iop Publishing Ltd, 2011) Sacchetto, Davide; Leblebici, Yusuf; N/A; Department of Mechanical Engineering; N/A; Yıldız, İzzet; Alaca, Burhanettin Erdem; Arkan, Evren Fatih; Researcher; Faculty Member; Researcher; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; N/A; 115108; N/AThe challenge of wafer-scale integration of silicon nanowires into microsystems is addressed by developing a fabrication approach that utilizes a combination of Bosch-process-based nanowire fabrication with surface micromachining and chemical-mechanical-polishing-based metal electrode/contact formation. Nanowires up to a length of 50 mu m are achieved while retaining submicron nanowire-to-electrode gaps. The scalability of the technique is demonstrated through using no patterning method other than optical lithography on conventional SOI substrates. Structural integrity of double-clamped nanowires is evaluated through a three-point bending test, where good clamping quality and fracture strengths approaching the theoretical strength of the material are observed. Resulting devices are characterized in resonator and switch applications-two areas of interest for CMOS-compatible solutions-with all-electrical actuation and readout schemes. Improvements and tuning of obtained performance parameters such as resonance frequency, quality factor and pull-in voltage are simply a question of conventional design and process adjustments. Implications of the proposed technique are far-reaching including system-level integration of either single-nanowire devices within thick Si layers or nanowire arrays perpendicular to the plane of the substrate.