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YARALIOĞLU, Göksen Göksenin

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Göksen Göksenin

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    Cantilever array oscillators with nonlinear optical readout
    (IEEE, 2015) Lüleç, S. Z.; Adiyan, U.; Yaralıoğlu, Göksen Göksenin; Leblebici, Y.; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    MEMS array oscillators typically require a separate detector and feedback loop for each oscillator. We show that grating-based-optical-readout induces nonlinearity, which enables simultaneous operation of an array-of-oscillators using only one detector and single electronic feedback-loop.
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    Conference ObjectPublicationOpen Access
    Microcantilever based LoC system for coagulation measurements
    (Chemical and Biological Microsystems Society, 2014) Çakmak, O.; Ermek, E.; Kılınç, N.; Barış, I.; Kavaklı, I. H.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    In this paper, a microcantilever-based system enabling multiple coagulation tests on the same disposable cartridge is demonstrated. The system consists of independent cartridge and reader unit. The actuation of the nickel cantilevers is conducted remotely with an external electro-coil and remote optical read-out is utilized for sensing. Both Prothrombin Time (PT) and activated Partial Thromboplastin Time (aPTT) tests can be conducted on the same cartridge. The system’s repeatability and accuracy is investigated with standard control plasma samples. The results are concordant with the manufacturer’s datasheet. The architecture of the system and the repeatable results makes the system suitable for Point-of-Care applications.
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    MEMS based blood plasma viscosity sensor without electrical connections
    (IEEE, 2013) Çakmak, O.; Ermek, E.; Urey, H.; Yaralıoğlu, Göksen Göksenin; Kılınç, N.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    A MEMS based viscometer is reported. The device has a disposable cartridge and a reader. The cartridge contains microfluidic channels and a MEMS cantilever sensor. The reader contains the actuator and the readout optics and electronics. A unique feature of the system is that both the actuation and the sensing are remote; therefore, no electrical connections are required between the reader and the cartridge. The reported sensor is capable of measuring viscosity with better than 0.01 cP resolution in a range of 0.8-14.1 cP, with less than 50 μl sample requirement. This range and sensitivity are sufficient for blood plasma viscosity measurements, which are in between 1.1-1.3 cP for healthy individuals and can be elevated to 3cP in certain diseases[1].
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    A pilot project for power quality improvements in distribution system by a Li-ion battery
    (IEEE, 2022) Çetin, A.; Ozen, C.; Bayatmakoo, A.; Kaya, K.; Poyrazoğlu, Göktürk; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    Power quality (PQ) metrics deterioration occurs in the distribution system by increasing the distributed generation plants, the existence of non-linear and harmonic loads. As a distribution system operator running under the Turkishelectricity regulation, a battery investment was made to improve PQ metrics to provide quality electricity service to customers by focusing on Volt/VAr optimization to obtain voltage stability parameters. The reverse power flow caused by the distributed generation can be eliminated and the power factor would be improved with the reactive support with this investment. This study includes the reasons for the battery pilot project, the engineering methodology, and post-solution improvements.
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    A prism-based non-linear optical readout method for MEMS cantilever arrays
    (Elsevier, 2016-10-15) Adiyan, U.; Civitci, F.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    This paper demonstrates the use of a single right-angle prism for the optical readout of micro-electro-mechanical systems (MEMS) cantilever arrays. The non-linear reflectivity arisen from the internal reflection at the right-angle prism’s hypotenuse plane enables the measurement of cantilever deflections. The cantilever arrays used in the experiments are made of electroplated nickel structures and actuated at resonance by an external electro-coil. A laser beam illuminates multiple cantilevers, and then it is partially reflected by the prism. The prism reflectivity changes with the cantilever deflection and modulates the laser intensity at the photodetector. The detection sensitivity of the optical readout system is determined by the initial angle of incidence at the prism’s hypotenuse plane, numerical aperture of the illumination system and the polarization of the laser beam. In this paper, we showed both theoretically and experimentally that self-sustained oscillations of two MEMS cantilevers with simple rectangular geometry is achievable using only one actuator and one photodetector. The gain saturation mechanism for the oscillators was provided by the optical non-linearity in the prism readout, which eliminates the requirement for separate sensing electronics for each cantilever. Based on our analytical and experimental data, we found that the prism incident angle around 41.2° is desirable in the closed-loop system due to high responsivity. Finally, we demonstrated simultaneous self-sustained oscillations of two cantilevers in closed-loop with resonant frequencies in the range 25–30 kHz. It was shown that multiple oscillations are obtainable if the cantilever resonant frequencies are separated from each other by at least 3 dB bandwidth.
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    Optical fiber array based simultaneous parallel monitoring of resonant cantilever sensors in liquid
    (Elsevier, 2016-05-01) Mostafazadeh, A.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    This paper reports a novel method for simultaneous resonance monitoring of MEMS cantilevers using phase based dynamic measurements without any electrical connections to the sensor array. MEMS cantilevers are made of electroplated nickel and actuated remotely with magnetic field using an electro-coil. To our knowledge this is the first demonstration of simultaneous parallel optical monitoring of dynamic mode micro-cantilever array in liquid environment. Illumination is generated using a laser source and a diffractive pattern generator, which provides 500 μW laser power per channel. A compact fiber array based pick-up was built for optical readout. Its main advantages are easy customization to different size and pitch of sensor array, and good immunity to electrical noise and magnetic interference as the photo detectors are located away from the electro-coil. The resonant frequency of the cantilever is tracked with a custom multi-channel lock-in amplifier implemented in software. For demonstrating the stability and sensitivity of the system we performed measurements using glycerol solutions with different viscosities. Measured phase sensitivity was 0.9°/1% of Glycerol/DI-water solution and the standard deviation of measured phase was 0.025°. The resulting detection limit for Glycerol/DI-water solution was 280 ppm. The proposed method showed robust results with low laser power and very good noise immunity to interference signals and environmental vibrations. The sensor technology demonstrated here is very significant as it is scalable to larger arrays for simultaneous and real- time monitoring of multiple biological and chemical agents during fluid flow.
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    Analysis of vibratory gyroscopes: drive and sense mode resonance shift by coriolis force
    (IEEE, 2017) Cetin, Hakan; Yaralıoğlu, Göksen Göksenin; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin; Cetin, Hakan
    In this paper, we demonstrate the analysis of coupling between drive and sense systems of vibratory gyroscopes. Vibratory gyroscopes have attracted a lot of interest recently with the development of MEMS gyroscopes. These gyroscopes made their way through portable devices and smart phones. Novel gyroscope architectures have been proposed and analyzed in detail. However, in most of these analyses, coupling between the sense and drive systems was ignored. We analytically show that drive and sense systems are coupled together via Coriolis and centrifugal force. As a result, system resonances shift as the rotation rate increase for linear and torsional gyroscope systems. Starting from a simple gyro system, we calculated the sense and drive resonant frequency shifts in various configurations. Then, for more complex systems where analytical solution is difficult to obtain, we used commercially available FEM tools to determine corresponding frequency shift. In general, we found that the shift is small and can be ignored for linear vibratory gyroscopes where Q of the sense system is less than 2500 for mode matched gyros. But for higher Q systems, the frequency shift may affect the linearity of these gyroscopes. This sets a fundamental limit for the linearity of vibratory gyroscopes. Based on our calculations the non-linearity is above 1% for linear 2-DOF mode-matched vibratory gyroscopes where Q is above 3000 and for torsional 2-DOF vibratory gyroscopes where Q is above 600. Multi-DOF and ring vibratory gyroscopes are also examined. We find that the effect is less pronounced for Multi-DOF gyros, whereas there is a large effect on the linearity of ring gyroscopes.
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    Portable low cost ultrasound imaging system
    (IEEE, 2016) Sobhani, Mohammad Rahim; Ozum, H. E.; Yaralıoğlu, Göksen Göksenin; Ergun, A. S.; Bozkurt, A.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin; Sobhani, Mohammad Rahim
    The applications of ultrasound in medicine have been increasing in the last decade either in diagnostics or in treatments. Ultrasound is routinely used in clinical examinations, such as pregnancy exams. On the other hand, a typical ultrasound system costs somewhere between 100k$ to 250k$ because of its (1) expensive ultrasound transducers, (2) large driving electronics, (3) processing and visualization units. High cost and large volume of the ultrasound systems prevent even wider usage of these systems. It is possible to extent the use of ultrasound in clinic environment like a stethoscope, if the size and cost had been reduced orders of magnitude. The aim of this work is to develop an ultraportable and very low cost diagnostic ultrasound imaging probe; by combining inertial sensors with the probes. The manual motion of the probe by the operator's hand movement enables scanning. The position of the probe is tracked using inertial sensors. Finally, the acoustic reflections are registered together by the help of position information of the probe to form an image.
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    Precision density and viscosity measurement using two cantilevers with different widths
    (Elsevier, 2015) Cakmak, O.; Ermek, E.; Kilinc, N.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    We introduce a novel method for fast measurement of liquid viscosity and density using two cantilevers with different geometries. Our method can be used for real-time monitoring in lab on chip systems and offer high accuracy for a large range of densities and viscosities. The measurement principle is based on tracking the oscillation frequencies of two cantilevers with a phase-locked loop (PLL) and comparing with reference measurements with a known fluid. A set of equations and a simple algorithm is developed to relate the density and the viscosity to the frequency shifts of the cantilevers. We found that the effect of the density and the viscosity can be well separated if cantilevers have different widths. In the experiments, two Nickel microcantilevers (widths 25 μm and 100 μm, length: 200 μm, thickness: 1.75 μm) were fully immersed in the liquid and the temperature was controlled. The actuation was using an external electro-coil and the oscillations were monitored using laser Doppler vibrometer. Thus, electrical connections to the cantilevers are not required, enabling measurements also in conductive liquids. The PLL is used to set the phase difference to 90° between the actuator and the sensor. Calibration measurements were performed using glycerol and ethylene glycol solutions with known densities and viscosities. The measurement error with the new method was lower than 3% in density in the range 995–1150 kg/m3 and 4.6% in viscosity in the range 0.935–4 mPa.s. Based on the signal-to-noise ratio, the minimum detectable difference in the viscosity is 1 μPa.s and the density is 0.18 kg/m3. Further improvements in the range and the accuracy are possible using 3 or more cantilevers with different geometries.
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    Vertical cavity capacitive transducer
    (American Institute of Physics Inc., 2021-04-01) Yaralıoğlu, Göksen Göksenin; Ergun, A. S.; Bozkurt, A.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    The capacitive micromachined ultrasonic transducer (CMUT) has inherent advantages, such as larger bandwidth and monolithic integration capability with electronics, when compared to the piezoelectric transducer. The most significant shortcoming of the device is the trade-off between input and output sensitivities. Adequate receive sensitivity requires an electric field intensity on the order of 105 V/m, which can be achieved by sub-micron gap heights. However, a small gap limits the device stroke and, consequently, the maximum output pressure. This paper addresses this problem by proposing a CMUT with a vertical cavity. The membrane of the device has a piston part that is surrounded by the sidewalls of a vertical cylinder formed in the substrate. The fringing electric field pulls the piston in the vertical direction; hence, the gap height remains fixed, which alleviates the hard limit on device stroke. The performance of the proposed device is compared to that of the conventional CMUT by theoretical and analytical methods, and a micro-fabrication method is devised. Additionally, a millimeter-scale device has been manufactured and tested as a proof of concept.