Researcher:
Ermek, Erhan

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Erhan

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Ermek

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Ermek, Erhan

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2011 - 202017

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    Precision density and viscosity measurement using two cantilevers with different widths
    (2015) Kılınç, Necmettin; Yaralıoğlu, G. G.; N/A; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Çakmak, Onur; Ermek, Erhan; Ürey, Hakan; PhD Student; Other; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; N/A; 8579
    Weintroduceanovelmethodforfastmeasurementofliquidviscosityanddensityusingtwocantilevers withdifferentgeometries.Ourmethodcanbeusedforreal-timemonitoringinlabonchipsystemsand offerhighaccuracyforalargerangeofdensitiesandviscosities.Themeasurementprincipleisbasedon trackingtheoscillationfrequenciesoftwocantileverswithaphase-lockedloop(PLL)andcomparingwith referencemeasurementswithaknownfluid.Asetofequationsandasimplealgorithmisdevelopedto relatethedensityandtheviscositytothefrequencyshiftsofthecantilevers.Wefoundthattheeffectof thedensityandtheviscositycanbewellseparatedifcantilevershavedifferentwidths.Intheexperiments, twoNickelmicrocantilevers(widths25 mand100 m,length:200 m,thickness:1.75 m)werefully immersedintheliquidandthetemperaturewascontrolled.TheactuationwasusinganexternalelectrocoilandtheoscillationsweremonitoredusinglaserDopplervibrometer.Thus,electricalconnectionsto thecantileversarenotrequired,enablingmeasurementsalsoinconductiveliquids.ThePLLisusedto setthephasedifferenceto90◦betweentheactuatorandthesensor.Calibrationmeasurementswere performedusingglycerolandethyleneglycolsolutionswithknowndensitiesandviscosities.Themeasurementerrorwiththenewmethodwaslowerthan3%indensityintherange995–1150kg/m3and 4.6%inviscosityintherange0.935–4mPa.s.Basedonthesignal-to-noiseratio,theminimumdetectable differenceintheviscosityis1 Pa.sandthedensityis0.18kg/m3.Furtherimprovementsintherange andtheaccuracyarepossibleusing3ormorecantileverswithdifferentgeometries.
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    MEMS biosensor for parallel and highly sensitive and specific detection of hepatitis
    (IEEE, 2011) Kavaklı, I.H.; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Ürey, Hakan; Ermek, Erhan; Timurdoğan, Erman; Alaca, Burhanettin Erdem; Faculty Member; Other; Undergraduate Student; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; College of Sciences; College of Engineering; College of Engineering; 8579; N/A; N/A; 115108
    A label-free biosensor array that offers highly sensitive, high-dynamic-range and highly specific detection of Hepatitis A antigen is reported. Sensor array consists of Ni cantilevers with surfaces functionalized with Hepatitis A antibody. Cantilevers are self-actuated at resonance using a single electromagnetic drive coil. Detection of resonance frequency is optical and facilitated by diffraction gratings embedded on cantilevers. All antibody-antigen interactions take place within undiluted bovine serum providing a high background noise due to unspecific molecules. A minimum detection limit of less than 0.1 ng/ml target molecule concentration is demonstrated. A high dynamic range is achieved, which is greater than 1000:1 concentration range. The proposed sensor array is shown to be compatible with most of the requirements of a hand-held biosensor including label-free, robust and real-time measurement with well integrated components.
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    MEMS based blood plasma viscosity sensor without electrical connections
    (IEEE Computer Society, 2013) Yaralıoğlu, Göksenin G.; N/A; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Çakmak, Onur; Ermek, Erhan; Ürey, Hakan; Kılınç, Necmettin; PhD Student; Other; Faculty Member; Researcher; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; 8579; 59959
    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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    MEMS biosensor for blood plasma viscosity measurements
    (Elsevier Science Bv, 2012) N/A; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; N/A; N/A; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Çakmak, Onur; Elbüken, Çağlar; Ermek, Erhan; Bulut, Selma; Kılınç, Yasin; Barış, İbrahim; Kavaklı, İbrahim Halil; Alaca, Burhanettin Erdem; Ürey, Hakan; PhD Student; Researcher; Other; PhD Student; PhD Student; Teaching Faculty; Faculty Member; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Department of Electrical and Electronics 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; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; N/A; N/A; 111629; 40319; 115108; 8579
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    Two cantilever based sytem for viscosity and density monitoring
    (IEEE, 2015) Yaralıoğlu, Göksenin G.; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Çakmak, Onur; Ermek, Erhan; Kılınç, Necmettin; Ürey, Hakan; PhD Student; Other; Researcher; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; College of Engineering; N/A; N/A; 59959; 8579
    Viscosity and density measurements in liquids in real-time is challenging. Previous MEMS based approaches use frequency sweeps for the purpose and those methods are slow and not real-time. We show that high precision viscosity and density measurements are possible using two cantilevers with different widths and by tracking their frequencies with a Phase-Locked-Loop in real-time.
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    In vitro validation of a self-driving aortic-turbine venous-assist device for fontan patients
    (Elsevier, 2018) Türköz, Rıza; Department of Mechanical Engineering; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Pekkan, Kerem; Aka, İbrahim Başar; Tutsak, Ece; Ermek, Erhan; Balım, Haldun; Lazoğlu, İsmail; Faculty Member; PhD Student; Master Student; Other; 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 Sciences; Graduate School of Sciences and Engineering; College of Engineering; 161845; N/A; N/A; N/A; N/A; 179391
    Background: Palliative repair of single ventricle defects involve a series of open-heart surgeries where a single-ventricle (Fontan) circulation is established. As the patient ages, this paradoxical circulation gradually fails, because of its high venous pressure levels. Reversal of the Fontan paradox requires an extra subpulmonic energy that can be provided through mechanical assist devices. The objective of this study was to evaluate the hemodynamic performance of a totally implantable integrated aortic-turbine venous-assist (iATVA) system, which does not need an external drive power and maintains low venous pressure chronically, for the Fontan circulation. Methods: Blade designs of the co-rotating turbine and pump impellers were developed and 3 prototypes were manufactured. After verifying the single-ventricle physiology at a pulsatile in vitro circuit, the hemodynamic performance of the iATVA system was measured for pediatric and adult physiology, varying the aortic steal percentage and circuit configurations. The iATVA system was also tested at clinical off-design scenarios. Results: The prototype iATVA devices operate at approximately 800 revolutions per minute and extract up to 10% systemic blood from the aorta to use this hydrodynamic energy to drive a blood turbine, which in turn drives a mixed-flow venous pump passively. By transferring part of the available energy from the single-ventricle outlet to the venous side, the iATVA system is able to generate up to approximately 5 mm Hg venous recovery while supplying the entire caval flow. Conclusions: Our experiments show that a totally implantable iATVA system is feasible, which will eliminate the need for external power for Fontan mechanical venous assist and combat gradual postoperative venous remodeling and Fontan failure.
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    Simultaneous self-sustained actuation and parallel readout with mems cantilever sensor array
    (IEEE, 2012) Leblebici, Yusuf; Department of Electrical and Electronics Engineering; Department of Mathematics; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; Ürey, Hakan; Mostafazadeh, Ali; Ermek, Erhan; Sağıroğlu, Cem; Timurdoğan, Erman; Lüleç, Sevil Zeynep; Faculty Member; Faculty Member; Other; Undergraduate Student; PhD Student; Other; Department of Mathematics; Department of Electrical and Electronics Engineering; College of Engineering; College of Sciences; College of Sciences; College of Engineering; Graduate School of Sciences and Engineering; N/A; 8579; 4231; N/A; N/A; N/A; N/A
    Parallel readout of a microcantilever array using single magnetic actuator and a single photo detector for concurrent detection is reported. The system includes MEMS cantilever array designed for different resonance frequencies, optical elements for laser beam shaping and focusing, one detector and feedback electronics, and single broadband actuator for parallel excitation. The cantilevers are made using a simple one-mask fabrication process with embedded amplitude gratings at the tips. A line shaped laser beam is used to illuminate the cantilevers. A single readout photodiode is placed at the first order diffraction beam location on the Fourier plane. The amplified photodiode signal is fed back into the magnetic actuation using a preamplifier and a broadband current amplifier. In this paper, we report for the first time parallel monitoring of the thermal resonance peaks of inherently frequency-multiplexed MEMS cantilevers. We demonstrated simultaneous self-sustained oscillations of seven cantilevers by using a single actuator and detector in air environment. The method is suitable for low-cost multiplexed portable biosensors.
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    Increased energy loss due to twist and offset buckling of the total cavopulmonary connection
    (ASME, 2017) Arnaz, Ahmet; N/A; Department of Molecular Biology and Genetics; N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Oğuz, Gökçe Nur; Pişkin, Şenol; Ermek, Erhan; Donmazov, Samir; Altekin, Naz; Pekkan, Kerem; PhD Student; Researcher; Other; PhD Student; Undergraduate Student; Faculty Member; Department of Molecular Biology and Genetics; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 148702; N/A; N/A; N/A; 161845
    The hemodynamic energy loss through the surgically implanted conduits determines the postoperative cardiac output and exercise capacity following the palliative repair of single-ventricle congenital heart defects. In this study, the hemodynamics of severely deformed surgical pathways due to torsional deformation and anastomosis offset are investigated. We designed a mock-up total cavopulmonary connection (TCPC) circuit to replicate the mechanically failed inferior vena cava (IVC) anastomosis morphologies under physiological venous pressure (9, 12, 15 mmHg), in vitro, employing the commonly used conduit materials: Polytetrafluoroethylene (PTFE), Dacron, and porcine pericardium. The sensitivity of hemodynamic performance to torsional deformation for three different twist angles (0 deg, 30 deg, and 60 deg) and three different caval offsets (0 diameter (D), 0.5D, and 1D) are digitized in three dimensions and employed in computational fluid dynamic (CFD) simulations to determine the corresponding hydrodynamic efficiency levels. A total of 81 deformed conduit configurations are analyzed; the pressure drop values increased from 80 to 1070% with respect to the ideal uniform diameter IVC conduit flow. The investigated surgical materials resulted in significant variations in terms of flow separation and energy loss. For example, the porcine pericardium resulted in a pressure drop that was eight times greater than the Dacron conduit. Likewise, PTFE conduit resulted in a pressure drop that was three times greater than the Dacron conduit under the same venous pressure loading. If anastomosis twist and/or caval offset cannot be avoided intraoperatively due to the anatomy of the patient, alternative conduit materials with high structural stiffness and less influence on hemodynamics can be considered.
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    Microcantilever based loc system for coagulation measurements
    (Chemical and Biological Microsystems Society, 2014) Kılınç, Necmettin; Yaralıoğlu G.G.; N/A; Department of Molecular Biology and Genetics; Department of Molecular Biology and Genetics; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Çakmak, Onur; Ermek, Erhan; Barış, İbrahim; Kavaklı, İbrahim Halil; Ürey, Hakan; PhD Student; Other; Teaching Faculty; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; College of Sciences; College of Sciences; N/A; N/A; 111629; 40319; 8579
    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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    LoC sensor array platform for real-time coagulation measurements
    (Institute of Electrical and Electronics Engineers (IEEE), 2014) Yaralıoğlu, Göksenin G.; N/A; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Çakmak, Onur; Kılınç, Necmettin; Ermek, Erhan; Mostafazadeh, Aref; Elbüken, Çağlar; Ürey, Hakan; PhD Student; Researcher; Other; Researcher; Researcher; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; College of Engineering; College of Engineering; College of Engineering; N/A; 59959; N/A; N/A; N/A; 8579
    This paper reports a MEMS-based sensor array enabling multiple clot-time tests in one disposable microfluidic cartridge using plasma. The versatile LoC (Lab-on-Chip) platform technology is demonstrated here for real-time coagulation tests (activated Partial Thrompoblastin Time (aPTT) and Prothrombin Time (PT)). The system has a reader unit and a disposable cartridge. The reader has no electrical connections to the cartridge, which consists of multiple microfluidic channels and MEMS microcantilevers placed in each channel. Microcantilevers are made of electro-plated nickel and actuated remotely using an external electro-coil. The read-out is also conducted remotely by a laser and the phase of the MEMS oscillator is monitored real-time. The system is capable of monitoring coagulation time with a precision estimated at 0.1sec.