Researcher:
Eris, Gamze

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Gamze

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Eris

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Eris, Gamze

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2013 - 20173

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Researcher Of Publications: search.filters.isAuthorOfPublication.02b91017-3615-4540-b8de-e741197be1bb

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    Characterization of fluid mixtures at high pressures using frequency response of microcantilevers
    (2017) Bozkurt, Asuman Aşıkoğlu; Jonas, Alexandr; Department of Chemical and Biological Engineering; N/A; Department of Physics; Department of Mechanical Engineering; Department of Chemical and Biological Engineering; Department of Physics; Department of Mechanical Engineering; Department of Chemical and Biological Engineering; Eris, Gamze; Baloch, Shadi Khan; Kiraz, Alper; Alaca, Burhanettin Erdem; Erkey, Can; Researcher; PhD Student; Faculty Memeber; Faculty Member; Faculty Member; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); 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 Sciences; College of Engineering; College of Engineering; N/A; N/A; 22542; 115108; 29633
    The frequency response of ferromagnetic nickel microcantilevers immersed in binary mixtures of carbon dioxide (CO2) and nitrogen (N-2) at 308 K and pressures up to 23 MPa was investigated. Experimental data were analyzed using the model developed by Sader for a clamped oscillatory beam immersed in a fluid and a very good agreement between the measured resonant frequencies and quality factors (Q factors) and the theoretical predictions of the model with cantilever characteristic parameters regressed from experimental data was observed. This suggested that the data could be used to simultaneously measure the density and the viscosity of fluid mixtures over a wide range of pressures. Subsequently, density and viscosity of binary mixtures of CO2 and N-2 were determined using N-2 as the reference fluid and compared to the predictions of Gerg equation of state and Chung equation, respectively. For the studied fluids with different compositions, the average relative difference between the experimental density values and the values predicted using Gerg equation of state and NIST database ranged from 1.0 to 13%. The average relative difference between the experimental viscosity values and the values obtained using Chung equation and NIST database ranged from 2.4 to 15%. Since the resonant frequency and Q factor were found to vary with composition at a fixed temperature and pressure, the technique can in principle also be used to measure the composition of a binary mixture at a fixed temperature and pressure. The study represents the first systematic attempt to use microcantilevers for the characterization of high-pressure fluid mixtures and paves the way for devising portable sensors for in-line monitoring of thermophysical properties and composition of fluid mixtures under a wide range of environmental conditions. (C) 2017 Elsevier B.V. All rights reserved.
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    Three-dimensional optofluidic waveguides in hydrophobic silica aerogels via supercritical fluid processing
    (Elsevier, 2013) Jonas, Alexandr; Department of Chemical and Biological Engineering; N/A; N/A; Department of Chemical and Biological Engineering; Department of Physics; Department of Physics; Department of Chemical and Biological Engineering; Department of Physics; Department of Chemical and Biological Engineering; Eris, Gamze; Şanlı, Deniz; Ülker, Zeynep; Bozbağ, Selmi Erim; Kiraz, Alper; Erkey, Can; Researcher; Researcher; PhD Student; Researcher; Other; Faculty Member; Faculty Member; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Engineering; N/A; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; College of Sciences; College of Engineering; N/A; N/A; 262388; N/A; N/A; 22542; 29633
    Optofluidic components enable flexible routing and transformations of light beams in integrated lab-on-a-chip systems with the use of carefully shaped fluid parcels. For structural integrity reasons, the working fluid is typically contained within a solid-material chip. One of the outstanding challenges in optofluidics is the preparation and processing of optofluidic waveguides. These require solid cladding materials that are sufficiently strong to contain the fluid while possessing optical properties that allow efficient confinement of light within fluidic channels. Here, we report on a new technique to obtain liquid-core optofluidic waveguides based on total internal reflection of light in three-dimensional water-filled channels embedded in hydrophobic silica aerogel. To form the channels, we employ a fiber made of cage-like silicon-oxygen compound - trifluoropropyl polyhedral oligomeric silsesquioxane (trifluoropropyl PUSS) - which has high solubility in supercritical CO2 (scCO(2)). A U-shaped fiber made of trifluoropropyl PUSS is obtained by melt/freeze processing of PUSS powder and subsequently placed in a silicate sol. After gelation of the sol and aging of the gel, scCO(2) extraction is used to dry the wet gel and extract the POSS fiber, yielding a dry silica aerogel with a U-shaped empty channel inside it. Finally, the silanol groups at the surface of the aerogel are reacted with hexamethyldisilazane (HMDS) in the presence of scCO(2) to render the aerogel surface hydrophobic and the channel is filled with water. We demonstrate efficient waveguiding by coupling light into the water-filled channel and monitoring the channel output. The presented procedure opens up new possibilities for creating complex three-dimensional networks of liquid channels in aerogels for optofluidic applications. (C) 2012 Elsevier B.V. All rights reserved.
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    Determination of viscosity and density of fluids using frequency response of microcantilevers
    (Elsevier Science Bv, 2015) Jonas, Alexandr; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Department of Physics; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Department of Physics; Department of Chemical and Biological Engineering; Eris, Gamze; Alaca, Burhanettin Erdem; Kiraz, Alper; Erkey, Can; Researcher; Faculty Member; Faculty Member; Faculty Member; College of Engineering; College of Engineering; College of Sciences; College of Engineering; N/A; 115108; 22542; 29633
    We report on the simultaneous measurement of density and viscosity of nitrogen in gas and supercritical phases at 308.15 K and pressures up to 24 MPa. The density and viscosity were extracted from the measured frequency responses of an oscillated microcantilever immersed in N-2. To this end, a model of oscillatory motion of immersed cantilevers incorporating the effects of hydrodynamic forces was employed. Using argon as a reference fluid of known density and viscosity, cantilever calibration parameters were obtained from nonlinear regression of cantilever resonant frequencies and quality factors recorded in argon. Subsequently, these calibration parameters were used in the model equations to determine the density and viscosity of nitrogen at the given experimental pressure and temperature. In the studied pressure range, the root-mean-square deviations of the measured density and viscosity of nitrogen from the reference values obtained from NIST database were 2.5% and 5.2%, respectively. (C) 2015 Elsevier B.V. All rights reserved.