Yazar "Guler, Mustafa Tahsin" seçeneğine göre listele

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    3B baskılanmış bir kanalda sıvı basıncının damlacık boyutu ile ilişkisi
    (Kırıkkale Üniversitesi, 2023) Guler, Mustafa Tahsin
    Bu makale 3B baskılanmış bir mikro kanalada damlacık oluşumunun sıvı basıncı ile olan ilişkisini inceler. SLA (stereyolitografi) 3B yazıcı ile reçineden şefff mikroakışkan çip imal edilmiştir. Yağ içinde su mikro damlacıkarı sıvı odaklama tasarımında oluşturulmuştur. Yağ ve su girişleri sabit basınç kayanağı ile sürülmüştür. Mikroakışkan çipin mikrodamlacık oluşturma başarımı mikroskop vasıtasıyla gözlenmiştir. Mikrodamlacıkların boyutları sıvı basıncına göre belirlenmiştir.
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    Alternative screening method for analyzing the water samples through an electrical microfluidics chip with classical microbiological assay comparison of P. aeruginosa
    (ELSEVIER, 2020) Bilican, Ismail; Bahadir, Tolga; Bilgin, Kemal; Guler, Mustafa Tahsin
    Pseudomonas aeruginosa is a pathogenic bacterium in fresh water supplies that creates a risk for public health. Microbiological analysis of drinking water samples is time consuming and requires qualified personnel. Here we offer a screening system for rapid analysis of spring water that has the potential to be turned into a point-of-need system by means of simple mechanism. The test, which takes 1 h to complete, electrically interrogates the particles through a microfluidic chip suspended in the water sample. We tested the platform using water samples with micro beads and water samples spiked with P. aeruginosa at various concentrations. The mono disperse micro beads were used to evaluate the performance of the system. The results were verified by the gold standard membrane filtration method, which yielded a positive test result only for the P. aeruginosa spiked samples. Detection of 0-11 k bacteria in 30 mu L samples was successfully completed in 1 h and compared with a conventional microbiological method. The presented method is a good candidate for a rapid, on-site, screening test that can result in a significant reduction in cost and analysis time compared to microbiological analyses routinely used in practice.
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    Assessment of PMMA and polystyrene based microfluidic chips fabricated using CO2 laser machining
    (ELSEVIER, 2020) Bilican, Ismail; Guler, Mustafa Tahsin
    Laser machining could be an alternative way for the fabrication of microchannels. In this study, laser machining of polymethylmethacrylate (PMMA) and polystyrene (PS) substrates were characterized in detail. A fabrication method preventing leakage at PS microchannel inlets was developed. The effect of laser parameters (power, speed and frequency) on engraving was analyzed by scanning electron microscopy. Laser ablation mechanism of both materials was explained through thermal analysis and material properties. Defocusing the laser beam was also analyzed as an additional parameter affecting the channel profile. Two parameters affecting the resolution were analyzed which are the minimum channel size that can be achieved by the laser beam and x-y stage of the laser engraver for straight and complex microchannel geometries. The hydrophilicity of the surface before and after laser machining was tested with contact angle measurements. The capabilities/limitations of machining were revealed through some complex channel structures. Finally, a passive micromixer and a droplet generator microfluidic devices were manufactured and tested, and promising results were obtained.
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    Capacitive detection of single bacterium from drinking water with a detailed investigation of electrical flow cytometry
    (Elsevier Science Sa, 2018) Guler, Mustafa Tahsin; Bilican, Ismail
    Pathogenic contamination of drinking water is critical in regard to human health. In this study, we investigated the electrical detection of single bacterium from drinking water. A microfluidics chip consisting of polydimethylsiloxane (PDMS) microchannel and gold microelectrodes was fabricated with conventional microfabrication techniques. Electrical characterizations were done with an LCR meter and the measurements were in good agreement with simulation results. The impact of channel and electrode dimensions was studied for the different type and size of particles, using both experimental and simulation techniques. In addition, the effect of excitation signal frequency and solution conductivity was analyzed employing both simulation and experimental methods. Finally, capacitive detection of a single Escherichia coli (E. coli) from drinking water was successfully carried out under optimum parameters and design geometries. (C) 2017 Elsevier B.V. All rights'reserved.
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    Capacitive solvent sensing with interdigitated microelectrodes
    (Springer, 2016) Bilican, Ismail; Guler, Mustafa Tahsin; Gulener, Neset; Yuksel, Mustafa; Agan, Sedat
    We were able to quantify dielectric properties of solvents such as DI water, isopropyl alcohol, and acetone using interdigitated microelectrodes (IMEs). IMEs were fabricated using conventional micro fabrication techniques. The fabricated IMEs were dipped into the solution, and the dielectric property of the medium was measured. A range of frequencies and excitation voltages were swept in order to determine the operation region that yields the highest signal to noise ratio. Measurements were performed at 1 MHz and 100 mV which resulted in best signal to noise ratio. We applied a simple analytical model for the calculation of the capacitance and measured the capacitance value using a simple parallel capacitor and resistor model which resulted in perfect agreement with theoretical results. The presented sensor provides a simple and accurate method to determine solvent type which may have possible future applications.
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    CO2 laser machining for microfluidics mold fabrication from PMMA with applications on viscoelastic focusing, electrospun nanofiber production, and droplet generation
    (Elsevier Science Inc, 2021) Guler, Mustafa Tahsin; Inal, Murat; Bilican, Ismail
    In this study, a new method for the fabrication of polydimethylsiloxane (PDMS) microchannels through the replication of plexiglass molds was developed. A plexiglass slab is machined with CO2 laser in the raster mode to produce the mold for the PDMS casting. Then, the PDMS replica of the mold is plasma bonded to a substrate by applying more pressure than standard to overcome the surface roughness inherited from the laser machining process. Depending on the channel complexity, a ready to cast mold in the size of a glass slide can be achieved in 5-20 min, including the design, machining, and cleaning steps. This fully automated and cost-effective mold making method proved to be the fastest among all methods, and it enables up to 2.5 aspect ratio microchannels, down to a width of 60 mm, and a height of 23 mm. The raster mode of the laser provides features lower, in size, then the laser beam waist radius. The produced microchannels were validated using several applications, such as droplet generation, nanofiber production, and viscoelastic microparticle focusing. (c) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
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    Focusing-free impedimetric differentiation of red blood cells and leukemia cells: A system optimization
    (ELSEVIER SCIENCE SA, 2020) Bilican, Ismail; Guler, Mustafa Tahsin; Serhatlioglu, Murat; Kirindi, Talip; Elbuken, Caglar
    A focusing-free microfluidic impedimetric cell detection system is developed. The effect of the channel dimensions, solution conductivity, excitation voltage, and particle size on impedimetric signal outputs were optimized to increase the sensitivity of the system. Conventional microfabrication techniques were adapted to obtain low height, resealable microchannels. The geometry optimization was performed by a combination of analytical, numerical and experimental approaches. The results demonstrate that reliable impedimetric particle differentiation can be achieved without any labeling or particle focusing. The system parameters were studied and rule-of-thumb design criteria were provided. Finally, using the developed system, red blood cells and leukemia cells were experimentally detected and differentiated. Thanks to its simplicity, the focusing-free cell differentiation system may find applications in several cellular diagnostic uses.
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    Impedance-based viscoelastic flow cytometry
    (Wiley, 2019) Serhatlioglu, Murat; Asghari, Mohammad; Guler, Mustafa Tahsin; Elbuken, Caglar
    Elastic nature of the viscoelastic fluids induces lateral migration of particles into a single streamline and can be used by microfluidic based flow cytometry devices. In this study, we investigated focusing efficiency of polyethylene oxide based viscoelastic solutions at varying ionic concentration to demonstrate their use in impedimetric particle characterization systems. Rheological properties of the viscoelastic fluid and particle focusing performance are not affected by ionic concentration. We investigated the viscoelastic focusing dynamics using polystyrene (PS) beads and human red blood cells (RBCs) suspended in the viscoelastic fluid. Elasto-inertial focusing of PS beads was achieved with the combination of inertial and viscoelastic effects. RBCs were aligned along the channel centerline in parachute shape which yielded consistent impedimetric signals. We compared our impedance-based microfluidic flow cytometry results for RBCs and PS beads by analyzing particle transit time and peak amplitude at varying viscoelastic focusing conditions obtained at different flow rates. We showed that single orientation, single train focusing of nonspherical RBCs can be achieved with polyethylene oxide based viscoelastic solution that has been shown to be a good candidate as a carrier fluid for impedance cytometry.
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    A simple approach for the fabrication of 3D microelectrodes for impedimetric sensing
    (Iop Publishing Ltd, 2015) Guler, Mustafa Tahsin; Bilican, Ismail; Agan, Sedat; Elbuken, Caglar
    In this paper, we present a very simple method to fabricate three-dimensional (3D) microelectrodes integrated with microfluidic devices. We form the electrodes by etching a microwire placed across a microchannel. For precise control of the electrode spacing, we employ a hydrodynamic focusing microfluidic device and control the width of the etching solution stream. The focused widths of the etchant solution and the etching time determine the gap formed between the electrodes. Using the same microfluidic device, we can fabricate integrated 3D electrodes with different electrode gaps. We have demonstrated the functionality of these electrodes using an impedimetric particle counting setup. Using 3D microelectrodes with a diameter of 25 mu m, we have detected 6 mu m-diameter polystyrene beads in a buffer solution as well as erythrocytes in a PBS solution. We study the effect of electrode spacing on the signal-to-noise ratio of the impedance signal and we demonstrate that the smaller the electrode spacing the higher the signal obtained from a single microparticle. The sample stream is introduced to the system using the same hydrodynamic focusing device, which ensures the alignment of the sample in between the electrodes. Utilising a 3D hydrodynamic focusing approach, we force all the particles to go through the sensing region of the electrodes. This fabrication scheme not only provides a very low-cost and easy method for rapid prototyping, but which can also be used for applications requiring 3D electric field focused through a narrow section of the microchannel.
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    Tape'n roll inertial microfluidics
    (Elsevier Science Sa, 2019) Asghari, Mohammad; Serhatlioglu, Murat; Saritas, Resul; Guler, Mustafa Tahsin; Elbuken, Caglar
    Particle focusing and separation in microfluidic devices are critical for biological and medical applications. Inertial microfluidics is used for high throughput bio-particle focusing and separation. Most of the inertial microfluidic systems use planar structures for squeezing the particles in streams. Particle manipulation in 3D structures is often overlooked due to the complexity of the fabrication. In this study, we introduce some novel microchannel designs for inertial microfluidics by using a simple fabrication method that allows construction of both 2D and 3D structures. First, inertial migration of particles in 2D layouts including straight, spiral, and square spiral channels is investigated. Afterward, by applying a "tape'n roll" method, helical and double oriented spiral channels are configured and unexplored inertial migration behaviours are observed. Thanks to the simplicity of the fabrication and the unique characteristics of the new designs, high performance microfluidic inertial migration results can be obtained without any need for complicated microfabrication steps. The design optimization cycle can also be shortened using a computational approach we introduce in this study. (C) 2019 Elsevier B.V. All rights reserved.