Yazar "Guler, M. Tahsin" seçeneğine göre listele

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    Definition and detection of simulation noise via imaginary simulated particles in comparison with an electrical microfluidic chip noise
    (SPRINGER HEIDELBERG, 2020) Guler, M. Tahsin
    Real problems in science and engineering generally do not have an analytical solution, which invariably leads to the application of numerical methods to analyze the problem. The numerical solutions to the same problem give different results due to variations in discretization, which are defined as simulation noise in this study. Microfluidics impedance flow cytometry is employed to demonstrate and compare experimental and simulated noise. For measurement of the simulation noise, an object is assigned with the same electrical parameters as the medium and moved along the electrode region through a microchannel. Since the object is no different to the medium in terms of material properties, forwarding of the object through the electrodes doesn't have any physical effect, but just reorders the meshing. However, the impedance, which is the calculated output parameter of the simulation, fluctuates due to the reordering of the meshes and is defined as the simulation noise. By employing the imaginary object method, noise can be measured for every Finite element method (FEM) simulation even if the problem has a different physical background.
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    Fabricating plasma bonded microfluidic chips by CO2 laser machining of PDMS by the application of viscoelastic particle focusing and droplet generation
    (Elsevier Sci Ltd, 2022) Guler, M. Tahsin
    In this study, direct CO2 laser machining of microchannels onto PDMS slabs and plasma bonding for sealing have been shown to provide the fastest method to fabricate PDMS microfluidic chips. Due to resolidification, the ashes and dust remains that cover the PDMS slab surface following this ablation process change the surface chemistry and prevent plasma bonding. Removing these remnants on the surface has been shown to be only possible via attaching and detaching a tape to the surface. The effect of laser frequency, speed and power settings has been investigated over the entire possible range with regards to channel geometry. The best laser settings were determined and the resulting output channels were examined under SEM and optical microscopes. PDMS spin coating after laser machining has been proposed as a pre-treatment process to improve the geometrical features of the channel. Water-in-oil droplet generation in the T-junction, as well as microparticle focusing in viscoelastic fluid - used to sample enrichment- have been shown as examples of applications that benefit from precise direct laser machined microchannels.
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    Rapid fabrication of microfluidic PDMS devices from reusable PDMS molds using laser ablation
    (Iop Publishing Ltd, 2016) Isiksacan, Ziya; Guler, M. Tahsin; Aydogdu, Berkan; Bilican, Ismail; Elbuken, Caglar
    The conventional fabrication methods for microfluidic devices require cleanroom processes that are costly and time-consuming We present a novel, facile, and low-cost method for rapid fabrication of polydimethylsiloxane (PDMS) molds and devices. The method consists of three main fabrication steps: female mold (FM), male mold (MM), and chip fabrication. We use a CO, laser cutter to pattern a thin, spin -coated PDMS layer for FM fabrication. We then obtain reusable PDMS MM from the FM using PDMS/PDMS casting. Finally, a second casting step is used to replicate PDMS devices from the MM. Demolding of one PDMS layer from another is carried out without any potentially hazardous chemical surface treatment. We have successfully demonstrated that this novel method allows fabrication of microfluidic molds and devices with precise dimensions (thickness, width, length) using a single material, PDMS, which is very common across microfluidic laboratories. The whole process, from idea to device testing, can be completed in 1.5 h in a standard laboratory.
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    A versatile plug microvalve for microfluidic applications
    (Elsevier Science Sa, 2017) Guler, M. Tahsin; Beyazkilic, Pinar; Elbuken, Caglar
    Most of the available microvalves include complicated fabrication steps and multiple materials. We present a microvalve which is inspired from macroplug valves. The plug microvalve is fabricated by boring a hole through a rigid cylindrical rod and inserting it through a microfluidic chip. It simply functions by rotating the rod which aligns or misaligns the valve port with the microchannel. The rod is made up of a rigid material for applying the valve to an elastic polydimethylsiloxane (PDMS) microchannel. The valve can also be used for a rigid channel by inserting the rod into an elastic tubing. Therefore, the presented microvalve can be used for both elastomeric and thermoplastic channels. The plug microvalve can be applied to a prefabricated microchannel and does not require modification of the mold design. We have verified the repeatability and robustness of the valve by repetitive operation cycles using a servo motor. The plug microvalve is adaptable to numerous microfluidic applications. We have shown three modes of operation for the microvalve including fluid flow control across multiple intersecting channels. Integrating the microvalve to some commonly used microfluidic designs, we demonstrated the versatility and the practicality of the microvalve for controlling flow focusing, microdroplet sorting and rapid chemical agent detection. This low-cost microvalve significantly minimizes the prototyping time for microfluidic systems. (C) 2017 Elsevier B.V. All rights reserved.