Browsing by Subject "Micro fluidic system"

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    A microfluidic erythrocyte sedimentation rate analyzer using rouleaux formation kinetics
    (Springer Verlag, 2017-03) Isiksacan, Z.; Asghari, M.; Elbuken, C.
    Red blood cell aggregation is an intrinsic property of red blood cells that form reversible stacked structures, also called rouleaux, under low shear rates. Erythrocyte sedimentation rate (ESR), commonly performed in clinics, is an indirect inflammation screener and a prognostic test for diseases. We have recently developed a microfluidic system for rapid measurement of ESR from 40 µl whole blood employing the aggregation dynamics. In this work, we propose the use of an aggregation inducer, dextran polyglucose, for the preparation of multiple blood samples with differing aggregation dynamics. Using these samples, we characterized the performance of the system with three aggregation indices and under varying experimental conditions. Additionally, using the same underlying principle, we improved the system for ESR measurement using both venipuncture and fingerprick whole blood samples depending on the user needs. The results demonstrate that the system performs equally well with both samples, which validates the compatibility of the system for both laboratory and point-of-care applications where venous and capillary blood are the primary samples, respectively. The detailed characterization presented in this study legitimates the feasibility of the system for ultrafast and facile measurement of ESR in clinics and diverse off-laboratory settings.
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    ItemOpen Access
    Modeling of electro-kinetic motion of Janus droplet
    (ASME, 2017) Öner, S. Doğan; Çetin, Barbaros
    Electro-kinetic manipulation Janus particles and droplets has attracted attention in recent years due to their potential application in microfluidics. Due to the presence of two different zone on the surface of particles with different charge distribution, the motion of the Janus particles are quite different than the that of regular particles. Therefore; the fundamental understanding of this motion is the key element for the further development of the microfluidic systems with Janus particles. In present study, electro-kinetic motion of Janus droplets inside a micro-channel is modeled using boundary element formulation. 2D formulation is verified against the reported experimental data in the literature. Results show that the 2D boundary element formulation is successful for the prediction of the electrophoretic velocity of the Janus droplets. The current formulation has a potential to model non-spherical particles and to study particle-particle and particle-wall interactions.
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    A versatile plug microvalve for microfluidic applications
    (Elsevier, 2017-10) Guler, M. T.; Beyazkilic, P.; Elbuken, C.
    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.