Browsing by Subject "Micro fluidic applications"

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Open Access
Numerical modeling of ultrasonic particle manipulation for microfluidic applications
(Springer Verlag, 2014) Büyükkoçak S.; Özer, M. B.; Çetin B.
A numerical simulation methodology for ultrasonic particle/cell separation and cell washing processes is introduced and validated by comparing with the results from the literature. In this study, a finite element approach is used for modeling fluid flow in a microchannel and analytical relations are utilized for the calculation of the ultrasonic radiation forces. The solutions in acoustic and fluidic domains are coupled, and the particle separation under the influence of ultrasonic waves is numerically simulated. In order to simulate the cell washing process, diffusion and fluid dynamics solutions are coupled and solved. A Monte Carlo approach is chosen where statistical distributions are implemented in the simulations. Uniform distributions for the starting locations of particles/cells in the microchannel and normal distributions for the size of the particles are used in numerical simulations. In each case, 750 particles are used for the simulation, and the performance of separation process is evaluated by checking how many microparticles resulted in the targeted outlet channels. Channel geometries for the numerical simulations are adapted from the experimental studies in literature, and comparison between the reported experimental results and the numerical estimations is performed. It has been observed that the numerical estimations and experimental results from the literature are in good agreement, and the proposed methodology may be implemented as a design tool for ultrasonic particle manipulation for microfluidic applications. © 2014, Springer-Verlag Berlin Heidelberg.
Open Access
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.