Browsing by Subject "Particle separation"

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Open Access
Microfluidic device with 3D electrode structure for high throughput dielectrophoretic applications
(2014-10) Zeinali, Soheila
Microfluidics is the combination of micro/nano fabrication techniques together with knowledge of fluid behavior at the microscopic level to pursue powerful techniques in controlling, manipulating and measuring chemical, physical and biological processes at micro/nano scale. Sorting and separation of bio-particles are highly considered in diagnostics and biological analyses. By implementing the characteristics of microscale flow phenomenon, dielectrophoresis (DEP) has offered unique advantages for microfluidic devices. In DEP devices asymmetric pair of planar or three dimensional (3D) electrodes could be employed to generate non-uniform electric field. In DEP applications, facing 3D sidewall electrodes is considered to be the key solution of increasing device throughput because of producing homogeneous electric fields along the height of microchannels. Despite all advantages, fabrication of 3D vertical electrodes requires considerable challenge. In this thesis, in order to highlight the advantage of 3D electrodes over planar electrodes, the simulations are performed. Based on the developed computational model, the design parameters are decided. For the fabrication of the device, two different fabrication techniques have been proposed. In the first method, both the mold and the electrodes are fabricated using high precision machining. In the second method, the mold is fabricated with tilted sidewalls using high precision machining and the electrodes are deposited on the sidewall using sputtering together with a shadow mask fabricated using wire electric discharge machining (WEDM). The both techniques are assessed as highly repeatable and robust methods. Only the manipulation of particles with negative-DEP has been demonstrated in the experiments, and the throughput values up to 105 particles/min have been reached in a continuous flow.
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.