Browsing by Subject "Dielectrophoresis"

Now showing 1 - 8 of 8

Open Access
DC-electrokinetic motion of colloidal cylinder(s) in the vicinity of a conducting wall
(Wiley-VCH Verlag GmbH & Co. KGaA, 2022-06) Atay, Atakan; Beşkök, A.; Çetin, Barbaros
The boundary effects on DC-electrokinetic behavior of colloidal cylinder(s) in the vicinity of a conducting wall is investigated through a computational model. The contribution of the hydrodynamic drag, gravity, electrokinetic (i.e., electrophoretic and dielectrophoretic), and colloidal forces (i.e., forces due to the electrical double layer and van der Waals interactions) are incorporated in the model. The contribution of electrokinetic and colloidal forces are included by introducing the resulting forces as an external force acting on the particle(s). The colloidal forces are implemented with the prescribed expressions from the literature, and the electrokinetic force is obtained by integrating the corresponding Maxwell stress tensor over the particles' surfaces. The electrokinetic slip-velocity together with the thin electrical double layer assumption is applied on the surfaces. The position and velocity of the particles and the resulting electric and flow fields are obtained and the physical insight for the behavior of the colloidal cylinders are discussed in conjunction with the experimental observations in the literature.
Open Access
Dielectrophoresis in microfluidics technology
(2011) Çetin B.; Li, D.
Dielectrophoresis (DEP) is the movement of a particle in a non-uniform electric field due to the interaction of the particle's dipole and spatial gradient of the electric field. DEP is a subtle solution to manipulate particles and cells at microscale due to its favorable scaling for the reduced size of the system. DEP has been utilized for many applications in microfluidic systems. In this review, a detailed analysis of the modeling of DEP-based manipulation of the particles is provided, and the recent applications regarding the particle manipulation in microfluidic systems (mainly the published works between 2007 and 2010) are presented. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Open Access
Fabrication of continuous flow microfluidics device with 3D electrode structures for high throughput DEP applications using mechanical machining
(Wiley-VCH Verlag, 2015) Zeinali, S.; Çetin B.; Oliaei, S. N. B.; Karpat, Y.
Microfluidics is the combination of micro/nano fabrication techniques with fluid flow at microscale to pursue powerful techniques in controlling and manipulating chemical and biological processes. Sorting and separation of bio-particles are highly considered in diagnostics and biological analyses. Dielectrophoresis (DEP) has offered unique advantages for microfluidic devices. In DEP devices, asymmetric pair of planar electrodes could be employed to generate non-uniform electric fields. In DEP applications, facing 3D sidewall electrodes is considered to be one of the key solutions to increase device throughput due to the generated homogeneous electric fields along the height of microchannels. Despite the advantages, fabrication of 3D vertical electrodes requires a considerable challenge. In this study, two alternative fabrication techniques have been proposed for the fabrication of a microfluidic device with 3D sidewall electrodes. In the first method, both the mold and the electrodes are fabricated using high precision machining. In the second method, the mold with tilted sidewalls is fabricated using high precision machining and the electrodes are deposited on the sidewall using sputtering together with a shadow mask fabricated by electric discharge machining. Both fabrication processes are assessed as highly repeatable and robust. Moreover, the two methods are found to be complementary with respect to the channel height. Only the manipulation of particles with negative-DEP is demonstrated in the experiments, and the throughput values up to 105 particles / min is reached in a continuous flow. The experimental results are compared with the simulation results and the limitations on the fabrication techniques are also discussed.
Open Access
Integrated microfluidic systems for droplet detection and sorting
(2015-09) İşgör, Pelin Kübra
Microdroplet based microfluidic systems have gained a lot of attention during the last decades due to enhanced analytical performance, low cost and high-throughput. One of the fundamental requirements of a droplet based system is detection of droplets. Capacitive sensing of droplets have been used for droplet detection, however they lack the required sensitivity for droplet content detection. Here a portable, low cost, scalable and highly sensitive droplet content detection system is demonstrated using coplanar electrodes. The designed microfluidic system enables droplet content modification on the run. While changing droplet content, i.e., dielectric content, capacitive signal amplitude is measured. The system resolves 3 unit of dielectric permittivity. 5% material change in droplet is detected. Following droplet content detection, sorting of laden droplets enables further experimentation with material of interest in the droplet. Dielectrophoresis is a commonly used method for droplet sorting. Dielectrophoretic sorting of droplets is demonstrated using two dimensional and there dimensional electrodes. Low cost and portable electronic components are integrated with microfluidic devices for droplet content detection and sorting using microfabricated electrodes. The cost and signal to noise ratio of the system are aimed to be decreased by implementing detection and sorting system on a printed circuit board. Sensing and sorting electrodes are fabricated and all of the electronic components are placed on a printed circuit board. Microchannels are reversibly placed over electrodes, therefore the platform becomes reusable. This feature of the system enables various experimentation using microdroplets on the same base platform. This approach will lead to microfluidic systems that are programmable and easy-to-use by means of off-the-shelf and low cost electronic components.
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
Modeling of dielectrophoretic particle motion: Point particle versus finite‐sized particle
(Wiley - V C H Verlag GmbH & Co. KGaA, 2017-02-06) Çetin B.; Öner, D. S.; Baranoğlu, B.
Dielectrophoresis (DEP) is a very popular technique for microfluidic bio‐particle manipulation. For the design of a DEP‐based microfluidic device, simulation of the particle trajectory within the microchannel network is crucial. There are basically two approaches: (i) point‐particle approach and (ii) finite‐sized particle approach. In this study, many aspects of both approaches are discussed for the simulation of direct current DEP, alternating current DEP, and traveling‐wave DEP applications. Point‐particle approach is implemented using Lagrangian tracking method, and finite‐sized particle is implemented using boundary element method. The comparison of the point‐particle approach and finite‐sized particle approach is presented for different DEP applications. Moreover, the effect of particle–particle interaction is explored by simulating the motion of closely packed multiple particles for the same applications, and anomalous‐DEP, which is a result of particle–wall interaction at the close vicinity of electrode surface, is illustrated.
Open Access
On-chip integrated nanowire device platform with controllable nanogap for manipulation, capturing, and electrical characterization of nanoparticles
(IEEE, 2009-05-27) Uran, C.; Unal, E.; Kizil, R.; Demir, Hilmi Volkan
We propose and demonstrate nanowire (NW) device platforms on-chip integrated using electric-field-assisted self-assembly. This platform integrates from nanoprobes to microprobes, and conveniently allows for on-chip manipulation, capturing, and electrical characterization of nanoparticles (NPs). Synthesizing segmented (Au–Ag–Au) NWs and aligning them across predefined microelectrode arrays under ac electric field, we controllably form nanogaps between the self-aligned end (Au) segments by selectively removing the middle (Ag) segments. We precisely control and tune the size of this middle section for nanogap formation in the synthesis process. Using electric field across nanogaps between these nanoprobes, we capture NPs to electrically address and probe them at the nanoscale. This approach holds great promise for the construction of single NP devices with electrical nanoprobe contacts.
Open Access
On-chip integrated nanowire devices with controllable nanogap for manipulation, capturing, and electrical characterization of nanoparticles
(IEEE, 2009) Uran, Can; Ünal, Emre; Kizil, R.; Demir, Hilmi Volkan
Dielectrophoresis (DEP) allows for electric field assisted assembly in spatially non-uniform field distribution, where the induced moment is translated into a net force on polarized particles towards the high field gradient. For example, for a spherical particle of radius r with a permittivity constant ofεp in a host medium with the permittivity ofε m, the dielectrophoretic force is given by (1): where r is the particle radius, ω is the angular frequency and Erms is the root mean square electric field. K is the Clausius-Mossotti function, which depends on the complex permittivity of the spherical particle and the medium [1].IEEE.