Nozzle-Shaped Electrode Configuration for Dielectrophoretic 3D-Focusing of Microparticles

Abstract

An experimentally validated mathematical model of a microfluidic device with nozzle-shaped electrode configuration for realizing dielectrophoresis based 3D-focusing is presented in the article. Two right-triangle shaped electrodes on the top and bottom surfaces make up the nozzle-shaped electrode configuration. The mathematical model consists of equations describing the motion of microparticles as well as profiles of electric potential, electric field, and fluid flow inside the microchannel. The influence of forces associated with inertia, gravity, drag, virtual mass, dielectrophoresis, and buoyancy are taken into account in the model. The performance of the microfluidic device is quantified in terms of horizontal and vertical focusing parameters. The influence of operating parameters, such as applied electric potential and volumetric flow rate, as well as geometric parameters, such as electrode dimensions and microchannel dimensions, are analyzed using the model. The performance of the microfluidic device enhances with an increase in applied electric potential and reduction in volumetric flow rate. Additionally, the performance of the microfluidic device improves with reduction in microchannel height and increase in microparticle radius while degrading with increase in reduction in electrode length and width. The model is of great benefit as it allows for generating working designs of the proposed microfluidic device with the desired performance metrics.

Microdevice With Planar Corrugated Electrodes for Dielectrophoretic Focusing of Micro-Particles

“…where � is the displacement vector, m is the mass, r is the radius, ρ is the density, g is the acceleration due to the gravity vector, μ is the viscosity, ε is the dielectric constant, ERMS is the RMS electric field vector, φRMS is the RMS voltage, u is the velocity vector, P is the pressure, x represents the xdirection, e represents micro-particles, and cf represents the carrier fluid. As mentioned earlier, the micro-particles must be subjected to nDEP, so the operating frequency must be very high (> 10 MHz) [14]; operating at high frequency eliminates the influence of electrical conductivity of the micro-particle and carrier fluid on the DEP and the risk of electrolysis on the electrodes [9,13,14]. The variation in the Clausius-Mossotti factor with respect to frequency for micro-particles such as polystyrene and silica microparticles as well as cells is available in the literature [13,14].…”

“…As mentioned earlier, the micro-particles must be subjected to nDEP, so the operating frequency must be very high (> 10 MHz) [14]; operating at high frequency eliminates the influence of electrical conductivity of the micro-particle and carrier fluid on the DEP and the risk of electrolysis on the electrodes [9,13,14]. The variation in the Clausius-Mossotti factor with respect to frequency for micro-particles such as polystyrene and silica microparticles as well as cells is available in the literature [13,14]. The initial conditions of (1) are the displacements and velocities at the inlet of the microdevice.…”

“…Equation ( 4) is calculated using FDM. For this, the 2 nd -order terms are exchanged with 2 nd -order central difference terms, which upon rearrangement results in (13). Equation ( 13) is applied to all nodes across the cross-section, except those on the boundaries, and this results in a system of linear equations.…”

“…The internode distances-i.e., ∆y and ∆z-are maintained at 0.5 µm for solving (4); r and s are the node numbers along the directions of the width (y-direction) and height (z-direction) of the micro-scale flow passage. It is stressed here that it is not necessary for the node numbers employed in (9) to match those employed in (13). The total numbers of nodes along the direction of width (y-direction) and height (z-direction) of the micro-scale flow passage are taken as m and n, respectively.…”

“…Alazzam et al [12] conceptualized a dielectrophoretic microdevice employing a continuous electrode on the microscale flow passage's upper and lower surfaces for 3D focusing micro-particles simultaneously at multiple locations in the direction of the width of the micro-scale flow passage; the lower electrode has perforations. Krishna et al [13] modeled 3D focusing in a dielectrophoretic microdevice using planar right-triangular electrodes located on the microscale flow passage's upper and lower surfaces. This is the first work to propose the electrode design shown in Fig.…”