This article presents a validated mathematical model of a dielectrophoresis (DEP)-based microfluidic device capable of 3D-focusing microscale entities at any lateral location inside the microchannel. The microfluidic device employs planar, independently controllable, interdigitated transducer (IDT) electrodes on either side of the microchannel. The developed model is used for understanding the influence of different geometric and operating parameters on 3D focusing, and it comprises of motion equation, Navier-Stokes equation, continuity equation, and electric potential equation (Laplace equation). The model accounts for forces associated with inertia, gravity, buoyancy, virtual mass, drag, and DEP. The model is solved using finite difference method. The findings of the study indicate that the 3D focusing possible with the proposed microfluidic device is independent of microscale entity's size and initial position, microchannel height, and volumetric flow rate. In contrast, 3D focusing achievable with the microfluidic device is dependent on the applied electric potential, protrusion width of electrodes, and width of electrode/gap. Additionally, the lateral position of 3D focused can be controlled by varying the applied electric potential. The advantage of the proposed microfluidic device is that it is simple to construct while capable of achieving 3D focusing at any lateral location inside the microchannel.

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In this communication, dynamic model for analysing micro‐objects’ path in dielectrophoresis (DEP)‐based microfluidic devices for executing field‐flow fractionation is formulated and subsequently employed for parametric study. Electrodes of finite length, that pass along the full width of the microchannel, are placed on the microchannel's upper and lower walls; each upper electrode and electrode gap aligns with a lower electrode gap and electrode, respectively. The model accounts for forces associated with inertia, sedimentation, DEP, drag and virtual mass. The model indicates that micro‐objects’ trajectory depends on actuation voltage, volumetric flow rate, micro‐object radius, electrode and gap dimensions, and microchannel height. The steady‐state levitation height is found to be independent of radius of micro‐object and volumetric flow rate while being dependent on electrode and gap dimensions, microchannel height and actuation voltage. The model predicts that there exists an optimal value of electrode and gap dimensions for which the steady‐state levitation height is maximum when all other parameters are kept constant. The efficacy of the device is demonstrated by separating a heterogeneous mixture of silica and polystyrene microparticles into homogeneous samples.

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