A Simplified Microfluidic Device for Particle Separation with Two Consecutive Steps: Induced Charge Electro-osmotic Prefocusing and Dielectrophoretic Separation

Abstract

Continuous dielectrophoretic separation is recognized as a powerful technique for a large number of applications including early stage cancer diagnosis, water quality analysis, and stem-cell-based therapy. Generally, the prefocusing of a particle mixture into a stream is an essential process to ensure all particles are subjected to the same electric field geometry in the separation region. However, accomplishing this focusing process either requires hydrodynamic squeezing, which requires an encumbering peripheral system and a complicated operation to drive and control the fluid motion, or depends on dielectrophoretic forces, which are highly sensitive to the dielectric characterization of particles. An alternative focusing technique, induced charge electro-osmosis (ICEO), has been demonstrated to be effective in focusing an incoming mixture into a particle stream as well as nonselective regarding the particles of interest. Encouraged by these aspects, we propose a hybrid method for microparticle separation based on a delicate combination of ICEO focusing and dielectrophoretic deflection. This method involves two steps: focusing the mixture into a thin particle stream via ICEO vortex flow and separating the particles of differing dielectic properties through dielectrophoresis. To demonstrate the feasibility of the method proposed, we designed and fabricated a microfluidic chip and separated a mixture consisting of yeast cells and silica particles with an efficiency exceeding 96%. This method has good potential for flexible integration into other microfluidic chips in the future.

Passivated‐electrode insulator‐based dielectrophoretic separation of heterogeneous cell mixtures

“…Although the use of DEP forces to separate heterogeneous mixtures have been reported by numerous groups, several of them have focused on particles with very distinctive particles sizes or have reported separation efficiencies lower than 90%. Chen et al., recently reported a two‐stage separation device which combined electroosmotic and DEP force with efficiencies that exceeded 96% for the separation of 4 μm silica particles from yeast cells [30]. Similarly, Shafiee et al.…”

“…also demonstrated the high separation efficiency between 13 μm and 5 μm beads with nearly 100% separation [32]. However, all these devices only reported investigations with particles of vastly different sizes or vastly different dielectric properties resulting in major shifts in Clausius–Mossotti factors [1,10,30,32,33]. Similarly, Zhou et al.…”

“…The OπDEP architecture was designed in contrast to other systems similar to those shown by Liu et al. and Ren et al, where electrothermal and electroosmotic forces are optimized for use in the platform [30,39,40]. Here, we minimize electrothermal and electroosmotic effects through manipulation of operational parameters such as assay time frames, excitation characteristics, and device design.…”

Continuous dielectrophoretic particle separation via isomotive dielectrophoresis with bifurcating stagnation flow

“…Such systems typically have limited throughput, although there are notable exceptions . Demonstrated continuous cell separators generally rely on coplanar electrodes to generate a non‐uniform DEP force . While such devices are typically simple to fabricate, they have difficulty separating particles with high purity and yield.…”

Flexible particle flow‐focusing in microchannel driven by droplet‐directed induced‐charge electroosmosis

“…Nevertheless, how to use ICEO fluid motion to achieve particle manipulation with intended functions has rarely been exploited. Recently, we first reported continuous‐flow focusing of micro‐particles with ICEO above a central gate electrodes (GE) . It is noteworthy that, since particle flow‐focusing by transverse ICEO is due to fluidic drag force, it has a longer function range than dielectrophoresis (DEP) or traveling‐wave DEP effect which exists merely in a field gradient or the presence of a spatial phase variation.…”