Continuous Submicron Particle Separation Via Vortex-Enhanced Ionic Concentration Polarization: A Numerical...

Area of Science:

• Electrokinetics
• Microfluidics
• Nanotechnology

Background:

• Submicron particle separation is crucial for desalination, chemical processing, and medical diagnostics.
• Ion concentration polarization (ICP) is an electrokinetic phenomenon at micro-nano interfaces for manipulating particles.
• The role of ICP-induced fluid flow in continuous particle capture is not fully understood.

Purpose of the Study:

• To comprehensively study low-voltage ICP for extracting submicron particles.
• To demonstrate a novel electrokinetic method for flow-enhanced particle redirection and capture.
• To investigate the influence of particle properties and operational parameters on separation.

Main Methods:

• A 2D-FEM model was employed to solve coupled Poisson-Nernst-Planck, Navier-Stokes, and continuity equations.
• Investigated four operational modes: Allowed, Blocked, Captured, and Dodged, based on particle charge and size.
• Analyzed the generation of ICP-induced vortices and their dependence on flow rates and voltages.

Main Results:

• Identified four distinct operational modes governing particle capture or release from ICP-induced vortices.
• Determined critical particle dimensions by tuning inlet flow rates (200-800 µm/s) and applied voltages (0-2.5 V).
• Vortices form above a non-dimensional ICP-induced velocity of U*=1, balancing ICP and lateral flow.
• For multi-target separation, particle surface charge is the primary determinant of trajectory, overriding size.

Conclusions:

• Provides a deeper understanding of ICP-based particle separation and isolation mechanisms.
• Establishes a foundation for designing and optimizing ICP-based particle sorting systems.
• Highlights the significance of flow-enhanced particle redirection for continuous capture.