High-Resolution Charge-Based Electrokinetic Separation of Almost Identical Microparticles

Area of Science:

• Microfluidics
• Biophysics
• Analytical Chemistry

Background:

• Existing nanosized particle separation techniques are insufficient for micron-sized particles.
• Insulator-based electrokinetics (iEK) shows promise for microparticle separation.
• Charge-based separation of similar microorganisms is highly desirable but challenging.

Purpose of the Study:

• To develop and validate a method for separating highly similar microparticles with minimal zeta potential differences.
• To push the discriminatory capabilities of iEK systems beyond previously reported limits.
• To demonstrate the utility of computational modeling in achieving challenging particle separations.

Main Methods:

• Utilized insulator-based electrokinetic (iEK) systems for microparticle separation.
• Employed COMSOL Multiphysics modeling to account for dielectrophoresis and electrophoresis.
• Validated model predictions by comparing calculated retention times with experimental data.

Main Results:

• Achieved charge-based separation of 5.1 μm microparticles with a zeta potential difference as low as 3.6 mV.
• Demonstrated that iEK systems can discriminate particles with charge differences <10% of those reported previously.
• Obtained highly reproducible separation results with minimal variation in retention times (9-11%).

Conclusions:

• iEK systems, guided by accurate computational modeling, can effectively separate highly similar microparticles.
• This technique significantly advances the ability to differentiate particles based on subtle electrical charge variations.
• The findings pave the way for improved separation of challenging biological entities like bacterial cells.