Combining DC and AC electric fields with deterministic lateral displacement for micro- and nano-particle separation

Area of Science:

• Microfluidics
• Particle Separation Technology
• Electrophoresis

Background:

• Deterministic Lateral Displacement (DLD) is a microfluidic technique for size-based particle separation.
• Traditional DLD primarily relies on particle size for binary separation in continuous flow.
• The integration of electric fields offers potential for enhanced control and fractionation capabilities.

Purpose of the Study:

• To investigate the behavior of particles in a DLD device under orthogonal DC and AC electric fields.
• To demonstrate tunable microparticle and nanoparticle separation and fractionation.
• To explore how electric fields can improve separation efficiency, especially for particles smaller than the critical diameter.

Main Methods:

• Utilized a DLD microfluidic device with DC and AC electric fields applied orthogonally to the fluid flow.
• Applied DC voltage, observing Faradaic processes and resulting electric field gradients.
• Employed AC electric fields to induce negative-dielectrophoresis for particle manipulation.
• Conducted experiments with various negatively charged particles (100 nm to 3 μm) and different zeta potentials.

Main Results:

• Achieved tunable separation and fractionation of microparticles and nanoparticles based on size and zeta potential.
• Demonstrated efficient separation of particles smaller than the DLD critical diameter using orthogonal electric fields.
• Observed particle focusing into tight bands due to non-uniform electrophoretic velocity, countering diffusion.
• Showcased the potential for nanoscale particle fractionation using combined DC and AC electric fields.

Conclusions:

• Orthogonal DC and AC electric fields significantly enhance particle separation and fractionation in DLD devices.
• The combined electric field approach allows for precise control over particle trajectories, enabling tunable separation.
• This method offers a promising strategy for advanced nanoscale particle manipulation and purification in microfluidic systems.