Impact of Coupled Concentration-Field Physics on Molecular Dielectrophoresis

Molecular dielectrophoresis is a microscale separation technique that is highly effective; however, there is a dearth of suitable models. This manuscript hypothesizes that incorporating positive feedback between local molecular concentration and local electric field strength will strengthen modeling efforts. The feedback effect occurs between the local electric field strength and the permittivity changes caused by variations in solute concentration but is challenging to integrate into conventional, force-based models of molecular dielectrophoretic transport. To address this gap, a continuum chemical transport model was constructed, and solute concentration transport was simulated in a simple microfluidic channel. By explicitly turning on and off the coupling between local electric field strength and local concentration, it was found that this coupling could be responsible for over a 20 fold increase in predicted solute concentration change. The magnitude of the synergistic increase in concentration changes is non-monotonic with both electric field gradient strength and average channel velocity, but is always strongly positive, suggesting that local electric field - concentration coupling is necessary for DEP modeling.