Numerical Study of Enhancement of Positive Dielectrophoresis Particle Trapping in Electrode-multilayered Microfluidic Device.

Enhancement of positive dielectrophoresis (pDEP) particle trapping by a co-occurring fluid flow under an AC electric field in an electrode-multilayered microfluidic device is investigated by three-dimensional particle-fluid flow simulations. The particle motion near one cross-section of the microfluidic device is simulated under a zero flow condition by the Eulerian- Lagrangian method incorporating the AC electrothermal effect, thermal buoyancy and dielectrophoresis. The mean trapping rate under the steady state Rm is evaluated from the simulated number of trapped particles Nt rap for 54 cases with four parameters: electrode excitation pattern, medium conductivity σ, applied voltage ϕe and the real part of the Clausius-Mossotti factor Re[K( ω)]. The simulated pDEP velocity in the upper part of the flow channel is validated by an experiment using cell suspension and is fitted so that the non-dimensional velocity error is within 15 % of a typical velocity of pDEP. The mean trapping rate Rm is greatly increased by the fluid flow only in the high conductivity and high voltage cases. Regardless of the electrode excitation pattern, Rm increased almost proportionally to the inflow rate into the capture region where the pDEP force is effective. From a fitted equation of the results, the increase of Rm when Re[K( ω)] = 0.1 to 0.5 is found to be about 20 % to 30 % of the number of particles transported into the capture regions. The results quantify the enhancement of pDEP trapping by the fluid flow occurring under practical conditions in the device.