Quantum mechanics

Magnetic field

Ecology

Biology

Microfluidics

Materials science

Chromatography

Magnetosphere particle motion

Electric field

Trapping

Geology

Oceanography

Physical chemistry

Physics

Nonlinear system

Nanotechnology

Dielectrophoresis

Particle (ecology)

Electrophoresis

Chemistry

Mechanics

Optoelectronics

Electrokinetic phenomena

Insulator (electricity)

Analytical Chemistry

The classic theory of direct-current (DC) insulator-based dielectrophoresis (iDEP) considers that, in order to elicit particle trapping, dielectrophoretic (DEP) velocity counterbalances electrokinetic (EK) motion, that is, electrophoresis (EP) and electro-osmotic flow (EOF). However, the particle velocity DEP component requires empirical correction factors (sometimes as high as 600) to account for experimental observations, suggesting the need for a refined model. Here, we show that, when applied to particle suspensions, a high-magnitude DC uniform electric field induces nonlinear particle velocities, leading to particle flow reversal beyond a critical field magnitude, referred to as the EK equilibrium condition. We further demonstrate that this particle motion can be described through an exploratory induced-charge EP nonlinear model. The model predictions were validated under an insulator-based microfluidic platform demonstrating predictive particle trapping for three different particle sizes (with an estimation error < 10%, not using correction factors). Our findings suggest that particle motion and trapping in "DC-iDEP" devices are dominated by EP and EOF, rather than by DEP effects.

Direct Current Electrokinetic Particle Trapping in Insulator-Based Microfluidics: Theory and Experiments