Combined negative dielectrophoresis and phase separation in nondilute suspensions subject to a high-gradient ac electric field

Abstract

Experiments were conducted on concentrated suspensions of neutrally buoyant particles which exhibit negative dielectrophoresis. We found that, due to interparticle electrical interactions, such suspensions undergo a phase separation when subjected to a high-gradient ac field (approximately kV/mm) and form a propagating distinct front between the regions enriched with and depleted of particles. A generalization of our theory for the thermodynamics of the field-induced phase transitions in suspensions of polarized particles [Phys. Rev. E 52, 1669 (1995); 54, 5428 (1996); 60, 3015 (1999)] is proposed for the front propagation, and its predictions are shown to be consistent with the experiments even though the model contains no fitting parameters. The combination of field-induced dielectrophoresis and phase transition provides a method for strongly concentrating particles in prespecified regions of dielectrophoretic devices.

Droplet Microreactors for Materials Synthesis

“…Otherwise, the force on the particle is toward the lower field region (negative DEP). This particle control using DEP has been used in many fields of application such as assembly of microwires from metallic nanoparticle suspensions [6,37,98,101], formation of colloidal crystals [55,56], and separation of dielectric particles [18,28,47,75]. Droplets flowing in a microchannel or floating on the surface of an immiscible liquid can be transported by DEP as explained further in the chapter.…”

Initial concentration and fluidic effects on the dielectrophoretic trapping of DNA

“…2.3 Particle steric effect modification on the particle concentration dynamics According to [7], the equation for the conservation of particles is: where v s is the velocity of the suspension, c = nV p is the particle volume fraction (n number density, V p particle volume) and j p is the particle flux in the reference system moving with the suspension. This flux can be written as…”

“…The modified NavierStokes equations for the suspension flow are given in equations 11 and 12 [7] [14].…”

“…Here, a numerical analysis is presented that takes into account ACEO and the particle steric effect (due to the crowding of the particles and the particle finite size) in order to produce more accurate simulation results. The particle steric effect becomes significant in regions of high particle concentration [7]. High local particle concentrations mean that the suspension effective viscosity and density are modified and these are taken into account by introducing modified Navier-Stokes equations.…”

Micro‐ and nano‐particle manipulation by dielectrophoresis: devices for particle trapping and the influence of steric effects

“…Previously, the Smoluchowski equation has been used to describe the dynamics of the particles. However, in this paper the equation is modified to include the steric effect in the particle concentration due to the finite particle dimensions [6]. This modification is necessary in order to obtain the simulated dynamics of the suspension concentration, and not the probability density function of an isolated particle being at a specific location.…”