Numerical study of interactive motion of dielectrophoretic particles

Dielectrophoresis is one of the popular ways to manipulate bio-particles. In this work, numerical simulations of two-dimensional interactive motion of multiple dielectrophoretic particles in an electrolyte subjected to a uniform DC electric field are performed. The dielectrophoretic forces on particles are calculated by an integral of the Maxwell Stress Tensor (MST) on both sides of the particle surfaces. It is shown that behaviors of interactive motion of dielectrophoretic particles are strongly affected by the difference in permittivity between the particles and the electrolyte. Similar particles (all positive or negative electrophoresis) will finally form a chain parallel to the electric field, whereas dissimilar particles (mixed positive and negative electrophoresis) will form a chain that is perpendicular to the electric field. The particle velocity and time behavior of interactive motion are investigated. The key findings are as follows: as the ratio (εp:εf) increases, the chain-formation time decreases for a P-P particle chain, but increases for an N-N particle chain. The chain-formation time will decrease with increase of the particle size ratio amax:amin for a three-particle chain with different particle sizes.