Interparticle Repulsion of Microparticles Delivered to a Pendent Drop by an Electric Field

Abstract

We report an unusually large spacing observed between microparticles after delivery to the surface of a pendent water droplet using a DC nonuniform electrostatic field, primarily via dielectrophoresis. The influence of particle properties was investigated using core particles, which were either coated or surface-modified to alter their wettability and conductivity. Particles that exhibited this spacing were both hydrophobic and possessed some dielectric material exposed to the external field, such as a coating or exposed dielectric core. The origin of this behavior is proposed to be the induced dipole–dipole repulsion between particles, which increases with particle size and decreases when the magnitude of the electric field is reduced. When the particles were no longer subjected to an external field, this large interparticle repulsion ceased and the particles settled to the bottom of the droplet under the force of gravity. We derive a simple model to predict this spacing, with the dipole–dipole repulsion balanced against particle weight. The external electric field was calculated using the existing electric field models. The spacing was found to be dependent on particle density and the induced dipole moment as well as the number of particles present on the droplet interface. As the number of particles increased, a decrease in interparticle spacing was observed.

Impact of high conductivity on particle transport to liquid droplets for liquid marble formation

“…24,45 A more complex model would be required to account for the dielectrophoretic forces present within an insulating particle. 46 As a general summary, the measured separation distances in Fig. 4 align with the model output above, as the larger the force displayed on the y -axis, the smaller the distance (closer) between the droplet and the particles required to initiate extraction.…”

Electrostatic Adsorption Behaviors of Polymer Plates to a Droplet

“…To gain fundamental insights into the particle transfer, the transfer of independent particles is important. Under this situation, particles in the tens of micrometer-to-millimeter-size range, with low dispersity in size and shape, have been designed and synthesized and were utilized as model particles for electrostatic particle transfer experiments. ,− For such large particles, gravity dominates over interparticle interactions and the particles therefore could be extracted and electrostatically transferred as single particles rather than as aggregates. Generally, it can be argued that the influence of these variables is far better understood for spherical particles than nonspherical particles, which have been found to exhibit additional characteristic behavior during the transfer and adsorption processes.…”