Effect of dielectrophoretic forces on nanoparticles

We have investigated the long term stability of nanofluids exposed to strong divergent fields. The nanofluids were made of conductive nanoparticles (magnetite) dissolved in a base transformer mineral oil. The results show that, due to dielectrophoretic forces, nanoparticles aggregation takes place under DC fields with modalities associated with the polarity of the applied voltage. Under AC fields, aggregation is still possible, but the fields needed are above streamer inception voltage. Comsol simulations and simplified analytical models are provided to investigate the nanoparticle concentration dynamics. The models confirm the role of dielectrophoretic forces as a driver for nanoparticle aggregation.