Analysis of SAW interaction with liquid nanocomposites

Abstract

The usage of surface acoustic waves (SAWs) is analyzed based on previous research in the investigation of behavior of liquid nanocomposites, such as doped liquid crystals and oil-based magnetic fluids namely under applied external magnetic field. The SAW propagation along the interface between fluid and substrate creates longitudinal wave the attenuation response of which can be measured and appears as a highly effective way to study processes induced by the external magnetic field. This is an advantage especially in the cases where the utilization of the longitudinal acoustic waves due to the higher viscosity of the investigated environment are not available. The interactions between the magnetic field and magnetic moments of nanoparticles in magnetic fluids give a rise to the aggregation of magnetic nanoparticles into chain or cluster formations that have a marked influence on the SAW attenuation. The measurement of the acoustic anisotropy is giving additional information about the structure of nanoparticles formation origination under an applied external field. In the case of liquid crystals doped with magnetic nanoparticles, the both threshold field and nematic-isotropic transition shift caused by the doping process with magnetic nanoparticles can be registered by SAW. The reason is in an orientational coupling between dipole moments of LC molecules and nanoparticles. The effect of particle concentration on the magnitude of structural changes invoked by the external field plays also an important role.