Quantitative nanoscale viscosity measurements using magnetic nanoparticles and SQUID AC susceptibility measurements

Abstract

The frequency dependent response of suspended thermally blocked magnetic nanoparticles in an oscillating magnetic field was used to quantitatively determine the nanoscale viscosity of a fluid at various temperatures. The nanoscale viscosity was found to be within 7% of the macroscale viscosity determined through rheology, except at low temperatures where crystallization occurs in the fluid. The range of viscosities accessible through this technique and criteria for selection of the magnetic nanoparticle material are discussed.