Ferrofluid viscometer: transient magnetic birefringence in crossed fields

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

“…In this approach the frequency dependent response of magnetic nanoparticles with a known, narrow hydrodynamic size distribution (determined in an independent reference fluid), suspended in a test fluid and subjected to an oscillating magnetic field provides a measurement of the rotational hydrodynamic resistance on the particles, and hence the viscosity of the test fluid. The approach is similar to a magnetobirefringence technique developed by Bacri and co-workers 16 and further extended by others, [17][18][19][20][21][22][23] in which the dynamics of particle orientation in constant and time-varying magnetic fields are monitored through the birefringence response of the particle suspension, resulting from the particle's optical anisotropy. Here, however, the particle response to the applied field is tracked through the suspension's net magnetization, making the technique suitable for opaque and optically complex fluids.…”

Experimental investigation on the magneto-optic effects of ferrofluids via dynamic measurements

“…They are interesting from both a static point of view and from a dynamical one [6,12,20,23]. For their part, the dynamical properties bring up important technological issues, such as viscometers, nanosizers or optical modulators [4,[30][31][32][33][34][35].…”

Comparison of the Symmetry Breaking in the Surface Molecular Structures of One- and Two-Dimensional Bis(ethylenedithio)tetrathiafulvalene Compounds

“…In this sense the rotational viscosity can be computed through a Green-Kubo formula [15] and, as in the case of the rigid dipole, exhibits a monotonic behaviour when represented as a function of the field. Additionally, from that formalism one can compute the time for relaxation of the magnetic moment towards the field for different substances [15] arriving at good agreement with birefringence experiments [16].…”