A magneto-optical method for viscosimetric measurements

Abstract

We present a magneto-optical method using Brown's relaxation in ferrofluids. This method permits one to make some viscosimetric measurements by putting a drop of miscible ferrofluid into a test liquid, glycerol or diethylene glycol (DEG). To test this method we have compared our results obtained for glycerol with those obtained from a more conventional method and we observed good agreement. After this validation, we were able to study the viscosity of DEG between −20 and +90 • C by using our magneto-optical method. The comparison of these results with those obtained in standard ways (in the temperature range from −10 to +20 • C) revealed very slight deviations.

Rheology and colloidal structure of silver nanoparticles dispersed in diethylene glycol

“…Higher yield stress was obtained as the solids concentration increased, regardless of the models used. In flocculated suspensions, Van der Waals attractions existing between particle surfaces cause particles to adhere to one another forming porous particulate network in liquid [14]. The geometry of the aggregates can be described by fractal analysis [15]:…”

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.…”

Homogeneous Biosensing Based on Magnetic Particle Labels

“…Magneto-optical methods are sensitive to changes in the Brownian relaxation time of magnetic particle suspensions, and, consequently, have been applied to study hydrodynamic particle diameter distributions [ 260 ] or medium viscosities [ 261 ]. A typical setup, as it is employed to magneto-optically (Cotton-Mouton effect) measure the relaxation of the magnetization of a particle ensemble after an externally applied uniaxial magnetizing field is turned off (MRX mode), is sketched in Figure 16 a [ 262 ].…”