Rotational magnetic particles microrheology: The Maxwellian case

Abstract

An experimental method based on the rotational dynamics of a magnetic probe is reported to measure the local viscoelasticity of soft materials on microscopic scales. The technique is based on the alignment of dipolar chains of submicrometer magnetic particles in the direction of an applied magnetic field. On one hand, light scattering is used to detect the chains' oscillations over a 0.001-100 Hz frequency range when submitted to an oscillating magnetic field and leads to global microrheological measurements. On the other hand, the chains' rotation toward a permanent magnetic field is observed with a microscope, allowing a local determination of viscoelastic properties on the scale of the chains of particles. We demonstrate the accuracy of both assays with a micellar Maxwellian solution and validate theoretical predictions.

Numerical and experimental study of a rotating magnetic particle chain in a viscous fluid

“…The first factor is the shape factor κ for a linear chain of spherical particles including the effect of hydrodynamic interactions. Specifically, Wilhelm et al [29] empirically derived a shape factor valid for any size of the chain:…”

“…The opposing viscous drag torque consists of 4 factors [11,27,29]. The first factor is the shape factor κ for a linear chain of spherical particles including the effect of hydrodynamic interactions.…”

“…R T is obtained by dividing the viscous drag torque [11,27,29] by the driven magnetic torque [11]. Just prior to chain fragmentation, the viscous torque equals the maximum obtainable magnetic torque, so that R T = 1 and the chain rotates following the magnetic field.…”

Magnetic wire-based sensors for the microrheology of complex fluids

“…These methods are both powerful and quantitative. Several studies, however, reported the use of anisotropic objects such as disks [13], rods [14][15][16][17][18][19][20] and wires [21][22][23], for both passive [13,21,23] and active [14, 16-18, 22, 24-28] µ-rheology. Some recent work has shown that rod or wire based µ-rheology experiments could also bring significant advances to the field [18-20, 23, 27].…”

Nonequilibrium molecular dynamics simulation of diffusion at the liquid-liquid interface

“…40 The method used here resembles an experimental technique where the mobility of a probe molecule is studied using a controlled external magnetic field. 41 The time evolution of the N-particle system under periodic boundary conditions is described bẏ…”