Passive Microrheology for Measurement of the Concentrated Dispersions Stability

Microrheology of magnetorheological silicone elastomers during curing process under the presence of magnetic field

“…1(b). 27,[36][37][38][39] Elasticity index (EI) calculated from inverse of MSD between 2.5 ms and 1.5 s of decorrelation time (generally in region II) quantifies the elasticity of the specimen. 27 specimen.…”

“…Note that extremely high SiCIP contents (above about 50%) should be avoided due to the inherent characteristic of light absorption of SiCIPs and the difficulty in identification of the spatially overlapped particles. [32][33][34][35][36][37][38][39][40] …”

“…MSD is calculated according to the variation of speckle images composed of dark and bright spots resulted from reduction or enhancement of light intensity. [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] MSD is usually reported as a function of decorrelation time t dec where the final speckle image differs from the initial one by a certain degree (here 70% of decorrelation is adopted) during once measurement. [36][37][38] The materials can be classified into viscous or viscoelastic ones according to the MSD curves shown in Fig.…”

“…However, MSD only quantifies global features of the moving probes. [33][34][35][36][37][38][39][40] Note that, the magnetic field is not high and in somewhat inhomogeneous due to the inherently small size of the chamber of the device. Fig.…”

“…3 presents MSD curves of the MREs under different magnetic field intensities at 25 • C. In the initial stage before silicone curing, MSD increases nearly linearly with t dec due to the free movement of SiCIPs in the viscous matrix with a relatively low viscosity. Accompanying with the silicone curing, the MSD curves can be roughly divided into three regions, [27][28][29][30][31][32][33][34][35][36][37][38][39] i.e., a nearly linear region (region I) at very short detection time (t dec ) where the movement of particles is unconstrained, a plateau region (region II) at medium t dec where the movement of particles is impeded by their neighbors and the curing medium, and another linear region (region III) at long t dec where the particles escape from obstacles formed by their neighbors and the medium, although the MSD curves do not show clear boundaries as the MSD of particles since the mean square displacement of particles are changing continuously as the result of varying viscoelastic properties of the material, as shown in Fig. 1(b).…”