micro Rheology
Formulaction have taken the DWS principle a step further with MS-DWS for Multiple Speckle DWS and offer an approach to accurately characterize the viscoelastic properties of soft materials without shearing them or deforming them.
From the MS-DWS you calculate the mean square displacement of the photons (MSD) and from de-correlated curion of a more complicate processves, using a Generalized Stokes-Einstein Relation (GSER) you can calculate the microrheology Viscous and Elastic moduli (G’’µR , G’µR).
This is a very simple description of a complicated process.
“Multi-speckle Diffusing Wave Spectroscopy micro-rheology (MS-DWS µRheology) is a recently introduced technique that greatly simplifies rheological measurements. No macroscopic deformation is applied to the sample. Instead, state-of-the-art optical techniques are used to measure the nanometer-scale motion of the sample constituents due to thermal energy. Rheological properties are deduced from this motion using a well-established formalism. “Luca Cipelletti
Professor University of Montpellier, Institut Universitaire de France Soft Material department.
Advantages of MS-DWS µRheology include:
- measurements in the linear regime
- no wall slip issues
- samples contained in standard vials
- no need to transfer the sample and clean the rheometer tools
- fast measurements that allow the sample evolution to be monitored
