The concept of micro-rheology describes particles when they move in non-Newtonian liquids. This motion depends not only on viscosity of the basic liquid but also on the dimensions of the additives molecules that make liquid non-Newtonian. Particles freely swim between them and experience only low viscosity of the basic liquid, when particle size is much less than dimensions of this additives. However, when particles are large, then they experience macro-viscosity that can be orders of magnitude larger than viscosity of the basic liquid. There are several publications presenting various details of this concept for variety of systems:
Acoustic spectroscopy offers very simple way of measuring micro-viscosity that particles experience when moving in particular non-Newtonian liquid. Therefore, attenuation frequency spectra depend on particle size and viscosity. Consequently, if particle size is known, then we can fit experimentally measured spectra with unknown viscosity number.
This method is implemented in the software of Models DT-1202 and DT-100.