Chapter 5
Microrheology
Page 5-14
MAN 0487
Mean Squared Displacement (MSD)
: a representation of the movement of the
tracer particles within the sample. A purely viscous (Newtonian) sample will show
a straight line.
Correlogram
: shows the base data from which the microrheology result is
calculated. The correlation function displayed is a measurement of the amount of
movement the probe particles make within the test sample over a range of time
scales.
Complex viscosity (
η
*
)
: shows the relationship of the complex viscosity to the
shear viscosity using the Cox-Merz rule.
This rule is generally only fully applicable for simple systems, and that the
differences between complex viscosity and shear viscosity increases as the sample
structure becomes more complex.
Viscoelastic Modulus (G)
: The Moduli tab shows the viscoelasticity of the
sample, it shows two sets of data on the chart - G', the elastic (storage) component
and G", the viscous (loss) component.
In a microrheology measurement it is expected that the viscous component will be
dominant for at least most of the measured frequency range. This is because the
technique relies on the tracer particles being able to move and therefore produce a
correlogram.
For example; a gel system where the elastic component (G') is dominant for all of
the frequency range, will hold the tracer particles still within the gel matrix, which
means that the correlogram will be close to a flat line, and the MSD will be
effectively 0.
Creep compliance (J)
: Creep compliance is another way of viewing the
viscoelasticity of a sample.
