Micro-rheological studies with Multiple Particle Tracking

M. A. K. Williams ^1,2 , R. R. Vincent ^1,2, D.N Pinder¹and Y. Hemar^2,3

¹ Institute of Fundamental Sciences, Massey University, NZ

² MacDiarmid Institute for Nanotechnology and Advanced Materials, NZ

³ Fonterra Research Centre, Palmerston North, NZ

It is well known that a plethora of biologically relevant soft materials exhibit heterogeneous hierarchical architectures, that arise naturally from the propensity of constituent biopolymers to self-assemble and aggregate¹. Thus, understanding how to probe the viscoelastic properties of such systems is expected to have wide relevance, both from the fundamental and the industrial view-points.

We describe micro-rheological measurements² carried out with multiple particle tracking (MPT) on a series of model biological systems of increasing structural and temporal complexity. We start with purely viscous media, progress to entangled polymeric solutions, gels, and ultimately systems with designed heterogeneous microstructures that exhibit a spatial distribution of mechanical properties. At each stage of the study we compare our MPT results with those obtained by additional passive micro-rheological experiments carried out using diffusing wave spectroscopy and those obtained using a conventional rheometer. Carefully consideration is given to the comparison of the results obtained by the different techniques.

References

[1] Hemar, Y. and Pinder D.N. DWS microrheology of a linear polysaccharide. (in Press) Biomacromolecules.

[2] Waigh, T.A., Microrheology of complex fluids, Reports on progress in physics, 68 (3), 685, (2005).