Microrheology of complex fluids

The field of microrheology is concerned with how materials store and dissipate mechanical energy as a function of length scale. Recent developments in the theory and instrumentation of the microrheology of complex fluids are reviewed. Equal emphasis is given to the physical phenomena probed, advances in instrumentation, and specific experimental systems in which this field has already had an impact. The inversion of the compliance data, measurement of sample heterogeneity, high frequency viscoelasticity, effects of shear flow, single molecule experiments, surface viscoelasticity and time evolution studies are considered. The techniques highlighted include particle tracking microrheology, diffusing wave spectroscopy, laser tracking, magnetic tweezers and atomic force microscopy. Specific examples of complex fluid systems are chosen from the fields of polymers, colloids and biological assemblies. (Some figures in this article are in colour only in the electronic version) 0034-4885/05/030685+58$90.00 © 2005 IOP Publishing Ltd Printed in the UK 685