  We review here different methods to measure the bulk viscosity of complex
fluids using micron-sized magnetic wires. The wires are characterized by length
of a few microns and diameter of a few hundreds of nanometers. We first draw
analogies between cone-and-plate rheometry and wire-based microrheology. In
particular we highlight that magnetic wires can be operated as
stress-controlled rheometers for two types of testing, the creep-recovery and
steady shear experiments. In the context of biophysical applications, the
cytoplasm of different cell lines including fibroblasts, epithelial and tumor
cells is studied. It reveals that the interior of living cells can be described
as a viscoelastic liquid with a static viscosity comprised between 10 and 100
Pas. We extend the previous approaches and show that the proposed technique can
also provide time resolved viscosity data, which for cells display strong
temporal fluctuations. The present work demonstrates the high potential of the
magnetic wires for quantitative rheometry in confined espaces.

Soft Condensed Matter