Microscopy images of magnetic wires

We synthesize micron-sized magnetic wires which lengths range from 10 to 100 µm for microrheology applications. The magnetic wires can be remotely actuated with an external magnetic field, and as such they behave as micro-rheometers embedded in a fluid. We exploit the technique of rotational magnetic spectroscopy (MRS) in which wires are submitted to a rotational magnetic field as a function of the frequency, and their motion is monitored by time-lapse microscopy. The MRS technique is successfully applied to model systems including viscoelastic liquids (e.g. wormlike micelles) and soft gel materials (polysaccharide gel), leading to the measure of the shear viscosity and shear elastic modulus.

Applied recently in the context of biology to measure intra- and extracellular body fluid viscosities, the approach demonstrates the potential of the wire-based spectroscopy as an accurate rheological tool to explore soft matter dynamics and flow. It also represents a robust alternative to bead microrheology.


F. Loosli, M. Najm, R. Chan, E. Oikonomou, A. Grados, M. Receveur and J.-F. Berret*
Wire active microrheology to differentiate viscoelastic liquids from soft solids
ChemPhysChem  17, 4134 – 4143 (2016)

J.-F. Berret*
Local viscoelasticity of living cells measured by rotational magnetic spectroscopy
Nature Communications 7, 10134 (2016)

A. Mateos-Maroto, F. Ortega, R.G. Rubio, J.-F. Berret,F. Martínez-Pedrero
Giant Vesicles with Encapsulated Magnetic Nanowiresas Versatile Carriers, Transported via Rotating and Non-Homogeneous Magnetic Fields
Particle and Particle Systems Characterization 36 (10), 1900239 (2019)

L.P.A. Thai, F. Mousseau, E.K. Oikonomou, M. Radiom and J.-F. Berret*
Effect of Nanoparticles on the Bulk Shear Viscosity of a Biomimetic Lung Surfactant
ACS Nano 14, 466 – 475 (2020)