Controlled Motion of Magneto-Elastic Filaments
J. Bibette (Paris) and H.A. Stone (DEAS)
Spherical paramagnetic particles, with diameters from tens to hundreds of nanometers, can be linked together to form a chain, which can be aligned with and controlled by, a magnetic field. In the experimental images on the left the chain begins perpendicular to the horizontal magnetic field and then deforms and unfolds progressively until it eventually is aligned with the field. Intermediate shapes of the filament include rather long-lived hairpin structures. Numerical simulations shown on the right capture the hairpin shapes (top) and the time-dependent evolution from the hairpin shape (bottom) to the final aligned equilibrium orientation (the details of the evolution depend on several dimensionless parameters). The present state of comparison of experiments and simulations is qualitative and on-going studies are aimed at providing a quantitative comparison. These magnetically controlled filaments offer new possibilities for transport and manipulation on the nano- and micro-scales.