Controlled propulsion in viscous fluids of magnetically actuated colloidal doublets.
We study the propulsion of a micron-size paramagnetic colloidal doublet dispersed in water and driven above a surface by an external precessing magnetic field. The applied field forces the doublet to precess around an axis parallel to the plane of motion and the rotation of the colloidal assembly is rectified into translation due to a periodic asymmetry in dissipation close to the bounding plate. These recent experimental findings [P. Tierno, R. Golestanian, I. Pagonabarraga, and F. Sagués, Phys. Rev. Lett. 101, 218304 (2008)] are complemented here with a theoretical analysis of the system and extended to more complex magnetic modulations such as elliptical driving fields. Experimental results show a good agreement with numerical simulations with the aim to find the best conditions toward the optimization of propulsion speed and swimming efficiency.
Tierno
Pietro
P
Departament de Química Física, Universitat de Barcelona, Martí i Franquès, Barcelona, Spain. ptierno@ub.edu
Güell
Oriol
O
Sagués
Francesc
F
Golestanian
Ramin
R
Pagonabarraga
Ignacio
I