Micrometric Assembly of Magnetotactic Bacteria and Magnetic Nanoparticles

BEKERIS V.; PETTINARI, M. J.; JORGE G. A.; MEYRA A. G.; GODOY M. S. ; ZARRAGOICOECHEA G. J.

Ölüdeniz

Conferencia; ICSM2016; 2016

International Conference on Superconductivity and Magnetism

The manipulation of magnetic nanoparticles into custom-made structures is particularly promising for applications in spintronics, novel memory devices, and in biology. In this talk I will discuss the micrometric periodic assembly of magnetotactic bacteria, Magnetospirillum magneticum AMB-1, which synthesize chains of magnetic nanoparticles inside their bodies, and of superparamagnetic Fe3O4 and ferromagnetic CoFe2O4 nanoparticles in aqueous suspensions using an alternative approach. The method requires no current bias and uses the magnetic field patterns generated by recorded audio tapes [1]. Computer generated bipolar square audio waves of different frequencies (100 Hz ? 5 kHz) were recorded and the distribution of the stray magnetic field at the surface of the tapes was determined analytically and experimentally by magneto-optic imaging. Drops of aqueous suspensions were deposited on the tapes and bacteria and particles were trapped at locations where magnetic energy is minimized, as observed using conventional optical microscopy. Suspensions of M. magneticum AMB-1 treated with formaldehyde and kanamycin were studied, and patterns of trapped dead bacteria indicated that magnetic forces dominate over self-propelling forces in these experiments, in accordance with calculated values. The behavior of the different types of particles with different degree of aggregation is discussed. Monte Carlo simulations considering both a magnetic dipolar interaction and a dispersive Hamaker potential between particles, which are able to move in a simulation cell over a magnetized substrate, show good agreement with experiments.