Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

Rajnak, Michal; Kurimsky, Juraj; Avdeev, Mikhail V.; Kopcansky, Peter; Timko, Milan; Dolnik, Bystrik; Feoktystov, Artem; Petrenko, Viktor I.; Ivankov, Olexandr I.

doi:10.1063/1.4929342

Journal Article

FZJ-2015-07142

Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

Rajnak, M. (Corresponding author) ; Petrenko, V. I. ; Avdeev, M. V. ; Ivankov, O. I. ; Feoktystov, A.FZJ* ; Dolnik, B. ; Kurimsky, J. ; Kopcansky, P. ; Timko, M.

2015
American Inst. of Physics Melville, NY

Applied physics letters 107(7), 073108 - (2015) [10.1063/1.4929342]

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Please use a persistent id in citations: http://hdl.handle.net/2128/17308 doi:10.1063/1.4929342

Abstract: Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

Keyword(s): Chemical Reactions and Advanced Materials (1st) ; Key Technologies (1st) ; Condensed Matter Physics (2nd) ; Magnetism (2nd) ; Materials Science (2nd)