TY  - JOUR
AU  - Rajnak, Michal
AU  - Petrenko, Viktor I.
AU  - Avdeev, Mikhail V.
AU  - Ivankov, Olexandr I.
AU  - Feoktystov, Artem
AU  - Dolnik, Bystrik
AU  - Kurimsky, Juraj
AU  - Kopcansky, Peter
AU  - Timko, Milan
TI  - Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids
JO  - Applied physics letters
VL  - 107
IS  - 7
SN  - 1077-3118
CY  - Melville, NY
PB  - American Inst. of Physics
M1  - FZJ-2015-07142
SP  - 073108 -
PY  - 2015
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000360390500051
DO  - DOI:10.1063/1.4929342
UR  - https://juser.fz-juelich.de/record/278972
ER  -