Driven by an external rotating field, a novel phenomenon of planetary-like double rotations, such as a local self-spin of individual drops and the global revolution of the drop array, is uncovered in arrayed ferrofluid drops. Because of the simultaneous realignments of the induced poles in the magnetized ferrofluids, the ferrodrops are elongated along the line of magnetic flux and spin nearly synchronized to the external field. On the other hand, the global revolution of the drop array is driven by the interactions between the magnetized drops, and might undergo a wave-like forth and back movement. The wavering behaviours array revolutions can be realized by the alternative magnetic torques acting on the array, which change sign when the phase lag between the orientations of the external field and the alignment of the array reaches multiples of π/2. Prominence of the net revolutionary movement is determined by strengths and the uniformity of the overall field distribution as well as the length of the array. In general, a stronger and more uniformly rotating field leads to a more prominent global revolution of the array. Such double rotations can be applied to enhance mixings of two fluids more effectively than a single self-spin drop.
Journal: TechConnect Briefs
Volume: 2, Nanotechnology 2014: MEMS, Fluidics, Bio Systems, Medical, Computational & Photonics
Published: June 15, 2014
Pages: 93 - 96
Industry sectors: Advanced Materials & Manufacturing | Sensors, MEMS, Electronics
Topic: Inkjet Design, Materials & Fabrication