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Issue 3, 2011
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Electromagnetic liquid pistons for capillarity-based pumping

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The small scales associated with lab-on-a-chip technologies lend themselves well to capillarity-dominated phenomena. We demonstrate a new capillarity-dominated system where two adjoining ferrofluid droplets can behave as an electronically-controlled oscillator or switch by an appropriate balance of magnetic, capillary, and inertial forces. Their oscillatory motion can be exploited to displace a surrounding liquid (akin to an axial piston pump), forming electromagnetic “liquid pistons.” Such ferrofluid pistons can pump a precise volume of liquid via finely tunable amplitudes (cf.pump stroke) or resonant frequencies (cf.pump speed) with no solid moving parts for long-term operation without wear in a small device. Furthermore, the rapid propagation of electromagnetic fields and the favorable scaling of capillary forces with size permit micron sized devices with very fast operating speeds (∼kHz). The pumping dynamics and performance of these liquid pistons is explored, with experimental measurements showing good agreement with a spherical cap model. While these liquid pistons may find numerous applications in micro- and mesoscale fluidic devices (e.g., remotely activated drug delivery), here we demonstrate the use of these liquid pistons in capillarity-dominated systems for chip-level, fast-acting adaptive liquid lenses with nearly perfect spherical interfaces.

Graphical abstract: Electromagnetic liquid pistons for capillarity-based pumping

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The article was received on 10 Sep 2010, accepted on 05 Nov 2010 and first published on 03 Dec 2010

Article type: Paper
DOI: 10.1039/C0LC00397B
Citation: Lab Chip, 2011,11, 393-397
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    Electromagnetic liquid pistons for capillarity-based pumping

    B. A. Malouin Jr, M. J. Vogel, J. D. Olles, L. Cheng and A. H. Hirsa, Lab Chip, 2011, 11, 393
    DOI: 10.1039/C0LC00397B

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