Issue 3, 2011

Electromagnetic liquid pistons for capillarity-based pumping

Abstract

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

Supplementary files

Article information

Article type
Paper
Submitted
10 Sep 2010
Accepted
05 Nov 2010
First published
03 Dec 2010

Lab Chip, 2011,11, 393-397

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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