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Issue 8, 2008
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Cross-scale electric manipulations of cells and droplets by frequency-modulated dielectrophoresis and electrowetting

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Abstract

Two important electric forces, dielectrophoresis (DEP) and electrowetting-on-dielectric (EWOD), are demonstrated by dielectric-coated electrodes on a single chip to manipulate objects on different scales, which results in a dielectrophoretic concentrator in an EWOD-actuated droplet. By applying appropriate electric signals with different frequencies on identical electrodes, EWOD and DEP can be selectively generated on the proposed chip. At low frequencies, the applied voltage is consumed mostly in the dielectric layer and causes EWOD to pump liquid droplets on the millimetre scale. However, high frequency signals establish electric fields in the liquid and generate DEP forces to actuate cells or particles on the micrometre scale inside the droplet. For better performance of EWOD and DEP, square and strip electrodes are designed, respectively. Mammalian cells (Neuro-2a) and polystyrene beads are successfully actuated by a 2 MHz signal in a droplet by positive DEP and negative DEP, respectively. Droplet splitting is achieved by EWOD with a 1 kHz signal after moving cells or beads to one side of the droplet. Cell concentration, measured by a cell count chamber before and after experiments, increases 1.6 times from 8.6 × 105cells ml−1 to 1.4 × 106cells ml−1 with a single cycle of positive DEP attraction. By comparing the cutoff frequency of the voltage drop in the dielectric layer and the cross-over frequency of Re(fCM) of the suspended particles, we can estimate the frequency-modulated behaviors between EWOD, positive DEP, and negative DEP. A proposed weighted Re(fCM) facilitates analysis of the DEP phenomenon on dielectric-coated electrodes.

Graphical abstract: Cross-scale electric manipulations of cells and droplets by frequency-modulated dielectrophoresis and electrowetting

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Publication details

The article was received on 25 Feb 2008, accepted on 23 Apr 2008 and first published on 28 May 2008


Article type: Paper
DOI: 10.1039/B803204A
Lab Chip, 2008,8, 1325-1331

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    Cross-scale electric manipulations of cells and droplets by frequency-modulated dielectrophoresis and electrowetting

    S. Fan, P. Huang, T. Wang and Y. Peng, Lab Chip, 2008, 8, 1325
    DOI: 10.1039/B803204A

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