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Issue 6, 2008
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All-electronic droplet generation on-chip with real-time feedback control for EWOD digital microfluidics

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Abstract

Electrowetting-on-dielectric (EWOD) actuation enables digital (or droplet) microfluidics where small packets of liquids are manipulated on a two-dimensional surface. Due to its mechanical simplicity and low energy consumption, EWOD holds particular promise for portable systems. To improve volume precision of the droplets, which is desired for quantitative applications such as biochemical assays, existing practices would require near-perfect device fabrication and operation conditions unless the droplets are generated under feedback control by an extra pump setup off of the chip. In this paper, we develop an all-electronic (i.e., no ancillary pumping) real-time feedback control of on-chip droplet generation. A fast voltage modulation, capacitance sensing, and discrete-time PID feedback controller are integrated on the operating electronic board. A significant improvement is obtained in the droplet volume uniformity, compared with an open loop control as well as the previous feedback control employing an external pump. Furthermore, this new capability empowers users to prescribe the droplet volume even below the previously considered minimum, allowing, for example, 1 : x (x < 1) mixing, in comparison to the previously considered n : mmixing (i.e., n and m unit droplets).

Graphical abstract: All-electronic droplet generation on-chip with real-time feedback control for EWOD digital microfluidics

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Publication details

The article was received on 12 Nov 2007, accepted on 19 Mar 2008 and first published on 21 Apr 2008


Article type: Paper
DOI: 10.1039/B717417A
Citation: Lab Chip, 2008,8, 898-906
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    All-electronic droplet generation on-chip with real-time feedback control for EWOD digital microfluidics

    J. Gong and C. “. Kim, Lab Chip, 2008, 8, 898
    DOI: 10.1039/B717417A

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