A simple capillary-based open microfluidic device for size on-demand high-throughput droplet/bubble/microcapsule generation

Liping Mei, Mingliang Jin, Shuting Xie, Zhibin Yan, Xin Wang, Guofu Zhou, Albert Van Den Berg, Lingling Shui* (Corresponding Author)

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

    13 Citations (Scopus)


    We report an easily-established capillary-based open microfluidic device (COMD) as a simple and robust method for size on-demand generation of monodisperse droplets of various fluidic materials with controllable volume. A device is set up in which a capillary is positioned with its tip close to a flat surface with a precise gap distance in a container. The continuous phase remains static in the container, and the dispersed phase is pumped through the capillary and forms droplets at the exit of the gap. Monodisperse droplets, bubbles and microcapsules of various fluids with diameters of 10-300 μm (picoliter to nanoliter) and generation frequency of 1-1000 Hz are obtained by controlling the gap distance in the range of 5-500 μm. The droplet formation is caused by capillarity-induced narrowing of the dispersed phase at the capillary exit, with droplet size being determined by the gap volume and fluid flow. We find that, at low flow rate, using the same COMD, the generated droplet size is constant, being determined by the gap size; however, at higher flow rate, droplet size increases with the flow rate. Droplet types can be managed by fluids and surface modification of the capillary and bottom surfaces. High throughput droplet generation is achieved by in-parallel integration of multiple capillaries in one device. Such a COMD is simple and easy-to-build without complex microfabrication requirements; however, it is highly robust, flexible and easy-to-operate for size on-demand droplet generation. It offers an opportunity for common laboratories to perform droplet-based assays, and has high potential for high throughput industrial emulsification applications as well.

    Original languageEnglish
    Pages (from-to)2806-2815
    Number of pages10
    JournalLab on a chip
    Issue number18
    Publication statusPublished - 1 Jan 2018

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