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Issue 10, 2013
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Droplet morphometry and velocimetry (DMV): a video processing software for time-resolved, label-free tracking of droplet parameters

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Abstract

Emerging assays in droplet microfluidics require the measurement of parameters such as drop size, velocity, trajectory, shape deformation, fluorescence intensity, and others. While micro particle image velocimetry (μPIV) and related techniques are suitable for measuring flow using tracer particles, no tool exists for tracking droplets at the granularity of a single entity. This paper presents droplet morphometry and velocimetry (DMV), a digital video processing software for time-resolved droplet analysis. Droplets are identified through a series of image processing steps which operate on transparent, translucent, fluorescent, or opaque droplets. The steps include background image generation, background subtraction, edge detection, small object removal, morphological close and fill, and shape discrimination. A frame correlation step then links droplets spanning multiple frames via a nearest neighbor search with user-defined matching criteria. Each step can be individually tuned for maximum compatibility. For each droplet found, DMV provides a time-history of 20 different parameters, including trajectory, velocity, area, dimensions, shape deformation, orientation, nearest neighbour spacing, and pixel statistics. The data can be reported via scatter plots, histograms, and tables at the granularity of individual droplets or by statistics accrued over the population. We present several case studies from industry and academic labs, including the measurement of 1) size distributions and flow perturbations in a drop generator, 2) size distributions and mixing rates in drop splitting/merging devices, 3) efficiency of single cell encapsulation devices, 4) position tracking in electrowetting operations, 5) chemical concentrations in a serial drop dilutor, 6) drop sorting efficiency of a tensiophoresis device, 7) plug length and orientation of nonspherical plugs in a serpentine channel, and 8) high throughput tracking of >250 drops in a reinjection system. Performance metrics show that highest accuracy and precision is obtained when the video resolution is >300 pixels per drop. Analysis time increases proportionally with video resolution. The current version of the software provides throughputs of 2–30 fps, suggesting the potential for real time analysis.

Graphical abstract: Droplet morphometry and velocimetry (DMV): a video processing software for time-resolved, label-free tracking of droplet parameters

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Publication details

The article was received on 15 Jan 2013, accepted on 07 Mar 2013 and first published on 08 Mar 2013


Article type: Paper
DOI: 10.1039/C3LC50074H
Citation: Lab Chip, 2013,13, 1892-1901
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    Droplet morphometry and velocimetry (DMV): a video processing software for time-resolved, label-free tracking of droplet parameters

    A. S. Basu, Lab Chip, 2013, 13, 1892
    DOI: 10.1039/C3LC50074H

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