Droplet Generation by Cylinder Extraction from a Free Surface (2016)

Undergraduates: Mitchell Underwood, Daniel Harris Post Doc

Faculty Advisor: Richard Mclaughlin
Department: Physics & Astronomy

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The generation of uniform droplets on demand is critical for droplet-based microfluidics, however, traditional nozzle-based methods are restricted in the range of droplet sizes that can be produced, and are often prone to clogging. In this work, we investigate a novel and robust method for the repeatable generation of single droplets by the extraction of a partially submerged cylinder from a fluid interface. When the cylinder is swiftly removed from the free surface, a liquid ligament is formed, which can contract to produce a single droplet whose size depends on the cylinder diameter, extraction speed, and initial immersion depth. The ligament break-up process is observed and measured using high-speed photography and the dependence of the resulting droplet size on the experimental parameters is rationalized by a simple model. The proposed method allows for a wide range of droplet sizes to be produced with a single setup and is effective for a wide range of working fluids.