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arXiv · 1210.2560

Swimming active droplet: A theoretical analysis

Maximilian Schmitt·Holger Stark
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Abstract

Recently, an active microswimmer was constructed where a micron-sized droplet of bromine water was placed into a surfactant-laden oil phase. Due to a bromination reaction of the surfactant at the interface, the surface tension locally increases and becomes non-uniform. This drives a Marangoni flow which propels the squirming droplet forward. We develop a diffusion-advection-reaction equation for the order parameter of the surfactant mixture at the droplet interface using a mixing free energy. Numerical solutions reveal a stable swimming regime above a critical Marangoni number M but also stopping and oscillating states when M is increased further. The swimming droplet is identified as a pusher whereas in the oscillating state it oscillates between being a puller and a pusher.

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Maximilian Schmitt, Holger Stark. 2012-10-09. Swimming active droplet: A theoretical analysis. https://doi.org/10.1209/0295-5075%2F101%2F44008

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