Abstract Due to its significance in oil recovery and droplet microfluidics, breakup of spherical droplets in a constriction (i.e., snap-off) is extensively studied. However, rectangular channels with large aspect ratios are commonly used in real applications, in which droplets usually present pancake shape. Since capillary pressures governing droplet’s snap-off depend strongly on droplet shape, we hypothesize that pancake droplets may exhibit different snap-off behaviors from spherical droplets. Via microfluidic experiments, we demonstrate that pancake droplets indeed present new snap-off behaviors in three aspects: (1) they snap off at high capillary numbers; (2) the interface breaks up at the rear meniscus instead of the front one; (3) the size of daughter droplets is dependent of mother droplet size instead of independent for spherical droplets. Besides, we reveal the underlying mechanism, i.e., pancake droplets show much lower velocity in the constriction than spherical droplets, via analyzing capillary pressures at the droplet’s two ends.

中文翻译：

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流过微流体收缩的薄饼液滴的破碎

摘要 由于其在采油和液滴微流体中的重要性，球形液滴在收缩（即折断）中的破碎得到了广泛的研究。然而，在实际应用中通常使用具有大纵横比的矩形通道，其中液滴通常呈现煎饼形状。由于控制液滴折断的毛细管压力很大程度上取决于液滴形状，我们假设煎饼液滴可能表现出与球形液滴不同的折断行为。通过微流体实验，我们证明煎饼液滴确实在三个方面呈现出新的折断行为：（1）它们在高毛细管数下折断；(2) 界面在后弯液面而不是前弯液面破裂；(3) 子液滴的大小取决于母液滴的大小，而不是独立于球形液滴。