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Centrifugal Step Emulsification: How Buoyancy Enables High Generation Rates of Monodisperse Droplets
Langmuir ( IF 3.7 ) Pub Date : 2019-07-08 00:00:00 , DOI: 10.1021/acs.langmuir.9b01165 Martin Schulz 1 , Felix von Stetten 1, 2 , Roland Zengerle 1, 2 , Nils Paust 1, 2
Langmuir ( IF 3.7 ) Pub Date : 2019-07-08 00:00:00 , DOI: 10.1021/acs.langmuir.9b01165 Martin Schulz 1 , Felix von Stetten 1, 2 , Roland Zengerle 1, 2 , Nils Paust 1, 2
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We demonstrate that buoyancy in centrifugal step emulsification enables substantially higher generation rates of monodisperse droplets compared to pressure driven set-ups. Step emulsification in general can produce droplets in comparatively simple systems (only one moving liquid) with a low CV of <5% in droplet diameter and with a minimum dead volume. If operated below a critical capillary number, the droplet diameter is defined by geometry and surface forces only. Above that critical capillary number, however, jetting occurs, leading to an increased droplet diameter and CV. Consequently, generation rates of monodisperse droplets are limited in pressure-driven systems. In this paper, we show that centrifugal step emulsification can overcome this limitation by applying sufficient buoyancy to the system. The buoyancy, induced by the centrifugal field and a density difference of the continuous and disperse phase, supports droplet necking by pulling the forming droplet away from the nozzle. The influence of buoyancy is studied using specific microfluidic designs that allow for supplying different buoyancies to the same droplet generation rates. For a droplet diameter of 100 μm, droplet generation at rates above 2.8k droplets per second and nozzle were reached, which is an increase of more than a factor of 8 in comparison to pressure-driven systems.
中文翻译：
离心步骤乳化：浮力如何使单分散液滴的高生成速率
我们证明，与压力驱动装置相比，离心步骤乳化中的浮力可大大提高单分散液滴的生成速率。通常，逐步乳化可以在相对简单的系统（仅一种流动液体）中产生液滴，液滴的CV小于液滴直径的5％，并且死体积最小。如果在临界毛细管数以下操作，则液滴直径仅由几何形状和表面力定义。但是，超过该临界毛细管数时，会发生喷射，从而导致液滴直径和CV增大。因此，在压力驱动的系统中单分散液滴的产生速率受到限制。在本文中，我们证明了通过对系统应用足够的浮力，离心步骤乳化可以克服这一局限性。浮力 由离心场和连续相和分散相的密度差引起的微分，通过将形成的液滴从喷嘴中拉出而支持液滴颈缩。使用特定的微流体设计研究浮力的影响，这些设计允许以相同的液滴生成速率提供不同的浮力。对于直径为100μm的液滴，以每秒2.8k个液滴和喷嘴以上的速率产生液滴，与压力驱动系统相比，其增加幅度超过8倍。
更新日期：2019-07-08
中文翻译：
离心步骤乳化：浮力如何使单分散液滴的高生成速率
我们证明，与压力驱动装置相比，离心步骤乳化中的浮力可大大提高单分散液滴的生成速率。通常，逐步乳化可以在相对简单的系统（仅一种流动液体）中产生液滴，液滴的CV小于液滴直径的5％，并且死体积最小。如果在临界毛细管数以下操作，则液滴直径仅由几何形状和表面力定义。但是，超过该临界毛细管数时，会发生喷射，从而导致液滴直径和CV增大。因此，在压力驱动的系统中单分散液滴的产生速率受到限制。在本文中，我们证明了通过对系统应用足够的浮力，离心步骤乳化可以克服这一局限性。浮力 由离心场和连续相和分散相的密度差引起的微分，通过将形成的液滴从喷嘴中拉出而支持液滴颈缩。使用特定的微流体设计研究浮力的影响，这些设计允许以相同的液滴生成速率提供不同的浮力。对于直径为100μm的液滴，以每秒2.8k个液滴和喷嘴以上的速率产生液滴，与压力驱动系统相比，其增加幅度超过8倍。
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