Oléron Mathieu, Clement Grégoire, Hidalgo-Caballero Samuel, Gunny Masoodah, Box Finn, Labousse Matthieu, McGraw Joshua D
Gulliver UMR 7083 CNRS, ESPCI-PSL, 10 rue Vauquelin, 75005, Paris, France.
IPGG, 6 rue Jean-Calvin, 75005, Paris, France.
Eur Phys J E Soft Matter. 2025 Jul 2;48(6-7):35. doi: 10.1140/epje/s10189-025-00493-4.
Droplet generation under steady conditions is a common microfluidic method for producing biphasic systems. However, this process works only over a limited range of imposed pressure: beyond a critical value, a stable liquid jet can instead form. Furthermore, for a given geometry, the pressure conditions set both the generation rate of droplets and their volume. Here, we report on-demand droplet production using a positive pressure pulse to the dispersed-phase inlet of a flow-focusing geometry. This strategy enables confined droplet generation within and beyond the pressure range observed under steady conditions, and decouples volume and production rate. In particular, elongated plugs not possible under steady conditions may be formed when the maximal pressure during the pulse reaches the jet regime. The measured volume of droplets-on-demand as well as the onset of droplet generation are both captured with a simple model that considers hydraulic resistances. This work provides a strategy and design rules for processes that require individual droplets or elongated plugs in a simple microfluidic chip design.
在稳定条件下产生液滴是一种用于制备双相系统的常见微流控方法。然而，该过程仅在有限的外加压力范围内起作用：超过临界值时，反而会形成稳定的液体射流。此外，对于给定的几何形状，压力条件既决定了液滴的产生速率，也决定了它们的体积。在此，我们报道了一种通过向流动聚焦几何结构的分散相入口施加正压脉冲来按需产生液滴的方法。这种策略能够在稳定条件下观察到的压力范围之内和之外产生受限的液滴，并使体积和产生速率解耦。特别是，当脉冲期间的最大压力达到射流状态时，可能会形成在稳定条件下无法形成的细长柱塞。通过一个考虑水力阻力的简单模型，可以捕捉到按需产生的液滴的测量体积以及液滴产生的起始情况。这项工作为在简单微流控芯片设计中需要单个液滴或细长柱塞的过程提供了一种策略和设计规则。
