Dewandre Adrien, Rivero-Rodriguez Javier, Vitry Youen, Sobac Benjamin, Scheid Benoit
TIPs Lab, Université libre de Bruxelles, Brussels, 1050, Belgium.
Sci Rep. 2020 Dec 10;10(1):21616. doi: 10.1038/s41598-020-77836-y.
Most commercial microfluidic droplet generators rely on the planar flow-focusing configuration implemented in polymer or glass chips. The planar geometry, however, suffers from many limitations and drawbacks, such as the need of specific coatings or the use of dedicated surfactants, depending on the fluids in play. On the contrary, and thanks to their axisymmetric geometry, glass capillary-based droplet generators are a priori not fluid-dependent. Nevertheless, they have never reached the market because their assembly requires fastidious and not scalable fabrication techniques. Here we present a new device, called Raydrop, based on the alignment of two capillaries immersed in a pressurized chamber containing the continuous phase. The dispersed phase exits one of the capillaries through a 3D-printed nozzle placed in front of the extraction capillary for collecting the droplets. This non-embedded implementation of an axisymmetric flow-focusing is referred to non-embedded co-flow-focusing configuration. Experimental results demonstrate the universality of the device in terms of the variety of fluids that can be emulsified, as well as the range of droplet radii that can be obtained, without neither the need of surfactant nor coating. Additionally, numerical computations of the Navier-Stokes equations based on the quasi-steadiness assumption allow to provide an explanation to the underlying mechanism behind the drop formation and the mechanism of the dripping to jetting transition. Excellent predictions were also obtained for the droplet radius, as well as for the dripping-jetting transition, when varying the geometrical and fluid parameters, showing the ability of this configuration to enventually enhance the dripping regime. The monodispersity ensured by the dripping regime, the robustness of the fabrication technique, the optimization capabilities from the numerical modelling and the universality of the configuration confer to the Raydrop technology a very high potential in the race towards high-throughput droplet generation processes.
大多数商用微流控液滴发生器依赖于在聚合物或玻璃芯片中实现的平面流聚焦配置。然而,平面几何结构存在许多限制和缺点,例如根据所涉及的流体,需要特定的涂层或使用专用表面活性剂。相反,由于其轴对称几何结构,基于玻璃毛细管的液滴发生器原则上不依赖于流体。然而,它们从未进入市场,因为其组装需要繁琐且不可扩展的制造技术。在此,我们展示了一种名为Raydrop的新设备,它基于两个浸入含有连续相的加压腔室中的毛细管的对齐。分散相通过放置在提取毛细管前方用于收集液滴的3D打印喷嘴从其中一个毛细管中流出。这种轴对称流聚焦的非嵌入式实现方式被称为非嵌入式共流聚焦配置。实验结果证明了该设备在可乳化流体种类以及可获得的液滴半径范围方面的通用性,既不需要表面活性剂也不需要涂层。此外,基于准稳态假设的纳维 - 斯托克斯方程的数值计算能够对液滴形成背后的潜在机制以及滴流到射流转变的机制做出解释。当改变几何和流体参数时,对于液滴半径以及滴流 - 射流转变也获得了出色的预测结果,表明这种配置最终能够增强滴流状态的能力。由滴流状态确保的单分散性、制造技术的稳健性、数值建模的优化能力以及配置的通用性赋予了Raydrop技术在高通量液滴生成过程竞争中非常高的潜力。