Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong, China.
Small. 2014 Feb 26;10(4):758-65. doi: 10.1002/smll.201202659. Epub 2013 Sep 13.
Air plugs are usually undesirable in microfluidic systems because of their detrimental effect on the system's stability and integrity. By controlling the wetting properties as well as the topographical geometry of the microchannel, it is reported herein that air plugs can be generated in pre-defined locations to function as a unique valve, allowing for the on-site formation of various emulsions including single-component droplets, composite droplets with droplet-to-droplet concentration gradient, blood droplets, paired droplets, as well as bubble arrays without the need for precious flow control, a difficult task with conventional droplet microfluidics. Moreover, the self-generated air valve can be readily deactivated (turned off) by the introduction of an oil phase, allowing for the on-demand release of as-formed droplets for downstream applications. It is proposed that the simple, yet versatile nature of this technique can act as an important method for droplet microfluidics and, in particular, is ideal for the development of affordable lab-on-a-chip systems without suffering from scalability and manufacturing challenges that typically confound the conventional droplet microfluidics.
气栓通常是微流控系统中不希望出现的，因为它们会对系统的稳定性和完整性产生不利影响。通过控制润湿性以及微通道的形貌几何结构，本文报道了可以在预定位置生成气栓，将其用作独特的阀门，从而能够现场形成各种乳液，包括单一组分液滴、具有液滴间浓度梯度的复合液滴、血滴、成对液滴以及无需精密流量控制的气泡阵列，而这是传统的液滴微流控技术难以实现的任务。此外，通过引入油相，可以轻易地使自生成的气阀失效（关闭），从而按需释放所形成的液滴以供下游应用。我们提出，这种简单而多功能的技术可以作为液滴微流控的一种重要方法，特别是对于开发经济实惠的芯片实验室系统非常理想，因为它不会受到传统液滴微流控技术通常面临的可扩展性和制造挑战的困扰。
