期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 115, 期 38, 页码 9479-9484出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1803644115
关键词
droplet formation; microfluidics; surface wetting; contact angle; step emulsification
资金
- Swiss National Science Foundation through the National Centre of Competence in Research Bio-Inspired Materials
- National Science Foundation [DMR-1708729]
- Harvard Materials Research Science and Engineering Center [NSF DMR-1420570]
- National Institutes of Health Grant [R01EB023287]
The formation of droplets is ubiquitous in many natural and industrial processes and has reached an unprecedented level of control with the emergence of milli- and microfluidics. Although important insight into the mechanisms of droplet formation has been gained over the past decades, a sound understanding of the physics underlying this phenomenon and the effect of the fluid's flow and wetting properties on the droplet size and production rate is still missing, especially for the widely applied method of step emulsification. In this work, we elucidate the physical controls of microdroplet formation in step emulsification by using the wetting of fluidic channels as a tunable parameter to explore a broad set of emulsification conditions. With the help of highspeed measurements, we unequivocally show that the final droplet pinch-off is triggered by a Rayleigh-Plateau-type instability. The droplet size, however, is not determined by the Rayleigh-Plateau breakup, but by the initial wetting regime, where the fluid's contact angle plays a crucial role. We develop a physical theory for the wetting process, which closely describes our experimental measurements without invoking any free fit parameter. Our theory predicts the initiation of the Rayleigh-Plateau breakup and the transition from dripping to jetting as a function of the fluid's contact angle. Additionally, the theory solves the conundrum why there is a minimal contact angle of alpha = 2 pi/3 = 120 degrees for which droplets can form.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据