Medically Advanced Devices Laboratory, in the Center for Medical Devices Department of Mechanical and Aerospace Engineering, Jacobs School of Engineering, Department of Surgery, School of Medicine University of California San Diego, La Jolla, California 92093, USA.
Phys Rev Lett. 2020 Oct 30;125(18):184504. doi: 10.1103/PhysRevLett.125.184504.
We study the nozzle-free ejection of liquid droplets at controlled angles from a sessile drop actuated from two, mutually opposed directions by focused surface acoustic waves with dissimilar parameters. Previous researchers assumed that jets formed in this way are limited by the Rayleigh angle. However, when we carefully account for surface tension in addition to the driving force, acoustic streaming, we find a quantitative model that reduces to the Rayleigh angle only when inertia is dominant, and suggests larger ejection angles are possible in many practical situations. We confirm this in demonstrating ejection at more than double the Rayleigh angle. Our model explains the effects of both fluid and input parameters on experiments with a range of liquids. We extract, from this model, a dimensionless number that serves as an analog for the typical Weber number for predicting single droplet events.
我们研究了在两个相反方向的聚焦表面声波驱动下，从固定液滴以受控角度无喷嘴喷射液滴的情况，这些声波具有不同的参数。以前的研究人员假设，以这种方式形成的射流受到瑞利角的限制。然而，当我们除了驱动力（声流）之外还仔细考虑表面张力时，我们发现一个定量模型，该模型仅在惯性占主导地位时简化为瑞利角，并表明在许多实际情况下可能存在更大的喷射角度。我们通过演示超过瑞利角两倍的喷射来证实这一点。我们的模型解释了实验中各种液体的流体和输入参数的影响。我们从该模型中提取了一个无量纲数，作为用于预测单个液滴事件的典型韦伯数的模拟。
