Bouncing droplets: from fundamentals to digital microfluidics

一系列实验将探索小液滴的新颖弹跳配置，这些小液滴可以在垂直振动的液体界面上无限弹跳。将开发相应的理论模型。在某些强制机制中，这些弹跳的液滴稳定地穿过界面;此外，这些弹跳者或步行者可以以各种方式相互作用，排斥或吸引，形成平移或旋转的稳定晶格结构，或合并以产生可与下面的浴合并的较大液滴。这种新颖的液滴悬浮方法为微流体应用中的液滴处理提供了一种有吸引力的替代方案，因为它避免了由流体-固体接触引起的复杂性。拟议的研究将致力于更好地了解弹跳液滴的丰富动力学，以期为新的数字微流体技术提供信息和开发。智力优势：这项工作建立在Yves Couder及其同事的观察基础上，他们证明了弹跳液滴实验非常丰富，展示了光学（衍射），量子系统（波粒二象性，隧穿），统计物理（相变）和天文学（复杂的轨道运动）的特征。最令人吃惊的是，毫米级的步行液滴表现出量子系统（例如光子）的特征，这些特征小100亿倍，并受量子力学概率定律的支配。一个突出的问题是，步行者通过狭缝的衍射是否是混沌动力学引起表观量子行为的一个例子。对弹跳动力学的更好理解将产生对弹跳液滴的量子性质的有价值的洞察。拟议的探索性检查液滴反弹旋转浴将提供一个新的系统的功能（引力，轨道运动和碰撞）类似于那些产生的天体动力学。因此，将多个步行者释放到旋转浴中将代表行星吸积和太阳系演化的简单而挑衅性的实验室模拟。更广泛的影响：液滴在振动界面上弹跳是一种视觉上引人注目的效果，可以通过简单的桌面实验重现。此外，行走的液滴表现出波粒二象性的特征，因此代表了量子力学系统的一个挑衅性的宏观模拟。因此，弹跳液滴非常适合吸引理科学生和公众的兴趣。PI在这方面的工作受到了媒体的广泛关注。这样的展示应该提高公众对科学的认识和欣赏，并引起科学博物馆的注意。该研究将部分由PI和co-PI监督的本科生进行。这些实验特别简单，因此为麻省理工学院的本科生提供了进入实验室环境的理想入口。PI的实验室通过麻省理工学院的UROP项目有着悠久的本科生参与历史，女性和代表性不足的少数民族优先被雇用。PI积极参与高中外展和麻省理工学院的科学与工程教师计划。

0966452BushA series of experiments will explore novel bouncing configurations of small liquid droplets that may bounce indefinitely on a vertically vibrated liquid interface. Accompanying theoretical models will be developed. In certain forcing regimes, these bouncing droplets walk steadily across the interface; moreover, these bouncers or walkers can interact in a variety of ways, repelling or attracting, forming stable lattice structures that translate or rotate, or merging to produce a larger drop that may coalesce with the underlying bath. This novel means of drop levitation provides an attractive alternative for handling droplets for microfluidic applications, as it avoids the complications resulting from fluid-solid contact. The proposed research will be directed towards better understanding the rich dynamics of bouncing droplets with a view to informing and developing new digital microfluidic technologies. Intellectual Merit: The work builds on the observations of Yves Couder and coworkers who have demonstrated that the bouncing droplet experiment is extraordinarly rich, exhibiting features of optics (diffraction), quantum systems (wave-particle duality, tunneling), statistical physics (phase transitions) and astronomy (complex orbital motions). Most startling is the fact that millimetric walking droplets exhibit features of quantum systems (e.g. photons) that are smaller by a factor of 10 billion and governed by the probabilistic laws of quantum mechanics. A salient question is whether the diffraction of walkers passing through a slit is an example of chaotic dynamics giving rise to apparent quantum behavior. An improved understanding of the bouncing dynamics will yield valuable insight into the quantum nature of bouncing droplets. The proposed exploratory examination of droplets bouncing on a rotating bath will provide a novel system with features (gravitational attraction, orbital motions and collision) analogous to those arising celestial dynamics. The release of multiple walkers onto a rotating bath will thus represent a simple and provocative laboratory analogue of planetary accretion and solar system evolution.Broader Impact: Droplets bouncing on a vibrated interface is a visually striking effect that may be reproduced with a simple desktop experiment. Moreover, walking droplets exhibit features of wave-particle duality, and so represent a provocative macroscopic analogue of a quantum mechanical system. As such, bouncing droplets are ideally suited to attract the interest of both science students and the general public. The PI's work on the subject has received considerable media attention. Such exposure should increase the general public's awareness and appreciation of science, and attract the attention of science museums. The research will be performed in part by undergraduate students supervised by the PI and co-PI. The experiments are particularly straightforward, and so provide an ideal entry into the lab environment for MIT undergraduates. The PI's laboratory has a long history of undergraduate involvement through MIT's UROP Program, with women and underrepresented minorities being hired preferentially. The PI is actively involved in both high school outreach and MIT's Science and Engineering Program for Teachers.