Metamaterial Architectures for Programmable Droplet Motion

该基金支持控制固体表面上液滴运动的基础研究。液滴控制的问题与许多工业应用相关，从自干燥表面和通过液滴冷凝的热传递到水收集和生物医学分析。因此，在这个方向上的研究可以导致具有巨大社会影响的发现。用于液滴运动控制的大多数策略涉及化学或机械地刮除与流体直接接触的表面，从而不可逆地改变其默认属性。该项目促进了一种不同的范式，利用移动液滴和振动表面之间的相互作用。该项目的想法围绕着使用新兴的工程超材料概念来设计具有空间可编程振动响应的表面，从而可以根据需要改变液滴运动的可用景观。此外，将利用超材料与流体运动的耦合能力，设计直观的演示设备，使人们能够用肉眼看到复杂的弹性波现象，使其成为科学推广和教授先进工程概念的理想选择。该项目的技术目标是设计振动超材料，用于对固体表面上的液滴运动进行编程。具体而言，本研究的目的是实现控制策略，允许深度操纵的流体运动时，振动状态，同时保持默认的系统条件下的关闭配置。利用共振超材料，可以调制表面不同区域的振动响应。通过结构设计和激励调谐的适当相互作用，可以选择性地编程在选择区域中的液滴去钉扎的开始，从而根据几乎无限的空间图案阵列在空间上设计液滴运动的可用景观。这样的设计灵活性可以被用来为液滴运动编程各种复杂的逻辑场景，例如基于液滴尺寸的聚类和分离。该研究得到了一系列通过激光测振仪和高速成像进行的桌面实验的支持。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This grant supports fundamental research for controlling the motion of liquid droplets on solid surfaces. The problem of droplet control is relevant for numerous industrial applications, from self-drying surfaces and heat transfer via droplet condensation to water harvesting and biomedical analysis. Therefore, research in this direction can lead to discoveries with vast societal impact. Most strategies for droplet motion control involve doctoring, either chemically or mechanically, the surface that is in direct contact with the fluid, thus altering irreversibly its default properties. This project promotes a different paradigm that exploits the interaction between moving droplets and vibrating surfaces. The project idea revolves around the use of emerging notions of engineering metamaterials to design surfaces with spatially programmable vibrational response that allows to alter the available landscape of droplet motion on demand. In addition, the ability to couple metamaterials with fluidic motion will be exploited to design intuitive demonstration devices that allow visualizing, with the naked eye, complex elastic wave phenomena, making them ideal for scientific outreach and for teaching advanced engineering concepts.The technical objective of the project is to design vibrating metamaterials for programming the locomotion of liquid droplets on solid surfaces. Specifically, this research aims to realize control strategies that allow deep manipulation of the fluid motion when the vibrating state is on, while preserving the default system conditions in the off configuration. With resonant metamaterials, it is possible to modulate the vibrational response available in different regions of a surface. Through a proper interplay of structural design and excitation tuning, one can selectively program the onset of droplet depinning in select regions, thus spatially engineering the available landscape of droplet motion according to a virtually endless array of spatial patterns. Such design flexibility can be leveraged to program a variety of complex logic scenarios for droplet motion, such as clustering and segregation based on droplet size. The investigation is supported by a series of table-top experiments via laser vibrometry and high-speed imaging.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.