Collaborative Research: Functional morphology of a high-efficiency filtration mechanism identified in manta rays

螳螂和魔鬼鱼是一种大型鱼类，它们通过吞噬大量海水，用特殊的过滤器结构提取浮游生物，并通过鳃缝隙排出过滤后的水。这些动物利用一种高效的过滤机制--弹跳分离，这与之前描述的生物或工业过滤过程不同。该项目将使用多学科方法来研究这一独特系统的流体动力学和过滤机制。这个项目将描述过滤结构的解剖结构，确定结构的形状如何影响过滤器周围的流动，并确定由此产生的流动模式如何影响颗粒过滤。这项工作将为生态上重要和受威胁的动物群体的生理学提供关键的见解。此外，从缓解大规模环境污染事件到常规废水处理，都需要改进过滤策略，以用于各种应用。该项目将阐明一种新的高效过滤过程的机理，并有相当大的潜力导致先进的、生物灵感的过滤系统。这项研究还将为本科生、研究生和博士后科学家提供有价值的培训，并支持吸引学龄儿童参与生物力学和生物灵感工程的活动。长期以来，人们一直认为铲子起到了筛子过滤器的作用，只是简单地捕获了大于孔径的颗粒。然而，最近的研究表明，RAKER利用了一种独特的过滤机制--弹跳分离，在这种机制中，复杂的流场会导致浮游生物颗粒从过滤器表面反弹，并集中在口腔腔内。这种过滤过程具有几个有利的特性，包括它可以有效地分离小于孔径的颗粒，高度抗堵塞，并且具有低的流体动力阻力。本项目将研究这一机制背后的流体动力学过程以及影响其性能的形态因素。这项研究采用了多管齐下的方法，包括解剖学研究(微型计算机断层扫描)、实验流体力学(粒子图像测速仪和过滤效率测量)和理论建模(计算流体动力学)。目标1将研究过滤器表面的小规模物理过程，确定单个浮游生物颗粒如何与过滤器相互作用，以及这种相互作用如何受到过滤器形态的影响。目标2将研究在口腔中形成的大尺度流动模式，并将确定这种流动如何影响过滤机制。AIM 3将利用对这些过程的理解来创建和优化生物灵感工程过滤系统。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Mantas and devil rays are large fishes that feed by engulfing massive volumes of seawater, extracting plankton with a specialized filter structure, and expelling filtered water through the gill slits. These animals utilize a highly-efficient filtration mechanism, ricochet separation, that is distinct from previously-described biological or industrial filtration processes. This project will use a multidisciplinary approach to examine the fluid dynamics and filtration mechanics of this unique system. This project will characterize the anatomy of the filtering structure, identify how the shape of the structure affects the flow around the filter, and determine how the resulting flow patterns affect particle filtration. This work will provide critical insights into the physiology of an ecologically important and threatened group of animals. In addition, there is substantial need for improved filtering strategies for use in applications ranging from mitigating large-scale environmental contamination events to routine wastewater treatment. This project will elucidate the mechanics of a novel and highly-efficient filtration process, and has considerable potential to lead to advanced, bioinspired filtration systems. This research will also provide valuable training for undergraduate, graduate, and post-doctoral scientists and support activities to engage school-aged students and expose them to biomechanics and bioinspired engineering.The filtering apparatus of mobulid fishes (mantas and devil rays) is a highly-specialized gill-raker structure. It has long been believed that the raker functioned as a sieve filter, simply trapping particles larger than the pore size. However, recent work has shown that the raker utilizes a unique filtration mechanism, ricochet separation, in which complex flow fields cause plankton particles to recoil off the filter surfaces and become concentrated within the buccal cavity. This filtration process has several favorable properties including that it efficiently separates particles smaller than the pore size, is highly resistant to clogging, and has low hydrodynamic resistance. This project will examine the fluid dynamic processes underlying this mechanism and the morphological factors that influence its performance. This research uses a multipronged approach that includes anatomical studies (micro computed tomography), experimental fluid mechanics (particle image velocimetry and filtration efficiency measurements), and theoretical modeling (computational fluid dynamics). Aim 1 will investigate the small-scale physical processes at the surface of the filter, identifying how individual plankton particles interact with the filter and how this interaction is affected by the morphology of the filter. Aim 2 will examine the large-scale flow patterns that develop in the mouth and will determine how this flow influences the filtration mechanics. Aim 3 will use an understanding of these processes to create and optimize bio-inspired engineered filtration systems.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.