Collaborative Research: bubble impacting a curved surface: a sustainable way to sanitize produce

在广泛的工业应用中，使用微气泡清洁实践已被证明是一种可持续和环保的卫生方法。当气泡流在表面上撞击和滑动时，由于气泡产生的强大力量，表面上的污染物可以被清除。像水果和蔬菜这样的农产品的气泡清洗尚未得到广泛的研究。由于气泡流可用于去除农产品表面的致病微生物并使其失活，因此这种方法有可能将每年影响数百万人的食物中毒病例降至最低。理解气泡与表面的相互作用是具有挑战性的，因为这一过程发生在多个长度尺度上，其中气泡的变形和轨迹发生在一毫米量级，而气泡和固体之间的液体膜仅涉及几百纳米。这个研究项目可能会导致一种对生水果和蔬菜无害的消毒过程的新技术。该方法甚至可以应用于半导体制造等其他技术过程。该研究项目是研究生和本科生进行前沿研究的训练基地。研究小组将制作一个关于如何制作气泡流水果清洁剂的教学视频，并通过康奈尔大学的社交媒体和网络渠道分享。农民们可以通过视频学习如何组装自己的泡沫清洁剂。这个合作研究项目的目标是研究气泡沿表面撞击和滑动的宏观和微观动力学。这项研究将阐明气泡如何从表面去除颗粒污垢或生物微生物。尽管气泡在许多工业过程中用于清洁各种表面，但对倾斜或弯曲表面上的气泡流动的研究有限。研究小组将使用高速摄影、粒子图像测速、压力分布测量和干涉测量显微镜技术来表征剪切和法向应力，以及气泡撞击表面时不对称薄液体膜的厚度分布。本课题包括三个方面的工作：1)表征气泡在表面上的宏观动力学特性，并将其描述为倾角和曲率的函数；2)实验测量和计算模拟近表面气泡的剪切应力和界面变形；3)利用农产品对细菌的颗粒清除和保留性能进行测试。这项研究的结果将导致对气泡消毒技术中潜在的流体力学的理解。该奖项反映了美国国家科学基金会的法定使命，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。

Cleaning practices using microbubbles have been proven to be a sustainable and environmently benign sanitation method in a wide range of industrial applications. When a stream of bubbles impact and slide on a surface, contaminants on the surface can be removed due to the strong force generated by the bubbles. Bubble-cleaning of agricultural produce like fruits and vegetables has not been studied extensively. Potentially, this method could be used to minimize cases of food poisoning affecting millions of people every year, since bubble streams could be used to remove and inactivate pathogenic microorganisms from produce surfaces. Understanding the bubble-surface interaction is challenging due to the fact that the process transpires over multiple length scales, in which bubble deformation and trajectory occur on the order of a millimeter while the liquid film between the bubble and solid involves only a few hundreds of nanometers. This research project could lead to a novel technology for an environmentally benign sanitization process for raw fruits and vegetables. The method could even be applied to other technological processes such as semiconductor manufacturing. The research project serves as a training ground for graduate and undergraduate students to perform cutting edge research. The research team will make an instructional video on how to make a bubble-stream fruit cleaner and share it via social media and web-based outlets at Cornell University. Farmers could use the video to learn how to put together their own bubble cleaners.The goal of this collaborative research project is to investigate both macro- and microscopic dynamics of a bubble impacting and sliding along a surface. This research will elucidate how bubbles remove particulate dirt or biological micro-organisms from a surface. There are limited studies in bubbly flows on tilted or curved surfaces, even though bubbles are used to clean various surfaces in many industrial processes. The research team will use high-speed photography, particle image velocimetry, pressure distribution measurements, and an interferometry microscopy technique to characterize shear and normal stresses, as well as thickness profiles of an asymmetric thin liquid film while bubbles impact on a surface. The research project involves three tasks:1) characterizing the macroscopic dynamics of a bubble on a surface as a function of the inclination angle and the curvature; 2) experimentally measuring and computationally modeling the shear stress and interfacial deformation of a bubble near the surface; and 3) testing the particle-scavenging and retaining performance of bacteria using agricultural products. The outcomes of this research will lead to an understanding of the underlying fluid mechanics in bubble sanitization technology.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.