ABSTRACT

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.

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