The aim of this research is to investigate the physics of particle adsorption and the spontaneous dispersion of particles that occurs when particles come in contact with a fluid-fluid interface. The dispersion of small particles, e.g., flour, pollen, etc., can occur so quickly that it appears explosive, especially on the surface of mobile liquids like water. This interfacial-force-driven dispersion of particles is important because it causes particles sprinkled over a small area to almost instantaneously disperse into a monolayer over an area that is several orders-of-magnitudes larger. While the Weber and Bond numbers, and the contact angle are the important dimensionless parameters that govern the motion of particles normal to the interface, it is not completely understood what parameters govern the lateral motions of the particles. Our main objectives are: (i) use experiments and direct numerical simulations to determine the dependence on important parameters of the speed at which particles disperse, and to quantify the enhancement resulting from dispersion in the rate of spreading on liquid surfaces of small particles including microbes and viruses. (ii) Model the fluid dynamics of the two-dimensional pollination process in hydrophilous plants. (iii) Model the mechanism that causes the breakup and spreading of agglomerates on liquid surfaces. Intellectual Merit. The focus of the past studies has been on understanding the mechanisms by which particles already trapped on fluid-liquid interfaces interact. The proposed study will, for the first time, consider the role of the sudden dispersion, which will improve our understanding of biological processes occurring over the surface of water, developing improved estimates for the rate at which small particles, including microbes and viruses, spread on interfaces, and improving the modeling of processes in the pharmaceutical and food industries that involve breakup and spreading of powders on liquid surfaces. Broader Impacts. This research will be fully integrated with education and outreach, involving graduate and undergraduate students, particularly women and under-represented minorities, with synergistic activities in our courses at the university, and in workshops in NJIT, and BBG educational programs for inner-city pre-college students to encourage then to explore careers in Science, Technology, Engineering and Mathematics (STEM). The proposed work will further our capability to understand and model the role of particles adsorbed at air-liquid and liquid-liquid interfaces which play an important role in many physical and biological processes, e.g., pollination of hydrophilous plants, the spread of microbes and germs on liquid surfaces, and formation of monolayers at fluid-fluid interfaces. This project has the potential to make a significant contribution to the understanding of the physics underlying the mechanisms that have evolved in plants that possess abiotic two-dimensional pollination systems.
