When small particles (e.g., flour, pollen, etc.) come in contact with a liquid surface, they immediately disperse. The dispersion can occur so quickly that it appears explosive, especially for small particles on the surface of mobile liquids like water. This explosive dispersion is the consequence of capillary force pulling particles into the interface causing them to accelerate to a relatively large velocity. The maximum velocity increases with decreasing particle size; for nanometer-sized particles (e.g., viruses and proteins), the velocity on an air-water interface can be as large as Ϸ47 m/s. We also show that particles oscillate at a relatively high frequency about their floating equilibrium before coming to stop under viscous drag. The observed dispersion is a result of strong repulsive hydrodynamic forces that arise because of these oscillations.adsorption ͉ capillarity ͉ fluid-fluid interfaces ͉ monolayers T he following experiment can be easily performed in any reasonably well-equipped kitchen. Fill a dish partially with water, wait for a few minutes for the water to become quiescent, and then sprinkle a small amount of wheat or corn flour onto the water surface. The moment the flour comes in contact with the surface it quickly disperses into an approximately circular shaped region, forming a monolayer of dispersed flour particles on the surface (Fig. 1A). The interfacial forces that cause this sudden dispersion of flour particles are, in fact, so strong that a few milligrams of flour sprinkled onto the surface almost instantaneously covers the entire surface of the water contained in the dish.The above experiment can be performed using other finely granulated powders (e.g., corn flour, salt, sugar, sand, etc.) or even small seeds, such as mustard and sesame seeds and pollen (Fig. 1B). The tendency of powders to disperse, however, varies. The fact that salt and sugar dissolve in water is not important in this experiment, because the dispersion occurs at a time scale that is much smaller than the time taken by particles to dissolve. Also, the speeds with which particles disperse increases with decreasing size.In 2003, we did experiments on the migration of small particles sprinkled onto a liquid surface. When sand was sprinkled on water in a Petri dish, it first dispersed violently at large speeds, which was followed by a phase that was dominated by attractive lateral capillary forces during which particles slowly came back to form monolayer clusters. The same dynamics were observed for more viscous liquids except that the dispersion speeds were smaller. The fluid dynamics of the attractive phase are well understood (1-7), but to our knowledge, there is no mention in the past studies of the initial violent dispersion despite the fact that this dispersion is ubiquitous, and occurs for many common liquids and particles. ResultsVertical Acceleration of a Particle. In this article, our focus is on the first (dispersive) phase. We show that when a particle comes in contact with a liquid surface, it experiences...

We present a technique that uses an externally applied electric field to self-assemble monolayers of mixtures of particles into molecular-like hierarchical arrangements on fluid-liquid interfaces. The arrangements consist of composite particles (analogous to molecules) which are arranged in a pattern. The structure of a composite particle depends on factors such as the relative sizes of the particles and their polarizabilities, and the electric field intensity. If the particles sizes differ by a factor of two or more, the composite particle has a larger particle at its core and several smaller particles form a ring around it. The number of particles in the ring and the spacing between the composite particles depend on their polarizabilities and the electric field intensity. Approximately same sized particles form chains (analogous to polymeric molecules) in which positively and negatively polarized particles alternate.

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Recently, the initiative to bring down the continuous increase in the level of greenhouse gas emissions has widely spread in many countries not only because of the stringent emission norms but also the rising fuel prices which have led to utilize renewable energy sources, more. When it comes to the different forms of renewable energy available, solar energy is considered to be the best option due to its abundant availability in nature. Still, there are a few hurdles to first get over when dealing with solar energy. For instance, the lack of effective technology has caused solar energy to be a costly endeavor and there are issues involved in the process of conversion of solar energy into useful forms of energy. Due to the recent developments in technology, the application of phase change materials (PCM) has become an attractive method to store solar energy. Among various sugar alcohols, Erythritol is the one which is higher in latent heat, more thermally stable, non-toxic, inexpensive, and easily available. In this paper, the phase change material, Erythritol (C4H8O4) is utilized to harness the solar energy and a novel method of transporting the solar energy from the location it was harnessed to a location where it can be utilized is also shown. The variation in the rate at which the solar energy is harnessed is also shown on five different days when the direct solar radiation was high and low on the location of experiment.

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