Behavior of fluids in nanoscopic space

摘要

Geometry plays a fundamental role in the evolution of a class of nonequilibrium systems called cellular structures. The evolution of stable cellular structures is characterized by universal or system-independent statistical distributions, which possess scaling properties. These systems play important roles in various technological applications. The uses of foams range from transport of granular media in pipes to fire suppression and explosion attenuation. Polycrystalline thin films are used in electronic devices such as MOSFET transistors, magnetic storage media, and conductors. The technological performance of these materials depends on the characteristics of their inherent cellular structure. For example, the strength of a polycrystalline metal under stress depends on the average grain size. The phenomenon of elec-tromigration, which occurs along grain boundaries in thin film conductors, is responsible for their electronic noise and eventual failure. Mean times to failure have been shown to depend on mean grain size and, surprisingly, on grain geometry. Controlled cellular structure formation in novel materials is, however, inherently interesting. The work by Chakrapani et al. (9) in a recent issue of PNAS demonstrated the formation of cellular structures out of vertical carbon nanotube arrays on silicon that can be floated off the substrate.