Lubrication Collapse: A Novel Mechanism for Micro-Particle Self-Assembly

Self-assembly is a “bottom up” materials fabrication method often seen in nature, which is responsible for some of the most elegant and functional structures known to man. Self-assembly will naturally occur amongst nanoparticles, where Brownian motion drives the nanoparticles to find the most thermodynamically favorable configuration. However, Brownian motion does not induce self-assembly among larger particles, such as microparticles or granular particles, on an experimentally relevant time scale. We have developed a method to organize microparticles using sonication to artificially thermalize particles and induce self-assembly even in highly dilute, untemplated systems. Our hypothesis is that a novel phenomenon we call “lubrication collapse” is responsible for this observed organization. Lubrication collapse arises from the spike in energy dissipation caused by lubrication forces between particles as they pass closely to one another. This poster describes our work in characterizing lubrication collapse using microscopy to observe the effects of sonication on solutions of dilute microparticles.