Molecular Dominoes

A press release from the National Institute of Standards and Technology (NIST) uses the above image to describe “the growth of a layer of molecules as they gradually cover the surface of a small silicon rectangle.” Unfortunately, the image doesn’t seem to illustrate much at all.

As usual, I’ll quote the entire caption… “Schematic of the monolayer self-assembly process studied by the NIST/NCSU team. The silicon substrate is approximately 1 x 5 cm in dimensions. The source (left) is a mixture of organosilane (OS) molecules and parafin oil (to control the evaporation rate.) The whole system is enclosed in a Petri dish. The concentration of OS molecules is higher near the source and the ordering process initiates near this region. Molecules behind the advancing self-assembly front are relatively ordered, while molecules ahead of the front are engulfed and incorporated as the front reaches them. The molecules at the leading edge of the front are less ordered and this region becomes broader as the front advances—this is the key phenomenon measured in the experiment.”

Um, right.

Basically, to illustrate such a phenomenon, you’re probably better off using a series (i.e., at least a pair) of images to show, for example, an “advancing self-assembly front.” As it stands (or, in the case of the molecules on the right-hand side, leans), the image doesn’t really reveal the process very well.

Furthermore, if you read the accompanying press release, you find that the actual observations show irregularities in the advancing front, with variations in density that the simple model does not explain. So although the illustration receives top billing with the press release, it doesn’t actually show us what’s interesting about the press release!

An AVI available with the release claims to show “a mean field reaction-diffusion model of the monolayer self-assembly process,” but I couldn’t get the movie to play on my Macintosh.

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