Materials Science

Unsteady As She Flows

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Science  21 Feb 2003:
Vol. 299, Issue 5610, pp. 1151
DOI: 10.1126/science.299.5610.1151b

Pattern formation caused by instabilities in thin fluid layers has attracted considerable interest because of the technological importance of thin films, and also because these systems allow for the detection and measurement of interfacial forces. In spinodal or spontaneous instability, pattern formation is driven by the relaxation from an unstable or metastable state once the thin film is heated above its melt or glass transition temperature. Schäffer et al. look at a very different case, where patterns are formed by the flow of heat between two surfaces held at different temperatures. Polymer films develop a characteristic wavelength as columns or stripes rise up to bridge between the two surfaces. Coating one of the substrates with gold led to a far greater change in the patterning than one would expect if surface forces were controlling the morphology. The key driving force appears to be the need for the system to maximize thermal conductivity between the two surfaces, which should only occur with high-molecular-weight polymers. — MSL

Macromolecules 10.1021/ma021080p (2003).

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