Patterning Thin Films with Water

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Science  01 Mar 2002:
Vol. 295, Issue 5560, pp. 1603
DOI: 10.1126/science.295.5560.1603c

Thin films can be assembled from alternating layers of polymer materials. When polyelectrolytes are used, the films are stabilized by electrostatic interactions. Weak polyacids that are stabilized via hydrogen bonds can also be used at low pH where the polyacids are not ionized. Yang and Rubner show that thermal treatment of layered poly(acrylic acid) and polyacrylamide generates imide cross links that serve to stabilize the films to physiological solutions (pH 7). Alternatively, the imidization reaction can be triggered by light after first adding a top layer containing a free-radical initiator. Patterns could be introduced in these films by using water as the etching or wash agent. For features in the 200-micrometer range, ink jet printing was used to select the areas to be removed; the printed sections that had been exposed to pH 7 water became ionized and did not react on heating. For smaller features, photolithography was used, and the masked areas, shielded from light, were then removed upon washing. — MSL

J. Am. Chem. Soc. 10.1021/ja017681y.

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