Applied Physics

Patterns of Light

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Science  11 Nov 2005:
Vol. 310, Issue 5750, pp. 947
DOI: 10.1126/science.310.5750.947a

Polymers have found use in the fabrication of optoelectronic and magnetic devices and as inexpensive, flexible, and lightweight templating materials. Patterns are created through the solvent or by thermally driven phase separation of a blend of homopolymers or block copolymers. One problem with using homopolymers is that it is difficult to create large areas that are defect-free yet retain precise patterning on a much smaller scale. Block copolymers are better for achieving this, but changes in the pattern can require the synthesis of a new copolymer.

Travasso et al. describe an alternative method for creating materials that are spatially patterned on the submicrometer scale and are defect-free on the millimeter to centimeter scale. They consider a ternary A/B/C blend of immiscible polymers. Polymers A and B are chosen so that the extent to which they interact or separate can be tuned by exposure to light. Initially, a uniform light source is used to create a homogenous mixture of A and B. By rastering over the sample with a higher-intensity secondary beam, defects in the local pattern can be annealed out. Polymer C is chosen to migrate to areas illuminated by the higher-intensity light. Thus, it is possible to write regions of polymer C onto a spatially patterned AB film. — MSL

Langmuir 10.1021/la052511a (2005).

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