5_07/2009Lithography: Small 7/2009

The cover picture shows how vacuum-assisted capillary force lithography allows the gap between microstructures to be bridged by partial curing and vacuum-assisted hydraulic filling. In the first step, the surface of molded microstructures is incompletely cured by exposure to ultraviolet light, owing to the high oxygen permeability of the poly(dimethyl siloxane) mold. During the curing process, oxygen inhibits crosslinking by scavenging initiator radicals in free-radical polymerization. Consequently, a small portion of the base microstructure (<4 µm) is molded to create a monolithic bridge structure by simply applying a nanoscale mold under a slight pressure (&ap;0.1–0.5 bar) with the impression of channels, meshes, or circles without collapse. In the second step, a low vacuum facilitates migration of the partially cured polymer into the void spaces imposed by the nanoscale mold, thereby forming a dual-scale bridge structure. For more information, please read the Communication “Fabrication of Monolithic Bridge Structures by Vacuum-Assisted Capillary-Force Lithography” by K. Y. Suh et al. beginning on page 790.

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