Nanomolding of PEG-based hydrogels with sub-10-nm resolution.

A simple, soft nanolithographic method is used to fabricate sub-10-nm structures on star polyethylene glycol-based hydrogels and perfluoropolyether-based materials. Very small features, for example, gold nanoparticles of size approximately 8 nm with an interparticle distance of approximately 100 nm, are successfully reproduced from a hard silicon master into both elastomers. Scanning force microscopy is used to investigate the replicas, and the original hexagonal pattern of the nanoparticles is clearly recognized. In addition, both replicas are usable as secondary, soft molds yielding positive copies of the primary, hard master. The results presented here show similar replication capabilities for both elastomers despite the markedly different properties of the precursors. Moreover, the hydrogel material can be easily peeled off from both soft and silicon masters without the need for surface treatment. The procedure allows nanopatterning of a biocompatible material over large areas, which is a useful tool to investigate cellular responses to defined nanotopography.