Fabricating precise biomolecular structures at extremely small scales is critical to the progress of nanotechnology and related fields.
Traditionally, one of the ways this has been accomplished has been through the use of rubber stamps with tiny features similar to those used by children in play, but detailed at the microscopic scale which are covered with molecular "inks" and then stamped onto substrate surfaces, creating a molecular patterns. But when using this technique at the nanoscale, molecules tend to diffuse on the surface both during and after stamping, blurring the patterns.
To address this problem, researchers at UCLA have turned this conventional "soft lithography" process on its head: Instead of using a stamp to transfer molecules onto bare surfaces, they have used chemically treated stamps to remove molecules already in place on gold substrates, essentially peeling away select molecules through chemical bonds to create precise patterns measuring just a few molecules across.
The new process, called chemical lift-off lithography (CLL), results in higher-resolution patterning and avoids the blurring problems of earlier techniques.
The findings are published Sept. 20 in the journal Science. The research was supported by the U.S. Department of Energy and the Kavli Foundation.
The stamp used in the new process is molded by using a "master" made with more sophisticated and expensive tools than those used in making rubber stamps for offices and children, but the stamps can be used over and over again. Between each use, they are simply reactivated by an oxygen plasma.
The chemical bonds formed at the stampsubstrate interface are sufficiently strong to remove not only molecules in the monolayers but also one layer of gold atoms from the substrate. This observation settled a long-running discussion over whether, for such monolayers, goldgold bonds break more easily than moleculegold bo
|Contact: Jennifer Marcus|
University of California - Los Angeles