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Soft Lithographic Approaches for Patterning Silicon Surfaces


Among the many individual accomplishments resulting from IGERT training has been the development of soft lithographic approaches for patterning silicon surfaces, work conducted by chemistry trainee Alex Shestopalov.

The challenges to solution of this important problem were many. First, poly(dimethyl)siloxane (PDMS) elastomeric stamps commonly used for soft lithography are not amenable to functionalization, removing them from consideration for catalytic lithography. Alex developed a novel polyurethane material that is elastomeric, can be functionalized with a wide variety of moieties, and allows construction of features with unusually high aspect ratios, a key attribute for the transfer of nano-scale features. Second, Alex required an acid catalyst to transfer patterns to surfaces. Previous reports in the literature of acid-catalyzed pattern transfer showed only modest success and produced incomplete transfer. Alex developed a novel sulfonic acid catalyst that produces exceptional pattern transfer in remarkably short time periods (seconds). Third, Alex required robust chemistries for the functionalization of surfaces: although functionalization of silica surfaces has been reported, none produced the dense, uniform patterns required for the work here. Working closely with the Clark group in Engineering, Alex developed a novel procedure for cleaning, activating and functionalizing silicon surfaces.

In conjunction with previous work on stamp and catalyst development, these studies have provided a robust reliable approach to soft lithography on silicon surfaces. The first two components of this work have already appeared in the literature, and the final report detailing catalytic patterning on silica will be submitted for publication this month.

Address Goals

This presents the state-of-the-art for silicon-based (hard materials) technologies.