Yun-Ching,

Have you tried other type of PDMS. For example, here is a paper from
Whitesides group titled "Improved Pattern Transfer in Soft Lithography Using
Composite Stamps". In this paper, they used hPDMS for very small pattern
transfer. It is probably of your interest.

Peng Peng
Graduate Research Assistant
Department of Mechanical Engineering
University of Minnesota
111 Church Street S.E.,
Minneapolis, MN 55455
Tel: (612) 626-2010