Dear MEMS experts,

I am trying to fabricate nanopillars by PDMS. I first make a silicon master with
nano holes. The holes are in depth of 1.5 um and diameter of 200 nm. I try to
fill these holes with PDMS.

PDMS (Sylgard 184) is prepared by the conventional method and poured onto the
template. After peeling off, I found the pillars are much shorter than they
should be, only 200 nm at most. Actually, they look much like in spherical, but
cylindrical shape.

I also observe the cross-section of the master after the release. It seems there
is no residue PDMS inside the master. I am thus wondering if PDMS is succesfully
filled into the hole.

Is that because of the surface tension that makes PDMS stopped from filling into
the holes? I've tried silization for surface treament and degassing for pulling
out the bubble. But they didn't seem much different from the previous work.

Does anyone have similar experience on this?

Experience on PDMS nanopillars in general is welcome as well.

Thank you,

Yun-Ching
Penn State Univ.