On Apr 7, 2005, at 3:05 PM, [email protected] wrote:

> Hi, everyone,
>      I am facing an alignment problem associated with PDMS shrinkage.


Yes, this is common.
Here are a couple of references:
http://thebigone.caltech.edu/foundry/mask-design.htm
Quoting from that Caltech Foundry web page:
"g) Any pattern corresponding to a thick layer of PDMS that is peeled
off the mold for subsequent alignment and bonding onto a patterned thin
layer should be scaled up by 1.5% (a factor of 1.015) to compensate for
the shrinkage of the PDMS after peeling."

They have some other useful PDMS device design information at:
http://thebigone.caltech.edu/foundry/design-rules.htm

Another shrinkage reference:
  Anderson, J. R., Chiu, D. T., Jackman, R. J., Cherniavskaya, O.,
McDonald, C., Wu, H., Whitesides, S. H., Whitesides, G. M., Anal. Chem.
2000, 72, 3158–3164.

Lower cure temp. (40 deg C) may reduce shrinkage according to this
reference:
Jin-Sung Kim Daniel R. Knapp, Miniaturized multichannel electrospray
ionization emitters on poly(dimethylsiloxane) microfluidic devices
Electrophoresis 2001, 22, 3993–3999 3993

Jim Beall
National Institute of Standards and Technology
Quantum Devices Group
Mailcode 817.03
325 Broadway 1C-110
Boulder, CO 80305-3328
303-497-5989
303-497-3042 (fax)