Hi Tsoll,

the only reasonable way I know of making such sloped channels is by
mechanical micromachining the master, e.g. in PMMA. Precision machining
nowadays can make you extremely precise structures (lateral and vertical
geometry +-1 µm), it usually takes a quite expensive bit of machinery to do
so (e.g. Kern, Precitech, Kugler) but the results are quite amazing. We
regularly use precision machining for mold inserts for injection molding of
microfluidic channels. The critical bit might be surface roughness, which is
higher compared to lithographically defined channels but there are ways of
mechanical or chemical polish.

With best regards
Holger

--
Dr. Holger Becker
microfluidic ChipShop GmbH
Carl-Zeiss-Promenade 10
D-07745 Jena
Germany
Tel. .+49 (0) 36 41 347 05 80
Fax: +49 (0) 36 41 347 05 90

Geschäftsführerin: Dr. Claudia Gärtner
Sitz der Gesellschaft: D-07745 Jena, Germany
Amtsgericht Jena: HRB 209251
USt.-IdNr.: DE 221812444


-----Ursprüngliche Nachricht-----
Von: mems-talk-bounces+hb=microfluidic-chipshop.com@memsnet.org
[mailto:mems-talk-bounces+hb=microfluidic-chipshop.com@memsnet.org] Im
Auftrag von Tsoll Doiiu
Gesendet: Montag, 28. Februar 2011 03:44
An: mems-talk@memsnet.org
Betreff: [mems-talk] Sloped microchannel

Hello MEMS community!

Does anybody have an idea how to prepare a sloped microchannel in PDMS?

Initially I've tried to do like this: spin-coat PR on Si wafer, than hold
the wafer vertically,
for like a 1h-4h, hoping  that gravity will make gradient in PR thickness,
than make UV.
Unfortunatelly, I did not achieve the slope. I used SU 25 for this.

Is there some other way to prepare oblique microchannel?
The desired sizes are: length - approx. 4cm, initial heigth 200um, final
heigth 20um.

I want to make like this:
http://img193.imageshack.us/img193/5440/46006411.jpg

Also the ways to prepare slopes with angles 30-70 degrees are strongly
wanted.

Thanks in advance!