Dear Tsoll Doiiu,

what are the sizes of microchannels? Height of 20um on one side and 200 um on
other side, i could understand, what are the widths of the channels? If you
are looking for 200 um wide channels, it is easy to micromill by fine
milling tools mechanical holding the job to whatever angle you want.
Initially keep the base material / substrate with that angle in a dish and
pour PDMS on the substrate, it will settle to whatever angle you want as the
substrate itself has slope. Use vibration free place to work.
Then place this finished substrate horizontal plate in milling machine (PCB
milling machine). Program the machine to move over 4 cm and you will find
microchannel with slop having 5mrad angles as you desired.
same principle you may use for 35-40 degree microchannels.

MAY I KNOW THE APPLICATION?
Nabhiraj
VECC
India


On Mon, Feb 28, 2011 at 8:13 AM, Tsoll Doiiu  wrote:

> 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!