Terry,

You can try 1:5 and 1:20.  Bake the two halves @ 70 degrees C for about 15 and
40 minutes respectively.

You can cut them out and put them together in the way you want them to adhere.
At this point the 1:20 is tacky and difficult to cut.  Thicker pieces of the
1:20 are more difficult and messy.  If possible keep this layer thin and
attached to the mold while it is adhering to the 1:5.  Bake them together
overnight.

The oxygen plazma method is generally easier if you have the equipment
available.

good luck,

Dwayne


Terry Barchfeld  wrote:

I'm quite new to MEMS. I'm a high-school teacher who
is working at the University of Central Florida due to

a NSF Research Experience for Teachers.

In this project, we're making microchannels. The channels
are going to be made out of PDMS. Essentially one-half of
the pipe is made at a time. And then the halves will be
assembled into making an entire pipe. We're hoping that
PDMS will essentially stick to itself so that another
bonding agent doesn't need to be used.

I have found a reference article suggesting that this
can be done. Since PDMS is typically mixed in a 10 to 1
ratio, the article says that if one half of the pipe
is mixed at a lower ratio and the other mixed at a
higher ratio, then the two halves will adhere.

I'm hoping to find some guidance here so that I don't
waste a lot of time to trial and error with this.
Have some of you tried this before? Do you have any
suggestions about mixing ratios that will work?
Also, I've seen that in some cases PDMS is baked to
make it set, yet in other cases PDMS simply hardens
in air over time. Do both methods work? Is one better
than the other?