Piranha will make things much worse. The PDMS isn't sticking to the
wafers because they're dirty. Piranha will temporarily decrease the
contact angle (the opposite of what you want).

If biocompatibility is your primary concern, you can just dip-coat in
a Teflon FEP emulsion (and bake), or spin-coat Teflon AF (and bake).
Both of those will solve your problem, but they'll leave micron scale
defects on the mold (dots in the case of FEP, or ripples, in the case
of Teflon AF).

If you're using PDMS microchannels in the standard way though, you
don't need to worry about FDTS toxicity. When you plasma clean before
bonding, you'll blast whatever unbonded FDTS residue might be there.
There are 100's of papers out there where people culture cells in PDMS
chips. There are biocompatibility issues with using PDMS (absorption
of small molecules -- see Beebe's work -- water, etc) but toxicitiy of
the mold release isn't one I've ever heard of.

- Kevin

On Mon, Mar 29, 2010 at 8:15 AM, Nathan McCorkle  wrote:
> Would piranha treatment work? I am concerned with biocompatibility.
>
> On Sun, Mar 28, 2010 at 4:00 PM, Harsh Sundani  wrote:
>> Nathan,
>>
>> Refer to
>>
>> E. Leclerc, Y. Sakai,
>> and T. Fujii, “ Cell culture in 3-Dimensional microfluidic structure of
PDMS,”
>> Biomedical Microdevices, vol. 5, pp. 109-114, 2003
>> - Harsh.D.Sundani.
>
> --
> -Nathan McCorkle