See this paper for some good tips on bonding and surface
preparation/cleaning:

*Three-dimensional micro-channel fabrication in polydimethylsiloxane
(PDMS) elastomer*
Jo, B.-H.; Van Lerberghe, L.M.; Motsegood, K.M.; Beebe, D.J.;
Microelectromechanical Systems, Journal of

Volume 9,  Issue 1,  March 2000 Page(s):76 - 81
Digital Object Identifier 10.1109/84.825780

I do the HCl cleaning of every PDMS sample before bonding, regardless of
how long it's been off the mold, and it works every time.

-Joe Grogan



Gareth Jenkins wrote:
> Bonding should occur immediately.
> However, I find the process very unreproducible so if anyone has any
> tips to improve the chances of success please let us know.
> Last week I managed to get very good bonding without any problems but
> yesterday it no longer worked.
> I use a PlasmaPrep II Plasma Etcher from SPI. This unit doesn't
> provide much control over the plasma conditions which may be part of
> the problem.
> What is the best way to prepare the surface of the glass?
> I also wonder if it is important to ensure the PDMS is thoroughly
> cured prior to bonding?
> Best regards
>
> Gareth
>
> g.balsubra manian wrote:
>> Guys.,
>>
>> What is the bonding time for oxidised PDMS with the
>> oxidised glass.
>>
>> Whether bonding occurs immediately after the surfaces
>> get into contact.