Hi

I already tried the HCl cleaning suggested by that paper but thanks anyway!
Maybe I'll also try leaving it for a while on a hotplate as I always
tend to test the bond a minute or so later.
However, I'm fairly sure my problem is my unreproducible plasma
conditions. In Beebe's paper they found optimum values for RF power and
pressure but I have no control over these in my plasma and am not even
sure what they are (probably 50-100W RF power but there is no pressure
gauge).
I have a feeling I "over expose" the surfaces as sometimes the bonding
is much worse than if no treatment was done - normally you would expect
some adhesion between clean glass and fresh PDMS but there are instances
when it doesn't even bond well enough to prevent it falling off if I
turn it upside down. I have tried shortening the time but never seem to
find a reliable process.
Does anyone know the chemistry of what happens if it gets over-cooked?
I know there is the generation of silanol groups which allows the
bonding to occur but there must be something else which inhibits the
bonding if it is over exposed.
Maybe if I know what it is I can do something to prevent it.
Best regards

Gareth

Joseph Grogan wrote:
> 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