Petru--
PDMS requires water vapor from the air to cure.
Looking at information on PDMS from Dow Corning at
http://www.dowcorning.com/content/publishedlit/52-1088-01.pdf  for a
different PDMS,
they say that the humidity should be 10-50%. Less is bad, and that also say
that more might be bad.
Perhaps the humidity in your lab decreased or increased with warmer
summertime weather?
I've seen similar issues with photoresist suddenly having poor adhesion.
You could buy an inexpensive hygrometer to monitor the humidity.
    --Kirt Williams

----- Original Message -----
From: "Petru Lunca Popa" 
To: "General MEMS discussion" 
Sent: Tuesday, May 27, 2008 1:15 PM
Subject: [mems-talk] my PDMS is not sticking anymore on SIO2

> Starting from 3 weeks ago I have problems with sticking PDMS on Silicon
> Oxide.
> I checked all again. I didnt change any parameters but sudenlly
> stopped to stick . I check the expiration date and all parameters
> Any ideea what can be ?
> I am using Sylgard 184 from Dow Corning  10 to 1 ratio between part A and
> B