Using UV Ozone to Bond PDMS to Glass
I talked with Jim last Friday about a second possible dialysis system using PDMS bound to a glass cover slip. I made a batch of PDMS and let it cure at room temperature over the past few days. Jim had suggested I try bonding the PDMS to a glass cover slip using the UV/Ozone system on the third floor clean room. Today I used the protocol posted online to run an experiment to try to form the PDMS-glass bond. I set the temperature to 25C and let the reaction (with “heat” and “UV”) run for 5 minutes followed by a 10 minute “rest period” with continued flow of recycled ozone as suggested by Tom. The results indicated no bonding between the PDMS and the glass. I read a few papers online and they seem to indicate similar results when the PDMS mixture is made at the suggested 10:1 ratio of elastomer base to curing agent respectively. I did read of one group having success when they changed the ratio to 3:1 of base to curing agent. I think I am going to give this a try and hopefully I will get some better results.
I hope I haven’t sent you down the wrong path. I’m pretty sure I’ve been told ‘plasma’ treatment bonds PDMS to glass – I don’t know if the UV/ozone system is generating the right type of plasma.
I have done plasma bonding of PDMS to glass at Drexel, if we have access to the equipment I can offer some insight and help out.
From what I’ve read, I think process temperature is the knob you should be turning. I would suggest running the stage heater at 80 C for 15 minutes and then flow ozone for a few minutes. Even better would be to heat up to 100 C but I’m not sure what the max temp rating is for the ozone system.
Here’s the article I found: PDMS bonding
As for the “right” kind of plasma, refer to this post by our friend Bill Moffat: Ozone vs. O2 plasma
If the ozone doesn’t work, we can throw it into the sputter system.
Just to clarify – you are running the ozone treatment on both binding surfaces separately, then putting them together ASAP, correct? I just want to make sure you are not putting them together first, in which case the ozone never would never touch the binding surfaces and never bind them. The time between treatment and bonding is critical and highly dependent on the humidity.
Check to make sure the PDMS surface is perfectly planar – if not, it will never bind.
I’m not sure if ozone works for this purpose. Without bombardment from a plasma, I’m not sure how many surface radicals will be produced. Are you using a protocol from a paper or some other reference for bonding?