PDMS-glass bonding

[Shramik Sengupta]

Hi guys,

I am having trouble with bonding PDMS with glass in an oxygen plasma. I
am trying to achieve the adhesion with plasma oxidation and application of
pressure for 5 min to seal the PDMS and glass. The bonding occurs only at
certain spots, if it happens, that is. I have tried a variety of plasma
conditions: pressure - 75 to 300 mTorr, flow rate- 20 sccm to 50 sccm, time
- 30 seconds to 7 minutes. I clean the PDMS substrate and the glass slide
with alcohol and blow dry them with N2 gun. I have also tried peeling off
the PDMS from the mold right before the O2 plasma step and feeding the
PDMS into the plasma. I have tried using precleaned glass slides. None of
these work. Maybe I am missing a trick. I am not sure if there is a
heating step after pressing the PDMS and glass together post oxidation.
Any guidance would be very helpful.

Thanks

Arun.

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[Rundel, Jack]

Arun,

Here are the parameters that I follow for O2 plasma bonding of glass/PDMS:
- 200 mTorr O2
- 400 W plasma
- 15 seconds exposure

I DO NOT clean the PDMS. It does not seem to matter whether it is fresh or several months old.

I DO clean the glass slides with methanol.

The two surfaces bond irreversibly within seconds after contact.

It seems that the bonding fails mostly due to over exposure. Try cutting your time even more.

Jack Rundel
Ph.D. Candidate
Department of Chemistry
Oregon State University

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[Taegon Kim]

Hi Arun.

I had a same problem. How much power applies to treat plasma?
If you apply 10 sec for 100 W or 1 min for 30 W, it is possible to bond, but
it depends on system.
I succeeded 20~30 W, 1 min in ICP and CCP type plasma system.
Using Harrick's basic plasma cleaner which has max. 18 W it is possible to
bond it during 1 min treatment.
It is need to treat PDMS and glass at the same time.
If not it is hard to bond in my experience.

Tae-Gon Kim, Ph.D. Student

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[Vladimer Michael]

Arun-

You should also leave the pdms and glass undisturbed for at least 1
minute after putting the two in contact. I've found that the
"instantaneous" seal actually takes a little while to form. If you're
overzealous in checking the bonding you'll ruin it before it happens.

Michael
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[Adrian Brozell]

Hey All,

You should be sure to oxidize your glass when doing the bonding. You
can do this chemically with a Phirana etch solution (4 sulfiric acid : 1
hydrogen peroxide) for 3 minutes right after mixing above 100 C.

Adrian
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