I have a structure on PMDS (produced by peeling off PDMS from SU8 mould). Now I would like to pour PDMS on this structured PDMS (which is now act as mould) and peel off it so that the structure from on PDMS. But when I do that PDMS bonding is being done (Of course, its inevitable). Is there any way out?
Yes, you can treat the PDMS that is to be your mold with a number of release agents. The method that I prefer is to plasma (or corona) treat the PDMS and then expose to a fluorocarbon terminated chlorosilane in a vacuum chamber. My preference is Trichloro(1H,1H,2H,2H-perfluorooctyl)silane, but there are other options as well. I use a custom built (by a couple of summer high school students) chamber that allows me to do both treatments without breaking vacuum, but you can do it in a glass desiccator with a couple drops of the silane solution on slide close to your PDMS. If you leave it in too long, the PDMS may get cloudy. Soak it in DI water for a while after treatment to get rid of the HCl and then put it in the oven for an hour to get rid of the cloudiness.
@ Ron Reiserer. Thank you very much for your detailed answer. Delighted.
Another question. What if we don't plasma treat and go for silane coating directly on PDMS?
You'll need to do some sort of surface treatment, otherwise there will be no reactive groups on the surface of the PDMS. I have successfully used 6M sodium hydroxide to oxidize PDMS via liquid only treatment.
You can easily do that by treating your PDMS master with Sigmacote as follow:
A. PDMS/PDMS molding
Here, we describe the protocol to perform PDMS/PDMS molding which may be proven very useful in various occasions.
Protocol
1. Plasma treat the PDMS template for 20s
2. Immediately immerse the PDMS template in Sigmacote
Note: It may be wise to pour a few mL of Sigmacote in a 50mL falcon tube and shake it to cover the entire plasma treated PDMS template. For PDMS piece that are too large to fit in a falcon tube, use a pipet Pasteur to dispense the sigmacote uniformly all over the PDMS template.
Attention! The PDMS template may be deformed during this procedure but will recover its initial shape after drying for a couple of hours.
Attention!! Sigmacote will release plasma bonding, thus do not treat PDMS constructs that were plasma bonded.
3. Let the PDMS dry on air
Note: Sigmacote being toxic, this procedure must be held under a chemical flow hood.
4. The sigmacoted PDMS template may now be used for standard replica molding
Note: The sigmacoted PDMS template may serve for multiple rounds of replica molding, thus pay attention not to destroy it during demolding.
Hello Ron,
I am doing the surface treatment with same protocol you mentioned above by using Trichloro(1/H/,1/H/,2/H/,2/H/-perfluorooctyl) silane.
But After Silanization on PDMS, I am getting some surface roughness (sort of surface irregularities ). Could you please suggest me to get rid of this or should I need to do some post process treatment also..?
thnakx in advance.
Hey Charchit,
I think you should try using shorter times of modification (1-3 hours) or lower volumes of the silane (10-30 uL).
I hope this will help you.
Lukasz Kozon
Hi, Lukasz,
I think residue silane (which came while peeling off PDMS from SU8) is making the PDMS-PDMS bonding difficult. Is there a way to wash away this residue silane on PDMS?
Thnakx in advance
can i de-bond the bond of PDMS PDMS created after plasma treatment by any chemical means?
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