I have seen procedures suggesting repeat spin-coating and curing. Others suggest simply pouring into a mold to desired thickness and curing.
I would like to use the stamp for transfer of nanostructures between substrates as described in the link.
Thanks
http://arxiv.org/ftp/arxiv/papers/1406/1406.5809.pdf
It should be quite simple to pour PDMS into 1-2mm films. Spinning won't gain you any accuracy at those thicknesses. You may also try casting the thickness you need between two pieces of polymethyl methacrylate (acrylic or Plexiglass), polyethylene terephthalate (PET or Mylar), or polyoxymethylene (acetal or Delrin). Casting has the advantage of being reproducible to 10's of microns but has the drawback of adding complexity to the process. When casting PDMS, it must be carefully degassed before curing or else you'll get bubbles in the film.
Thank you very much. I think I will try the simple pouring method first. Do I still need to degas before curing? I'm worried about bubbles that may be introduced during manual mixing of the solution.
Hello Timofey,
As Ron recommends, you should definitely degas the PDMS before curing. I usually use a desiccator for 10-50 minutes depending on the geometry of the mould. I also found that introducing a temperature ramp before reaching the set temperature improved things for my PDMS devices.
You may also want to consider a release agent or a silanisation step.
Jules.
Thanks for your suggestions. I've been able to make PDMS by pouring method. After degassing the viscous mixture, I found that very slowly pouring onto cleaned glass microscope slides introduces minimal bubbles which go away after leaving it in ambient for ~30min. I was able to remove the cured film without too much difficulty as long as it was at least ~0.5mm thick. Of course this method does not yield a perfectly uniform thickness, but that's not necessary for my application.
I recommend just pouring it to the thickness you want.
Andrew H. Cannon, Ph.D.
researchmicrostamps.com
No doubt moulding is the most easiest way to fabricate thick PDMS sheet. But it results in non uniform sheets. Can we fabricate 2mm uniformly thick PDMS sheets over larger area?
6d ago
hi, may i know the best way to coat a copper beam with pdms 2-3 mm thick? I intend to do a mould for the pdms using arcylic but didn't know whether it works or not. This is my first time dealing with PDMS, so really need a helping hand. thanks.
Aditionally, you can remove the bubbles once casted (if not too many) puncturing them with a needle
Kajal
You can get a larger area uniformly thick 2 mm PDMS sheet by creating a mold that dictates the shape of the PDMS, and then pressing or casting the PDMS into that mold. Let me know if you need help.
Andrew H. Cannon, Ph.D.
researchmicrostamps.com
Zati
Acrylic should work well for a PDMS mold. Just watch out for any adhesives you use when constructing the acrylic mold. Some such as JB Weld will inhibit the curing of PDMS. Sulfur inhibits PDMS curing.
Andrew H. Cannon, Ph.D.
researchmicrostamps.com
Thanks Andrew for your suggestion.
Now this time I tried with a closed mold with required spacer(smaller dimension to check whether it is possible to take PDMS out neatly and easily) and finally got the thick uniform PDMS film. But I would like to recommend all of you to either adhes the spacer lightly(low grade tape) or some temporary adhesion like paper clips can be used allowing easy detachment of film with the mold.
Kajal Chaudhary
PhD
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