I have a Si mold with 5:3, 15:6 dia:depth ratio for microstamp. Upon peeling the 15:7 peels off without any issue, but the 5:3 (100micron dia and 60 micron depth) upon peeling all the pillar like structures break. Please advise
Srikanth,
Have you silanized Si mold before pouring PDMS? If not then silanization might help (Trideca floor-1,1,2,2-Tetra Hydro Octyl -1-Trichloro Silane is one option), otherwise it could also be an issue due to the photo-resist.
We have developed a new method for microfabrication of thin PDMS film with well defined pore size ranging from 10-60 microns. The method is described in the following paper to appear in Biomaterials soon.
J. Li, M. Chu, C. R. Gordijo, A. Abbasi, K. Chen, A. Giacca, O. Plettenburg, M. Löhn, X. Y. Wu, Microfabricated microporous membranes reduce the host immune response and prolong the functional lifetime of a closed-loop insulin delivery implant in a type 1 diabetic rat model. Biomaterials, DOI: 10.1016/j.biomaterials.2015.01.005
Hi,
Simply apply some any low viscous oils on to your Si structures by dip coating or by spinning. After that pour the pdms, Once it is cured, start peeling off the pdms very slowly. It will take some time but it works very efficiently. After it comes off, wash the pdms suface with ethanol to remove the excess oil, if at all it is present.
It will take some time for you to adapt to this manual technique, but rest assured it works to produce wonders!!!!
Vishal's option works well. For silanization I use 1H,1H,2H,2H-Perfluorodecyltrichlorosilane. Place 50ul in a ceramic dish in a glass dessicator. Put in your Si wafers. Leave over night at 100mbar. The treatment is best if used sooner rather than later.
Thank you All
Vishal I have modified the Si mold surface using (Tridecafluoro-1,1,2,2-Tetrahydrooctyl) trichlorosilane in heptanol yet I see breakage
Do you think vapor phase modification using chloro propyl trifuloro silane might be a better option?
If you have any other suggestion please let me know.
Xiao - I am not able to locate the publication I guess its still in press or not online yet
Tom - What do you exactly mean by sooner. Should I do the treatment as soon as I develop plasma treat or after plasma treatment only.
To clarify. What I do does not involve plasma treatment. More specifically, the silanization treatment (to reduce PDMS sticking) works best directly after. So once you have exposed the wafer to the silane vapor (as stated), pour on you PDMS and cure it. You can re-use the wafer, but after approximately 5-10 uses, you may have to make a new wafer.
Tom - Thank you just a question. what organic solvent did you use? any alkane is good or something specific
Srikanth, a simple thing I would try is Pluronic F127. It is a PEG based surfactant. Simply dissolve it in water as a 1% solution. Plasma clean your mold and coat it with Pluronic solution for 30 min at room temp. Then wash your mold with water and let dry in open air. It helps PDMS release and does not require any vapor deposition. Sigma has Pluronic
Thanks Siwei - The only reason why I was hesitating to use Pluronic was if it diffuses into the PDMS then it could be bad for the application that I am working on. Still I guess it is something to try. Thanks
maybe also give room temperature curing (48 hours) a try if not already tried. pdms stays soft and can take a bit more strain before breaking.
An excellent alternative to a silanization step is - provided the mould has been fabricated using deep reactive ion etching (DRIE) - to finish the process on a deposition step (C4F8) rather than an etching one, essentially depositing teflon on your surface, so you don't have to run another process after you've etched your Si.
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