I want to seal a tissue/glass interface. The tissue should not be out of the water (buffer) for too long, so I am wondering if I could apply PDMS in liquid form and let it cure under water? (temperature would be between 4 and 37°C). Any information and shared experience is highly appreciated!
Cheers
Jörg
Hello
Links here will help you
Good Luck
https://photonics.byu.edu/PDMS.parts/paper5.pdf
http://pubs.rsc.org/en/content/articlehtml/2014/lc/c4lc00045e
Hello Saleh Alkarim,
thank you for those links. They are indeed interesting, especially using Polystyren as PDMS substitute.
However i could not find any information on curing PDMS in water, so I am still looking for an answer for that question.
Best regards
Jörg
Yes, PDMS will cure when in direct contact with water. Make sure to thoroughly degas the PDMS before pouring it to minimize bubbles. it may also help to have your sample in a "cooling" state as well. Since aqueous solutions increase gas solubility as temperature goes down, if your sample is cooling during the cure, bubbles are less likely to form. You may also want to make some sort of dam around the sample so the PDMS doesn't run off. If you cover a thick sample, most of the PDMS will run off to the sides leaving a very thin layer on the sample (this could also be desirable). Remember, PDMS is water permeable and your sample will still dry out even when potted in thick PDMS.
Hi Ron,
thank you very much for your comment.
But are your sure PDMS is permeable to water and not just water vapour? I read that PDMS is not infiltrated by water and other hydrophilic liquids like ethanol (for example here: http://www.elveflow.com/microfluidic-tutorials/microfluidic-reviews-and-tutorials/the-poly-di-methyl-siloxane-pdms-and-microfluidics/).
This is actually an important point because I want the seal to be water tight.
Cheers
Jörg
Technically, PDMS is gas and water "vapor" permeable and the liquid does not actually flow (as liquid) through the PDMS as though it were a sponge or something. But for the purpose of keeping in any liquid with a vapor pressure equal to or greater than water, PDMS is not the material that you want. Fluidic devices are constantly perfused and they stay wet without many problems as long as the perfusion continues. But, if they are left without a source of perfusion and not in a high humidity environment, they do dry out. If you are planning to keep your tissue wet by providing some source of media, then you won't need to worry about the tissue drying out.
I won't be providing medium flow or input for on side of the tissue, but the timeframe of the experiment where a constant volume is important is going to be only a few hours.
Another point is the permeability of PDMS for small molecule substances. In the long term (project wise) I need the seal to be impermeable for those as well, time frame here would probably be at least 24 h. Do you think I can use PDMS for that? (Thickness of PDMS is going to be about 1 mm).
Thanks a lot for your advice!
Jörg
If you keep your sample in high humidity for the duration of the experiment, it should not dry out. You may also want to try some other options like epoxy, polyester, or acrylic clear casting resins.
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