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I am planning to use polydimethylsiloxane (PDMS) to create a phantom for mimicking tissue for imaging. For this, I plan on using SYLGARD® 184, which is a viscous liquid. When adding other components to it, air bubbles will be introduced.

I have learned that one way (available to me) to remove bubbles / de-gas the solution is by using a vacuum pump to create negative pressure. What negative pressure is sufficient to remove the air from the gel-like solution?

Air
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Nazar
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  • The answer will also depend on the amount of time the negative pressure is applied. – Chris Mueller Mar 20 '15 at 16:35
  • @ChrisMueller I would want to limit it to less than one hour. Any practical suggestions? – Nazar Mar 20 '15 at 17:18
  • Use an old vacuum and find out. If the negative pressure is too strong, introduce a leak into the system; if it's too weak you need a bigger vacuum or you have a leak. Just remember that vacuums use the airflow through them to cool themselves and you will be putting a lot of load on the pump to maintain a negative pressure, so make sure you don't fry it by running it for too long consecutively. –  Mar 20 '15 at 17:22
  • @thepowerofnone [Here](http://www.amazon.com/gp/product/B002VBW9R8/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=ATVPDKIKX0DER) I found a good size vacuum desiccator, so I hope after getting some negative pressure, I can just close the valve and let it stay. It should hold the vacuum up to 24 hours. At this point I just need to select a reasonably strong pump, so I would like to know what minimum negative pressure it should create. – Nazar Mar 20 '15 at 17:37
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    Practical tip. As the the dissolved gas leaves the resin, it may cause the resin to foam-up and overflow the bucket. Use a bucket that's 2x the volume of your batch. It may also help to outgas gradually. – Nick Alexeev Mar 21 '15 at 05:03
  • U$190 for 10g, too bad you couldn't find something less expensive ... – Rob Jun 08 '18 at 17:23

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15-30 mins under any vacuum pump will be fine. If there are any air bubbles still there at the surface I recommend to burst it with pressurized air gun. Make sure that your vacuum chamber lid is sealed well. Some time it is useful to use vacuum grease to achieve that.

Nabeel Kadhim Abbood
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