Electronics > Projects, Designs, and Technical Stuff
silicone (PDMS) slipperyness?
ChristofferB:
Hi! Not strictly speaking electronics related (yet), but I need a rather involved liquid valve - 6 port rotary valve for sample introduction in a scientific instrument i'm designing.
I'm thinking of making it myself, having a flat sheet of soft polydimethylsiloxane gel, the standard 2 component silicone, with in/out ports punched in it, and then have a round top disc of acryllic with the interconnecting channels milled in it. It's going to operate at very low positive pressure and low flows.
Is it realistic to get an arrangement like this to seal, and would you think the slipperyness is sufficient that the valve can be turned without any lubricant?
Here's an image of the valve I'm trying to recreate. The commercial ones are MAD expensive. https://www.vici.com/support/images/app11.gif
Thanks!
--Chris
coppercone2:
I think this might be useful, not for design but application specific from the best.
https://www.swagelok.com/downloads/webcatalogs/en/MS-02-479.pdf
I think others may be illuminated by this, you probably know most of those details.
I think you want to polish that acrylic after it was milled to make sure there is no burrs that will dig into the gasket. But for your main question I don't know.
coppercone2:
make a sample without the channels and leave it compressed at your expected operating tension for a while.
All valves should be periodically cycled because they stick as part of a valve maintence procedure.
The friction should not change much because of a small sampling system that is built into it.
See if it operates and what the recommended maintence cycling time should be, then make a test groove and put the valve on tester to test 10k actuation to see when failure occurs and inspect visually.
\
should be a non expensive test
Teflon vs acrylic too. or hhigh density poly ethylene
jeremy:
In my experience, PDMS is the exact opposite of slippery; heck, I’ve used it for it’s stickyness. Situation would be worse under pressure too.
I think the key polymers used in this area are PTFE and POM
ChristofferB:
Okay, so PDMS is out. The idea with the testing is good, and the acryllic being translucent, any leak will be very apparant.
I'll try putting a layer of soft slippery polymer (PTFE, PE) between the port layer and the flow layer. See attached.
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