What's the viscosity of the coating and does it stick to the tube material? Spin coating is used successfully in semiconductor manufacturing to produce consistent submicron coatings of photoresist.

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Thanks @IRstuff

viscosity is about 0.013 Pa s. The coating adheres to the tube material.

I'll look into spin coating.


Thanks for the suggestion

0.5 mm inside diameter and you want to coat the inside diameter?

That's what I was thinking.

What thickness of coating and what size hole do you have left?

Why bother springs to mind...

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Also: If you get a response it's polite to respond to it.

This is a datasheet for the photoresist I was thinking about; can't find the viscosity, but one particular model will produce a 1 micron thick layer when spun at around 6000 rpm. That's for a flat surface, so I've no idea what that would look like in a skinny tube. I would imagine filling the tube and installing it centered on the center of a spinner table and running the rpms up, which should empty most of the liquid except for what sticks to the walls. https://amolf.nl/wp-content/uploads/2016/09/datash...

However, your liquid appears to be about 16x more viscous, so that's a potential problem, although you seem to be implying in the OP that getting it hotter might make it less viscous?

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@3DDave, yes I want to coat the inside diameter.

The coating itself can be superficial as the material readily bonds to the coating.

I was experimenting just having a bucket of liquid coating and just dunking the tubing all together. At the end of it, it's no more than .1 mm coating given that excess was not removed.
I imagined that keeping the solution hot keeps it less viscous and an unnecessary amount of coating on the tubing.

I'll look into the given solution and see if it is feasible in addition to some of my own ideas.

Thanks

Quote:

I was experimenting just having a bucket of liquid coating and just dunking the tubing all together.

You could possibly spin the tubing on its long axis, which would force the liquid against the inner wall and possibly push out some of the excess.

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How do you keep the tube from plugging?

Dip bundles of tubes and blow them out with air. If the coating is electrostatic, or bonds to the tube surface strongly enough, air will remove only liquid coating that hasn't been activated by touching the bonding surface.

Although at 0.5mm ID, capillary action may make it very difficult to coat the inside of the tube with just a gravity fed liquid.

Alternatively, swab the tube with a brush on the end of a wire pulled through the ID. 0.5mm would give you clearance for a 0.3mm or so wire which ought to clear without issue. You can control coating thickness with a silicone 'wiper' ball on the end of the wire. You may have to tune the exact size of the ball to deliver the coating thickness you want - the larger the ball, the higher the pressure against the tube wall will be and the thinner your coating layer will get. This method won't work if you need to make 10,000,000 of these a day, but could be automated at low rates. I've done a machine for a similar automated process before.

You may get some ideas if you look into the horizontal centrifugal casting process.
https://youtube.com/shorts/wjnv5YkdySE?feature=sha...