Centrifuges: what do they do and how do they work?

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Centrifuges: what do they do and how do they work?

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Think about how a balloon full of helium floats. The helium is less dense than the rest of the air, so as gravity pulls on everything it pulls on the helium just a little less, and the rest of the air a little more, and the helium gets kind of squeezed to the top.

That happens whether or not the helium is concentrated in a balloon, but without the rubber to hold it in place the helium gets scattered a lot. Sure, it’ll make its way up but it’ll bounce around a lot and get mixed up with regular air.

Liquids and colloids (particles suspended in liquids) will do the same thing, but liquids have a much harder time moving past each other.

A centrifuge causes a kind of artificially stronger gravity by spinning really fast, causing centrifugal force. That extra force makes the liquid separate much faster (or at all) than it would normally. Once separated that way, you can siphon off the different components and take what you want, and ditch the rest.

This is really useful for something like donating plasma from your blood. The red blood cells can be separated out from the liquid so they can keep the plasma (which doesn’t have a blood type) and give back the cells.

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