Hi there, I'm Jamie Dyer.
This is a centrifuge.
This is a microcentrifuge. It's smaller.
They both do the same thing.
What a centrifuge can do is separate particles from liquid.
I have here some sandy creek water. Let's watch what happens if I let it sit.
Eventually, gravity makes all the sand and silt settle to the bottom of the jar, but it takes a long time.
A centrifuge does the same thing but faster, because, instead of using gravity, it uses
centrifugal force.
That's why it's called the centrifuge.
Centrifugal force is the outward pull you feel when you spin around in circles.
Centrifuges can spin really fast to apply a strong centrifugal force.
Scientists use centrifuges to separate all kinds of particles from liquid.
For example, in this 2020 cool paper, scientists studied a type of fish that can
rapidly change the number of red blood cells in its blood, depending on whether it's resting or exercising.
To study this, the researchers used a centrifuge to measure the fish's hematocrit, which is a measure of the number of red blood cells in the blood.
To measure hematocrit, you take a blood sample, put it in a capillary tube,
and use a centrifuge to separate the red blood cells from the rest of the liquid in the blood.
Scientists use centrifuges to separate more than just red blood cells.
You can separate any of these particles from liquid, just using a centrifuge.
Centrifuges apply very high forces,
so make sure you use a tube that's designed to be used in a centrifuge.
Once you have your samples ready you can put them in the centrifuge, but
a centrifuge is unbalanced if the tubes are unequally distributed,
or if the tubes have very different amounts of liquid in them.
Putting unbalanced tubes in a centrifuge is like two people of different sizes spinning around.
The heavier person will pull the lighter person off balance.
It might be fun for people, but it can damage a centrifuge.
So always make sure that each tube is balanced.
If you have a tube that doesn't have a partner across from it, use an extra tube with a similar volume as a balance.
You can balance a centrifuge by placing tubes directly across from each other, or,
by making sure they are equally distributed in the rotor.
Once you've loaded the centrifuge, if it has an internal lid, put it on. Close the lid and set the speed and time according to your protocol.
The units for speed are either RPM (revolutions per minute) or RCF, which is related to g-force.
Higher speeds mean more centrifugal force.
When the centrifuge is done, take out the tubes carefully, because if you jostle them you'll mix up the particles again.
After centrifugation, the particles in your sample will be all smashed down in the bottom of the tube.
That pile of smashed down particles is called the pellet and the liquid on top is called the supernatant.
Depending on how many particles were in your starting sample, the pellet can be large or small.
Small pellets can sometimes be hard to see.
When you use a microcentrifuge, make sure the hinges of your tubes are pointing out.
That way you'll always know where in your tube to find your pellet.
Depending on your research question, you might use just the pellet, just the supernatant, or both.
Centrifuges are a powerful tool that can be used to answer questions like,
"Can this fish increase its number of red blood cells significantly more than blood doping athletes?"
"Can we develop a low-cost electricity-free method of detecting the coronavirus for use in resource-limited areas?"
What cool questions do you get to ask using a centrifuge?