Thanks to Brilliant for supporting this SciShow video! As a SciShow viewer,
you can keep building your STEM skills with a 30 day free trial
and 20% off an annual premium subscription at Brilliant.org/SciShow.
When you think of the places fossils are found, you probably are imagining a museum,
an excavation pit in the desert, maybe even, like, a beach.
But head to your local hardware or gardening store,
and you can probably buy fossils by the millions.
Alongside the pesticides and roach traps, you’ll find bags of diatomaceous earth,
a white, powdery substance that’s a great, nontoxic method for killing bugs.
If you got there, and you pick that up, what you are holding
is actually a big bag of fossil algae called diatoms.
And millions of years after these little animals died,
we are using these fossils to do a lot more than kill ants.
Diatoms turn out to be great for everything from
cleaning up cat pee to building nanotechnology.
[INTRO]
The term “diatom” refers to lots of different kinds of phytoplankton,
a sort of single-celled algae that lives in lakes and oceans.
Diatoms first evolved some time in the late Jurassic period, about 160 million years ago.
These primeval plankton are only about as big as the width of human hair!
And today, there are at least twenty thousand different species of them around.
In fact, scientists suspect there could be as many as millions of kinds of diatoms,
since we keep discovering new kinds every year.
What diatoms lack in size, they make up for in their enormous presence in the world.
So much so that their combined photosynthesis produces
something like a quarter of all the oxygen in the atmosphere.
So, if nothing else, we have diatoms to thank for the literal air we breathe!
But hiding behind this biological benevolence are the makings of a secret killer.
Take a look under a microscope and you’ll see all kinds of strange and beautiful shapes.
As we mentioned, there are a lot of different types of these critters!
And their ethereal beauty comes down their cell walls,
which are there for more than just looking cool.
The cell walls of a diatom are made up of frustules:
sturdy barriers made of the material silica,
which they produce from the silicic acid floating about in the water around them.
And that silica is basically the same stuff as glass,
which is what makes a diatom’s cell walls so durable, and also mega-pretty.
So diatoms definitely should not throw stones, they are literally living in glass houses.
As well as providing a cozy little home for a diatom,
silica frustules have some pretty funky properties as a mineral.
Despite the reputation of glass as a fragile material when it’s in a large,
thin pane like a window, silica is actually pretty strong as far as materials go.
And that silica has another unique property, which is the reason
you might encounter it at the bottom of a shoebox.
You know these tasty little DO NOT EAT packets?
That is silica!
Not eating silica, by the way, is great advice because
those beads are a major choking hazard and
can totally mess up your respiratory system and digestive tract!
So, again, like it says, do not eat.
So those tiny beads of silica are actually there
because silica is amazing at absorbing moisture!
Materials like these with moisture sapping superpowers are called desiccants.
They are great for preventing mold forming on all that porous material,
like the kind your sneakers are made out of.
And, as little water-sucking sponges, they come in handy for
all kinds of situations, as we will see in a moment.
The final trick up silica’s sleeve is the fact it's inorganic.
While “normal” fossils are made as minerals replace harder bits of an animal’s remains,
like bones, diatom frustules don’t dissolve or get broken down by smaller organisms.
So diatom fossils are basically identical to diatoms
you’d find around today, just, you know, empty and dead.
And because diatom frustules persist for so long,
and there are so many of them kicking around in bodies of water,
their remnants deposit themselves to make vast layers of silica-laden sand.
That sandy silica made of diatom corpses is precisely
what you can buy at the hardware store as diatomaceous earth!
And all of those properties of silica that we just mentioned
come together to deliver a fatal blow to bugs.
For starters, the tiny size of diatoms means that the silica particles can easily
stick onto the exoskeletons of passing insects that come into contact with it.
Once they’re on there, the remarkable moisture sucking property of silica
takes hold and absorbs the oils and fat on the insect’s soft outer shell, breaking it apart.
And, all those sharp edges start to cut up the bug’s cuticle pretty badly,
which breaks it open and allows the water out of the insect’s body until it dehydrates!
After getting cut up and dried, creatures like slugs, beetles and worms
crawling along your prized petunias won’t get very far.
And while this is pretty gruesome for the insect, the way diatomaceous earth
works is mostly mechanical, meaning it relies on physically hurting an
insect rather than trying to poison it with toxic chemicals.
All in all, this could be much kinder to the surrounding environment than
other kinds of pesticides that can wreak havoc in the local ecosystem.
It’s kind of fascinating that these fossil organisms have evolved for
millions of years and became incredible pest-killers, basically by coincidence.
But like we said at the beginning, we have found uses for diatoms
well beyond gardening and insect-killing!
There are lots of places where the humble diatom’s absorbing,
durable and scratchy frustule finds a purpose.
For instance, that great absorption quality means that diatomaceous earth
often finds its way into cat litter. It’s excellent at soaking up those
interesting smells that your cat leaves in the tray when it is in there.
And in the food industry, diatomaceous earth is used to absorb contaminants
from certain products, helping to purify and filter out unwanted liquids
in the process of making vegetable oil, sugar, syrup, wine and even beer!
Those frustules’ tough, pointy exteriors come in handy as a kind of abrasive, too.
Diatom frustules are great for smoothing down and
polishing metals like bronze and aluminum,
and even ceramics like marble and glass.
But maybe the place you might least expect to find millions of years old
fossils of algae cell walls is as hidden nanotechnology components.
Take the field of plasmonics, where researchers need to create tiny optical
and electrical components, just a few molecules large,
which can manipulate light signals on tiny scales.
These have a whole host of applications from telecommunications to things like
chemical sensing, biomedicine and even quantum computing!
As great as that all sounds, and it does sound great,
the hard part is often actually creating nanoscale components
with intricate patterns capable of manipulating light in the required way,
such as tiny well-organized structures that can refract and reflect light.
But guess what happens to form in tiny, sturdy geometric shapes?
Yes, diatoms.
Silica, as we mentioned, is basically just glass that can refract light
in a way that plasmonic nano-components need.
But the real magic happens when you combine diatoms with metal.
Coat a bunch of diatoms with a light dusting of silver nano-particles,
and you can make a surface that detects the presence of certain chemicals.
For instance, the illegal food additive melamine can lead to kidney disease
and even death, so knowing when food is laced with it is pretty important.
In a 2016 study at Oregon State University, researchers dropped
melamine laced samples onto a silver and diatom coated surface
and shone a laser on it to measure the spectrum of light
that was refracted off of that surface.
In the presence of melamine, the spectrum had a tell-tale fingerprint that
indicated the presence of the offending molecule!
Basically, if there’s melamine on the sensors, the reflected laser signal can pick it up.
And, those same diatoms could detect the compound Xylene,
which pollutes air, water and soil and irritates your skin if you encounter a lot of it.
Not only that, the diatom sensor did a better job at
detecting Xylene than their other technique!
Admittedly, this is pretty early days for this kind of technology.
But it’s well within the realm of possibility that diatom sprinkled nano-sensors
could be monitoring many aspects of our environment before long.
From pollutant detection to pest protection, there’s not much we can’t do with diatoms.
We owe a lot to those funky little guys, just doing their thing
and making their little silica houses.
But just like the packet says, they still don’t make a very good snack,
nobody’s perfect.
Thanks to Brilliant for supporting this SciShow video!
Brilliant’s interactive online learning platform has thousands of lessons
to choose from in math, science, and computer science.
And right now, you can go from the teeny tiny nano-sensors in this video
to the vastness of infinity in Brilliant’s Number Theory course.
This course doesn’t just teach you about divisibility and arithmetic.
It applies those concepts to interactive logic puzzles
and shows you how it’s all related to art and code-breaking.
There might be more creativity in math than you thought.
So you can start expanding your view on math out to infinity by
heading to Brilliant.org/SciShow. That search will start you off with
a free 30-day trial and 20% off an annual premium Brilliant subscription.
Thanks for watching this SciShow video and staying curious!
[OUTRO]