- Corals have had millions of years to evolve
and adapt to life in the Earth's oceans.
In that time, they've managed to optimize
light management,
dinoflagellate cell density,
and photosynthesis
nearly to the theoretical limit of all that.
Hi, guys and girls.
I'm ReefMan.
And this time, we're talking about
bionic 3D printed corals.
First off, there's a link down below to the paper.
The paper is titled "Bionic 3D Printed Corals"
and it was published in Nature Communications
in April of 2020.
Algae provides a lot of the food
that our corals need for life,
but it can also be used in reactors
to produce oxygen that we would breathe,
and to remove nutrients
and things like that from water.
The more algae that you have in a reactor,
the more effect it's gonna have on the water
that's passing through,
but there is a limit.
As some of the algae grows,
it shades other parts of the algae
and that limits the overall growth
that can be achieved in the reactor.
That's where millions of years come in
that the coral has had to adapt.
Coral is very good at growing symbiotic algaes,
and it turns out that we can apply
some of the same principals
to algae reactors of our own design.
Coral skeletons are not just structures
that provide support for the organism.
It turns out they're actually actively involved
in scattering light
back into the coral's tissues
where the algae lives,
and they're not just directly scattering
it directly back.
They do it in such a way that
the photons kind of bounce around
and they hit lots of different algae cells
before they finally maybe make it back out
into the ocean water.
This scattering is key to the overall efficiency
that we see in corals
and their photosynthesis.
In the paper, the team is 3D printing
both skeletons and the living tissue
that containing the algae on top of them.
They even 3D print little bionic polyps on the tissue.
That's right, bionic coral polyps
are very much a thing living on this planet today.
The team is able to print these structures
with micron-scale precision
using light activated polymers
that they mix with algae cells
that they developed as part of this study.
Take a look at how your own stony corals grow.
How are the branches shaped?
They actually grow in such a way
that prevents shading themselves as much as possible.
And using the fast growing Pocilloporidae corals,
the team studied that shape
and their individual corallites in the skeletal structure.
Light can enter the coral's tissue
much easier than it can escape back into the water,
in part due to differences in
the refractive index of the tissue
compared to that of seawater.
The skeleton itself does plays a role,
as I mentioned,
capturing light and then reflecting it
deep into the corallites
where the tissue might not otherwise
be able to get enough light.
The team used these corals as a model,
and iterated through several designs
to find an optimal design to print.
They optimized for things like printability,
for keeping the algae cells just alive in general,
and also the optical performance.
And they settled on corallites that are about
a millimeter in size and depth.
In order to 3D print their bionic polyps,
they developed a bio-ink solution
in which they could suspend Symbiodinium algae cells.
And to that mix,
they added a tiny bit of cellulose nanocrystals
just to help scatter the light in the tissue.
They then used a special polymer base
that's gonna harden when you expose it
to a certain wavelength of light.
Not UV light,
'cause that would kill the algae.
And then they developed a special printer
that could use that light to print nano-scale structures
and they used a mask to mask off where
they didn't want the light to hit
that they developed from real coral.
And from there,
it's just like your home 3D printers.
Just a matter of slicing up the structures
and then building them up layer by layer
using the printer.
They also 3D printed the skeleton
over which the polyps were printed
using much the same material,
only, of course, without the algae cells being mixed in.
Compared to simply printing a flat sheet of algae,
their 3D printed structures showed a more than
a 1.5-fold photosynthetic improvement
due to reduction in self-shading in the tissues.
They also saw an order of magnitude
higher cell density in their 3D printed tissue
compared to just growing algae in a solution in a flask.
Again, because of the better optical properties
which allow for the higher densities
by not shading other algal cells as they're growing.
So what use could we have for bionic corals?
Well, as I mentioned earlier,
we use algae reactors
to process all sort of things
like waste water, industry stuff.
Reactors based on this research
could be much better and more efficient
than the current generation that we use today.
Maybe we'll also see bionic coral reactors
generating oxygen or cleaning water in space.
The paper is linked down below,
so if you're interested,
please do check it out.
It's a really cool read.
We're really living in the future.
3D printing is cool and all,
but the overall concept has applications
beyond anything that you and I can imagine today.
Who would've guessed 3D printed bionic corals?
If you wanna do some of your own research,
the keyword that I'd recommend searching for
is called "bioprinting."
And here, you'll find things like ears and noses
that people have printed.
So, you know,
if they can do those things,
why not coral?
It really is pretty cool.
If you do have a 3D printer,
the team did publish all their STL files.
So it might be fun to try and print some yourself.
They're linked down below in
the supplemental material for the paper.
I hope you enjoyed the video.
Remember to subscribe
and have a great day.
Stay safe, be kind to each other,
and I'll see you next time.
Bye.