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Catalyst -

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(generated from captions) ANJA TAYLOR: Titanium implants
are a favourite among surgeons. They're light, durable and strong and
readily accepted by the human body. But with each surgery comes
a small but potentially deadly risk - infection through
the introduction of bacteria.

The infection rate for orthopaedic
surgery is about 2%. That's with multiple levels
of safety. We ensure that the implants
are sterile when they're inserted into
the patient. Unfortunately, to get to the bone, they've got to go through skin, and skin is often embedded
with these bacteria. ANJA, V/O: The most common and deadly
bacterium is Staphylococcus aureus, or golden staph. Of the patients unlucky enough to be infected with
the antibiotic-resistant strain, around 35% die.

The problem is while human cells
readily grow on the surface of titanium, bacteria love it too, so researchers are looking at ways
to alter the surface and make it resistant to bacteria while still being compatible
with human cell growth. ANJA, V/O: But as it is with many of
the most complex puzzle in science, nature solved it long ago.

Although smooth to the human eye, from the perspective of a bacteria, a titanium implant is a landscape
full of homely valleys, and that's where
they like to replicate. Initial studies saw that if there were any nanogrooves on the surface of the titanium, that's where the bacteria
would start to grow.

ANJA, V/O: Professors Russell
Crawford and Elena Ivanova joined forces seven years ago to try to crack the problem
by altering the titanium surface. RUSSELL:
The medical implant companies were trying to make
the surface nanosmooth. The assumption was that bacteria
wouldn't grow on the smooth surfaces, but that assumption was wrong. It was very surprising initially.
They're quite adaptive organisms. On a nanosmooth surface,
the bacteria change their tactics and secrete a sticky substance
to help them attach. Once secure, they form multiple
layers in a protective biofilm that's extremely difficult
to eradicate.

All bacteria are waterborne, and so we started
looking at surfaces that were naturally resistant
to water. Nature already has such a surface.

The lotus leaf is famous for
its ability to stay dry and clean. You literally can't get it wet.

Look closely at a lotus leaf
and you'll find out why. It's covered in
a microscopic layer of bumps which are in turn covered by another
layer of even smaller nanohairs.

In effect, if a water droplet
was coming down onto the surface, it would be seeing mostly air. ANJA, V/O: Any dirt or contaminants
just roll right off with the water. We were able to find a company and they were able to take
the surface of the titanium and pulse lasers which caused
the surface to reconfigure itself into a structure that was very
similar to that of the lotus leaf. The new surface showed encouraging
results, but wasn't a success. While some of the rod-shaped bacteria
were repelled with the water, the nasty of all nasties wasn't. Golden staph actually found the
modified surface more attractive than the unmodified surface,
which was a real problem for us. And that was absolutely unexpected observation which we didn't want to find, but that was the fact.

ANJA, V/O: But it's not
just the lotus leaf that has a novel and clever
surface to mimic. In fact, the world is brimming
with potential candidates.

And Dr Gregory Watson is a man
with an eye for finer detail.

I was walking through the bush
many years ago and I came across a cicada and I noticed that it didn't really
reflect a lot of light on the wing. I took it back to our laboratory
and imaged the wing and we found these extremely
small structures on there - smaller than the wavelength
of visible light. ANJA, V/O: It was just like
the lotus leaf's surface, but with thinner,
sharper-looking bumps. We took off various sections,
or height, of these little bumps, and as we made them shorter
and shorter, they became less effective at taking
the light right through the wing. It was clear the tiny pillars
were responsible for the wing's
anti-reflective properties.

That was enough to get Greg out
looking for cicada species wherever he could find them.

We started looking at potentially
all the other functions that these structures
may serve the insect. (Thunder claps) So when we were out in the field
collecting the insect, we noticed when it was raining that the water drops
hit the actual wings of the cicada and bounced off very quickly. ANJA, V/O: Just like the lotus leaf,
cicada wings were super hydrophobic. If we just place a droplet
on the wing, it can't find a stable region
to stay there and it just rolls off automatically. With high-speed cameras, Dr Watson and collaborators captured
the extraordinary 'cicada effect' where even without rain, droplets
condense from the atmosphere and jump right off the wing. And as the droplets merge, there's enough surface energy
for them to propel off the surface and take away the dirt. It's a handy trick for a humid
tropical environment like Townsville where often
it doesn't rain for weeks. The wings automatically clean
themselves, so there's obvious implications
in there for man-made surfaces, how we can transfer this technology. So what we've managed to do is replicate the surface of
the cicada wing with a polymer. Is it water-repellent?
It certainly is. And you can see here the water
just rolls off the surface. Fantastic. It's just like
the real thing.Yeah.

But that wasn't the half of it.

The humble cicada had another even
more exciting secret left to uncover. So it seemed to us that the cuticle
and the rest of the insect body was quite susceptible
to the elements, but the wings seemed to be more
immune to this process.

And I thought that it will be
quite interesting to test the surfaces and see how bacteria would respond
on these surfaces. ANJA, V/O:
What happened when bacteria were introduced to the surface
was completely unexpected. So basically we thought that
bacterial cells would repel from the surfaces the same was as water repels
from the surfaces. However, we found
absolutely the opposite. Instead of being repelled, the rod-shaped bacteria
proliferated on the surface, but there was something terribly
wrong with them.

Like latex drawn over a bed of nails, the membrane of the bacteria
had stretched and ruptured as it settled on the nanopillars
and all of them were dead. That was absolutely unexpected
and an unbelievable observation, so we had to test it now a few times
to confirm the results. But despite their extraordinary
bacteria-shredding properties, cicada wings failed
the ultimate test. When Staphylococcus aureus
was introduced to the surface, all of them survived. RUSSELL: In fact,
a sphere is well known as the most stable geometric shape, and it can resist all sorts
of external forces compared to other shapes. It was a great disappointment.

But amongst the samples, Gregory
had also included a dragonfly.

ELENA: Dragonfly wings
are random arrays of slightly different geometrical
shapes of the pillars. And that was the magic structure that shred every type of bacteria,
including golden staph. RUSSELL: Anything we put in contact with the surface of
the dragonfly wing was killed. We were very excited about the fact
that gram-negative, gram-positive, spherical, rod-like bacteria
and even bacterial spores were susceptible to the action
of the structure on the surface of
the dragonfly wing. ANJA, V/O: When you think about it
in hindsight, it all makes perfect sense. Dragonflies spend much of their life
around and even in water, and may need a more efficient way to
deal with the associated pathogens. He'll never know it, but we may one day thank the
dragonfly for making surgery safer.