- Hi there, I'm Frank Graff.

Shining a light on new solar power research, how a tiny device could save deep sea fisheries, and a Tar Heel poet heads to space.

Engineering science, next on "Sci NC".

- [Narrator] Quality public television is made possible through the financial contributions of viewers like you, who invite you to join them in supporting PBS NC.

[soft music continues] [soft music continues] - Hi again, and welcome to "Sci NC".

Solar power is an important part of North Carolina's energy production.

Producer Michelle Lotker shines a light on North Carolina state's solar powered research.

[soft music] - [Michelle] Generating electricity from the sun is efficient and renewable, but solar installations can take up a lot of land, and often, the best sites to build them on are farmland.

- Typically, they have a comfortable slope and level.

They're typically already clear.

And they're always, you know, full exposure to the sun.

However, you know, that farmland is needed to produce food.

And if we remove the capability of producing food in this farmland, we have removed our ability to feed the population in the world, so there is a conflict.

- [Michelle] That conflict could be resolved by combining solar energy generation with farming through something called agrivoltaics.

- Agrivoltaics is the combination of agriculture and photovoltaic panels, and the idea behind it is, can we use the land for dual purposes?

Can we grow crops in the field, in soil, and can we harvest the solar energy to generate electricity?

Great idea, but there is some challenges around it.

- [Michelle] Solar panels and crops in the same field compete for sunlight because the solar panels are harvesting the same light that plants need to grow.

So the challenge is designing a way that plants and panels can share.

Ricardo is part of a multinational team working to solve this challenge by splitting the sunlight between solar panels and the crops around them.

Sunlight can be broken down into different types of radiation based on wavelength, ranging from 320 nanometers, all the way up to 3,000 nanometers.

And a portion of those wavelengths is what we call visible light.

Visible light ranges from around 380 nanometers to 750 nanometers.

- Our eyes can detect that light.

Similar range is also for the plants to do photosynthesis.

If you deploy these panels, you're gonna be removing those essential wavelengths, and the plant will actually have a big penalty in the air.

We don't want to penalize the production of food or the production of plant growth because we already don't have enough farm land in the world to grow crops.

We want to prioritize plant growth.

So in order to do that, we're trying to actually split the sun.

[soft music] - I visited a greenhouse on NC State's campus to learn more about how the team is splitting sunlight.

Tell me about this piece of glass here.

It looks like an ordinary piece of glass, but what is unique about it?

- Yeah, so this piece of glass has optics in the middle.

It's a film, and this film is what causes the reflection of absorption of a specific wavelength.

- Glass like this is often used in office buildings where architects want to reduce the heat load of sunlight coming into the building without reducing the amount of natural light.

So they use glass designed to let visible light through while reflecting radiation with a longer wavelength, like infrared light.

Ricardo and his team are hoping to use glass like this to let plants get the spectrum of light that they need to grow while harvesting the rest of the sunlight's radiation for solar energy production.

Sensors show us that the glass is blocking about half of the total light or solar radiation that is present in the greenhouse, and a slightly lower percentage of the photosynthetically active radiation.

This is measuring what plants would use to live, grow, and do their thing.

- And do photosynthesis.

So we want to maximize the amount of light that reaches the plant, so we want to reduce the amount of light that is reflected or absorbed by the optics.

We still remove some because of the inefficiencies, so that's an improvement that we can do through research.

But then you can see that you still have a lot of light going through.

- Still a lot of light that if this was in the field and sun was coming through, a lot of light could still get to the plants underneath.

- Correct.

- [Michelle] A third sensor tells us what part of the sunlight spectrum the glass is reflecting.

- [Ricardo] And this is actually what's inside the greenhouse now.

You can see it's a pretty balanced spectrum.

But now if we move that sensor and it's right on the glass, you're gonna see how that spectrum changes.

- [Michelle] This sensor shows us that the wavelengths of light reflected by the glass are mostly useless to plants, but could be harvested for solar energy production.

- You can see how we actually- - Wow.

- Remove some of those wavelengths that are closer to the infrared.

- And the plants really don't need that additional piece of the light spectrum.

It's just really making them hot and thirsty.

- It's making them transpire.

Exactly.

Making them hot and thirsty, yes.

- To use this glass in combination with solar panels, some changes have to be made to the traditional setup.

What is it gonna look like when it's in the field as you start to develop it?

How will this be set up with a solar panel to actually gather electricity and also let light through to the plants?

- Yeah, so the basic idea is you have your solar panel that is oriented.

You know, instead of having the sun on top and harvesting, you're oriented this way.

And then you have, so can you stand your hand?

This is your solar panel, oriented.

It's not like this.

It's like this.

And then you have this glass on a 45 degree angle, right?

So the sun, the visible radiation is gonna go through, and then the infrared is gonna bounce on a 45 degree angle, because this is a 45, and capture by the portable side.

And you have a mirror image of the same thing on the other side.

- Okay, so from both sides, we have... Our panel is straight up and down instead of at an angle, but we're bouncing light and hitting both of those sides of the panel.

- Both sides.

- Very cool.

For Ricardo and his collaborators, the goal is for solar installed alongside agriculture to have minimal impact on the farmland's productivity.

- The number one priority of this research is to minimize the yield penalty, maximize plant growth, but still be able to collect enough energy to make the technology feasible for growers.

So we don't want to eliminate the revenue stream of the crop, but we want to add an additional revenue stream by creating energy.

[upbeat music] - [Michelle] To test how much impact new solar panel designs might have on crops, they use mathematical models with known information about how a lettuce or tomato plant reacts to things like less light to predict the crop's yield in different scenarios.

Shade loving crops, like lettuce, only need a few more days in the field to have the same yield.

But for sun loving crops like tomatoes, the penalty is much higher, up to 25 to 30% reduction in yield, so there's still room for improvement.

- So there's still a lot of research for this to be something tangible, but at least we have that small piece of evidence that we were looking for.

And we want to prevent the farm from becoming real estate.

We want to prevent the farm from becoming only solar farm.

So we want to preserve our farmland in North Carolina.

If this will allow farmers to keep the land farming with additional revenue income, that's already a win.

If we can preserve 10 acres from switching, that's already a win.

- UNC Chapel Hill alum Zena Cardman is poised to be NASA's first poet in space.

- That's right, yeah.

So our goal really is just to make it to the International Space Station and come home again safely.

We'll be participating in a lot of experiments while we're on board the International Space Station, it's actually a floating laboratory.

A lot of those experiments will be on me, I'll be the research subject.

And we'll be doing a lot of maintenance as well, taking care of the space station, doing preventative maintenance, just like you would on your car, and also repairing things when they break.

It's been up there for more than 20 years now, so there's a lot to take care of.

I am no longer the person doing my own research.

I will be the eyes and ears and hands and lab notebook for somebody else's research in a much bigger project than I could ever do on my own, and I really actually like that.

I think a lot of the laboratory skills are very transferrable.

I'll be working in a glove box a lot.

I'll be pipetting a lot.

We do a lot of medical research, biomedical research.

We will actually probably be doing a spacewalk that is looking for microorganisms on the exterior of the space station pretty soon, so that could be very interesting.

But I will not specifically be doing my own research, and I think it's just more of those transferable skills that I'll be leaning on.

- What has the training been like?

Grueling?

More than you expected?

Less?

- Yeah, every day is different, which I actually really enjoy.

It's a lot like our initial training to be astronauts.

We spend the first two years just doing kind of this basic background training, I would call it.

We do everything from learning all of the systems of the International Space Station, to learning space walking.

I think that's the most physically demanding thing that we do, but also one of the most fun.

- Why physically demanding?

I mean, someone who's watching this thinking you're floating in zero-G, this has gotta be fun.

This can't be that grueling.

But I've heard that before, it's fairly grueling.

- Yeah, it's definitely fun, that's for sure.

It'll be a privilege, and I hope I get to do a spacewalk.

But these suits are pressurized.

They also weigh more than 300 pounds.

And, of course, you're weightless, but you still have inertia, you still have momentum.

And so starting motion and stopping motion, you've got to accelerate this massive thing.

But I think working against those pressurized bearings and squeezing a pressurized glove is one of the most physically demanding parts of it.

Imagine squeezing a tennis ball over and over again for six and a half hours.

Starts out not so bad, but your arms fatigue pretty quickly.

And then spacewalking is almost a misnomer.

It's more like you're jungle jimming around the space station.

And so again, operating around these pressurized bearings.

The suits come in medium, large, and extra large, and so for me, a pretty small person, the shoulder bearings are spaced far apart, and so you have to really be creative with your body positioning to get to where you need to get.

- What are your degrees at UNC besides marine science and biology and everything?

Was also, I think, a minor in poetry, I believe.

- That's right, yeah.

- Why should a poet go into space?

Are you gonna be doing some poetry while you're there?

- [laughs] I don't know about poetry specifically, but I really hope that my ability to write and share what I'm experiencing will help bring that to people who are watching and following along back home.

- [Frank] What do you tell folks?

- Yeah, my goodness.

Just trust your instincts.

Don't wait for someone else to tell you what you're supposed to be doing or how you should go about doing that.

Just go for it.

Don't be the person who holds yourself back.

It's really, a lot more is possible than you can imagine.

- Now to the tiny device scientists hope will save a deep sea fishery.

You might be wondering what this angler is doing.

He's attaching what's called a descending device to a scamp grouper, which is a deep water dwelling fish.

The fish is suffering from barotrauma.

More on that in a moment.

That device will save the grouper's life.

Now, watch what happens to the fish and the descending device.

Fish that live in deep water are essentially incapacitated when they are brought to the surface.

Descending devices slowly return the fish to deeper water and release them.

Watch this fish recover and swim away.

The device is brought back to the boat.

It's part of a unique effort to save an important fishery.

- [David] Another little grouper.

That's another little scamp.

- [Frank] Here's the challenge in fishing for deep water dwelling fish.

- [David] So the way barotrauma works is fish are at really deep depths, and their swim bladder, which is filled with gas, is compressed.

When they're pulled to the surface, that swim bladder expands because there's a reduce in pressure.

- [Frank] If that sounds just like the bends, the condition that affects scuba divers when they come to the surface too fast without decompressing, you're right.

- A lot of times when you pull into the surface, that swim bladder expands so much that they can't swim off on their own because they're bloated.

You'll see things like the stomach protruding from the mouth or eyes bulging, and they'll just float off at the surface.

But these devices, with the proper weight, can get the fish back to depth really quickly and allow that bladder to recompress and allow them to swim off pretty easily.

[soft music] - The ocean, it's a huge, open place, and it still seems to be the sort of frontier that we don't completely understand.

- [Frank] Captain Tom Roller is working with other charter boat captains to adopt the use of descending devices.

[water splashes] - [Tom] It feels like the right thing to do.

People say it's easier just to throw the fish back.

I would disagree with that statement.

I think it's harder to go fishing and see the impact of your own actions, to see yourself take a fish that for whatever reason, you don't want to keep, you can't keep, 'cause the season's closed, and have to throw it back in not as good a condition as it could be.

- You're good.

- Do you want anybody, I'll fish in the back?

- You can fish wherever, just, like, from here up, just from console up.

That way I can see, we can de-hook stuff better.

The first time I used a good descending device, I could not believe how cool it was.

It felt like I was actually doing the right thing when I was bottom fishing for the first time.

Not to say that bottom fishing is bad, it's just the nature oof this style of fishing is you're going to have discards.

And for the first time, I felt like I could really do something really effective and really easy.

- [Frank] Until now, those fish would be tossed away, left to float on the surface and die.

The descending device slowly takes the fish down into deeper water and releases it at a specific depth.

- The regulation is that you have to have a descending device readily available on a vessel when fishing for snapper group or species in the South Atlantic.

The way these devices work, this device in particular, there's several depth settings you can set it to, and it's pressure triggered.

And so this particular one, it has a 50 foot depth, a 100 foot, and a 150 feet.

And so if I caught the fish in a 100 feet, I want to set it to 100 feet.

And then you'll actually kind of clip this onto the fish's mouth and then literally just drop the fish over the side of the rail of the boat and then send it down, and then once it gets to that 100 foot depth, this device will just pop right back open.

The fish will just swim right back off and you'll just reel it up to do it again.

- [Frank] Keep watching.

The fish is approaching the depth set on the descending device.

A little closer, and there, it's released, and it swims away.

Marine scientists say their research shows fish recover quickly when descending devices are used.

- [Tom] Oh, big grunts.

That's a good one right there.

- [Frank] And that's important to preserving an iconic and valuable fishery.

- The snapper grouper complex is comprised of probably 55 different species, different snappers, different groupers.

It's a bottom fish fishery.

It's very important to both recreational anglers and commercial harvesters, and it's also a favorite of consumers.

- [Tom] Yeah, that's a big trigger.

Check this bad boy out.

That is a nice one right there, man.

[gentle music] - [Frank] But the data shows the fishery may be in trouble.

- Some of the stocks of these species are doing very well.

Some of them are increasing and others are not doing very well.

Some are are decreasing.

And yeah, one concerning trend that we've seen over the past couple of decades is in the grouper species and the sea basses and porgies, that they've had a decrease, and we think that it is due to poor recruitment or not producing enough baby fish over time.

And we're not sure why that's occurring.

We're doing research into why that may be, whether it's environmentally driven or fishery driven or ecologically driven.

- [Frank] And because this is a multi-species fishery in which anglers target a lot of different species using the same techniques, nobody knows what fish will be pulled up from the bottom.

That puts all species at risk for barotrauma.

- For the red snapper fishery, the stock assessments estimate that overfishing has been occurring.

And the primary source of overfishing in this case is discard mortality.

And so this is a key example of how using descender devices can help mitigate overfishing by reducing discard mortality.

- [Frank] Which is why scientists and fisheries manager believe descending devices are an easy way to help preserve a valuable resource.

- It's not only important for fishermen to use descending devices and use their best fishing practices, but it's just as important for them to tell us when they're doing that.

That helps us to get a better understanding of a release fish's chance of survival, and that helps us to take that into account when making management decisions in the future.

- We have to worry about the future.

We have to worry about the availability and abundance of fish.

And unfortunately, I can sit here and tell you stories about many fisheries that I've lost in my lifetime.

And I mean, I'm 42 and are already talking about the way things used to be.

That's not a good thing.

So we have to worry about all these species.

We have to take care of everything.

And if we take care of the fish that we're allowed to harvest, hopefully that will give us longer seasons, more availability in the future.

I mean, and all of us, it takes our part in which to do that.

- And let's check in with Adrian Smith with the North Carolina Museum of Natural Sciences.

[gentle music] - [Adrian] Believe it or not, these are the same animal.

On the left is something you might recognize, an adult cat flea.

But on the right is something that up to a year or so ago, I had never even seen.

This is a larval cat flea.

And the clip you see now is part of a research project we've been doing in the lab describing how fleas in this worm-like legless stage are still able to move around their environment.

So the jump of an adult flea is one of the most famous insect movements, and it's something that's been on my list of things to film for a long time.

So while we had the larvae in the lab to study them, I also filmed some adults.

And let me tell you, it was a challenge.

Here, let me show you that footage and a little bit about what I had to do to gather it.

At the bottom of the screen, these two brown dots are adult fleas about to jump.

You're seeing them here filmed at 20,000 frames per second.

In this clip, the flea on the right travels around 34 body lengths in just 1/50 of a second.

In other words, they're tiny, incredibly fast, and not at all easy to wrangle and keep in front of the camera.

So this is what the film set looked like for that clip.

Now normally, I don't use a cage or anything when I'm filming insects, but for fleas, it's a different story.

Now, the jumping platform was right in there, but they'd still aim their jumps at me or at the camera, and I'd spend 20 minutes after each film attempt on the floor, looking for a flea.

Now, I didn't end up losing any fleas and I did manage to get some good shots.

So fleas launch themselves into the air by loading an internal spring that moves this part of their hind leg when it's released.

That bit of anatomy is called the trochanter, and here it is on the flea in the video.

When it rotates, that movement is transferred through the hind legs, down to the tibia and tarsus, which are covered in backward facing spines.

Those spines catch onto the ground and allow the flea to push off in an upward and forward facing direction.

If the spines don't catch and the back legs slip, the jump can end up like this where the flea tumbles end over end as it launches itself into the air.

So at this point, you might be wondering where I got all these fleas from in the first place.

Well, it turns out you can order them.

For our work, we weren't actually interested in the adult fleas, so what came in the box was a little bit more than that.

The dishes that arrived to the lab looked like this.

They were filled with a granular substrate and lined at the brim with eager adult fleas, which, as you might imagine, made them a real pain to get open.

That substrate was mostly food for the larva fleas with a bunch of unhatched flea eggs mixed in.

And if you're wondering what food for larva fleas is, well, here's perhaps the grossest recipe ever.

You mix together sand, dried cow blood, cat chow, and adult flea feces.

Yum.

After a few days in the lab, the flea eggs start to hatch.

I was able to catch a few eggs hatching by setting up a time-lapse video.

Here you can see one emerging from the eggs.

Watching this happen up close, you can see how the fully formed larvae is actually already mobile when it's still inside the egg.

It twists and turns until its head lines up with a spot where the egg has been slashed through and broken open.

Once it pokes through that spot, it wiggles the rest of its body free and dives down into the larval substrate.

In time-lapse, you can see how mobile these newly hatched fleas are.

They immediately burrow and dive around the clumps of hatched and unhatched eggs.

So this is where our research comes in.

We wanted to know exactly what these larvae were doing to move around.

It turns out that bit of their biology hadn't really been well described.

Of course, before this, people knew that cat flea larvae move.

Here's what larval movement looks like in real time.

When past researchers have mentioned and described this movement, here's what they said was going on.

In a paper from 1914, "The larvae bends down the head, hooking what one may call its chin over some relatively fixed object.

Then muscle draws up the rest of the body."

And then later in the 1930s, one German paper on bat fleas noted that the larvae used their mouth and hind end to move, while a later one attributes the movement to the front part of their head.

From there on, we haven't found many more detailed descriptions.

So the first thing we did was see if we could film how the larvae were interacting with the ground.

The shot you see here shows that these two projections sticking down from the head are what the larvae are using while they crawl.

They anchor them into the ground, then pull the body forward by flexing the head down and under.

Each step is extending the head forward and reaching to repeat the process.

I should also say that these shots were not easy to get.

What you're seeing here was filmed at five times magnification and at 600 frames per second.

The long and stiff hairs lining their body project backwards and seem to be supporting them and keeping them upright while they move.

They also probably prevent them from slipping backwards when they reached their head forward during each step of the crawl.

So after we saw that it was a specific head structure being used to interact with the ground, the next step was to image it.

Here's a view of a larvae we got under a scanning electron microscope.

The whole body's on the left, and the middle is showing you the front and underside of the head.

These projections off the head are the antennae, and these on the bottom are what you saw it use to pull itself across the ground, the maxillary palps.

Maxillary palps are kind of a standard issue pair of insect mouth parts, usually with sensory functions.

And for the cat flea image, we didn't find any evidence of modifications that would hint at their involvement in larval movement.

The only part hinting at that was how they project down and out of the head.

It seems like this is the case for a lot of different fleas too.

For instance, here's an SEM of a bat flea larvae where you can see the maxillary palps also stick out and down.

Next, we wanted to see if this movement strategy changed across their development.

So we filmed and measured crawling like this across 50 different individuals.

After doing that, Jake here, a student researcher on the project, measured the head width of each of the larvae to determine which stage of development each one is at.

Doing this sorts the larvae into three size classes that correspond to the three stages or instars of larval development.

And the first instars move the slowest at 1.2 millimeters per second, while the second and third move about the same speed at 2.6 and 2.5 millimeters per second.

But when scaled to body length, all larvae move at similar rates, ranging from 0.7 to 0.6 body lengths per second.

And that's actually pretty fast.

For instance, an earthworm only averages around 0.1 body lengths per second.

As a last step, we filmed the larvae in a 3D environment, a carpet sample, to see if they still moved in the same way.

And they do.

So no matter what larval stage or environment they find themselves in, cat fleas seem to use this movement and this behavioral strategy for pulling themselves across the ground.

So for us, this has been an interesting thing to film and describe.

Relative to other insects we've worked on, fleas are really well studied, so it's cool to still be able to contribute something new to our understanding of these organisms.

Everything you just saw here will eventually be published in the scientific literature, but for now, that's it for the flea research.

Thanks for watching.

- And that's "Sci NC".

I'm Frank Graff.

Thank you for watching.

[soft music] ♪ [soft music continues] ♪ - [Narrator] Quality public television is made possible through the financial contributions of viewers like you, who invite you to join them in supporting PBS NC.