NATURE PODCAST

Meet the inflatable, origami-inspired structures

The self-supporting structures that snap into place, and how a ban on fossil-fuel funding could entrench poverty in sub-Saharan Africa.

Listen to the latest science news, with Benjamin Thompson and Shamini Bundell.

In this episode:

00:45 Self-supporting, foldable structures

Drawing inspiration from the art of origami, a team of researchers have demonstrated a way to design self-supporting structures that lock into place after being inflated. The team hope that this technique could be used to create arches and emergency shelters that can be quickly unfolded from flat with minimal input.

Research Article: Melancon et al.

News and Views: Large-scale origami locks into place under pressure

Video: Origami-inspired structures could be deployed in disaster zones

07:32 Research Highlights

Nocturnal fluctuations cause scientists to underestimate rivers’ carbon emissions, and the ‘island rule’ of animal size-change is seen around the world.

Research Highlight: Rivers give off stealth carbon at night

Research Highlight: Animals around the world follow the ‘island rule’ to a curious fate

09:55 Banning fossil-fuel funding will not alleviate poverty

A ban by wealthy nations on the funding of overseas fossil-fuel projects would do little to reduce the world’s climate emissions and much to entrench poverty in sub-Saharan Africa, argues economist Vijaya Ramachandran.

World View: Blanket bans on fossil-fuel funds will entrench poverty

17:17 Briefing Chat

We discuss some highlights from the Nature Briefing. This time, the first powered flight on another world, and estimating how many Tyrannosaurus rex ever lived.

News: Lift off! First flight on Mars launches new way to explore worlds

Video: Flying a helicopter on Mars: NASA’s Ingenuity

News: How many T. rex ever existed? Calculation of dinosaur’s abundance offers an answer

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Transcript

Listen to the latest science news, with Benjamin Thompson and Shamini Bundell.

Host: Benjamin Thompson

Welcome back to the Nature Podcast. This week, structures inspired by origami…

Host: Shamini Bundell

And how banning fossil fuel projects could entrench poverty in sub-Saharan Africa. I’m Shamini Bundell.

Host: Benjamin Thompson

And I’m Benjamin Thompson.

[Jingle]

Host: Shamini Bundell

First up this week, Noah Baker has been imaging a future where we all live in origami bouncy castles. It’ll make more sense in a minute.

Interviewer: Noah Baker

When I think of origami, the first thing that comes to my mind is a paper crane.

Interviewee: David Melancon

This is kind of the first thing I guess you fold when you start origami, and I did not succeed on the first try. It took me a couple of tries to get it right.

Interviewer: Noah Baker

This is David Melancon, an engineer from Harvard University. When he thinks of origami, he sees much more than paper cranes.

Interviewee: David Melancon

To make a shape, it’s very powerful. So, there are mathematical proof that tells you from a 2D sheet of paper you can introduce any fold that you want to get an arbitrary 3D object. But also, most importantly, there’s this property introduced by these origami creases that you can get and it’s called bistability. So, what that means is your structure has more than one stable state. So, a stable state would be a state in which the structure can stay without any force applied on the structure, so it’s happily staying there. You don’t have to force it to stay there.

Interviewer: Noah Baker

To David, the flexibility and bistability of origami made it a great candidate for making deployable structures – portable, compressible, storable 3D objects, with uses ranging from project packaging to emergency shelters, or even satellite solar panels. But folding a structure from a flat sheet is not especially practical or quick. Plus, as anyone who has seen my attempts at a paper crane will attest, origami requires a degree of skill. So, David and his team adapted the art.

Interviewee: David Melancon

I believe what we’re doing is kind of origami plus. It’s not the most purist form of origami where you start with a sheet of paper and then you introduce folds. For us, we’re thinking of fabrication methods that basically you don’t have to be good at origami to create the shapes.

Interviewer: Noah Baker

Specifically, David applied elements from origami to another type of deployable structure – inflatables.

Interviewee: David Melancon

The advantage with that, it’s very easy to deploy. You have a pump and then you can deploy. You think of these bouncy castles or these big shelters for sports events. This is very good, but again there is a disadvantage where you need to have a seal there or a continuous supply of pressure to keep it deployed.

Interviewer: Noah Baker

But a flat sheet of paper isn’t blow-up-able, and that’s were their innovation came in.

Interviewee: David Melancon

A 2D sheet of paper is a surface. From that surface, we needed to close it to form a cavity in order to be able to inflate it, and this really closed the loop. So, we had an origami cavity you can deploy with pressure, and because you introduced this multistability – more than one stable state – then you can snap it to the deployed state and then you don’t need this force, this pressure, anymore to keep it there. So, you can disconnect and it stays there in the deployed configuration.

Interviewer: Noah Baker

An origami structure but that you can blow up with pressure. Imagine a bouncy castle but with folds that make it stable when it’s blown up. What’s more, you can quickly pull it down again by sucking the air out, and it will fold back down into its compressed, stable state. David pointed out that, in theory, this concept doesn’t only work for flatpack structures but also for structures with two three-dimensional stable states.

Interviewee: David Melancon

For instance, you can think of transforming a structure from a bird to a rabbit. Why would that be useful? I’m not sure, but this is quite exciting to think that you could do that.

Interviewer: Noah Baker

This isn’t the first time that principles from origami have been used in engineering. But up until now, most of the focus has been on much smaller scales, and there are several reasons for that. Here’s Sigrid Adriaenssens, a structural engineer from Princeton University, who’s written a News and Views article about David’s paper.

Interviewee: Sigrid Adriaenssens

The challenge of scaling it up is that at the smaller scale, gravity doesn’t really matter. We could assume that paper theoretically doesn’t have a thickness and doesn’t weigh anything, but from the moment you start scaling this up, you cannot really build a shelter out of paper. Your material has to be thicker. So, one challenge is mass. It also has to maybe be waterproof. So, basically your material has to maybe fulfil more functions. And then of course, if we put it outside, you’ve got the wind blowing on it, you’ve got snow. Those are all quite large loads that also start acting on this system. All these things are challenges at the larger scales.

Interviewer: Noah Baker

To tackle these challenges, David and his team went back to mathematical principles. Here’s Sigrid again.

Interviewee: Sigrid Adriaenssens

First of all, they present a design methodology, so they present a whole description of what kind of triangles you can use and what their angles have to be to geometrically fit this together. And then they use basically two approaches to test this. One, is they use numerical finite elements – modelling – so they basically model the system in the one state, they start inflating it and then see how it gets into the other state. And during that entire process they model the stressors that are occurring, the displacements of all the points. But of course, any computational model is only as good as you make the model or as the questions that you ask, right? So, to kind of make sure that their models are accurate, they also make prototypes.

Interviewer: Noah Baker

Now, the prototypes are currently mostly for testing purposes, and much of David’s work is still a proof of principle, but he has high hopes for these sorts of inflatable origami structures in the future.

Interviewee: David Melancon

I’m really interesting in transitioning this fundamental research to solve real world problems. If you want to use them in extreme scenarios – as I propose, emergency response or space exploration – to have both the numerical tools to show that and also the material platform to withstand these extremes. So, I’m very interested in that. However, I’m also interested in these environmentally friendly materials. So, I believe origami is a very good design platform, but I’m very interested in finding materials that could be degradable, that could reusable, that could be recyclable, and still have the same properties. To me, that would be very exciting.

Host: Shamini Bundell

That was David Melancon. Before him, you heard Sigrid Adriaenssens. The package was edited by Noah Baker and reported by Nick Petrić Howe. And if you now really want to see these origami structures in action, we have you covered. Check out the show notes for a link to a video all about the paper.

Host: Benjamin Thompson

Coming up, we’ll be hearing how an economist thinks that banning funding for fossil fuel projects could hamper efforts to alleviate poverty in sub-Saharan Africa. Right now, though, it’s time for this week’s Research Highlights, read by Dan Fox.

[Jingle]

Dan Fox

Carbon dioxide released from streams and rivers is an important source of global emissions. But researchers may have been underestimating the amount of CO2 released because all their measurements were taken during the day. Researchers have known that carbon gets into rivers from rocks, soil and organisms and then gets released into the atmosphere as carbon dioxide. But what wasn’t understood was that the levels don’t stay the same overnight. A team of researchers analysed 66 rivers around the world and found that night-time CO2 emissions are on average 27% higher than those during the day. Perhaps because during daylight, some of the CO2 gets fixed by photosynthesis. This is important new information for modelling the planet’s carbon cycle. Absorb more of that research over at Nature Geoscience.

[Jingle]

Dan Fox

An analysis of more than 1,000 species shows that birds, mammals and reptiles living on islands tend to be either miniature or gigantic versions of their mainland counterparts – evidence that the so-called ‘island rule’ applies across a wide variety of vertebrates. Big mainland animals often evolve smaller bodies on islands, whereas small mainland species become larger, for instance, the world’s largest lizard, the island-dwelling Komodo dragon. Researchers set out to settle the debate as to whether examples like the dragon were mere flukes or part of a broader evolutionary pattern. The team gathered data from multiple studies to examine over 1,000 island species and their mainland counterparts. While the evolutionary reasons behind these size changes are complex, the authors found widespread evidence for the island rule around the world, with the most extreme shifts in body size occurring for mammals and reptiles on smaller, more remote islands. Take in the scale of that research at Nature Ecology and Evolution.

[Jingle]

Interviewer: Benjamin Thompson

In the past few months, the United States outlined its intention to stop funding for overseas fossil fuel projects, mirroring similar calls made by a number of European countries. On the face of it, that seems like a sound plan. The world needs to reduce global carbon emissions after all. But for economist Vijaya Ramachandran, director for energy and development at the Breakthrough Institute, these decisions are short-sighted. She’s written a World View for Nature, where she suggests that this will do little to reduce emissions and much to entrench poverty in places like sub-Saharan Africa. I gave her a call and she laid out why.

Interviewee: Vijaya Ramachandran

I think there are some reasons to be worried about this ban. About 600 million people in Africa lack a reliable source of electricity. From my perspective, the main challenge for Africa is to increase and expand its supply of energy, and we need to do that with as broad a portfolio of sources as possible. Taking sources off the table at this point, I think, is detrimental to development and to poverty alleviation in Africa. Sub-Saharan Africa accounts for, in the most recent year, about 2% of total emissions. I don’t think these are the countries that need to bear the burden of a ban on fossil fuels. The US, the EU, Japan and other rich countries still rely on fossil fuels. I think it is the height of climate injustice to impose restrictions on poor countries that are most in need of modern infrastructure, and least responsible for the world’s climate challenges.

Interviewer: Benjamin Thompson

And your World View is really looking at striking that fine line between economic development and climate change, and you suggest that maybe natural gas is one way to alleviate energy poverty.

Interviewee: Vijaya Ramachandran

So, natural gas is a fossil fuel, but I think it could do much to lift communities out of poverty. It’s roughly twice as carbon efficient compared to coal, and it produces radically lower levels of water and land pollution. And Africa has abundant sources of natural gas. The top six countries – Nigeria, Algeria, Mozambique, Egypt, Libya, Angola and the Democratic Republic of the Congo – have vast resources of untapped natural gas that could be used to expand their supply of electricity.

Interviewer: Benjamin Thompson

And in your World View you list some of the ways that natural gas could be used. Maybe you could lay out some of those ideas for us?

Interviewee: Vijaya Ramachandran

Certainly, so, natural gas, for one thing, is the most effective form of energy to use in the production of fertiliser, and sub-Saharan Africa uses very little fertiliser. Yields are very low compared to Asia or to Latin America, and in order to expand the amount of fertiliser that is used on African farms, we will need to make fertiliser using natural gas, so that’s one really important use. The other uses are thing like in liquified or compressed form, it can be used to power vehicles, and again that’s a much cleaner form of powering transportation than our traditional fossil fuels that we’ve been using in the past.

Interviewer: Benjamin Thompson

And yet it is still a fossil fuel, though, right, and of course, extracting natural gas isn’t without its issues.

Interviewee: Vijaya Ramachandran

It isn’t without its issues and of course there’s been a lot of controversy around the hydraulic fracturing of natural gas, but it is also the case that there are better ways to extract natural gas and that it can serve as a bridge fuel for a very long time. In the US, it is now the largest source of energy for generating electricity. So, I think we cannot dismiss it as a very useful and important source of energy.

Interviewer: Benjamin Thompson

You mention using gas as a ‘bridge’ fuel, and that’s a term that’s used a lot to maybe kind of stretch out getting to renewable energy, but it’s not an uncontroversial subject. There are people that say that there’s no such thing as a bridge fuel, right – it’s dirty fuel or it’s clean fuel. Is there the potential that if gas is cheap to produce and use that really it will stimie growth towards renewable energy?

Interviewee: Vijaya Ramachandran

Yeah, I don’t find that argument convincing. I think countries are exploring a whole range of energy sources because the energy gap is so large. And in my view, the investments in renewables will come as the technologies become more cost effective and more accessible to poor countries. That’s really what’s going to drive the development of renewables. It’s not that if we ban oil and gas or if we ban natural gas that these countries are going to develop their renewables sector faster. You can even make the case that you need energy to develop new sources of energy. And by cutting off energy sources, you’re cutting off the ability of businesses to do their work, of research companies to do their work, of any kind of technology adaptation, of any kind of climate mitigation. All of that needs energy, so I think the idea of not having intermediary fuels would then spoil the development of renewables, I don’t find that argument convincing.

Interviewer: Benjamin Thompson

Which maybe brings us back to the subject of your World View which is, of course, this ban by rich countries – the US and the EU. Is there some nuance, do you think, that could be struck between this ban and clearly the need to lift people out of poverty.

Interviewee: Vijaya Ramachandran

Yes, I think there is a way to do that. One possibility is to allow an exemption for very poor countries, and the World Bank has a classification of countries by income. Something that allows greater flexibility than a blanket ban on the financing of fossil fuels. Another way to do it is to provide an exemption to the countries that are the lowest emitters or the lowest consumers of energy or countries that have very little access to renewable energy technologies. I think there are ways to do this in a reasonable manner rather than imposing a blanket ban on the international financing of fossil fuels. One point, Ben, in that context is that for larger countries, this ban doesn’t matter too much. They can raise money on private markets to finance any kind of energy they want. This ban is going to hurt poor, African countries the most. I really do hope that countries will think this through, particularly rich countries which are the largest shareholders in the multilateral development banks, in the financing vehicles that poor countries use, that they’ll come up with something much more reasonable that allows these countries to develop their renewable resources but at the same time also prioritises economic development, poverty alleviation, girls education, the growth of agriculture, the kinds of things that are really, really important for poor countries.

Interviewer: Benjamin Thompson

That was Vijaya Ramachandran. You can find a link to her World View in the show notes.

Host: Shamini Bundell

Now, finally on the show, it is time for our weekly Briefing chat, where we pick our favourite stories from the Nature Briefing. So, Ben, is there anything that has piqued your interest this week?

Host: Benjamin Thompson

Oh, absolutely, Shamini. What cost US$85 million, is 1.8 kilograms, 49 centimetres tall and achieved something remarkable 300 million kilometres away?

Host: Shamini Bundell

I think, if I hadn’t already had a strong inkling based on knowing what you were going to cover, I think the 300 million kilometres away gives it away a bit. So, NASA flew a helicopter on Mars.

Host: Benjamin Thompson

That’s right. So, the Ingenuity helicopter successfully managed a 39.1 second powered flight, and I underlined the word ‘powered’ there, which is the first time that has been achieved on another planet. Kind of amazing, right?

Host: Shamini Bundell

This does imply that there’s been unpowered flights, like some sort of glider zooming around on other planets before. Or is it just the parachutes when they kind of drop down from the satellites?

Host: Benjamin Thompson

Yeah, there have been other experiments where sort of balloons have kind of meandered through atmospheres and what have you, but this is a very, very small helicopter, which was attached to the bottom of the Perseverance rover which obviously landed on Mars a little while back, and was dropped off onto what they’re calling an airfield, which I think to the untrained eye looks like a relatively flat bit of Mars, and after a little bit of a delay for some sort of software issues and what have you, it successfully took off on Monday.

Host: Shamini Bundell

So, does that mean that now it’s going to be gathering all sorts of data and exciting science about Mars?

Host: Benjamin Thompson

I mean, the short answer is no, in this instance, Shamini, but it is kind of collecting data in so much as will this even fly? So, Mars has a very different atmosphere to Earth – it has just one 1% of the density – and of course calculations on aerodynamics that are done here on Earth might not necessarily apply. So, this first test flight which was just fly up for a few metres, turn around I think 96 degrees and fly down, was just to work out what’s the power needed to do this kind of thing, will it work, and it successfully did. Now, what I will say is this wasn’t kind of done live by someone with a sort of Xbox controller back on Earth. Obviously, it’s a very, very long way away, so this was kind of autonomous and the signal from the helicopter was beamed to the rover, that was then beamed to an orbiter, which was then beamed back to a big dish here on Earth, and then the need came through for people to watch. So, obviously there was a bit of waiting to see what happened. And I will say I watched the live stream of this and it was quite low frame rate to begin with, so what came back was it was on the ground and the next frame it was up in the air, so I was like, ‘Wow, JPL and NASA have built an infinity-miles-an-hour helicopter,’ but then the later feed came in and there it is quite serenely going up and going down. And more flights are planned for the next few weeks to try and put it through more of its paces.

Host: Shamini Bundell

It sounds like it should be easy somehow. I don’t know why I think that. But the aerodynamics people, they can fly planes and all sorts, it’s just a helicopter on Mars, but, yeah, at first there’s the, ‘How do you test it,’ well, you have to go to Mars and then the whole issue of over those distances, everything they do has to be pre-programmed. They can’t sort of respond live. So, wow, they must have been pretty relieved that that worked.

Host: Benjamin Thompson

Well it seemed like it. There was a lot of cheering, as you might imagine. But in terms of sort of testing it, you’re right, it is hard to test. We actually have a video on our YouTube channel where we’ve been looking at how you put something through its paces like this and the mission, and how it was tested in this kind of low-density sort of chamber on Earth and all the sorts of issues to think about, so I’d recommend that listeners go and check that out once the podcast is finished. And there’s one more little titbit, Shamini, if I may. So, something that I didn’t know until I was doing some research into this was that this little helicopter had a tiny little patch of material attached from the Kitty Hawk, the Wright brothers’ plane, the first powered flight.

Host: Shamini Bundell

Oh!

Host: Benjamin Thompson

Yeah, I know, right, isn’t that amazing? There is a tiny piece of the Wright brothers’ plane up there on Mars.

Host: Shamini Bundell

That’s pretty cool. And yeah, do check out the video. So, there’ll be a link to our YouTube channel in the show notes where you can have a watch of that.

Host: Benjamin Thompson

Well, moving on then, Shamini, what have you got for me this week?

Host: Shamini Bundell

I am happy this week because I have dinosaurs and you know how I feel about dinosaurs. I’m very pro-dinosaurs. So, the big questions that everyone wants to know. We all know Tyrannosaurus rex, big stompy carnivore. What I feel that we always wanted to know but didn’t was how many T. rexes were there?

Host: Benjamin Thompson

I mean, this sounds like I’m in a tech company interview. You’ve just asked me to work out how many T. rexes, what, that ever lived? And I’ll show my workings, I’ll show my ignorance on the podcast if you want. I mean, I imagine, we have some fossils I guess, but that’s not all of the fossils. If it was, there’d only be like, what, 12 Tyrannosaurus rexes that ever lived, so I guess you have to try and work out the density of fossils in area and do some complicated maths maybe?

Host: Shamini Bundell

Yeah, it’s basically maths and complicated estimations, and a team from the University of California, Berkeley have basically done that in a paper in Science, and there’s a lot of guesses and uncertainties in their maths, but the main figure they needed was looking at modern animals, you’ve got a correlation between how big an animal is and how much land it needs. So, a field might be able to support one elephant or it might be able to support a tonne of mice. So, if you took a T. rex, how much land, how much area do you think would be needed per T. rex? So, that gives you a very rough estimate of the population density, and then they take what they know about where T. rexes live, which is kind of based on where the fossils are, but it’s basically sort of modern North America or part of it, and they’ve done some maths and they concluded that at any one time, there would have been about 20,000 T. rexes living, and that’s actually not a lot. So, their example was if you take an area the size of Washington DC, it could probably support, they reckon, two T. rexes, given the massive size of these things. But I said about 20,000 because there was a little note saying it could be out by a factor of ten in either direction.

Host: Benjamin Thompson

Oh, well, okay, alright, but I suppose you have to start somewhere.

Host: Shamini Bundell

Yeah, and you can sort of scale this one up, so the big number that’s sort of been in the headlines is how many were there ever, and multiply it by roughly how long T. rexes were around for, which was maybe I think 2.5 million years, and that gives you the big exciting number of around 2.5 billion T. rexes that ever lived.

Host: Benjamin Thompson

I mean, great, they have an estimate now. To what end?

Host: Shamini Bundell

Well, the thing that they were actually really interested in, aside from going, ‘Yay, 2.5 billion, we have an estimate’, was to try and understand more about fossilisation and the fossil record because, as you mentioned, there aren’t many T. rex fossils that we know of. We have 32 separate adult T. rexes that have been discovered as fossils ever, and so what this number gives us is we have 32 fossils out of potentially 2.5 billion T. rexes. So, what this tells us is that the chance of being fossilised, and this is for huge T. rexes that lived over a wide range for millions of years, the chances are tiny that we can actually find fossil evidence of them.

Host: Benjamin Thompson

Right, I mean, I guess that means that maybe, if they’re that vanishingly rare, what else have we never seen that maybe existed all over the place, but just chance, sort of digging it up thus far, hasn’t happened.

Host: Shamini Bundell

Yeah, exactly. It really highlights the limit of our understanding of these times. Like I said, this is just an estimate. We don’t fully know what kind of territories these animals were living in, how much space they needed, and these are some of the better known ones, so yeah, think about all the species that we may never even get a glimpse of.

Host: Benjamin Thompson

Well, Shamini, that is an amazing story, and listeners, if you’re interested in other stories like this but you prefer them delivered direct to your inbox, then make sure to sign up for the Nature Briefing. And we’ll put a link in the show notes for where you can do just that.

Host: Shamini Bundell

That’s all for this edition of the Nature Podcast. Do not forget, head over to our YouTube channel, and we’ve got videos of the origami structures we were talking about and a video of a helicopter on Mars – very cool.

Host: Benjamin Thompson

And as always, you can reach out to us on Twitter – we’re @NaturePodcast. Or you can send us a email – we’re podcast@nature.com. I’m Benjamin Thompson.

Host: Shamini Bundell

And I’m Shamini Bundell. Thanks for listening.

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