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This video was created in partnership with Bill Gates, inspired by his new book “How to Avoid a Climate Disaster.” Find out more here: http://gatesnot.es/3qLlFgq

Throughout history humans have come up with lots of different ways to build shelters for themselves. But sometimes, inspiration for better construction materials comes from nature, in structures you might not expect — like the scales on a fish or the sweat glands in our own skin!

Hosted by: Hank Green

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This video was created in  partnership with Bill Gates, inspired by his new book “How  to Avoid a Climate Disaster.” You can find out more about  how we can all work together to avoid a climate disaster in the link below. [♪ INTRO].

One of the basic human needs is shelter. And over the short time humans have been on Earth, we’ve come up with a lot of  different ways to shelter ourselves — from mud huts, to wooden buildings, to  the towering skyscrapers of many cities.

But many of those materials  aren’t as strong as they could be. And the ones that are can have  an outsized impact on our planet. So now, architects and engineers are  turning to nature for inspiration for more resilient materials — stuff  that improves on what we use now, and that often minimizes the  impact we have on this planet.

From cement that acts like sweat glands  to glass that mimics fish scales, here are some biology-inspired materials that could  transform the future of construction. One major threat to buildings is fire. When a fire sweeps through a structure, it often means a lot of new  construction is on the way.

That often means more cement and steel — and making both of those involves  a lot of greenhouse gases. Thankfully, there are all kinds of ways  to make a building safer in a fire. In addition to fire alarms,  extinguishers, and sprinklers, you can add fireproof materials to  the building’s support structure to keep it from failing, as well as  to the walls, floors, and ceilings, to keep fire from spreading.

But these are all passive methods.  And because they’re extra materials, they add extra cost and take extra energy to make. So it would be helpful if  there were materials that could actively prevent fire damage, plus be supportive. Well, researchers in China  may have invented just that, using human sweat glands for inspiration.

In a paper published in 2019,  they shared their development of a fire-retardant cement blend,  which stops fire from damaging a building’s structure sort of like  how sweat keeps human bodies cool. The cement is a blend of three materials:  a set of compounds named APP-PER-EN, some reinforcing fibers, and a concrete binder. Under normal conditions,  it does what you’d expect — it holds up the weight of a building.

But if there’s a fire, it goes through four  stages to stop that fire in its tracks. First, as temperatures rise between  100 and 160 degrees Celsius, the reinforcing fibers and  the APP-PER-EN start to melt — kind of like how sweat glands make  sweat when you start to get warm. When the temperature reaches  above 170 degrees Celsius, micro-channels and cracks form.

Then, temperatures above 300 degrees  cause the APP-PER-EN to foam, filling the micro-channels and cracks and forming a  fire insulation layer like sweat on skin. And finally, as the insulating layer forms,  gases get released, including water vapor. This mimics the cooling mechanism of sweat — how when sweat evaporates, it takes  some of the body heat with it.   This insulating layer protects the  cement from falling under high heat by taking on a honeycomb shape.

This adds strength while also  insulating against heat transfer using the air trapped in the honeycombs.  I know! It sounds like science fiction! Then, after a fire, you can remove the  honeycomb layer and repair the material instead of having to replace the entire  cement structure, saving costs and resources.

Next, speaking of heat, humans have  been passively heating their homes with sunlight for thousands of years. But we couldn’t control the release  of this heat until the 20th century. Only then did we invent collectors like  thermal walls, which could absorb heat from sunlight and slowly release it over  time, keeping us warm throughout the day.

The trouble is, most of these  collectors are made from rigid, heavy materials, which means  their uses are limited. So engineers are looking to polar bears as  inspiration for textile-like solar collectors, which would be more efficient, lightweight,  and flexible than their predecessors. Polar bears have white fur and black skin  that work together as a natural solar collector and insulator, which helps them  stay warm in the extreme cold of the Arctic.

Their outer fur is actually  transparent — it only looks white because of the way it’s structured. That transparency allows the  sunlight to reach their dark skin, which converts the sun’s energy into warmth. Another layer of dense underfur close  to their skin is spaced just right, creating little pockets of air that  trap heat close to the bear’s body.

In fact, they radiate so little heat that  they’re almost invisible to infrared detectors. The surface of their coats looks the  same temperature as their environment! Inspired by this heat-trapping ability,  researchers based in Germany and Austria shared a new type of solar  collector in a 2015 paper.

They imagine it being used as part of solar power, but this general idea could  also help with buildings, too. The collector has two layers of  transparent plastic and silicone that let light pass through to the bottom layer. These layers are positioned around a  centimeter apart, trapping a layer of air between them and minimizing heat  loss like a polar bear’s underfur.

The bottom layer is black silicone,  which absorbs the sun’s light and converts it to heat. And the warm air can be pumped out  by a fan and stored for later use. Early tests show that this collector  is able to generate temperatures of up to 150 degrees Celsius —  although right now that only works when it’s in direct sunlight.

Still, while those extreme temperatures  might be helpful for solar power, that’s also not the kind of  heat you’d need in a building. So, this idea could really come in handy, especially as textile-based  buildings become more mainstream. These futuristic buildings are  constructed from lightweight materials stretched over a frame or woven together, and are making everything about  a building more sustainable, including its design, materials, usage, and  even how it’s recycled at the end of its life.

Adding a polar bear-inspired heating  system would make them even more versatile. Buildings also need to stay  comfortable in hot weather, though — and traditional cooling systems  aren’t always the most efficient way of managing a building’s temperature. Also, heating and cooling  systems account for a lot of the greenhouse gases we emit as a planet.

Architects in the U. S. may have  come up with a more efficient way of regulating a building’s temperature, though, and once again they have drawn on  inspiration from the human body. In 2011, they released a  prototype of a building exterior modeled after a biological process  that’s similar to a thermostat — if a thermostat could control  more than just temperature.

That process is called homeostasis,  and many organisms use it to keep their bodies functioning  within pre-set limits, like an ideal temperature range or fluid balance. Basically, it allows things  to remain stable on the inside even as conditions change on the outside. The team designed a glass building facade inspired by the way human  muscles maintain homeostasis, by expanding and contracting to regulate  heat as they work inside our bodies.

Similarly, the facade helps regulate  the internal temperature of the building by opening and closing itself. The exterior of the building is  made up of two layers of glass, and sandwiched between them  are swirling silver lines. Those lines are made up of ribbons  of a special type of polymer that can have an electric current applied to it.

It also has a silver coating that  distributes an electrical charge across the entire surface. When sunlight warms the silver coating, the polymer expands and shades the building. Then, when the building cools off, the polymer  contracts and allows more light inside.

That way, the building responds to changing  environmental conditions throughout the day, helping manage energy use in  a more efficient and sustainable way. Now, this tech might not be best for  places where you want extra sunlight — like, in the middle of a cold winter. But for a lot of climates, it  could be a great step forward.

Next up: concrete. Like we mentioned earlier, making concrete  is a major contributor to climate change, but sometimes, it seems like there’s  only so much you can do about that. Like, if a building is  damaged during an earthquake… well, you’re gonna have to build another one.

Some teams are looking into  concrete recipes or processes that are overall better for the planet,  but some are taking another route. Like, researchers at Purdue University  are trying to strengthen concrete instead… by using cracks. More specifically, in 2018, they  developed 3-D printed cement structures inspired by the mantis shrimp.

Mantis shrimp hit their prey  with a club-like front claw at an extremely high speed,  which generates a lot of force. But even then, that claw does  not crumble under pressure, thanks to the way the shell’s  microscopic layers are arranged. The layers are stacked in a spiral, each  layer slightly offset from the next.

When stressed, cracks form in the  microscopic layers, but the twisted structure keeps the cracks from spreading  through the entire club. Specifically, the spiral forces  the cracks to form parallel, or side to side within a layer, instead  of perpendicular — or top to bottom. And every time a crack has to change direction, it requires a lot of force to do so, which  causes it to lose some of its energy.

If a crack does spread top to bottom, the  next layer vibrates as the crack reaches it, absorbing the energy from the crack, keeping  it from traveling into the next layer. Ultimately, these tiny twisting cracks  stop the club from falling apart, by preventing larger cracks from forming  that would compromise the structure. Using this club for inspiration, the  researchers 3D printed a cement paste that’s laid out in a similar spiral design.

Poured cement is brittle and when stressed, large cracks can form and  lead to catastrophic failure. Not so with this 3D-printed material.  Here, tiny cracks are stopped so they don’t spread throughout the  layers, just like with the mantis shrimp. So the concrete is inherently stronger.

The goal is to eventually use this  type of material to build more earthquake-resistant structures.  And that means less wasted concrete! Finally, windows. Windows can be an  incredibly important part of a building on an aesthetic level.

But since they’re  so fragile, they’re also the weakest. Except, by mimicking an overlapping  pattern found in fish scales, researchers may have found a way to  improve the strength of laminated glass, while still preserving the  ability to see through it. Laminated glass is created by sandwiching a soft, polymer-based layer between  two layers of regular glass.

This keeps the glass together  if it breaks, making it safer. But it is not stronger — or at least  it wasn’t until researchers in Canada discovered a way to improve  the lamination process. In a paper published in 2018,  they outlined their process for strengthening glass with  a new lamination technique.

They started by coating two  sheets of glass with a flexible, heat-resistant polymer film, and then etched  straight lines into the glass with a laser. The polymer film holds the glass  together through the etching process. Then, they laid the sheets of  glass on top of each other, with another layer of flexible  polymer sandwiched between.

They also rotated the top sheet of  glass so the etched lines go in the opposite direction — known  as cross-ply architecture — and that gives the glass added  strength and flexibility. When this type of glass is stressed, the  cross-ply architecture and stretchy polymer middle work together to help the glass  be stretchy and tough instead of brittle. Testing revealed this glass to be  50 times tougher than regular glass, while still maintaining its see-through qualities.

If this kind of glass spread, that would  mean stronger, safer windows that might need to be replaced less often — all  thanks to a pattern inspired by fish. Nature has been around for a long time,  and we’re only beginning to tap into the engineering insights you can get  from billions of years of evolution. But with materials like these, we’re  looking at a future of buildings that are safer, more resilient,  and better for our planet.

When you think about things  contributing to climate change, construction materials might  not be what comes to mind first. But making things like cement, steel, and  plastic releases a lot of greenhouse gases. And if you want to keep learning more  about how we can make those things better, you can read Bill Gates’s new book  “How to Avoid a Climate Disaster.” It talks about manufacturing, but also food, heating and cooling, transportation, and more.

If you’re interested, you can find out more about how we can all work together to avoid  a climate disaster in the link below. [♪ OUTRO].