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  • Thanks to Brilliant for supporting this whole week of SciShow!

  • Go to Brilliant.org/SciShow to learn more.

  • {♫Intro♫}

  • You can probably spot fake wood a mile away.

  • Something about the grain, the texture,

  • the consistency... it's all wrong.

  • And you might wonder why we even bother trying.

  • I mean, wood literally grows on trees.

  • But we have some good reasons for

  • wanting to make fake wood -- and some good reasons

  • why it's really hard to do.

  • One reason we want fake wood is saving our forests.

  • The thinking is if we can make something

  • that looks like wood and has its properties,

  • we don't have to keep cutting down actual trees.

  • Plus, wood has an incredibly complex architecture

  • that makes it light yet strong

  • -- and this has actually inspired materials scientists

  • to try copying that structure for

  • new lightweight materials.

  • But it's not actually that easy.

  • Scientists have been having a tough time

  • making artificial wood.

  • The main reason is because wood has

  • a pretty unique structure.

  • You can see and feel the grain,

  • the knots -- nothing else really has that.

  • But if you put wood under a microscope,

  • it gets even weirder.

  • You'll see this sort of scaffolding that looks like a bunch of tubes squished together.

  • These tubes are actually the tree's cells, meant to channel water throughout the plant.

  • Those cells' walls are, in turn, made of cellulose fibers embedded in a blob of hemicellulose

  • and lignin -- all chemicals that contribute to a fibrous, rigid structure.

  • And those cellulose fibers aren't just tossed willy nilly into the tree, either.

  • They're oriented to match the direction of the tree or branch they're on.

  • This means that the tree's properties are anisotropic: they're different in different

  • directions.

  • For example, thanks to those aligned bundles of cellulose fibers, trees are stronger across

  • the grain rather than along it.

  • If you try to chop a tree horizontally, lumberjack-style, these super-strong cellulose fibers will bear

  • the brunt of the force and make it hard to chop.

  • But if you try to cut wood vertically, you'll be hitting the not-as-strong lignin-hemicellulose

  • matrix -- which happens to be much easier to break.

  • This complexity explains other things, too.

  • Like why some woods can be 1000 times stiffer than others, since their microstructures and

  • even their exact compositions can be vastly different.

  • This complexity also means that wood, and all its awesome properties, are super hard

  • to mimic.

  • There has been at least one attempt in the scientific literature.

  • A 2018 paper published in Science Advances described a way of making artificial wood

  • using special water-soluble polymers frozen in liquid nitrogen and alcohol to create a

  • desired configuration.

  • Then they removed the solvents to lock-in that configuration, and heated the whole thing

  • to make it harden.

  • The authors found that by varying the cooling rate, they could fine-tune the properties

  • of their fake wood.

  • And some of those had similar properties to real wood, like how much they could be compressed.

  • They even looked similar to real wood, with some advantages like being more resistant

  • to flames.

  • These results do seem promising.

  • But it's important to note that this was done entirely inside a lab with a homemade

  • contraption.

  • This probably won't translate easily to a much larger scale, so you will likely not

  • see these artificial woods in stores anytime soon.

  • There are other methods scientists could use to make wood-like structures, but they have

  • similar drawbacks.

  • As a result, many commercial attempts at making artificial wood only focus on replicating

  • a couple key properties.

  • And that inability to mimic all the properties of wood rather than just one or two means

  • that fake wood won't fool us -- for now, at least.

  • Many wood substitutes, for example, are made by mixing actual wood byproducts like wood

  • flour with some sort of plastic or adhesive.

  • That's basically really fine sawdust, not a gluten-free cupcake ingredient.

  • You've probably seen these wood-plastic composites in decks or lining your door.

  • Since these composites are made of, well, wood and plastic, they very often have properties

  • that lie in between those of their constituent materials.

  • So they are usually less stiff than solid wood but more rigid than plastic -- in general,

  • anyway.

  • And plastic here actually gives the material another advantage: it won't absorb as much

  • moisture, so it's less vulnerable to rot.

  • But what about products that don't have any wood at all?

  • One material that's gained traction as a wood alternative is something that's used

  • as trims for houses called cellular PVC.

  • Cellular PVC is made by blowing bubbles through melted plastic and other additives to form

  • a solid material with little bubble-like holes throughout it, giving it more structure at

  • a microscopic level -- like real wood.

  • But while that makes cellular PVC more lightweight, it just isn't like wood.

  • There are still some key differences.

  • And even if it's more durable than wood, this plastic substitute certainly doesn't

  • feel or look like wood.

  • Unless, of course, you do a fancy paint job -- which can help with the looks, but that's

  • about the extent of it.

  • So even if wood's been around a while, we're still working on ways to improve on nature's

  • original design.

  • And maybe in the future, that'll not only help us save the trees but also synthesize

  • a whole range of materials we've never even dreamed of.

  • Outro: Imitating the structure of materials like

  • wood requires understanding space, shapes, and angles -- the kind of thing you learn

  • in a geometry course.

  • And if that's piqued your interest, Brilliant offers a brand new course on Geometry Fundamentals

  • that can start you off right.

  • It's an intuitive introduction to the geometry that's all around us.

  • Brilliant also offers over 50 other courses in science, engineering, computer science

  • and math, all with hands-on and interactive components to help you learn.

  • So there's something for everyone, to learn a bit of everything.

  • Brilliant courses are now available offline using their iOS and Android app.

  • So even if you're traveling or have a spotty internet connection, you'll be able to keep

  • learning.

  • The first 200 people to sign up at Brilliant.org/SciShow will get 20% off the annual Premium subscription.

  • Thanks for checking it out -- and for supporting us!

  • {♫Outro♫}

Thanks to Brilliant for supporting this whole week of SciShow!

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