Is spider web really stronger than steel?

0:00 This is the largest amount of spider silk that's

0:02 ever been put together for a test like this.

0:05 So I'm gonna put it to the ultimate test,

0:06 and try to be the first person ever to swing from spider silk.

0:10 I don't know if it's going to hold my weight, so let's see.

0:12 In three, two, one.

0:15 (Derek yelling)- In "Spider-Man Two," Peter Parker

0:19 is on a runaway train full of passengers.

0:21 And to stop it from derailing, he stands in front of the train,

0:24 fires webs at the buildings around him, and holds on.

0:27 The webs stretch, some of them snap,

0:29 but they do just enough to slow down the train and save everyone on board.

0:33 It sounds like something straight out of a comic book.

0:36 But real spider silk, the fiber that makes up a spider's web,

0:39 well, it truly might be this incredible.

0:42 It's reportedly stronger than steel.

0:44 It's pretty strong.

0:45 That's crazy!

0:46 And 10 times tougher than Kevlar.

0:49 To find out if that's really true,

0:50 I went to the Blackledge Spider Lab at the University of Akron,

0:53 one of the world's leading research centers studying spider silk.

0:56 Before I went to the lab,

0:58 I'd always assume that a spiderweb was made from just one kind of silk.

1:01 But that's actually not the case.

1:03 One type of silk anchors the web to a surface.

1:05 Another forms this stretchy spiral, and a different sticky silk catches prey.

1:10 Once something's trapped, the spider switches to yet another silk to wrap it up.

1:14 The threads are all thinner than your hair,

1:16 so they're going to look pretty similar

1:17 to each other unless you use a microscope.

1:20 [Henry] All in all, there are seven different types of silk,

1:22 but the strongest is the dragline silk, which holds the web in its place.

1:27 We've got the two main structural threads in this web.

1:30 So the spokes on the wagon wheel and the outer framework here,

1:34 that's all the dragline silk.

1:36 It's called major ampullate silk if you want the fancy word.

1:39 The major ampullate is that one that commonly compared to steel?

1:44 Yes!

1:44 Okay.

1:45 Absolutely.

1:46 And that's partly because it's function in a web like this.

1:49 A bug hits it, to stop that moving bug,

1:52 most of the work is done by the dragline silk.

1:55 [Henry] To do this, the dragline silk has to be incredibly strong.

1:58 So to find out how it compares to steel, we wanted to run a test,

2:02 but it turns out that getting the sample isn't so easy.

2:05 All right, we've taken a garden variety

2:07 spider and knocked it unconscious using CO2.

2:10 We brought it over here and we put it down with tape.

2:12 I then started pulling out the dragline silk by hand.

2:15 It's so light that you can barely feel it.

2:17 We've attached it to this big rotating

2:19 mechanism which they custom made to milk spiders.

2:22 (bright music) No spiders were harmed in the making of this video.

2:29 Now that we've got our silk,

2:30 we can put one strand into a machine that slowly pulls on our sample.

2:34 And as it pulls, we'll monitor two key properties.

2:37 When you pull on the silk,

2:38 that force is spread over a tiny cross-sectional area.

2:41 If you divide the force by that area, you get the stress.

2:44 Now, as you pull, the silk is also stretching.

2:47 To see just how much, we divide the change in length by the original

2:50 length to get a measure called the strain.

2:53 At first, as the stress increases, the strain increases roughly in proportion.

2:57 And if we stop pulling here, the silk would spring back to its original length.

3:01 But keep pulling and eventually it passes

3:03 a point where some of that stretching becomes permanent.

3:06 And it's pulling.

3:09 [Videographer] All right.

3:09 You film that, I'm going to be filming this.

3:11 [Henry] And it broke.

3:13 [Videographer] Wow!

3:14 [Henry] Eventually, if you keep pulling on the silk, it will break.

3:16 And at that point, the force applied,

3:18 divided by the cross-sectional area is called its ultimate tensile strength.

3:22 We're at about 600 megapascals.

3:25 [Henry] To put that in perspective, if you had a rope of spider silk

3:28 that had a cross-sectional area of one square centimeter,

3:30 roughly the size of your little finger,

3:32 it could support about 60,000 newtons of force.

3:35 That's the weight of a fully grown African elephant.

3:38 And that's not even the strongest spider silk out there.

3:41 Breaking stress wasn't incredible for this piece of silk.

3:45 [Henry] Deep in the jungles of Madagascar lives the Darwin's bark spider.

3:48 Its diet consists of flying insects that zip over wide rivers.

3:51 So to catch its prey, the Darwin's bark spider has to spin giant webs

3:55 that stretch up to 25 meters over open water.

3:59 And to survive that kind of distance and tension,

4:01 its silk has to be incredibly strong.

4:03 It has an ultimate tensile strength of around 1,600 megapascals.

4:07 That's more than twice the strength of our sample.

4:09 But experimental ultra high strength steels can reach

4:12 an ultimate tensile strength of nearly 3,000 megapascals.

4:15 That's about three times that of typical dragline silk,

4:18 but steel is also about six times denser.

4:21 So for two ropes with the same mass and length,

4:23 the silk rope has six times the cross-sectional area.

4:26 Six times the area at one third the strength, well,

4:28 that gives a rope that can take twice the force before it snaps.

4:31 This measure of strength relative to mass is called specific strength.

4:35 And it means that for the same mass and length,

4:37 spiderwebs can withstand roughly twice the force

4:39 of ultra high strength steel before breaking.

4:42 So that's where ounce for ounce, spider silk is quite strong.

4:46 You got to think about what is

4:48 the application you're talking about using this material in.

4:51 Is it somewhere where you don't care about weight, and you need the strength?

4:54 Then steel's going to be perfectly fine.

4:55 But if weight matters,

4:57 spider silk is really the champion there for tensile strength.

5:01 [Henry] But strength alone isn't enough.

5:03 To see why, look at rock climbers.

5:05 If a rock climber was just hanging,

5:07 all we would care about was if the rope could support their weight.

5:09 That's strength.

5:10 But climbers don't just hang, they fall.

5:14 And now the rope has to bring them to a stop,

5:16 which means absorbing that kinetic energy.

5:18 Stop the fall in a short distance, and the energy has to be absorbed quickly.

5:22 The forces are enormous.

5:23 Stretch it out and that same energy is absorbed gradually,

5:26 so the forces are lower.

5:28 So to absorb more energy without snapping, it has to stretch further.

5:32 And that's actually not so different from spider silk.

5:35 So a bug hits this web,

5:37 you've got to stop the flight of that bug pretty quickly.

5:40 And you could do it by just building a really stiff structure.

5:43 Think like a brick wall, you throw a tennis ball against it.

5:46 You're gonna stop that ball instantly.

5:48 But that doesn't work very well if you want to catch a meal.

5:51 It'll bounce off.

5:52 Because it'll just fall out.

5:53 And so it helps to slowly decelerate the insect

5:56 so that the web has time to stick to it,

5:59 and keep the meal for the spider to subdue.

6:02 [Henry] So the spider silk has to be quite stretchy.

6:05 This piece of silk stretched to 70% of its length before it broke,

6:10 which is really exceptional for dragline silk.

6:13 [Henry] Now, every tiny bit of stretching absorbs a little bit of energy.

6:16 If you add all these tiny amounts together,

6:18 the result is the total energy the material absorbs before breaking.

6:21 On a stress/strain graph, it's proportional to the area under the curve.

6:25 This is the material's toughness.

6:27 Kevlar, the material used in bulletproof vests,

6:29 whose whole job is to take the energy of a bullet

6:31 and spread it out before it reaches the body,

6:34 well, it has a toughness of up to 50 megajoules per cubic meter.

6:37 Experimental ultra-high strength steel has a toughness

6:40 of around 170 megajoules per cubic meter.

6:42 But spider silk?

6:45 This piece of silk had a toughness of about 205 megajoules per cubic meter.

6:51 Oh, okay.

6:51 So that might be like four times Kevlar.

6:53 But the silk from the Darwin's bark spider can

6:55 have a peak toughness of 520 megajoules per cubic meter.

6:59 That's roughly three times the strongest steel out there,

7:01 and 10 times as tough as Kevlar.

7:03 See, Kevlar has a very high tensile strength, but it's also quite stiff.

7:07 Compared with stretchy spider silk,

7:09 that means that the stress/strain graph rises sharply

7:11 and fails before it can stretch very far.

7:14 So it's not able to absorb as much energy.

7:16 And that's why spider silk wins on toughness.

7:19 But it's the ultimate in green chemistry.

7:21 They're not using the high temperature,

7:23 or the caustic solvents that most of the polymer

7:27 industry uses to make high performance threads.

7:30 They're doing it at room temperature, inside a living body,

7:33 with the same basic building blocks that you

7:35 use to build your hair and your skin.

7:38 Now, the secret to spider silk's unbelievable natural

7:40 strength lies in how those building blocks are arranged.

7:43 If you look inside a silk fiber,

7:45 you'll find spider silk proteins called spidroins.

7:48 In some regions, the spidroins are arranged in similar size and shape,

7:52 and they're closely aligned along its length.

7:54 They're kind of like stacked egg trays.

7:56 These are nanocrystals.

7:58 In other areas, the spidroins aren't so uniform.

8:00 Here they're less ordered, and they can move and change shape more freely.

8:04 These are called the amorphous regions.

8:06 Together, they work like a network

8:08 of tiny rigid blocks connected by elastic cords, which I have in front of me.

8:12 When I pull on the network, the cords stretch, and they absorb energy.

8:15 The blocks don't stretch much, but each one connects to several cords,

8:18 which spreads the pull across the network.

8:21 So the amorphous regions let the silk stretch while

8:24 the nanocrystals help it withstand a much larger pull.

8:26 Together, they allow the silk to absorb

8:28 a tremendous amount of energy before breaking, which makes it so tough.

8:32 The result is a material that's stronger than

8:33 steel by weight and also tougher than Kevlar.

8:37 It sounds perfect for making climbing ropes,

8:39 parachute cords, airbags, even bulletproof vests.

8:42 But we actually aren't using spider silk for any

8:44 of that, even though we've been trying to for centuries.

8:47 In 1709, a Frenchman named Francois Xavier

8:50 Bon painstakingly collected hundreds of spider egg sacs,

8:53 boiled them, combed them like wool, spun them into thread,

8:57 and then used them to make stockings

8:58 that attracted the attention at the royal court.

9:01 But this was harder than it sounds.

9:03 As he later said, "The only difficulty now lies in procuring a sufficient

9:07 quantity of spider bags to make any

9:09 considerable work of it." Three centuries later,

9:11 Simon Peers and Nicholas Godley led a years long project in Madagascar,

9:15 in which teams of Malagasy workers gathered more than

9:18 a million golden orb weaver spiders in the jungle by hand.

9:21 They extracted their silk and painstakingly wove

9:24 and embroidered it into a single golden cape.

9:27 Why hadn't they tried farming the spiders instead?

9:29 Well, attempts to do that all run into the same problem.

9:32 Spiders are cannibals.

9:34 The big problem with spiders is that they eat each other?

9:38 That's one of the big problems.

9:39 And then you can't just keep them in a tiny little container.

9:42 You're going to have to have a lot of real estate

9:43 if you're going to have a farm with 10,000 spiders on it.

9:47 [Henry] Even if you could get your hands on that many spiders,

9:49 as we've seen, milking them is difficult,

9:51 and the spiders don't always cooperate.

9:53 Really cooperative spider will give you 300 yards of silk.

9:57 100's a lot more typical,

10:00 but they kind of have their own individual personalities.

10:02 Some of them will just break the thread right away,

10:04 and not even cooperate with you.

10:06 That's why natural spider silk is so scarce.

10:08 One supplier charges $700 for 100 milligrams,

10:11 which works out to roughly $7 million per kilogram.

10:14 That's roughly 50 times the price of gold.

10:17 Okay, so we can't farm spiders for their silk,

10:19 but we know what the proteins are, so surely we can just make them?

10:23 Well, scientists have tried.

10:24 By the late 1990s, researchers at DuPont took the genes

10:27 that code for spider silk proteins and put them into E.

10:30 coli and yeast.

10:31 These living cells are like protein factories.

10:34 One engineered cell quickly becomes millions.

10:37 It worked, but scientists wanted an even more efficient method.

10:40 So in 2001, a team in Germany tried implanting

10:43 spider silk genes into plants like tobacco and potatoes.

10:46 But if you really want to produce a lot

10:48 of protein in a concentrated form, look at milk.

10:51 To feed their young, mothers produce milk with high concentrations of proteins.

10:55 So around the same time,

10:57 a Canadian company called Nexia tried something much stranger.

11:00 They put spider silk genes into goats,

11:02 creating genetically modified spider goats.

11:05 No, no, really, they made spider goats.

11:07 These goats produce milk chock-full of spider silk proteins.

11:11 In one sense, it worked.

11:12 All the experiments were able to produce spider silk proteins,

11:15 but they ran into the same problem.

11:17 From E.

11:18 coli or yeast, these proteins were purified as a fine white powder.

11:21 From plants, the purified proteins formed a viscous, gelatin-like liquid.

11:26 And from goats, it was dissolved in the milk.

11:28 None of these even vaguely resemble spider silk.

11:31 And that's one of the secrets that any company

11:34 that really wants to mimic spider silk at an industrial

11:37 scale needs to kind of figure out is

11:40 how to process silk proteins the way spiders do.

11:44 But that's easier said than done.

11:46 In a spider, it all starts in the silk gland in a region called tail.

11:50 Cells here make proteins called spidroins,

11:53 and they secrete them into the fluid inside the gland.

11:56 Every spidroin has three main parts.

11:58 One end is called the N-terminal, and the other the C-terminal.

12:01 And between them is a long repeating sequence of amino acids.

12:05 This is called the repetitive region.

12:06 Once inside the tail, the C-terminal ends pair up,

12:09 which links neighboring spidroins together.

12:11 But the N-terminal ends stay mostly separate.

12:14 So the spidroins are still loose enough to bend, coil, and move around.

12:18 Next, they move into the storage sac,

12:20 where they're packed together at high concentrations.

12:23 Normally, proteins this concentrated would stick to each other,

12:26 and clump into a solid,

12:27 but this can be modified with a careful balance of salts and by changing the pH.

12:31 The pH is a measure of the concentration of hydronium ions in a solution.

12:35 And because hydrogen ions are little positive charges,

12:38 you can think of the pH like a dial

12:40 that controls the electrical charge on different parts of the protein.

12:43 In the storage sac, the pH is tuned so

12:45 that the N-terminal ends carry a net negative charge.

12:48 Every protein carries the same charge.

12:50 And since like charges repel, when you crowd them together,

12:53 they shove apart instead of sticking together.

12:55 Now, the spidroins are still crowded in this aqueous solution,

12:58 and at such high concentrations, they begin to gradually rearrange.

13:01 The N-terminals are attracted to water.

13:03 These are hydrophilic.

13:04 While the repetitive region is repelled by it, this is hydrophobic.

13:08 So the spidroins rearrange,

13:10 and you end up having these hydrophilic parts facing outward towards the water.

13:13 And hydrophobic parts tuck themselves inside away from it.

13:16 They then form these tiny structures called micelles.

13:19 And the micelles cluster together into larger globules.

13:23 These globules next enter the spinning duct.

13:26 For the dragline silk, the duct is kind of S-shaped,

13:30 but it gets skinnier and skinnier.

13:33 [Henry] As the globules go through the narrow duct,

13:35 the liquid near the walls rubs against the surface,

13:37 and it moves more slowly, while the liquid in the middle moves faster.

13:41 So the layers slide past each other, which is known as shear.

13:44 These shear forces stretch and deform the globule.

13:48 You also remove some water, so water goes out.

13:51 You get a drop in pH,

13:53 so it becomes a little bit more acidic as you go down this duct.

13:59 So the proteins are then being changed in two ways at once.

14:01 Mechanically, they're being pulled and aligned.

14:04 And chemically, that drop in pH means that there

14:06 are now more positive hydronium ions in the solution.

14:09 These bind to the negative parts of the proteins, neutralizing them.

14:13 Now all the proteins don't repel each other as strongly,

14:15 and so the N-terminal ends begin pairing, linking the proteins into long chains.

14:20 These chains are pulled through a tiny narrowing called the drawdown taper,

14:23 which leads to the spigot.

14:25 Here, the spider pulls the liquid through a small opening.

14:27 This forces the liquid to speed up.

14:29 And as it speeds up, it stretches.

14:31 It's this final stretch that pulls

14:33 neighboring spidroins tightly alongside one another.

14:36 Now, depending on the sequence of amino acids,

14:38 some sections fold into zigzag strands.

14:41 These strands then interlock and rows of hydrogen bonds stitch them into rigid,

14:44 sheet-like structures, which stack together into the nanocrystals

14:48 that give the spider silk its strength.

14:50 In other sections, the spidroins don't fold as neatly.

14:53 That's how you get the amorphous regions which give the silk its stretch.

14:56 Exactly how the proteins assemble inside

14:58 the spinning duct is still being studied.

15:00 No one fully understands it yet,

15:02 and that makes recreating the process in a lab quite difficult.

15:05 So scientists wondered, "What if instead of starting from scratch,

15:08 you used an animal that already has a spinner?"

15:11 This is exactly what researchers at Kraig BioCraft Laboratories,

15:14 a biotech company in Michigan, have been working on.

15:17 What's more, they're doing it with an insect

15:18 that humans have been farming for nearly 5,000 years.

15:23 According to legend, a Chinese empress was relaxing in her garden,

15:26 when something fell into her teacup.

15:28 She looked inside, and saw a cocoon.

15:31 The hot water loosened it.

15:32 And when she lifted it out, it unraveled into a single shimmering thread.

15:36 So long that it stretched across her entire garden.

15:39 This was silk.

15:41 Whether or not that story's true,

15:42 people eventually learned to farm the insect that made the thread.

15:46 (jaunty music) Silkworms.

15:47 They're the caterpillars of the domesticated silk moth.

15:50 Silk quickly became one of the most valuable materials in the land.

15:53 It dressed emperors and spurred trade connecting East Asia and Europe.

15:57 So much so that it gave the trade route its name, the Silk Road.

16:01 For nearly 2,000 years, China guarded the secret.

16:04 But of course, people were always trying to steal it.

16:08 By the mid-sixth century, the Byzantine Empire was in trouble.

16:12 Plague had devastated the population.

16:13 And on top of that, the purchase of silk was draining its gold.

16:17 The problem was that Byzantines couldn't make silk.

16:19 Most of it had to come through Persia, the very empire it was fighting.

16:23 So Emperor Justinian made a secret deal with two monks.

16:27 They would travel east, find the source of silk, and then smuggle it back.

16:31 They returned with a secret hidden inside their hollow canes.

16:34 Silkworm eggs.

16:36 This may be the first recorded case of industrial espionage in history.

16:39 With that, Byzantium could finally make its own silk.

16:43 Nowadays, we farm them by the millions.

16:46 One moth lays 500 eggs.

16:47 [Henry] Okay.

16:48 So when you talk about growing productions, right?

16:50 Like my wife and I had a baby.

16:53 These guys, they have 500 babies.

16:55 And they do it every 30 days.

16:57 So the researchers at Kraig wondered, "What if we could make the silkworm spin

17:00 spider silk instead?"- When we create a transgenic silkworm,

17:04 we're taking the genetics of a silkworm,

17:06 and the genetics of a spider, and we're putting those together.

17:08 We're taking the best aspects of both.

17:10 And that's what we're doing to create our fibers.

17:12 [Henry] They start by gluing eggs onto a slide,

17:14 which they line up under a microscope.

17:16 So this is the microinjection station.

17:18 We're talking about eggs that are the size of the head of a pen.

17:21 We're talking about needles that are half a micron in diameter.

17:24 This part is the, I want to inject.

17:26 So as you see, this is the tungsten needle and this is the glass capillary.

17:32 And first we poke a hole with the tungsten needle.

17:36 I will actually move the eggs to the capillary and poke.

17:41 The fluid carrying the spider DNA is then injected

17:43 into the part of the egg that will eventually become the silkworm.

17:47 But at this point, the genes are still separate.

17:49 They have to become part of the silkworm's own DNA.

17:52 And luckily, nature already has a way of doing that.

17:54 If you take an insect like a moth and look inside its genome,

17:57 you'll see some stretches of DNA that move around.

18:00 They jump from one place in the genome to another.

18:03 These are called jumping genes, or transposons.

18:06 One specific one is called piggyBac,

18:08 and it was first identified in a cabbage looper moth.

18:12 PiggyBac is a piece of DNA with two short sequences at its ends,

18:15 and it works together with an enzyme that recognizes these ends,

18:18 cuts the whole piece out, and inserts it somewhere else in the genome,

18:22 kind of like a natural cut and paste system.

18:24 What scientists realized is that if the enzyme only looks at the two ends,

18:28 then you can keep those ends the same, but change what sits in the middle,

18:31 and use that to implant the DNA of your choosing.

18:34 So in the lab, the DNA in the middle is replaced with the spider silk gene.

18:38 This, together with separate instructions for making the enzyme,

18:40 is what's then injected into the silkworm egg.

18:43 And inside the egg, the enzyme recognizes the familiar end sequences

18:46 and cuts and inserts the spider silk gene into the silkworm's DNA.

18:50 If everything works, it becomes a permanent part of the silkworm's genome.

18:55 Now with silkworm where the edit worked

18:56 looks almost exactly like one where it didn't.

18:59 [Jon] The first approach we used

19:00 was creating transgenics with the glowing cocoon.

19:03 A green fluorescent protein is what's making these guys glow that green color

19:08 under this particular wavelength with that particular

19:10 light filter in front of it.

19:12 [Henry] It feels magical.

19:13 And there's a living thing inside of it.

19:15 [Jon] Mm hmm, yep.

19:16 [Henry] And it's creating the glowing effect.

19:18 [Jon] Yeah.

19:18 [Henry] But even if the DNA insertion is successful,

19:21 it might not have ended up in the right place.

19:23 If I create the world's best recipe for chocolate chip cookies,

19:26 and I stick it in the pasta section-- [Henry] Yeah.

19:29 You're probably not going to make a lot of chocolate chip cookies, right?

19:30 'Cause you're not going to see it.

19:32 [Henry] Yeah.

19:32 Same thing for this, right?

19:33 We want the recipe in the right section of the right cookbook.

19:37 That's why getting the spider silk gene into the silkworm isn't enough.

19:40 We really want the spider silk get incorporated into their silk gland,

19:45 not any other tissue.

19:47 [Henry] But piggyBac only looks for a four-letter DNA sequence.

19:51 TTAA.

19:53 There's so many TTAA in their genome.

19:56 You couldn't really control where they were.

19:59 [Henry] So it's like there are a lot of different places where they could park.

20:02 Yeah, yeah, that's true!

20:03 And that means that it won't spin pure spider silk.

20:06 If you had to estimate, of the transgenic silk,

20:08 like what percentage is spider DNA?

20:10 Like 6%, 10%.

20:12 That's insane to me!

20:13 So even with this limited gene transfer,

20:15 the fibers still achieve much of the mechanical performance of pure spider silk.

20:19 Our average samples are usually about 60% of spider silk, right?

20:24 Which, show me any other place in the world where you can get materials

20:27 that perform at 60% the strength of spider

20:29 silk that you can make cost effectively, right?

20:31 [Henry] To push the 60% average even higher,

20:33 the insertion needs to be more targeted.

20:36 The next step is to create pure,

20:38 what are called knock-in/knockout transgenics where we will completely remove

20:41 all aspects of the silkworm's native DNA for the silk,

20:44 and replace that completely with the spider silk protein.

20:47 And to do that, most of the leading labs in the field are exploring CRISPR-Cas9.

20:51 This tool has two parts.

20:53 The first is a guide,

20:54 a short piece of genetic code designed to match one exact stretch of DNA.

20:58 Unlike piggyBac, which recognizes a sequence just four DNA letters long,

21:02 this guide matches about 20 letters, making it far more specific.

21:06 The second is a cutting protein.

21:07 When the guide finds its matching sequence, the protein cuts the DNA.

21:11 Here, that spot is inside the silkworm's own gene for making silk.

21:15 The cell immediately tries to repair the break,

21:17 and scientists take advantage of this by also injecting donor DNA,

21:20 carrying the spider silk gene.

21:22 As the cell repairs the cut, it copies in that donor DNA,

21:26 stitching the spider silk gene into this one precise location.

21:29 But this process is still an active development.

21:31 And Kraig is not the only group chasing the dream of spider silk.

21:35 In Germany, AMSilk is making proteins for fibers,

21:38 coatings, powders, and hydrogels.

21:40 And in Japan, Spiber is brewing protein fibers through fermentation.

21:44 Brands like Goldwin and The North Face have already

21:46 used a version of these fibers in their clothing.

21:49 And the military has been interested too.

21:51 In 2016, the US Army funded Kraig to produce ballistic shoe packs,

21:54 panels layered with transgenic silk that are designed as potential body armor.

21:59 And it's even being explored in medicine.

22:01 For centuries, surgeons have stitched wounds together with silk.

22:04 But now a company called Newrotex is

22:07 using spider silk to help repair damaged nerves.

22:10 So if it can be produced cheaply, spider silk could find its way into clothing,

22:13 armor, implants, even nerve repair.

22:16 But to do that, we're going to need a lot of it.

22:19 And this is our specialized spider silk.

22:22 There you go.

22:24 This is the transgenic spider silk.

22:25 [Jon] This is spider silk.

22:26 This is transgenic spider silk.

22:28 What?

22:28 This is like a bale.

22:29 This is a hay bale of spider silk.

22:31 So last year we produced about a half a ton of spider silk cocoon.

22:36 Half a ton.

22:37 And this is silk from that.

22:39 But what about our original question?

22:40 Can you use transgenic spider silk to swing like Spider-Man?

22:44 So Derek, I've got you here in a climbing gym for a very good reason.

22:49 And the reason is underneath this dirty dish towel.

22:52 Unveil it, unveil it.

22:53 Yeah, go.

22:53 All right, okay.

22:55 This looks very uninspiring.

22:58 [Henry] So what's interesting is this is one continuous filament.

23:02 This is just one strand.

23:03 But each one of these strands is actually

23:05 10 individual silk filaments that are kind of connected.

23:09 All right.

23:09 So you want me to hang from this?

23:11 I do want you to hang from it, yes.

23:13 I actually want you to do more than just hang from it.

23:14 I want you to swing.

23:16 This will be the first time ever anyone has ever swung from actual spider silk.

23:22 Granted this spider silk came from other organisms, but...

23:25 (mysterious music) I don't know if it's going to hold my weight, so let's see.

23:32 In three, two, one.

23:41 You really came close!

23:42 (Derek and Henry laughing) (dramatic music) (dramatic

23:55 music continues)- Don't tell anyone, but Spider-Man.

24:02 (dramatic music)- Okay, so we've seen it can hold your weight pretty reasonably.

24:10 We could swing, but I do want to put

24:12 it to the ultimate test and get you up there.

24:15 How much do you trust spider silk?

24:16 Tensile strength doesn't lie.

24:18 All right, let's get you up there.

24:20 (tense music)- We used the title,

24:22 "Risking my life to settle a physics debate" too early.

24:26 (tense music) It feels like it's going to dig into my fingers.

24:34 [Speaker] This is crazy.

24:36 (tense music) (tense music continues) (Derek yelling)- I'm going to go.

24:49 I'm going to go!

24:50 (tense music)- [Henry] Whoo!

24:53 (Derek yelling) Let's go!

24:57 You got to see my finger, man!

25:00 [Henry] Ooh, damn!

25:01 Yeah.

25:02 This is the problem with spider silk.

25:05 Just, it's thin, it's strong, and it just rips you open.

25:11 Now, if it isn't clear, we're not exactly web-swinging experts.

25:14 But we'd love to get the silk into of the hands of someone who is.

25:18 Tom Holland, this is a challenge.

25:19 Yeah, I'm calling out Tom Holland.

25:21 I'm calling out all them guys.

25:22 Andrew Garfield, Tobey McGuire.

25:27 That's right.

25:27 Come at me, bro.

25:30 (electronic music)- See,

25:34 spider silk is so strong and so thin that it actually cut Derek's skin.

25:37 And that's actually a great way to explain the design flaw with modern razors.

25:40 Thanks to Henson Shaving for sponsoring this video.

25:43 See, facial hair resists more than you think.

25:45 And many razor blades are engineered so

25:47 thin that they bend under that resistance.

25:49 This is called blade flex.

25:51 Now, most razors actually build this flex in.

25:53 They use springs, pivots, and flexible mounts that allow the blade to move.

25:58 It's supposed to make the shave feel gentler,

26:00 but it means that the cutting angle is constantly changing.

26:02 When unsupported, the blade bends mid-stroke and instead of slicing cleanly,

26:06 it tugs the hairs, micro-cutting the skin.

26:09 That's what causes irritation.

26:11 The usual fixes are lubrication strips or extra blades,

26:14 but they don't solve the real problem.

26:16 The blade is still allowed to flex.

26:18 We assume that razor bumps and irritation are inevitable,

26:21 but that's shaped by bad design.

26:23 But Henson is designed by aerospace machinists

26:26 who control cutting forces with high precision.

26:28 And their razors use a single precisely-machined blade.

26:31 Instead of letting it move,

26:32 Henson's design supports the cutting edge with tight machining tolerances,

26:36 holding the blade securely so the angle is consistent.

26:39 Remove the flex, remove the irritation.

26:41 Use code "Veritasium" for 100 free blades with any razor purchase.

26:44 Just add both the razor and blades to your cart.

26:46 Thanks to Henson Shaving, and as always, thanks for watching.