Key Moments
Is spider silk really stronger than steel?
VeritasiumWant to know something specific about what's covered?
We've already dissected every moment. Ask and we will deliver (with timestamps).
Key Moments
Spider silk is stronger and tougher than steel and Kevlar on a weight-for-weight basis, but its extreme thinness makes it dangerous for direct human use.
Key Insights
The strongest spider silk, from the Darwin's bark spider, has an ultimate tensile strength of around 1,600 MPa, more than twice that of typical dragline silk.
For the same mass and length, spider silk can withstand roughly twice the force of ultra-high-strength steel before breaking, due to steel being six times denser.
Spider silk's toughness can be up to 520 MJ/m³, roughly three times that of the strongest steel and 10 times tougher than Kevlar.
Natural spider silk is incredibly scarce and expensive, costing around $7 million per kilogram, approximately 50 times the price of gold.
Transgenic silkworms, modified to produce spider silk, currently yield fibers that perform at about 60% of pure spider silk's strength.
The extreme thinness of spider silk, even when strong, can cause it to cut skin, as demonstrated by a test where it sliced the host's finger.
Spider silk's surprising strength compared to steel
Spider silk is often touted as being stronger than steel, a claim Veritasium's host, Derek Muller, investigates. While direct comparisons are complex, spider silk excels in specific metrics. The dragline silk, used for structural support in webs, has an ultimate tensile strength of around 600 MPa. The Darwin's bark spider produces silk with an even higher strength of approximately 1,600 MPa. While experimental ultra-high-strength steels can reach nearly 3,000 MPa, steel is significantly denser. When comparing ropes of equal mass and length, spider silk, despite having lower tensile strength, can withstand twice the force of steel due to its lower density. This makes spider silk the champion for tensile strength when weight is a critical factor, though steel may be preferred when weight is not a concern.
Toughness: Absorbing energy without breaking
Strength alone doesn't tell the whole story; toughness, the ability to absorb energy before breaking, is crucial for applications like climbing ropes or airbags. Spider silk's unique structure allows it to stretch significantly, absorbing kinetic energy gradually. While Kevlar has a toughness of up to 50 MJ/m³ and steel around 170 MJ/m³, spider silk can reach 205 MJ/m³, and the Darwin's bark spider's silk up to 520 MJ/m³. This exceptional toughness, roughly three times that of steel and ten times that of Kevlar, is attributed to its molecular structure. The silk proteins, or spidroins, are arranged in a combination of rigid nanocrystals and flexible amorphous regions. These regions work in tandem, allowing the silk to stretch and absorb energy without snapping, making it remarkably tough.
The intricate structure of spider silk proteins
The remarkable properties of spider silk stem from its protein structure, spidroins. Within the silk gland, these proteins are stored in a liquid form. The process of transforming this liquid into a solid fiber involves a complex series of mechanical and chemical changes within the spider's spinning duct. As the fluid moves through the S-shaped duct, it undergoes shear forces that align the proteins. Simultaneously, a drop in pH and the removal of water neutralize the proteins' electrical charges, allowing them to link together. Further mechanical stretching in a narrow taper pulls neighboring spidroins tightly together. This precise assembly creates the dual structure of nanocrystals (responsible for strength) and amorphous regions (responsible for elasticity), a feat that industrial processes struggle to replicate.
The scarcity and prohibitive cost of natural spider silk
Despite its incredible properties, natural spider silk is not widely used due to its extreme scarcity and cost. Historically, attempts to harvest silk involved collecting large quantities of wild spiders, a labor-intensive process. A famous example is a golden cape woven from the silk of over a million spiders. Spiders are inherently difficult to farm due to their cannibalistic nature and territorial needs, making mass production impossible. Milking spiders by hand is also inefficient, with a cooperative spider yielding only about 300 yards of silk. This scarcity drives up the price dramatically, with one supplier charging around $700 for just 100 mg, translating to approximately $7 million per kilogram—fifty times the price of gold. This prohibitive cost makes widespread application impractical.
Attempts to replicate spider silk through biotechnology
Scientists have explored various biotechnological approaches to produce spider silk. Early attempts involved genetically engineering bacteria (E. coli) and yeast to produce silk proteins, which were then purified as a powder. Another method involved implanting spider silk genes into plants like tobacco and potatoes, resulting in proteins in a liquid form. A more ambitious approach, pioneered by Nexia, involved creating genetically modified 'spider goats' whose milk contained silk proteins. While these methods successfully produced silk proteins, they failed to replicate the precise processing that occurs within a spider's gland, resulting in materials that did not closely resemble natural silk. The key challenge lies in mimicking the spider's natural protein processing mechanisms.
Transgenic silkworms: a promising, yet imperfect, solution
A more recent and promising avenue involves genetically modifying silkworms to spin spider silk. Companies like Kraig Biocraft Laboratories are injecting spider silk genes into silkworm eggs. These genes are integrated into the silkworm's DNA, often using 'jumping genes' like piggyBac. While this allows silkworms to produce silk that incorporates spider silk proteins, the current reality is that the resulting fiber is not pure spider silk. The integration is not always precise, leading to a blend where only a percentage, perhaps 6% to 10%, is of spider origin. Even with these limitations, the transgenic silk achieves about 60% of the mechanical performance of natural spider silk and can be produced more cost-effectively. Future research aims for 'knock-in knock-out' transgenics using CRISPR-Cas9 for more targeted gene insertion, potentially leading to pure spider silk production.
Practical applications and the danger of thinness
If produced affordably, spider silk has vast potential applications, from advanced clothing and body armor to medical implants and nerve repair. However, the very properties that make spider silk remarkable also present challenges for direct human use. In a demonstration, the host attempted to swing from a strand of transgenic spider silk. While it held his weight, the extreme thinness of the silk, coupled with its strength, caused it to cut into his finger. This highlights a design flaw common in modern razors as well: when a material is both strong and incredibly thin, it can act like a fine blade. This inherent danger of sharp, strong fibers means that while spider silk is ideal for many applications, direct human interaction, like web-slinging, is far more perilous than depicted in fiction, demanding careful handling and engineering.
Mentioned in This Episode
●Products
●Software & Apps
●Companies
●Organizations
●Concepts
●People Referenced
Spider Silk: Strength and Applications
Practical takeaways from this episode
Do This
Avoid This
Material Strength and Toughness Comparison
Data extracted from this episode
| Material | Ultimate Tensile Strength (MPa) | Toughness (MJ/m³) | Density (relative to steel) |
|---|---|---|---|
| Garden Variety Spider Silk | ~600 | ~205 | Much lighter than steel |
| Darwin's Bark Spider Silk | ~1600 | ~520 | Much lighter than steel |
| Ultra-High-Strength Steel | ~3000 | ~170 | 1 |
| Kevlar | High | ~50 | Lighter than steel |
Spider Silk Production Methods and Challenges
Data extracted from this episode
| Method | Description | Challenges |
|---|---|---|
| Natural Harvesting | Collecting silk directly from spiders. | Extremely low yield, spiders are cannibalistic, difficult to manage large populations, spiders have individual 'personalities' affecting cooperation. |
| Genetically Modified E. coli/Yeast | Engineering microorganisms to produce spider silk proteins. | Proteins purified as powder; processing difficulty in mimicking natural silk structure. |
| Genetically Modified Plants | Implanting spider silk genes into plants like tobacco. | Proteins form a viscous liquid; processing difficulty. |
| Genetically Modified Goats | Engineering goats to produce spider silk proteins in milk. | Proteins dissolved in milk; processing difficulty. |
| Transgenic Silkworms | Genetically modifying silkworms to spin spider silk (or a blend). | Gene insertion can be imprecise (piggyBac), leading to lower percentage of spider silk; requires advanced techniques (CRISPR) for targeted insertion. |
Common Questions
By weight, spider silk is significantly stronger than steel. While steel has a higher ultimate tensile strength, spider silk's lower density means a silk rope of the same mass as a steel rope can withstand twice the force before breaking.
Topics
Mentioned in this video
The protagonist of Spider-Man 2, who uses webs to stop a runaway train.
A Frenchman from 1709 who attempted to make stockings from spider silk.
Led a project in Madagascar to create a golden cape from spider silk.
Collaborated with Simon Peers on a project to create a golden cape from spider silk.
An actor who plays Spider-Man, called out to challenge the host to a spider silk swinging contest.
An actor who has played Spider-Man, called out by the host for a spider silk swinging challenge.
An actor who has played Spider-Man, called out by the host for a spider silk swinging challenge.
Location of the Blackledge Spider Lab, a leading research center for spider silk.
A species of spider from Madagascar known for spinning exceptionally strong and large webs.
Bacteria used in biotechnological processes to produce proteins, including spider silk proteins.
A brand that has used spider silk-derived fibers in its clothing.
Funded Kraig Biocraft Laboratories in 2016 to produce ballistic shoot packs using transgenic silk.
A company that experimented with using E. coli and yeast to produce spider silk proteins in the late 1990s.
A Canadian company that created genetically modified goats to produce spider silk proteins in their milk.
A biotech company working on creating transgenic silkworms that spin spider silk.
A company in Germany that produces spider silk proteins for various applications.
A company in Japan that brews protein fibers through fermentation for use in clothing.
A brand that has used spider silk-derived fibers in its clothing.
A company using spider silk for nerve repair applications.
A company that sponsors the video, whose razors are presented as an example of good design, contrasting with the potential danger of thin, strong materials like spider silk cutting skin.
More from Veritasium
View all 103 summaries
36 minWhy does every mammal get 1 billion heartbeats in their life?
40 minThe Scariest Chart In Electrical Engineering
24 minForensic Science Is Not As Accurate As You Think
42 minThe Man Who Worked At Subway, Then Solved An "Impossible" Problem
Ask anything from this episode.
Save it, chat with it, and connect it to Claude or ChatGPT. Get cited answers from the actual content — and build your own knowledge base of every podcast and video you care about.
Get Started Free