What Makes Spider Silk So Special?

While watching one of the countless Spiderman movies made in recent years, have you ever considered what would happen if the same webs he spun to climb, jump and do all his superhero “stuff” could also be used to do things in the real world too?

Well, many people probably wouldn’t have thought about the practical applications while watching the movies (as they are all too damn good), but I’m sure that some people out there are curious about the real-world role of spider silk.

So, let’s start with the basics. What makes webs spun by spiders (and yes, Spiderman) so special?

What is Spider Silk?

Spider silk is a protein fiber spun by spiders, and these clever arachnids use this silk to do all sorts of things. They spin webs using this silk to protect themselves and their offspring from predators, capture and immobilize prey, and also suspend themselves in midair. In some rare cases, spider silk can also be used by spiders as a source of food when there is a limited amount of available prey. It is made of protein, after all!

Spider Silk

Credits:Bo Valentino/Shutterstock

Despite many claims about spider’s silk being used to travel over long distances (such as Spiderman’s city swoops in the movies), it has been observed that a spider’s threads usually finish after a few yards. However, there have been claims by sailors who suggest that spiders were found on their ships’ sails, even when their ships were far from land.

Types of Spider Silk

If you thought that there was only one kind of silk that did all these things, you would be very wrong. A spider produces 7 different kinds of silk from 7 different glands, all of which have different qualities and functions.  These glands and the type of silk they produce are as follow:

  1. Ampullate (Major): Produces dragline silk, which is used for the web’s outer rim and spokes.
  2. Ampullate (Minor): The silk produced here is used for temporary scaffolding during web construction.
  3. Flagelliform: Produces capture-spiral silk, which is used for the capturing lines of the web.
  4. Tubuliform: Produces egg cocoon silk, which is used for protecting egg sacs.
  5. Aciniform: The silk produced here is the real killer, as it is used to wrap and secure freshly captured prey.
  6. Aggregate: This silk is a kind of glue composed of sticky globules.
  7. Pyriform gland: Produces a kind of silk that attaches threads, i.e., anchors a thread to a surface or another thread.

Fantastic Properties of Spider Silk

Credits: Jan Miko /Shutterstock

Credits: Jan Miko /Shutterstock

Now that you have more of an idea about spider silk, let’s take look at some of its eye-popping properties. It is evident from its portrayal in popular culture that spider silk is one of the best tools for offense and defense, and often both at the same time. Now, let’s get into the real details and qualities of this versatile material.

Strength: In terms of strength, spider silk is unbelievable. Can you believe that spider silk is comparatively stronger than steel, a high-grade alloy steel? That’s pretty impressive as a natural byproduct of a creature! Spider silk has the ability to absorb immense amounts of kinetic energy, which means that it’s great for blast protection.

Density: Strong as it is, the silk is also incredibly light. It is much lighter than steel itself, and its density (1.31 g/cm3) is actually one-sixth of the density of steel. If you take equal weights of both steel and spider silk, the latter would be 5 times stronger than the former. Can you imagine all the practical applications of this in the world??
If you took a thread and wound it around the Earth, the weight of all that thread would not be more than half a kilogram!

Artificial_Spider_Silk_Strand

Artificial Spider Silk Strand

Extensibility: Needless to say, spider silk is highly extensible, which means that it can be stretched five times its original length without snapping

Toughness: The incredible strength and ductility give spider silk tremendous toughness. Its toughness is equated with that of “commercial polyaramid (aromatic nylon) filaments, which themselves are benchmarks of modern polymer fibre technology”.

Supercontraction: This is one particularly wicked attribute of spider silk. When underwater, spider silk undergoes contraction and shrinks to 50% of its original size. It becomes something akin to weak rubber under tension when submerged.

Temperature Resistance: Spider silk can function properly at temperatures as low as -40 degrees Celsius.

With all these super qualities of spider silk, don’t you think that nature seems a bit biased towards these eight-legged arachnids? However, spiders probably think the same way about all these ‘weird creatures who walk on two long things and make a mess out of every silk-spun web they walk through’.

Next time you’re walking through the forest and a spider web sticks to your face, try not to flail and destroy the web entirely… some poor spider worked very hard on that!

References:

  1. Spider Silk – Wikipedia
  2. What Is The Spider Silk Made Of And How Can It Be So Strong To Hold A Spider? – University of California, Santa Barbara Science Line
  3. Scientific American
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About the Author:

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.

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