Geckos and Adhesion

Gecko. Credit: Pixabay

Have you ever dreamed of climbing walls like Spiderman?

The superhero’s powers are based off spiders, but what if there was another animal that could inspire us to do the same, but in real life?

Everyone knows geckos, the lizards that cling to ceilings. Many are fascinated by the way they defy gravity. Stickiness is the conclusion for most, but this is far from the truth.

If a gecko’s feet were sticky, how would it move? Stickiness isn’t something that can just turn off at will, it’s set into the properties of a substance. Instead, geckos make use of Van der Waals forces to cling to walls.

What are Van der Waals Forces?

Van der Waals forces exist as slight attractions between molecules. Molecules can have positively and negatively charged sides, which then stick together like the north and south poles of magnets. Molecules that are charged in this way are called polar.

Electrons (negative charge) go to where there are more protons (positive charge). Therefore, the charge on that side is slightly negative. The electrons aren’t as much around the other side, giving it a slightly positive charge. When polar molecules interact, the opposing charges stick together. The bonds, however, are weak due to the weakness of the charges.

Geckos’ Trick

Geckos make use of this by have a lot of hairs on their feet with polar molecules. It seems, though, that this would create the same problem as the stickiness. These forces can’t be turned on and off, so how can the geckos move?

It turns out that when the hairs are standing straight with only the tips touching the walls, there isn’t a lot of attraction. The gecko only sticks to the walls when it pushes down its foot so that the entire length of the hairs are exposed. As a whole, there is enough attraction to lift the gecko and defy gravity.

Application

So now, how can we apply this to design? Something that many people dream up is scaling a wall or a building like a gecko or Spiderman. With enough ingenuity, we could possibly create gloves and boots to do this. The problem with people is that we are bigger and heavier than geckos, so the amount of Van der Waals forces also must be significantly larger, or we could find a way to strengthen them. Some applications that are closer to reality for the general public could be patches used to attach decorations to walls or wipes to clean up dust and dirt.

A gecko-inspired adhesive being tested. Credit: NASA’s JPL

For NASA, however, gecko-inspired grippers already being tested on the International Space Station. Next in space could be gecko-inspired robots used for operations that could benefit from this technology. Although becoming Spiderman (or Geckoman) isn’t possible here on Earth yet, researchers have worked on a climbing device inspired by gecko feet and were able to climb 25 feet up a glass building.

🔑 Takeaways

  • Geckos use Van der Waals forces to climb walls; they aren’t sticky
  • Van der Waals forces are weak attractions between polar molecules
  • Gecko-inspired designs are already in use in space
  • Earthlings can also learn to climb walls

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Hi! I'm a 15 year old with an interest in psychology, biomimicry, and neuroscience.

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Sydney Lie Merrill

Sydney Lie Merrill

Hi! I'm a 15 year old with an interest in psychology, biomimicry, and neuroscience.

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