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Van der Waals Forces

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Sticky Gears

Sticky Gears

Credit: Casc2282
Source: https://commons.wikimedia.org/wiki/File:Gecko_namibia_an_zimmerdecke.jpg
License: CC BY-NC 3.0

How do they do it? Geckos and spiders can walk across a ceiling up-side down and not fall off. The secret is in the tiny hairs that cover their feet. These extremely small structures can interact with solid material by way of van der Waals forces – the weakest interaction that can occur between two structures. But this weak force is enough to allow the creature to travel up-side down.

Amazing But True

  • As progress in nanotechnology continues, scientists are beginning to run up against a problem that they learned about in freshman chemistry class in college (or maybe even in high school). It is easy to think about the strong intermolecular forces that cause materials to interact, but often forgotten are those weak forces that come and go. The van der Waals force is usually concerned to be a minor concern, but is coming to be a critical issue in the nanoworld.
  • As parts get smaller and smaller, the individual pieces begin to interact in altogether different ways. Those seemingly minor van der Waals forces play critical roles in the movement of the separate pieces of a nanodevice. Because of the small sizes and the close fitting of the different components, the weak interactions influence movement of the parts much more than devices in the macro-world.
  • Significant insights into the influence of van der Waals forces have been gained from studies in nature. Research on geckos and spiders are showing how these creatures can stick to a variety of surfaces. Knowledge obtained from these studies will contribute to better nanotechnology products in the future.
  • Credit: Cooks & Kitchens
    Source: http://www.flickr.com/photos/cooks-and-kitchens/5023480824/
    License: CC BY-NC 3.0

    Despite their ability to climb on almost any surface, geckos have trouble adhering to Teflon surfaces such as non-stick frying pans. This is due to the low surface energy and weak van der Waal's forces [Figure2]

     

  • Watch a video about nanotechnology at the link below:

https://www.youtube.com/watch?v=e8zn_mpJ_P4

Show What You Know

Use the links below to learn more about nanotechnology. Then answer the following questions.

  1. How large is the nanoscale robot made out of DNA?
  2. What are gold “nanostars” used for?
  3. When atoms are shot through a grating, what attracts the atoms to the solid material?
  4. What weight can a spider hold?
  5. How did scientists determine that geckos use van der Waals forces to stick to surfaces?

Image Attributions

  1. [1]^ Credit: Casc2282; Source: https://commons.wikimedia.org/wiki/File:Gecko_namibia_an_zimmerdecke.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: Cooks & Kitchens; Source: http://www.flickr.com/photos/cooks-and-kitchens/5023480824/; License: CC BY-NC 3.0

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