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Robots That Bounce on Water

Posted by CmdrTaco on from the something-about-tigger-goes-here dept.

inghamb87 writes "The way water striders walk on water was discovered years ago. The insect uses its long legs to help evenly distribute its tiny body weight. The weight is distributed over a large area so that the fragile skin formed by surface tension supports the bug on the water. However, the ability of water striders to jump onto water without sinking has baffled scientists, until now." If nothing less, you need to see the picture: it's awesome.

5 of 137 comments (clear)

  1. The Picture Might Be Worth It... by __aagmrb7289 · · Score: 3, Interesting

    But I believe we've had a theory for this for awhile now. In August of 2003, MIT published some information on the subject. Here's a link:

    http://web.mit.edu/newsoffice/2003/robostrider.html

    Here's some relevant content from that link:

    MIT researchers report in the Aug. 7 issue of Nature that they now understand how the insects known as water striders skim effortlessly across the surface of ponds and oceans.

    And:

    Using mathematics, high-speed photography and a variety of flow visualization techniques, Bush, mathematics graduate student David L. Hu and mechanical engineering graduate student Brian Chan uncovered the true way in which water striders walk on water.

    As the insect rests on the surface, the tips of its thin legs create miniscule valleys. It sculls the middle set of its three pairs of legs like oars, causing the water behind those legs to propel it forward as the surface of the valley rebounds like a trampoline. Although the rowing motion does create tiny waves, "the waves do not play a significant role in the momentum transfer necessary for propulsion," the researchers wrote. "The momentum transfer is primarily in the form of subsurface vortices."

    1. Re:The Picture Might Be Worth It... by __aagmrb7289 · · Score: 2, Interesting

      Article Content (even Google cache is REALLY slow):

      The way water striders walk on water was discovered years ago. The insect uses its long legs to help evenly distribute its tiny body weight. The weight is distributed over a large area so that the fragile skin formed by surface tension supports the bug on the water. However, the ability of water striders to jump onto water without sinking has baffled scientists, until now.

      A team of researchers at Seoul National University, led by Ho-Young Kim and Duck-Gyu Lee, has finally answered that question. By using a highly water-repellent sphere, which mimicked the actions of the water strider's highly water-repellent legs, they were able to determine a small range of speeds at which the sphere or insect could hit the water and not sink.

      If the sphere hit too fast, it would shoot through the surface of the water. If it hit too slow, it would not bounce back and sink. The water strider is one of the fastest moving insects in the world. It can travel up to 100 times the length of its body in one second, equivalent to around 400 mph in human terms.

      Scientists hope to adapt this technology to the obvious sector; creepy sounding robots. One team at Carnegie Mellon University has already developed a small spider robot that can walk on water like the strider.

      The Korean scientists believe their discovery will help create robots that can travel over still bodies of water. They say the robots can be used to explore or monitor water quality. Also they could, and it's highly likely that they will, be used as a form of spy robot.

      While this is all well and good, and a touch unnerving since it reminds me of several scary sci-fi books, I'll be a lot more interested when they invent something that allows humans to walk on water this quickly.

  2. Rather short on information... by damn_registrars · · Score: 4, Interesting

    I managed to view the site before it went down in flames under the slashdot effect. The picture was cool, but the article left much to be desired:

    How big is the robot?
    How much does it weigh?
    How fast can it move?
    How is it controlled?
    What is the range of speeds for this that was mentioned in the article?
    They mentioned applying it to sampling water quality, but wouldn't that disrupt the surface tension to sample the water right under the robot?

    --
    Damn_registrars has no butt-hole. Damn_registrars has no use for a butt-hole.
  3. Mirror - Slashdotted by mastershake_phd · · Score: 2, Interesting

    http://freedomsforums.com/viewtopic,p,1696.html

    --
    Libertarian Leaning Political Discussion Forum.
  4. Water Striders... by homgran · · Score: 2, Interesting

    I remember going to a conference presentation by John Bush back in 2005 which detailed the physics behind water striders. His presentation was very good, and the video footage he presented was absolutely fantastic (see here and here). I think the work referenced in the main article isn't quite as groundbreaking as they'd have you believe. There has been quite a lot of work in this area over the last five years.