Engineers from Cornell University have designed very small and fast switches which reproduce the behavior of palm beetles. When they're attacked, these insects stick to the leaves they're on with an adhesive strength equal to a hundred times their own body weight. These new switches, which are just using water and electricity, can scale from less than a size of less than a micron to arrays leading to future powerful adhesives. But the researchers are quick to admit that they really don't know what could be the future applications for their switches. They compare them to the transistor, which hadn't any apparent possible use when it was invented. Read more...
Here is the opening of this Cornell University news release.
Imagine this: A tiny, fast switch that uses water droplets to create adhesive bonds almost as strong as aluminum by borrowing a mechanism found in palm beetles.
The new beetle-inspired switch, designed by Cornell University engineers, can work by itself on the scale of a micron -- a millionth of a meter. The switches can be combined in arrays for larger applications like powerful adhesive bonding. Like the transistor, whose varied uses became apparent only following its invention, the uses of the new switch are not yet understood. But the switch's simplicity, smallness and speed have enormous potential, according to the researchers.
Below is a diagram of this beetle-inspired micro-switch (Credit: Michael J. Vogel, Peter Ehrhard, and Paul H. Steen, Copyright PNAS).
The droplet switch shown here toggles between a big droplet positioned above and below the plate using applied voltage. This novel electro-mechanical switch is capable of working by itself or in larger arrays, and has fast switching times with low voltages, no moving solid parts and can be made very small. Applications are envisioned in the areas of mechanics, micro-fluidics and optics, among others.
Here is a link to a larger version of this illustration.
Now, let's look at a comparison between the palm beetle and the new micro-switch.
When attacked, the palm beetle attaches itself to a leaf until the attacker leaves. It adheres with 120,000 droplets of secreted oil, each making a bridgelike contact between the beetle's feet and the leaf. Each droplet is just a few microns wide. Whereas the beetle controls the oil contacts mechanically, Steen's switch uses water and electricity.
For the switch to make or release a bond created by surface tension, a water droplet moves to the top or bottom of a flat plate surface using electricity from electrodes. The electricity moves positively charged atoms, called ions, in the water through the minute capillaries of a thin disk of porous glass embedded in the plate. The water moves and wells up into a micrometer-sized droplet on the plate surface. The exposed droplet can then stick to another surface. To break the bond, electricity pulls the exposed water back through the capillary pores.
The research work has been published online by the Proceedings of the National Academy of Sciences on August 22, 2005 under the name "The electroosmotic droplet switch: Countering capillarity with electrokinetics." Here is a link to the abstract.
And just in case you want to know more, Wikipedia tells us that "in physics, electro-osmosis is the motion of polar liquid through a membrane or other porous structure."
So, is this the birth of a new industry, such as the one which started with transistors? One of the authors of the research paper, Paul Steen, said that "almost all the greatest technological advances have depended on switches." We'll see in the coming years if he was right.
Sources: Cornell University News Service, via EurekAlert!, August 22, 2005; and various web sites
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10:02:19 PM
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