This Polymer Device Can 'Walk' When Illuminated
Scientists in the Netherlands and US have created what they're calling the world's first "light powered walking device."
The tiny device, developed by scientists at Eindhoven University of Technology in the Netherlands and Kent State University in Ohio, is about the size of a paperclip and can "walk" at the speed of a caterpillar when illuminated. The device itself has just two parts: a rectangular frame and a piece of special polymer material that can "undulate and ... propel itself forward under the influence of light," according to a news release.
When exposed to light, one side of this new type of liquid crystal polymer contracts while the other side expands, causing it the material to "bulge." When the light goes away, the deformation "disappears instantaneously."
The material looks transparent, but fully absorbs violet light, which the scientists used in their tests, creating a shadow. The research team, led by Eindhoven University of Technology professor Dick Broer, managed to get their device to move continuously on its own using this so-called "self-shadowing" effect.
"They attached a strip of the material in a frame shorter than the strip itself," the release explains. "Then they shone a concentrated ... light on it, from in front. The part of the strip that is in the light starts to bulge downward, creating a 'dent' in the strip. As a consequence, the next part of the strip comes in the light and starts to deform. This way the 'dent' moves backwards, creating a continual undulating movement. This sets the device in motion, walking away from the light."
When the device is placed upside down, the wave travels in the opposite direction, causing it to move towards the light.
The scientists, who published their findings today in the scientific journal Nature,say that in the future, their device could possibly be used to transport small items in hard-to-reach places, or clean the surface of solar cells. "The mechanism is so powerful that the strip can even transport an object that is much bigger and heavier than the device itself, uphill," according to the release.