|Credit: Sung Hoon Kang, Boaz Pokroy, and Joanna Aizenberg, Harvard University|
This stunning image shows tiny plastic fibers, each with a diameter of 250 nanometer or 1/500th of a human hair, spontaneously wrapped around a plastic ball when they were immersed in an evaporating liquid.
The finding demonstrates, first reported in 2009, is a new way of controlling the self-assembly of polymer hairs. This image is called "Save our earth. Let's go green," created by Sung Hoon Kang, Joanna Aizenberg, and Boaz Pokroy from Harvard University. The scientists produced the image with a scanning electronic microscope and digitally enhanced it for color.
In the image, the hairlike fibers of epoxy resin assemble around a polystyrene sphere, which is about 2 micrometers in diameter. When the scientists added a drop of water to the spheres, the hairs stood straight up around them. But when the liquid began to evaporate, the fibers wound around the sphere. The hairs aren't attracted to the sphere chemically or magnetically but instead through capillary action. Capillary action occurs when fluids are drawn into other substances through cohesion. For example, when a towel is dipped into water, capillary action is the principle behind how the water gets absorbed or drawn into the towel.
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