A matter of capillary action: colloid crystals as molds for nanorings
It isn't only prospective bridal couples that are interested in rings; engineers and scientists are also fascinated by the apparently near-magical properties of ring-shaped objects. For example, magnetic fields can induce a permanent eddy current in conducting rings, and a tricky mixture of rods and rings act as coils and antenna and thus lead to materials with amazing optical properties, like negative refractive indices. These phenomena are size dependent. Especially when the rings are meant to interact with visible light, it is necessary to control their size at the sub-micrometer level. But how can such tiny rings be made? Werner Goedel and Feng Yan from the Technical University in Chemnitz have developed a new "three-dimensional" strategy in which crystals act as a sort of mold for the production of rings.