University of Twente nanotechnologists create minuscule soccer ballsNew self-assembly method produces almost perfect sphere packing27 September 2012 |
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Nanotechnologists at the University of Twente’s MESA+ research institute have developed a method whereby minuscule polystyrene spheres, automatically and under controlled conditions, form an almost perfect ball that looks suspiciously like a football, but about a thousand times smaller. The spheres organize themselves in such a way that they approach the densest arrangement possible, known as ‘closest packing of spheres’. The method provides nanotechnologists with a new way of creating minuscule 3D structures. The research was published this week in the leading scientific journal Proceedings of the National Academy of Sciences (PNAS). The method developed by the University of Twente scientists involves placing a drop of water containing thousands of polystyrene spheres one micrometre in size (a thousand times smaller than a millimetre) on a superhydrophobic surface. As the drop is allowed to evaporate very slowly under controlled conditions the distances between the spheres become smaller and smaller and surprisingly they form a highly organized 3D structure. The spheres were found to organize themselves of their own accord in such a way that the ball they form approaches the most compact arrangement possible (‘closest packing of spheres’), with 74% of the space filled by the spheres. Like a football, the structures that form are almost perfectly spherical, consisting of a large number of planes. The researchers have therefore dubbed their material ‘microscopic soccer balls’. The minuscule footballs are a hundred to a thousand micrometres in size, containing from ten thousand to as much as a billion of the tiny polystyrene spheres. The research at Twente has produced a new method of creating complex 3D structures of this kind by means of self-assembly. As the scientists are able to precisely control the number of polystyrene spheres and the evaporation rate, they can determine the structure of the end-product with great precision. The method thus provides nanotechnologists with a new way of creating minuscule structures efficiently. They could eventually be used e.g. for medical purposes and in the food industry. The research was done by Álvaro Marín, Hanneke Gelderblom, Arturo Susarrey-Arce, Arie van Houselt, Leon Lefferts, Han Gardeniers, Detlef Lohse and Jacco Snoeijer of the Physics of Fluids, Catalytic Processes and Materials and Mesoscale Chemical Systems research groups of the UT’s MESA+ research institute. It received financial support from the Netherlands Organisation for Scientific Research (NWO). The results were published on 24 September in the leading scientific journal Proceedings of the National Academy of Sciences (PNAS). For more information, images or a digital version of the article Building microscopic soccer balls with evaporating colloidal fakir drops please contact UT’s Science Information Officer, Joost Bruysters (+31 (0)53 489 2773 / +31 (0)6 1048 8228). |
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