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ePaper created 2013-08-02, 08:40:53 | version 1.25.20
12 P ing-pong balls, soap bubbles, Christ- mas tree decorations – we all know spherical shells from our everyday lives. However, it is a less well-known fact that such shells are also used in nano- technology: as microscopically small capsules that release their contents at the right time and the right place. For ex- ample, medical scientists have made good progress in their plans to use microcapsules the size of a blood cell to deliver drugs exactly where they are to take effect instead of distributing them in the entire body, which is the case when you take them in the form of tab- lets. Odoriferous substances and insec- Research in Jülich 2|2013 ticides could also be transported in this targeted manner. However, it is not known exactly how shells will behave when they are shrunk to a size of only a few micrometres. “There are many theories to describe what happens on a large scale, but quite often these no longer apply on a smaller scale”, says Gerard Vliegen- thart, “because there are effects that are irrelevant on a large scale but make a big difference in the microworld. We are extending the theoretical structure of physics onto the microscopic level.” At the Institute for Complex Systems (ICS), he and Gerhard Gompper are looking into such an effect – thermal fluctuations – and investigating its im- pact on the stability of shells small enough to be considered by medical scientists for use as microcapsules. To- gether with colleagues from Harvard, they were able to confirm their assump- tion that, due to these thermal fluctua- tions, microcapsules are considerably less stable than previously believed. HEAT CREASES SURFACE Thermal fluctuations are a type of back- ground noise of matter. “Atoms only stand still at absolute zero. Otherwise, they hop around their basic position and Spherical shells are useful for many purposes. For examples, medical scientists hope to be able to use them as microcapsules releasing drugs in a selective manner. Jülich researchers have now found out that these ‘nanoferries’ are significantly less stable than previously assumed.