discovered_01_2015 - A Sieve for Molecules

FOCUS// THE HZDR RESEARCH MAGAZINE WWW.HZDR.DE 08 09 A FLIMSY AFFAIR: Richard Wilhelm studies membranes that are no thicker than a few layers of atoms. Photo: André Forner // While working on his doctorate at HZDR, Richard Wilhelm made an astounding observation: when highly charged ions fly through a nanomembrane, they are either almost completely unaffected or they suffer a massive loss of energy. _TEXT . Roland Knauer A SIEVE FOR MOLECULES The ultra-thin membrane looks as if it had been hit by a hail of bullets. Well, that is more or less what happened, except that the bombardment could not be observed with the naked eye because it happened in the nano- world. The membrane itself is only one nanometer thick, which means one millionth of a millimeter. The diameters of its pores also measure mere nanometers. Many bio-molecules, such as proteins, are a good deal larger than that and can therefore be sifted out with such a nanosieve. This is similar to the process of washing the blood of a patient with a failed kidney: a membrane allows small molecules, such as urea, to pass though tiny pores, while larger proteins cannot fit through and are thus channeled back into the body where they are still needed. Many other applications in technology and science require such molecular sieves. Yet the mission of Richard Wilhelm from the Institute of Ion Beam Physics and Materials Research at the Helmholtz-Zentrum Dresden-Rossendorf is not to develop such applications - his field is basic research, and he came across nanosieves as he tested a well- established scientific phenomenon.

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