A pea-shooter for molecules
Like a pea going through a straw, tiny molecules can pass through microscopic cylinders known as nanotubes. This could potentially be used to select molecules according to size — for example, to purify water by allowing water molecules to pass through while blocking salt or other substances. Now, researchers at MIT, Seoul University in Korea and Ursinus College in Pennsylvania have found that such tubes are more selective than had been thought: Molecules of a precise size can zip through five times faster than those that are a bit smaller or larger. The new findings are published in the journal Nature Communications by MIT professor Michael Strano, graduate students Wonjoon Choi and Zachary Ulissi, and three others.This size-dependence in nanotube transport was completely unexpected, says Strano, a professor of chemical engineering at MIT. “This work illustrates how transport in pores of this type remains exotic and relatively unexplored,” he says....