Previous attempts to do this have coated the threads with metal. But that is expensive.As they describe in ACS Nano, Dr Stachewicz and her student Daniel Ura have done it by changing the way the threads are spun, which is cheap.At the moment, those threads are created by a process called melt-spinning.This involves melting the polymer and pushing the resulting liquid through a hollow needle, out of a hole in the needle's tip and onto a spinning drum, where it cools and solidifies.Dr Stachewicz and Mr Ura propose instead to use a technique called electrospinning. This also involves a hollow needle.But instead of being melted, the polymeris dissolved in a solvent, and instead of being propelled from the needle's tip by pressure from behind,it is attracted to the drum by the creation of an electrical potential difference between the drum and the needle.As the stream of dissolved polymer travels through the air, the solvent evaporates, leaving behind a solid thread.One consequence of electrospinning is that the voltage attracting the thread from needle to drum also attracts or repels, according to their polarity, the charges on the molecules within.This reorients those molecules, aligning them (and thus their charges) in a way that does not happen in a melt-spun thread.That can create the sort of polarity difference between the interior and the exterior of a thread the two researchers were looking for.Dr Stachewicz and Mr Ura experimented with different potential differences between needle and drum and eventually found one that resulted in meshes able to collect 50% more water than commercial versions, at no extra cost of production.
