2021年经济学人 新款集水网--天网恢恢,疏而不漏(2)（在线收听）

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.

之前的尝试是在螺纹上涂上一层金属，但成本很高。正如他们在《ACS Nano》杂志中描述的那样，斯塔切薇兹博士和她的学生丹尼尔·尤拉通过改变纺线的方式实现了这一目标，这种方式成本很低。

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.

目前，这些线程是通过一种叫做熔融纺丝的过程创建的。其中包括熔化聚合物，将产生的液体通过一根空心的针，从针尖的洞里出来，放到旋转的圆筒上，在那里冷却并凝固。斯塔切薇兹博士和尤拉先生提议使用一种叫做静电纺丝的技术，这也涉及空心针。但是聚合物并没有融化，而是溶解在一种溶剂中，而且它不是被来自针后的压力从针尖推进，而是被针和针之间产生的电位差吸引到针筒上。当溶解的聚合物在空气中流动时，溶剂蒸发，留下一个固体线。

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.

静电纺丝的一个结果是，根据针管内部分子的极性，将线从针管吸引到滚筒的电压也会吸引或排斥其中的电荷。这就会改变这些分子的方向，使它们(以及它们的电荷)排列整齐，而这在熔融纺线中是不会发生的。这可以产生两位研究人员正在寻找的线的内部和外部之间的某种极性差异。

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. At the moment these are just prototypes, but they expect soon to have a practical version which can be made available for sale. And that will certainly improve the lives of people who rely for their survival on drawing water not from a well, but from thin air.

斯塔切薇兹博士和尤拉先生对针和滚筒之间的不同电势差进行了实验，最终找到了一种能比商业版本多收集50%水的网眼，而且不需要额外的生产成本。目前这些还只是原型，但他们希望很快就能有一个可供出售的实用版本。这肯定会改善那些不是从井里，而是从稀薄的空气中取水为生的人们的生活。