The nanorods were formed when Satish Nune, of the U.S. Department of Energy’s Pacific Northwest National Laboratory, was experimenting with solid, carbon-rich nanorods. These were being used in conjunction with a vapor analysis instrument. Through one study, Nune noticed that the nanorods lost weight as the humidity levels increased. This wasn’t the intended role of the research, but the observation led to something significant. The serendipitous nature of the discovery has piqued interest on social media, with environmental group EcoInteractive (@EcoInteractive) tweeting: “Scientists accidentally created nanorods that harvest water from the air!”
When the nanorods were investigated under a microscope, it was found that fluid (water) was appearing on the sticks and then oozing out. Describing the effect, a second researcher, Dr. David Lao told Controlled Environments magazine: “Our unusual material behaves a bit like a sponge; it wrings itself out halfway before it’s fully saturated with water.”
The nanords were behaving in a different way than most materials. Ordinarily, materials absorb water as humidity increases. The nanorods do the reverse, they release water. Initial studies have shown that the nanorods can release between 50 and 80 percent of their volume as water. Interestingly, the water releasing effect is repeated each time the humidity is increased.
The technology is further explained in this video:
The importance of the finding is that it should lead to a range of low-energy water harvesting and purification methods, many of which can be used to aid less technology-rich regions of the world. One example is with the development of a wearable fabric that pulls sweat away from the body and releases it as a water vapour. This purified water could then be drunk to hydrate a person. In addition, the process could be used in remote deserts, where water could be collected from the air and later harvest for people or animals to drink.
The next stage of the research is to find a steady way to control the size and shape of the nanorods. Formation is important, since the water emerges at the point where nanorods intersect. It is though this meeting of nanorods forms a bridge and the process of water capture and release is a form of capillary condensation. The release of the water is a product of changes to surface tension.
The research has been published in the journal Nature Nanotechnology. The research paper is titled “Anomalous water expulsion from carbon-based rods at high humidity.”
