Nature provides inspiration for researchers developing selective membranes
Current synthetic membranes are effectively microscopic sieves, but Technion researchers hope that in the future they will be able to choose which molecules to let through.
By DONNA RACHEL EDMUNDSA microscope photograph of an epidermis in the laboratory at the Institute for Stem cell Therapy and Exploration of Monogenic Diseases (ISTEM) in Evry, near Paris November 27, 2009.(photo credit: REUTERS/HO/HO/ISTEM/XAVIER NISSAN)
The ingenuity of nature will be the inspiration behind synthetic membranes of the future, which will be able to select which substances they allow to pass through and which are filtered out, researchers at the Technion Faculty of Civil and Environmental Engineering have said.Currently, synthetic membranes used in desalination and other technologies effectively work as microscopic sieves: Minuscule pores in the membrane allow water molecules to pass through while holding back larger impurities in the water such as charged atoms or molecules, known as ions, or bacteria.However, in an article published in the peer-reviewed journal Nature Nanotechnology, Assistant Prof. Razi Epsztein and his postdoc mentor, Prof. Menachem Elimelech from Yale University have detailed how, in the future, the membranes may be engineered with the ability to select which substances they allow through, even to the point of distinguishing between very similar ions such as potassium and sodium.Looking to nature for inspiration, the researchers note how, using mechanisms such as the potassium channel, cells are able to choose which substances they allow to pass through the cell's membrane to enter and leave the cell, and which they hold back.Potassium channels are almost ubiquitous throughout biological organisms, controlling a wide variety of functions. In humans, for example, they are responsible for controlling the secretion of hormones such as insulin to the correct level, or within the mechanism that causes brain cells to communicate or heart cells to beat.The researchers hope to harness this level of specificity for processes such as desalination, the most common technological use of membranes. Although the current method provides an energy efficient way to remove salts and impurities from water, the inability to select which ions are held back means that some of them have to be added back in for drinking water to be safe. In addition, the strongly saline waste brine that is left behind is currently an environmental concern.Epsztein’s lab plans to focus on studying both natural membranes and advanced materials, following which they hope to be able to manufacture a membrane capable of selection at the molecular level.Emphasizing the potential of ion-selective membranes, Epsztein said: "Selectivity is fascinating and important at the same time. Improving our ability to discriminate and separate between small ions and molecules can be super beneficial for water-treatment processes, as well as for resource recovery, energy production, sensing and even medicine."
