Researchers from the University of California, Irvine, along with colleagues from Tel Aviv University and other institutions, announced on March 16 the development of a new membrane device that moves charged molecules using only a rapidly switching low-voltage signal. This “ratchet-based ion pump” operates without moving parts or chemical reactions.
The innovation could have significant implications for water desalination, lithium ion harvesting, heavy-metal removal from drinking water, battery recycling, and biomedical applications. The findings were published in Nature Materials.
The research team demonstrated that their device uses the unique properties at the interface between metals and liquid electrolytes to drive an ionic current. By modulating voltage between ultrathin metallic layers on both sides of a nanoporous insulating wafer, they created a persistent flow of ions across the membrane through what is known as a ratchet effect. “Ratchets are nonequilibrium devices that use temporally controlled input signals and spatial asymmetries to drive a steady-state particle flux,” said Shane Ardo, UC Irvine professor of chemistry and co-lead author. “The combination of structural asymmetry and the unique nanoscale properties of metal-electrolyte interfaces provides the necessary ingredients that make the ratchet work.”
The team showed that this ion flux can be maintained against opposing forces—a key requirement for practical ion pumps—and built an electrically driven deionization system achieving 50 percent salt removal at very low voltages. Gideon Segev, associate professor of electrical engineering at Tel Aviv University and co-lead author, said: “Selective separation can be useful for a wide variety of applications – more effective drinking water purification for one, but also harvesting lithium ions from seawater, a range of biomedical devices and recycling battery materials.” He added: “The ability to remove trace amounts of ions from a liquid mass can be transformative for treating water contaminated with heavy metals. For example, even a few particles per billion of lead ions make water nonpotable. A simple technology that can remove these ions without extracting necessary minerals can help improve access to safe water for millions of people worldwide.”
University of California Irvine’s teams participate in NCAA Division I athletics according to the official website. The university has earned a Carnegie classification for very high research activity according to its official website and functions within the University of California system according to its official website. UC Irvine focuses on advancing knowledge through research, education and public service with an emphasis on inclusive excellence according to its official website. The university also engages in research collaborations and international programs to enhance its global influence according to its official website, and holds accreditation from the Western Association of Schools and Colleges Senior College and University Commission according to its official website.
This project received support from several organizations including the U.S. National Science Foundation, Department of Energy, and European Research Council.