Research group co-led by UC Irvine develops first-of-its-kind ion pump

• A research team co-led by a UC Irvine chemistry professor has developed a new device that removes salt and other charged compounds from water efficiently and effectively.
• The ratchet-based ion pump works without moving parts or chemical reactions.
• Applications include desalination, harvesting lithium ions from seawater and biomedical devices.
• Funding was provided by the National Science Foundation, the U.S. Department of Energy and the European Research Council.

Irvine, Calif., March 16, 2026 - Researchers at the University of California, Irvine, Israel's Tel Aviv University and other institutions have developed a first-of-its-kind membrane through which charged molecules pass using nothing more than a rapidly switching low-voltage signal. This "ratchet-based ion pump" has no moving parts and requires no chemical reactions.

The device opens the door to advances in water desalination, lithium ion harvesting from seawater, heavy-metal removal from drinking water, battery recycling and various biomedical applications. The team's findings are outlined in a paper published recently in Nature Materials.

Controlling the movement of charged molecules through liquids is fundamental to various processes, ranging from industrial water purification to biological cell function. Until now, most engineered ion pumps have relied on energy-intensive electrochemical processes that impose significant efficiency limits and require complex and often costly chemistries.

The UC Irvine- and Tel Aviv University-led team has demonstrated an entirely different approach. Its ratchet-based ion pump exploits the unique electrical and chemical properties at the interface between metals and liquid electrolytes to drive an ionic current. By rapidly modulating the voltage between ultrathin metallic layers deposited on both faces of a membranelike, nanoporous, insulating wafer, the device generates a persistent and directed flow of ions across the membrane in what physicists call a ratchet effect.

"Ratchets are nonequilibrium devices that use temporally controlled input signals and spatial asymmetries to drive a steady-state particle flux," said co-lead author Shane Ardo, UC Irvine professor of chemistry. "The combination of structural asymmetry and the unique nanoscale properties of metal-electrolyte interfaces provides the necessary ingredients that make the ratchet work."

The researchers showed that this ion flux can be sustained against an opposing force, a key benchmark for any practical ion pumping device. Then, as evidence of its applicability, they constructed an electrically driven deionization system operating with no moving parts or electrochemical reactions, achieving 50 percent salt removal with extremely low voltages.

The ratchet-based ion pump has a capacitorlike structure with nanometer-sized pores: Thin metal electrode layers coat both surfaces of an insulating layer without blocking its holes, allowing ions to pass through it while still permitting the application of a rapidly switching electric field.

The effectiveness of the mechanism stems from unequal charging and discharging processes at the interfaces between the two metal layers and the electrolyte. Since these charging-discharging processes do not fully compensate for each other, a voltage builds up between the solution compartments on each side of the membrane. This voltage drives an ion flux across the membrane, but unlike analogous systems, the ratchet-based ion pump does not require that electrochemical reactions occur at the electrode contacts.

To demonstrate water deionization, the device was combined with two ion-selective membranes, forming an ionic circuit in which the voltage induced by the ratchet-based ion pump extracts salt out of a dilution cell.

While the Nature Materials paper focuses on deionization as proof of concept, the team emphasizes that a longer-term and potentially more aspirational goal is ultraselective ion separation, sorting ions of the same charge based on minute differences in their response to electric fields.

"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," said co-lead author Gideon Segev, associate professor of electrical engineering at Tel Aviv University.

"The ability to remove trace amounts of ions from a liquid mass can be transformative for treating water contaminated with heavy metals," he added. "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."

Joining Ardo and Segev on this project, which received financial support from the U.S. National Science Foundation and Department of Energy and the European Research Council, were Rylan Kautz and Ethan Heffernan of UC Irvine's Department of Materials Science and Engineering; Alon Herman, Keren Shushan Alshochat, Eden Grossman and Rahul Saxena of Tel Aviv University's School of Electrical & Computer Engineering; Camila Muñetón of UC Irvine's Department of Chemistry and the University of Massachusetts Boston's Department of Chemistry; and David Larson, Joel Ager III and Francesca Toma of Lawrence Berkeley National Laboratory. Toma is also affiliated with the Helmholtz-Zentrum Hereon research institute in Geesthacht, Germany.

About the University of California, Irvine: Founded in 1965, UC Irvine is a member of the prestigious Association of American Universities and is ranked among the nation's top 10 public universities by U.S. News & World Report. The campus has produced five Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UC Irvine has more than 36,000 students and offers 224 degree programs. It's located in one of the world's safest and most economically vibrant communities and is Orange County's second-largest employer, contributing $7 billion annually to the local economy and $8 billion statewide. For more on UC Irvine, visit www.uci.edu.

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