Researchers at EPFL have created a new membrane using lipid-coated nanopores that boosts the efficiency of blue energy production from mixing saltwater and freshwater. The innovation allows ions to pass through more smoothly, generating up to three times more power than existing technologies. This advance could make osmotic energy a more viable renewable source.
Blue energy, or osmotic energy, harnesses electricity from the natural mixing of saltwater and freshwater. Ions from the saltwater move through an ion-selective membrane toward the freshwater, creating a voltage that can be converted into power. However, previous systems struggled with slow ion transport and poor charge separation in membranes.
A team from the Laboratory for Nanoscale Biology at EPFL's School of Engineering, led by Aleksandra Radenovic, addressed these issues by coating nanopores with lipid molecules. These coatings form liposomes that reduce friction inside the pores. The hydrophilic heads of the lipid bilayers attract a thin layer of water, preventing direct ion contact with the pore surface and allowing smoother passage.
The researchers fabricated a silicon-nitride membrane with 1,000 stalactite-shaped nanopores in a hexagonal pattern. Testing under conditions simulating seawater and river water mixing yielded a power density of 15 watts per square meter—two to three times higher than current polymer membrane technologies.
"Our work brings together the strengths of two main approaches to osmotic energy harvesting: polymer membranes, which inspire our high-porosity architecture; and nanofluidic devices, which we use to define highly charged nanopores," Radenovic said. The findings, published in Nature Energy, also involved imaging support from EPFL's Interdisciplinary Centre for Electron Microscopy.
LBEN researcher Tzu-Heng Chen noted, "By showing how precise control over nanopore geometry and surface properties can fundamentally reshape ion transport, our study moves blue-energy research beyond performance testing and into a true design era."
First author Yunfei Teng highlighted the broader potential: "The enhanced transport behavior we observe, driven by hydration lubrication, is universal, and the same principle can be extended beyond blue-energy devices."
This development combines scalable membrane design with precise nanofluidic engineering, advancing osmotic energy toward practical applications.
