Along the world's coasts where fresh water flows and saltwater that circulates in the world's seas and oceans meet, there is a largely untapped source of energy, the difference in salinity between seawater and fresh water, and a new nanodevice could exploit this difference to generate energy, new research has revealed.

A team of researchers at the University of Illinois Urbana-Champaign has announced the design of a fluid nanodevice capable of converting the ion-induced salinity flow between the two waters into usable electrical energy, and the team is expected to publish its findings in the December 2023 issue of the journal Nanoenergy.

The energy of these flows can be harvested because they are made up of electrically charged molecules called ions (Gringer School of Engineering)

The idea of the work of the device

When two bodies of water with different salinity meet, such as when a river flows into the ocean, salt molecules naturally flow from the highest concentration to the lower concentration, and the energy of these flows can be harvested because they are made up of electrically charged molecules called ions that form from dissolved salt.

The group of Jean-Pierre Liburton, a professor of electrical and computer engineering at the university, designed a nano-level semiconductor device that takes advantage of the flowing ions and electrical charges in the device. When ions flow through a narrow channel in the device, the electric forces cause charges to move from side to side, creating voltage and electric current.

While they expected the device to work primarily through the forces of attraction between opposing electric charges, the simulations indicated that the device also works well if the electric forces are repelling, so both positively and negatively charged ions contribute to the device's work.

The device can be used to extract energy from ionic flows at the confluence of seawater and fresh water (Shutterstock)

Multiple applications and development awaited

Leporton Group graduate student and lead author of the study, Minji Xiong, said: "Because moving ions are so huge compared to the device's charges, they transfer large amounts of momentum to charges, amplifying the basic current.

In a press release published on, project leader Leburton said: "While our design is still just a concept at this stage, it is versatile and already demonstrates strong potential for energy applications."

"We believe that the energy density of the instrumentation array could equal or exceed the density of solar cells," he adds, "not to mention potential applications in other fields such as biomedical sensing and nanofluids."

The team believes its predicted device could be used to extract energy from natural ionic flows at seawater and freshwater convergence, so the organizers are patenting their findings and studying how to scale up these devices for energy generation in practice.