It’s possible to generate energy using nothing but the difference between fresh and salt water. When fresh and salt water are separated by a membrane that blocks the passage of certain ions, there is a force that drives the freshwater into the salt water to even out the salt concentration. That force can be harvested to produce energy, an approach termed osmotic power.

But the generation of osmotic power is highly dependent on how quickly ions can cross the membrane—the thicker (and more robust) the membrane, the slower the ions will flow. Theoretically, the most efficient osmotic power generation would come from an atomically thin membrane layer. But can this theoretical system be achieved here in reality?

Recently, scientists answered that question using atomically-thin membranes composed of molybdenum-disulfide (MoS₂). In the paper that resulted, they describe a two-dimensional MoS₂ membrane containing a single nanopore, which was used to separate reservoirs containing two solutions with different concentrations of salt in order to generate osmotic power.