A new type of desalination membrane works faster and requires less pressure and energy than existing technology. The device designed at the University of Tokyo is composed of a series of nanoscale tubes lined with a Teflon-inspired material that repels salts while allowing water to flow through with little friction.

Fluorine, a hydrophobic material that gives Teflon its famous non-stick properties, is the key ingredient. Stacks of fluorine-based nanoscale rings are embedded in a lipid layer that is impermeable to water. The fluorine enables water to slip through the rings with very little friction while its negative charge repels salts, preventing them from passing through.

The technique was tested with membranes containing fluorine nanorings 0.9 nm to 1.9 nm wide. After saltwater flowed through the system, the amount of chlorine ions — a major component of salt — on either side of the membrane was measured. The results reported in Science confirm that the fluorine rings filtered the water faster and more effectively, using less pressure and energy than other desalination methods.

Fluorine nano-rings allow water to pass through with little friction while the negative charge repels ions in salt. Source: 2022 Itoh et al.

The researchers observed that the new membranes worked around several thousand times faster than typical industrial devices, and around 2,400 times faster than experimental carbon nanotube-based desalination devices. Research will next focus on reducing the energy needed to fabricate the fluorine nanoring membranes and scaling up the devices.