Scientists from Fudan University in Shanghai have discovered that silver-plated nanoparticles suspended in water might be the right recipe for an invisibility cloak.
According to lead researcher Ji-Ping Huang, the fluid contains magnetite balls 10 nanometres in diameter, which is coated with a 5-nanometre-thick layer of silver, possibly with polymer chains attached to ensure they don't clump.
The team said that in absence of a magnetic field, the nanoparticles would simply float around in the water, but with the introduction of the field, the particles would self-assemble into chains whose lengths depend on the strength of the field, and which can also attract one another to form thicker columns.
The chains and columns would lie along the direction of the magnetic field.
Huang said if they were oriented vertically in a pool of water, light striking the surface would refract negatively - bent in way that no natural material can manage.
The researchers said that such a feature could help in development of invisibility devices, directing light around an object so that it appears as if nothing is there.
It could also be put to use in lenses that could capture finer details than any optical microscope.
Huang said that the fluid could negatively refract all wavelengths in the visible spectrum, provided the nanoparticles had the right coating.
"One can reduce the thickness of the [fluid] sample in order to reduce the loss. As a result, the dark spots can disappear," New Scientist quoted him as saying.
The study appears in Physical Review Letters.