Harry Potter and the new-age stealth submarines: Chinese researchers create 'cloak of invisibility'

Two teams of scientists have created new materials to hide submarines from their enemies' underwater sonar systems - one that transforms the vessel into a "chameleon", and the other a prototype of a Harry Potter-like invisibility cloak.

The chameleon-like ceramic-type material, created by researchers at the Chinese Academy of Sciences' Shenzhen Institutes of Advanced Technology, manipulates sound waves that come into contact with it, such as pulses generated by anti-submarine vessels that can identify underwater threats.

This ability means sonar operators analysing the submarine's acoustic pattern can be fooled into thinking it is a whale, a huge shoal of fish, or even a friendly submarine.

Researchers call such materials "phononic" crystals. In recent years, various forms of phononic crystals have been developed to control, direct and manipulate the transmission of sound in gases, liquids and solids, but they all suffered one limitation.

Once created, their physical properties were fixed forever, giving the enemy tracking it the opportunity to trace its acoustic traits.

But the Chinese team, led by Professor Zheng Hairong, solved the problem by making it possible to control the crystal's ability to change its acoustic pattern in a way similar to a chameleon changing its colour.