An unusual material hailed as an "invisibility cloak" when it was invented may help to improve sea defences, researchers believe. Mathematicians at the University of Liverpool are testing metamaterial to discover whether it could be used to redirect large waves without breaking them up. The material, which was invented by Sir John Pendry at Imperial College London, has a unique structure that uses rigid pillars to guide waves along concentric corridors, diverting the water without disturbing its flow. Researcher Sebastien Guenneau said: "What is unique about this new structure is that it interacts with the water, guiding it to a particular destination rather than breaking it up and sending it everywhere. It is as though the defences are invisible to the wave and as such it does not recognise the structure as an obstacle."