This creation pushes the boundaries of metamaterials – a new class of finely-engineered surfaces that perform nature-defying tasks. These materials have already shown remarkable results with light manipulation, allowing scientists to create a real-life version of Harry Potter’s invisibility cloak, for example. But a research team from the Universities of Sussex and Bristol have now shown that they also work with sound waves, which could transform medical imaging and personal audio. Large versions could be used to direct or focus sound to a particular location and form an audio hotspot. Much smaller versions could be used to focus high intensity ultrasound to destroy tumours deep within the body. Here, a metamaterial layer could be tailor-made to fit the body of a patient and tuned to focus the ultrasound waves where they are needed most. In both cases the layer could be fitted to existing loudspeaker technology and be made rapidly and cheaply.