Engineered “meta-material” reflects light and sound in tailored directions

The nature and behaviour of waves is one of the most complex subjects in physics. Whether they are pressure fluctuations within a material, such as sound waves, or electromagnetic phenomena such as light and its associated radiation spectrum, the study of these phenomena, which are crucial to the nature of matter itself, has occupied some of the most brilliant scientific minds in history and continues to befuddle laymen and students. Meta-materials, recently discovered structures which  do not interact with waves in the same way as conventional matter, have been used to bend light in such a way that they can render objects invisible and manipulate sound to produce acoustic illusions.

Meta-materials work because of their surfaces, which generally feature patterns with repeating or “periodic” structures smaller than the length of the wave with which they are designed to interact. The discovery by nano engineers and electronic engineers at Aalto University in Helsinki allows surfaces to be designed that will reflect waves in any direction or even split the reflection so that waves travel from the surface in different directions. It can also change the shape of the wave, and may have applications in disciplines such as optical computing and acoustic engineering.