Standard waveguides allow waves to pass through in both directions, but Feng's team realized that adding extra layers of
materials with different reflective and refractive properties,
at specific
points along the tunnel, could
break this symmetry.
The technique can also be used to predict how much
materials will expand when heated and contract when cooled, which will help engineers build chips that are less prone to
breaking at points where one
material touches another, such as when a two - dimensional
material chip makes contact with a wire.