Vibration in one direction only
(PHYSorg.com Chemistry)

Electronic components such as transistors transmit electric currents in one direction only. What if we could create materials that could achieve similar effects for mechanical vibrations? For many applications, having materials that transmit vibrations in one direction, but not in the other, would be extremely useful. In nature, such materials do not exist, but a group of physicists from the University of Amsterdam has now designed a metamaterial that can do just that.