Graphene-like material has piezoelectric properties

Ars Technica : Piezoelectric materials develop an electric field when they are stretched or compressed. Practical piezoelectrics tend to be bulk crystals or crystalline thin films, but piezoelectricity has been predicted in crystals just one atom thick. Now, molybdenum disulfide (MoS₂), which is not piezoelectric in bulk, has been shown to be piezoelectric under certain interesting conditions. The material is strongly piezoelectric when it is just one atom thick, but the effect is eliminated when a second layer is added. With a third layer, it is piezoelectric again, but less so than before. Experimentation revealed that the material is piezoelectric only when there is an odd number of layers, and that its strength decreases as the number of layers increases. Computational modeling suggests that the layers have random orientations, causing them to cancel each other out. Further testing also showed that the more single-layer flakes that are arranged in series, the higher the produced voltage. That means that MoS₂ could potentially be used for powering nanoelectronics and wearable technologies.