Researchers from Columbia Engineering and the Georgia Institute of Technology have developed the first experimental observation of piezoelectricity and the piezotronic effect in an atomically thin material (2-D molybdenum disulfide). The result has potential to be useful in devices that are optically transparent, light, and stretchable. The piezoelectric effect in this material had previously been predicted theoretically. There are two keys to using molybdenum disulfide for generating current: using an odd number of layers (an even number of layers cancels out the piezoelectric effect) and flexing it in the proper direction (the material is only piezoelectric in certain crystalline orientations). The researchers placed thin flakes of molybdenum disulfide on flexible plastic substrates and determined how the crystal lattices were oriented using optical techniques. They then patterned metal electrodes onto the flakes to monitor the conversion of mechanical to electrical energy and observed voltage and current outputs. The researchers also noted that the output voltage reversed sign when they changed the direction of applied strain.
Source: Columbia University
