How thin can an electrical generator possibly be? Thanks to a study published yesterday in Nature, the answer is about as thin as possible. Using molybdenum disulfide, researchers from the Georgia Institute of Technology and Columbia Engineering proved that a layer just an atom thick can generate an electric charge.
The key to this charge is piezoelectricity, or the electric generated from pressure, usually from stretching or compressing a material. With the molybdenum disulfide, the researchers found that it generated electricity in layers that were an odd number of atoms thick, including layers as thin as one atom.
A single monolayer flake strained by 0.53% generates a peak output of 15 mV and 20 pA, corresponding to a power density of 2 mW m−2 and a 5.08% mechanical-to-electrical energy conversion efficiency. In agreement with theoretical predictions, the output increases with decreasing thickness and reverses sign when the strain direction is rotated by 90°.
Single-atom-thick materials are exciting, because they open up new possibilities for materials science, like making tiny transistors. Molybdenum disulfide is particularly interesting because of its potential as a thin transistor incorporated into other materials. Now that scientists have shown atom-thin layers of it can generate electricity, future designers and engineers might incorporate it into very small and self-powering machines. Because it needs to stretch to generate power, it might not work well on a tablet-like device, but imagine it built into a shoe with a display that can tell how many steps you’ve made that day.