It is probable that in the future our clothes will be equipped with tiny power generators, which could be used for charging mobile phones and other gadgets. U.S. researchers created the world’s thinnest generator based on the properties of a new layered material, which has a thickness of just one atom and is able to produce electricity when bent or stretched.
The microscopic generator consists of the atomically thin molybdenum disulfide (MoS2), a material in which all the atoms are arranged in the same plane. It means that the material is technically two-dimensional as it has only length and width, while its thickness is negligible and comprises only a single atomic layer.
Researchers at Columbia Engineering and the Georgia Institute of Technology, who published their findings in the journal «Nature» on October, 15, 2014, demonstrated that, in contrast to the molybdenum disulfide in its bulk form, the monoatomic layers of MoS2 exhibit the so-called piezoelectric effect — they produce electricity when compressed or stretched.
The study is the first to demonstrate the piezoelectric properties of two-dimensional materials, which earlier had been predicted theoretically. “This adds another member to the family of piezoelectric materials for functional devices,” says Wenzhuo Wu of Columbia University, a member of the research team.
Two conditions must be satisfied to use molybdenum disulfide for generating electricity: using an odd number of atomic layers and flexing the material in the proper direction. Since MoS2 is highly polar, an even number of atomic layers cancels out the piezoelectric effect.
“What’s really interesting is we’ve now found that a material like MoS2, which is not piezoelectric in bulk form, can become piezoelectric when it is thinned down to a single atomic layer,” says Lei Wang of Columbia University, who took part in the study.
This happens due to a fact that a single atomic layer of MoS2 has a structure that breaks central symmetry, while in bulk MoS2, the oppositely oriented layers generate positive and negative voltages which cancel each other out, resulting in the absence of piezoelectric effect.
Thanks to its amazing properties and microscopic size, the material could find a number of applications – from wearable chargers for daily use gadgets and medical implants to robotics and flexible electronics.
“This material—just a single layer of atoms—could be made as a wearable device, perhaps integrated into clothing, to convert energy from your body movement to electricity and power wearable sensors or medical devices, or perhaps supply enough energy to charge your cell phone in your pocket,” says James Hone of Columbia University, a co-leader of the research.
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