The device described in the Nano Energy journal under the title "High output voltage generation of over 5V from liquid motion on single-layer MoS2" is made of molybdenum disulfide (MoS2) flexible thin films, it generates electricity when drops of salted water slide down on its upper surface. Previously, it has been shown that a graphene sheet could generate electricity from the liquid movement across its surface, but output voltage was limited to about 0.1V, making it impractical for energy harvesting. To make use of MoS2 for the generator, the researchers had to figure out a way to fabricate a large-area single-layer MoS2 film on a plastic film, something unachievable with conventional methods.
"In our study, we succeeded in fabricating this form of MoS2 film by means of chemical vapor deposition using a sapphire substrate with molybdenum oxide (MoO3) and sulphur powders. We also used a polystyrene film as a bearing material for the MoS2 film, so that we were able to transfer the synthesized MoS2 film to the surface of the plastic film quite easily", explained Professor Ohno of the Institute of Materials and Systems for Sustainability at Nagoya University.