In their research, published in the journal Nano Energy, the Japanese researchers focused on energy from the movement of liquid and created a device capable of generating electricity from the movement of a liquid droplet. The device was fabricated using flexible thin films made from molybdenum disulfide (MoS2) instead of graphene as the generator’s active material. This makes it possible to generate over five volts from a single liquid droplet. In contrast, graphene’s output voltage is limited to 0.1 volts. This is not enough to power electronic devices.
"To use MoS2 for the generator, it was necessary to form a large-area single-layer MoS2 film on a plastic film. With conventional methods, however, it was difficult to grow MoS2 uniformly on a large-area substrate," says Professor Ohno of the Institute of Materials and Systems for Sustainability at Nagoya University.
"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."
When water droplets slide down the device’s upper surface, electricity is generated from the natural energy that is produced and harvested.