A New Method to Harvest and Generate Electricity by Manipulating Liquid

February 24, 2020 by Luke James

Researchers from Nagoya University and Kyushu University have used the energy harvested from the movement of liquid and developed a device that generates electricity.

With constant innovation in electronics bringing to market brand new sensors, wearables, and other small electronics, battery technology is struggling to keep up. Although significant research is currently going into the development of new batteries, it is also put towards alternative solutions such as energy harvesting.

As a technology that is used to transform small quantities of naturally occurring energy, such as light, heat, and vibration, energy harvesting holds much promise and is gaining attention as a worthy contender to replace batteries in the powering of smaller devices. It also helps reduce environmental impacts and can potentially power electronics in the long-term, unlike batteries that need recharging and replacing over time. 

Now, researchers in Japan have devised a new way to harvest energy produced by the movement of water.


The Research

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. 


A graphic depicting a droplet moving on MoS2 generating voltage.

A graphic depicting a droplet of water moving on MoS2 generating voltage. Image used courtesy of Adha Sukma Aji via Nagoya University


Harvesting Energy from Various Environments

It is expected that this type of technology could be applied to self-powered devices that are exposed to some form of liquid element, such as sensors monitoring industrial wastewater quality. Energy generated from liquid flow exists in various industries and environments, such as the insides of factory pipes and micro-fluid devices. Up until now, however, this type of energy has not been used effectively.

Professor Ohno says, "Our MoS2 nanogenerator is able to harvest energy from multiple forms of liquid motion, including droplets, spraying, and sea waves. From a broader perspective, this device could also be used in applications involving hydrodynamics, such as generating electricity from rainwater and waterfalls."

The Japanese researchers’ device is flexible enough to be installed on curved surfaces and thus ideal for use in plumbing. One potential application with lots of hope, therefore, is its use in acid raid monitors, water quality sensors, and self-powered rain gauges.