A new moisture-driven electricity generation (MEG) device has been created by researchers from the College of Design and Engineering (CDE) of the National University of Singapore (NUS). It is made of a thin fabric layer with a thickness of about 0.3 millimetres (mm), sea salt, carbon ink, and a unique water-absorbing gel.
“Sea salt was chosen as the water-absorbing compound due to its non-toxic properties and its potential to provide a sustainable option for desalination plants to dispose of the generated sea salt and brine,” says Assistant Professor Tan Swee Ching, who also led the research team.
The foundation of MEG technology is the capacity of various materials to produce electricity through their interaction with atmospheric moisture such as self-powered gadgets. The gadget being saturated with water when exposed to ambient humidity and poor electrical performance are two main problems with current MEG technologies. Traditional MEG systems cannot generate enough electricity to sustainably power electrical equipment as a result.
To address these issues, the researchers developed a novel MEG device with two regions of different properties that continuously maintain a difference in water content across the regions to generate electricity and enable electrical output for hundreds of hours.
The carbon nanoparticle-coated fabric layer that makes the MEG gadget is quite thin, so scientists used a commercially available polyester-wood pulp fabric. The part of the fabric that is covered with a hygroscopic ionic hydrogel is called the “wet zone.” The unique water-absorbing gel is made from sea salt and can take in more than six times its own weight in water. It is used to pull water from the air. The dry end of the fabric, which is its opposite, is devoid of the hygroscopic ionic hydrogel layer. To keep this area dry and keep water in the wet area, is being done.
After assembling the MEG device, electricity is generated when the ions of sea salt are separated as water is absorbed in the wet region. The negatively charged carbon nanoparticles attract positively charged free ions that cause changes to the fabric’s surface, creating an electric field across it. These surface modifications also enable the fabric to store electricity for later use.
NUS researchers were able to maintain high water content in the wet region and low water content in the dry region by using a unique design of wet-dry regions. This will keep the power on even when the wet region is saturated with water. After 30 days in an open humid environment, water was still retained in the wet region, demonstrating the device’s effectiveness in sustaining electrical output.
The team’s MEG device was also extremely flexible, withstanding stress from twisting, rolling, and bending. Interestingly, the researchers demonstrated its exceptional flexibility by folding the fabric into an origami crane, which had no effect on the device’s overall electrical performance.
Because of its ease of scalability and commercially available raw materials, the MEG device has immediate applications. One of the most obvious applications is as a portable power source for mobile electronics powered directly by ambient humidity.
The NUS team has also demonstrated the scalability of its new device in producing electricity for various applications. The NUS team joined three pieces of the power-generating fabric and placed them in a 3D printed case the size of an AA battery.
The voltage of the assembled device was tested to reach 1.96V, which is higher than the 1.5V of a commercial AA battery and sufficient to power small electronic devices such as an alarm clock.