Although there are now a number of devices that generate electricity via movement, most of them only work in dry environments. A new one, however, also functions underwater – meaning it could be used in aquatic settings, implants, or wearables that regularly get exposed to sweat.
Developed by scientists at North Carolina State University, the experimental energy harvester consists of a liquid metal alloy core composed of gallium and indium, which is encased within a stretchable, flexible strip of hydrogel.
Like other hydrogels, this one takes the form of a polymer that is plumped with water. That water in turn contains ions, which are dissolved salts. Those ions are naturally attracted to the surface of the liquid metal, inducing an electrical charge within it.
When the surface area of the metal expands – such as when the energy harvester is stretched, squished or twisted – its capacitance likewise increases, generating an electrical current. That current travels into an electrical wire attached to the device, allowing the electricity to be utilized or stored.
In lab tests performed so far, deforming the device by even just a few millimeters generated a power density of about 0.5 milliwatts per meter squared, which is reportedly “comparable to several popular classes of energy harvesting technologies.” Unlike those other harvesters, however, this one can function while completely immersed underwater – or in otherwise wet conditions.
With that added functionality in mind, the scientists are now exploring its use in applications such as wearable medical or athletic devices, underwater sensors, and marine wave energy systems.
A paper on the research was recently published in the journal Advanced Materials.
Liquid-metal energy harvester works underwater – and on dry land [New Atlas]