North Carolina State University researchers have created a soft, stretchable device that converts movement into electricity and works in both dry and wet environments. The soft, stretchable device that converts movement into electricity and works in both dry and wet environments.

Michael Dickey, corresponding author of a paper on the work and Camille & Henry Dreyfus Professor of Chemical and Biomolecular Engineering at NC State said, “Mechanical energy – such as the kinetic energy of wind, waves, body movement and vibrations from motors – is abundant. We have created a device that can turn this type of mechanical motion into electricity. And one of its remarkable attributes is that it works perfectly well underwater.”

The paper has been published in the journal Advanced Materials.

The heart of the energy harvester is a liquid metal alloy of gallium and indium. The alloy is encased in a hydrogel – a soft, elastic polymer swollen with water.

The water in the hydrogel contains dissolved salts called ions. The ions assemble at the surface of the metal, which can induce charge in the metal. Increasing the area of the metal provides more surface to attract charge. This generates electricity, which is captured by a wire attached to the device.

Dickey explained, “Since the device is soft, any mechanical motion can cause it to deform, including squishing, stretching and twisting. This makes it versatile for harvesting mechanical energy. For example, the hydrogel is elastic enough to be stretched to five times its original length.”

In experiments, researchers found that deforming the device by only a few millimeters generates a power density of approximately 0.5 mW m-2. This amount of electricity is comparable to several popular classes of energy harvesting technologies.

“However, other technologies don’t work well, if at all, in wet environments,” Dickey said. “This unique feature may enable applications from biomedical settings to athletic wear to marine environments. Plus, the device is simple to make. There is a path to increase the power, so we consider the work we described here a proof-of-concept demonstration.”

The research team already has two related projects under way.

One project is aimed at using the technology to power wearable devices by increasing the harvester’s power output. The second project evaluates how this technology could be used to harvest wave power from the ocean.


Lets see, 1/100th of a meter would be about 4″ square and the output is ½ of 1/1000th watt. That’s actually quite good.! And it works! With the note that more power is in the research path forward there is something worthwhile to look forward to.

The question that comes to mind is: “Is there any toxicity in the components?”

One has to wonder just how many imaginative devices that are low power are yet to be invented that this type of power would enable? Good work NC State!


Name (required)

Email (required)


Speak your mind