This Is Nuts!

The best part of tiny portable and wearable electronic devices is that they can disappear into the background as they do their jobs while we go about our normal, daily routines. The worst part about these gadgets is that they all have batteries, and they all want to be plugged in on a regular basis for recharging. This may not rank very high on the list of the worst problems in your life, but it is annoying all the same.

To rid us of this annoyance, teams of engineers have been experimenting with some pretty wild solutions, like this self-powered yarn, this 3D-printed triboelectric nanogenerator, and this Scotch tape-powered energy harvester. But now a team at the University of Waterloo has come up with a solution that is even wilder. So much so, in fact, that you might even say they have gone completely nuts. They have developed a device that harvests energy from the unmodified shells of nuts. Unconfirmed reports indicate that new business registrations by squirrels have just hit all-time highs on this news.

The team’s device is called a water-induced electric generator (WEG), and it produces electrical energy as water evaporates from the porous structure of nutshells. The effect results from a process known as hydrovoltaic energy harvesting, in which moving water carries ions through a material’s microscopic channels creating a charge imbalance and thus generating electricity. These types of generators typically require carefully engineered nanomaterials for operation.

After cleaning, polishing, and shaping the shells, the researchers built prototype WEGs, each one a coin-sized package of shell fragments, electrodes, wiring, and a 3D-printed case. With just a few drops of water, the team was able to generate enough power to run an LCD calculator by connecting four units together.

A single walnut-based generator can output more than 600 millivolts with a power density near 6 microwatts per square centimeter. With an optional chemical treatment to boost porosity, the devices achieved up to 1.21 volts and over 347 microamps per square centimeter. This level of performance rivals or surpasses most alternative WEGs. Furthermore, it was shown that they can keep up this level of performance for more than a week with nothing more than ordinary water.

The team is already working on wearable versions of their technology that could harvest energy from sweat or rain, offering a steady trickle of power for fitness trackers, medical sensors, or environmental monitoring equipment. Other experiments even suggest wood could serve as a viable replacement, expanding the range of natural, sustainable sources.

WEGs are not going to replace power plants or charge your laptop any time soon, but for small devices that need only modest amounts of power, especially in remote or off-grid locations, the technology could be transformative. Imagine forest sensors powered by dew, disaster-relief tools fueled by rain, or wearable health monitors that never need recharging. Not bad at all for agricultural waste that would otherwise be thrown away.