You can charge your cell phone battery with your sweat

As wearables colonize our daily lives, whether through smartwatches or fitness trackers, the need to find energy sources to power these miniature devices requires new technological solutions. If some time ago, we talked about the human body as a new renewable energy, either because of its kinetic energy or the heat emitted, this time we will focus on the possibilities offered by a substance such as sweat. The Grenoble Alpes University in collaboration with the University of San Diego (USA) has just developed a new flexible and stretchable device that is placed on the skin and is capable of producing electrical energy from one of the most common "biofuels" : human sweat.

This innovative technological project has been the result of uniting the knowledge of bioelectrochemistry of the University of Grenoble Alpes and the experience of its American counterpart in nanomachines and nanobioelectronics. The operating principle is based on the reduction of oxygen and the oxidation of lactate present in sweat. Regarding the materials used, the developers of this technological project have resorted to a mesh of nanotubes, polymers and enzymes that have a series of flexible connectors printed directly on the surface. The anode is an enzyme that obtains electrons from lactate and transfers them to an electron-receiving molecule that acts as a cathode.

Although they have ended up creating a biobattery, the initial objective of the technological project was to develop a lactate sensor to measure physical effort in real time. Ironically, in the initial tests they found that the people with the worst physical condition were the ones that generated the greatest amount of electricity. This responds to the fact that, when performing physical exertion, sedentary people secrete a greater amount of lactate, which is responsible for the muscle pricks experienced when exercising.

For now, the sweat battery they have developed is not going to replace nuclear power plants in terms of electricity supply, as it only generates enough energy to light an LED diode. According to scientists, they are currently capable of producing 70 microwatts per square centimeter. However, this type of battery is a cheap and easy-to-manufacture technology that researchers are confident they can optimize to power more energy-hungry devices.

The battery developed by the Grenoble Alpes University is not the only technology that is trying to harness sweat to generate electricity. Two years ago, researchers at Binghamton University in New York presented another battery model based on an elastic material with bacteria that generate electricity by feeding on sweat. The idea is to integrate the material into athletes' clothing, in such a way that it can supply electricity to IoT devices. The developers of this new technology are also exploring the possibility of harnessing the electrical charge of the millions of bacteria that inhabit our bodies.