BY MARIA BURKE | 8 MAY 2024 | IMAGE: SHUTTERSTOCK
The use of wearable electronics for healthcare is driving interest in green energy sources to power and make them maintenance-free.
Researchers in Australia say they have developed wearable devices that can generate enough energy from sweat to power a smartwatch or a Fitbit. What’s more, the energy generated can be stored.
The device is a hydroelectric nanogenerator (HENG). The functional groups on certain nanomaterials absorb water molecules and interact with them to form an electric double layer in the nanochannels of the material. Capillary force drives the absorbed water to flow in these charged channels, generating an electric current as there is a potential difference between the dry and wet ends. However, until now HENGs have not been able to generate enough energy for real-world applications.
The team from Deakin University, Australia, designed their HENG using single-layer nanosheets of MXenes – two-dimensional inorganic compounds consisting of atomically thin layers of transition metal carbides, nitrides, or carbonitrides – integrated into a wool cloth.
They chose MXenes because they have a high affinity for ions that promote energy density and electric potential. As MXenes are liable to oxidation, which reduces hydrophilicity, the researchers added oxidised ketjenblack (a superconductive carbon black) nanoparticles to the MXene matrix.
Using artificial sweat, their HENGs generated enough energy to power small wearable electronics: a current of 1.994 mA, and a voltage of 0.687 V. They could also output 1.47V when in series, suitable for conventional electronic devices such as a stopwatch (Device, DOI: 10.1016/j.device.2024.100356).
‘Imagine a tiny device that you could wear, like a bracelet or headband, that could generate electricity from something as simple as your sweat,’ said co-author Jingliang Li. ‘The device needs a small amount of sweat to operate – only a few drops to cover the surface of the device. Operation-wise a device needs sweat to generate the current, but since the device is attached to a capacitor, the current can be stored. This does not require the wearer to sweat continuously. Similar to a solar panel generating electricity, the generated current can be gradually stored in another device.’
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