Researchers at the Nanyang Technological University, Singapore (NTU Singapore) have developed a sweat-powered battery that can make wearable devices more convenient for the user. It eliminates the need to recharge of wearable devices. 

The prototype of the NTU battery is only 2cm by 2cm and as thin as a paper bandage. It consists of printed silver flake electrodes with a capacity to generate electricity as the flakes come in contact with human sweat. The battery is affixed to a soft, hydrophilic, stretchable textile that is easy to attach to wearable devices, such as smartwatches and arm straps. 

Scientists at NTU demonstrated the potential use of this battery in wearable devices by testing the device with artificial human sweat. In another trial, researchers demonstrated that a person wearing the battery around his wrist while cycling on a stationary bike for 30 minutes can generate 4.2 volts voltage and 3.9 mW of output power that is sufficient to charge/recharge a commercially available temperature sensor. 

Using a ubiquitous material such as human perspiration to power the battery is an environmentally friendly option. But how would the batteries get power when the person is not sweating?

Researchers solved this problem by affixing the battery prototype on a highly absorbent textile that would retain the sweat for times when the person is not sweating. This consideration was extremely important as the amount of sweat secreted by the body varies based on the area of the body, temperature, physical activity, and other factors. 

The sweat powered battery could solve two major problems. Most wearable devices have Lithium-ion (Li-ion1) and Lithium-ion polymer (LiPo, Li-Po, LIP, Li-poly) batteries which are harmful to the environment. The sweat-powered battery developed by team NTU does not have lithium or other harmful chemicals in it. Secondly, wearable electronics are fully covered to avoid contact with sweat that could harm the device. The latest development at NTU turns sweat into an asset permitting new, less encapsulated designs of wearables.