Researchers at Nanyang Technological University in Singapore have developed a new type of battery that could be ideal for future wearable products. This battery is stretchable and gets the energy it needs from sweat. It is also soft and the shape is described as stretchable to be as flat as a bandage. Measuring just 2cm x 2cm and attached to a flexible, sweat-absorbing textile, the battery can also be easily attached to wearable devices, including smart watches, medical devices and a variety of other wearable electronics.
Project scientists conducted an experiment in which testers wore the battery on their wrists and rode on a stationary bicycle for 30 minutes. During that time, the wearer generated 4.2 volts of output power and 3.9 milliwatts of power, enough to run a commercial temperature sensor and transmit data from the sensor to a smartphone via Bluetooth. The battery does not contain any heavy metals or harsh chemicals like those that can be found in current batteries.
The researchers say they have created a battery that can run on sweat, providing a guaranteed power source generated from the human body for electronic wearable devices. The team anticipates that this battery will be able to operate a wide variety of devices. In addition, because the team designed the new battery with no harsh chemicals inside, there would be no concern about acid or other irritants being spilled on the wearer in an accident when the battery breaks.
The Nanyang Technological University researchers created the battery using an ink-printing technique that contains silver sheets and hydrophilic polyurethane-acrylate (HPUA). When the silver flakes come into contact with sweat, the chloride ions and acids in the sweat cause the silver flakes to clump together, increasing their electrical conductivity. The chemical reaction also causes an electric current to flow between the electrodes, as shown in the video below.
The stretchable textile used has a good absorption capacity and can retain a large amount of sweat, giving a steady power source even if the person doesn't sweat much. Another benefit is that the team expects the battery to be more durable than existing batteries. The researchers are currently working to further investigate how the battery's performance is affected by body temperature and other factors.