New Sweat-Powered Battery Is Stretchable And Very Flat
Researchers at NTU Singapore have developed a new type of battery that might be ideal for future wearable products. The battery is stretchable and gets the power it needs to operate from sweat. The battery is also soft and described as being as flat as a bandage. The battery is 2cm x 2cm and is attached to a flexible and sweat absorbent type of textile that can be easily affixed to wearable devices, including smartwatches, medical devices, and various other wearable electronic devices.
Project scientists conducted a trial where a tester wore the battery around their wrist and rode on a stationary bike for 30 minutes. During that time, the wearer generated 4.2 volts output power and 3.9mW, sufficient to run a commercial temperature sensor and transmit data from the sensor to a smartphone via Bluetooth. The battery (PDF) is green containing no heavy metals or harsh chemicals like current batteries.
Researchers say they created a battery that can run using perspiration, providing electronic wearable devices a guaranteed source of power produced from the human body. The team expects the battery will be able to operate a wide variety of devices. In addition, since the new battery the team is designed has no harsh chemicals inside, there's no concern of ruptured battery spilling acids or other harsh substances on the wearer in an accident.
NTU created the battery using a printer ink that contained silver flakes and hydrophilic poly urethane-acrylate (HPUA). When the silver flakes contact sweat, the chloride ions and acidity in the sweat causes the flakes of silver to come together and increase their electrical conductivity. The chemical reaction also leads to a current flowing between the electrodes, as shown in the video below.
The stretchable textile used is absorbent and can retain a lot of sweat, allowing for a consistent power source even if the person isn't sweating much. Another benefit is that the team expects the battery to be more durable than existing batteries. Currently, researchers are working to further investigate how the battery's performance might be impacted by body heat and other factors.