Hikers, soldiers and schoolchildren know the weight of a heavy backpack well. Now researchers have developed a prototype that not only makes loads feel about 20 percent lighter, but also harvests energy from human movements to power small electronic devices. The new backpack, whose study is reported in ACS Nano, would be particularly useful for athletes, explorers and disaster responders working in remote areas without electricity.
Backpacks are widely used in everyday life for hands-free carrying loads. Over time, however, walking or running with a heavy backpack can cause back and neck pain. With this in mind, backpackers in wilderness areas (or even those in cities away from a charger) might happily greet such an item. A backpack that collects the mechanical energy of walking. To do what? Obviously, to power portable electronic devices or health monitoring sensors.
The old attempts
Previously, the researchers used nanogenerators triboelectrics (TENG) (small devices that convert mechanical energy into electricity) to make a backpack that collects energy. but those bags had relatively low power outputs and provided no additional benefits, such as load relief or shock absorption. Zhong Lin Wang, Jia Cheng and colleagues wanted to design a prototype that would overcome these limitations.
The solutions for the light backpack that generates energy
To save work and absorb shock, the researchers incorporated it into the backpack two elastomers. System that stretch and shrink, keeping the bag steady as the wearer walks. This provided a weight reduction of around 20% on the wearer. Meanwhile, the movement between the backpack frame and its load while walking prompted a TENG to convert mechanical energy into electricity, with an efficiency of 14%. The researchers proved that the backpack could power LEDs, an electric clock and fluorescent tubes. Once some challenges are overcome, such as improving energy conversion efficiency, the backpack has promising potential as a power source for small-scale portable and wearable electronic devices, GPS and health sensors, say the researchers.
The abstract of the paper is available here.
