Load-Reducing Backpack Powers Electronics as Wearer Walks

(CN) — Backpacks are the lifeblood of city commuters, a hiking necessity and a middle school rite of passage. With new energy-harvesting technology, the packs could become more than a vessel for your stuff: They can also use your body’s energy and to charge electronics. 

An international team of researchers say they have developed a prototype for a backpack that both lightens the load for people trekking long distances, and converts energy from walking into power for small wearable and portable electronics, like GPS systems. 

“Backpacks are widely used in everyday life,” the study authors write in describing the backpack, but note that over time “walking or running with a heavy sack can cause back and neck pain.” 

“Also, backpackers in wilderness areas (or even those in cities who don't have ready access to a charger) might wish for a bag that could harvest the mechanical energy of walking to power portable electronics or health-monitoring sensors,” they add.

The “load-suspended backpack for harvesting the wasted energy of human motion” relies on what’s called a triboelectric nanogenerator (TENG), which converts mechanical energy — from objects in motion, like humans walking — into electricity. 

The self-powered TENG technology was first developed in 2012 by Zhong Lin Wang, a professor at the Georgia Institute of Technology who also co-led the new study published Wednesday in the journal ACS Nano. 

Wang wrote in 2013 that “TENG is possible not only for self-powered portable electronics but also as a new energy technology with potential to contribute to the world energy in the near future.” 

The notion of harvesting human energy may sound like a futuristic vision, but Wang’s technology advances an idea that scientists have been working on for years. 

In fact, in 2005, researchers from the University of Pennsylvania presented a spring-loaded backpack that would generate electricity as the pack bounces up and down while its wearer walks. 

With the new study, Wang and colleagues from Beijing’s Tsinghua University add a new detail: Their backpack also lightens the load for walkers. 

Thanks to its elastomers, a rubber-like material, the backpack reduces the effort required to carry it, making the load feel more than 20% lighter to whomever is wearing the backpack. 

The elastomers stretch and shrink with motion, which helps to stabilize the weight and keep the backpack steady. In turn, the lack of motion reduces the amount of labor the walker has to put in, and the rubbery materials absorb shock. 

Meanwhile, the efficiency of converting human mechanical energy to electricity is around 14% under “normal walking conditions,” the researchers say. 

As for what the prototype bag can actually power, researchers tested the device on LED lights, an electric watch and fluorescent tubes. 

But before the backpack can reach its full potential as a power source, researchers will have to overcome challenges like improving upon the pack’s energy conversion efficiency. Once that happens, researchers say the pack “has the promising potential to be an energy source for the wearable and portable [electronics] and sensors.”

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