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This Ultrathin Device Turns Your Movements Into Electricity

In the very near future, you’ll be able to slide a tiny device into your clothing that will track your own motion to create power for electronic personal devices like cell phones and fitness trackers.

Researchers at Vanderbilt University’s Nanomaterials and Energy Devices Laboratory have developed the energy harvesting system, which forms electrical currents with every step, wave, jump and turn you take. Electricity can now be generated in a tiny device that draws power from human motion… and is small enough to fit in a piece of clothing.

Every move you make can be a source of power. 

The little gadget is made out of multiple layers of black phosphorous just several-atoms thick. Utilizing battery technology, the machine generates electricity anytime it’s bent, pressed, or moved—as it would be, say, anytime your legs swung forward while walking.

“In the future, I expect that we will all become charging depots for our personal devices by pulling energy directly from our motions and the environment,” Cary Pint, Vanderbilt’s assistant professor of mechanical engineering and head researcher for this project, said in a press release.

The breakthrough relies on its sensitivity to slow motion.

In recent years, there have been several innovations that allow energy to be harvested by motion; whether ocean tides or wind. But most of these energy-harvesting platforms rely on motion greater than 10 Hertz (10 cycles per second). Human motion occurs much more slowly than that, generally even at less than 5 Hertz. This new energy harvester, however, can create power at frequencies as low as 0.01 Hertz.

“Compared to the other approaches designed to harvest energy from human motion, our method has two fundamental advantages,” Pint said. “The materials are atomically thin and small enough to be impregnated into textiles without affecting the fabric's look or feel and it can extract energy from movements that are slower than 10 Hertz—10 cycles per second—over the whole low-frequency window of movements corresponding to human motion.”

When you imagine commuters in Grand Central Station or everyone moving through the Denver airport, you start to get an idea of just how much electricity could be produced by human movement on a daily basis.

“When you look at Usain Bolt, you see the fastest man on Earth,” doctoral student Nitin Muralidharan told Vanderbilt University. Muralidharan co-led the manufacturing and testing of the new device. “When I look at him, I see a machine working at 5 Hertz.”

The science behind the energy harnessing device is fully documented in “Ultralow Frequency Electrochemical Mechanical Strain Energy Harvester using 2D Black Phosphorus Nanosheets,” a paper published July 21 in the online journal ACS Energy Letters.

Efficiency is key.

Another exciting element to this breakthrough is its efficiency.

While other energy harvesters work best while drawing strength from frequencies of more than 100 Hertz, they barely draw anything from human movements. That drives efficiency down to less than 10 percent.

“Our harvester is calculated to operate at over 25 percent efficiency in an ideal device configuration, and most importantly harvest energy through the whole duration of even slow human motions, such as sitting or standing,” Pint told Vanderbilt University.

The secret to that is in the batteries. The research team discovered differences in voltage when battery parts were stressed. Under tension, the voltage rose. During compression, the voltage dropped. So Pint’s team remade batteries that produce energy when bent or twisted, allowing human motion to create electricity.

Motion-derived electric can power your phone—or change your clothing. 

Pint said he sees multiple exciting, futuristic possibilities for this technology.

Beyond powering fitness devices and your cell phone, the phosphorous strips could power clothing embedded with liquid crystal that could change colors and patterns through a smartphone app—kind of like Hypercolor shirts on steroids.

“We are already measuring performance within the ballpark for the power requirement for a medium-sized low-power LCD display when scaling the performance to thickness and areas of the clothes we wear,” Pint said in a press release.

He also pointed to potential records of human motion for advanced VR technology. “When incorporated into clothing, our device can translate human motion into an electrical signal with high sensitivity that could provide a historical record of our movements. Or clothes that track our motions in three dimensions could be integrated with virtual reality technology. There are many directions that this could go.”   

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