Energy harvesting foil generates electricity from human motion

July 28, 2017 // By Nick Flaherty
Researchers at Vanderbilt University's (Nashville, TN) Nanomaterials and Energy Devices Laboratory have developed an ultrathin system that harvests energy from motion at very low frequencies, one of the major challenges of such systems.

The system uses atomic layers, or 2D nanosheets, of black phosphorus that generate small amounts of energy when it is bent or pressed, even at the low frequencies of human movement.

"When you look at Usain Bolt, you see the fastest man on Earth. When I look at him, I see a machine working at 5 Hz," said Nitin Muralidharan, a doctoral student who co-led the project with Mengya Li 

Most energy harvesting systems based around piezoelectric crystals operate at around 100Hz and have to be tuned to the resonant frequency to be most effective. The 2D nanosheets can pick up much of the energy generated at frequencies down to 0.01Hz, meaning most of the energy from the movement is collected.

"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," said Cary Pint, Assistant Professor of Mechanical Engineering at the Lab who directed the research.

"Compared to the other approaches designed to harvest energy from human motion, our method has two fundamental advantages," he 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 Hz over the whole low-frequency window of movements corresponding to human motion."