Scientists in India and Germany have unveiled a material that generates tiny amounts of electricity from mechanical stresses like a person’s touch or step. The idea is to create a biodegradable energy source that can pump electricity into a storage supercapacitor to power electronics, replace batteries and safely break down without polluting the environment. 

Their material, described in the journal Applied Materials & Interfaces, is a biodegradable plastic polymer called polyvinylidene difluoride sandwiched between conducting carbon electrodes. Interestingly, they mixed DNA with the plastic because the genetic material is biodegradable while having properties that help harvest electricity. In fact, DNA is known for its ability to accumulate electric charge when mechanical stress is applied to the molecule, a property called piezoelectricity.

In lab tests, a researcher pressing on a small piece of the prototype material generated enough electricity to light 55 blue LEDs. Putting the material on a shoe and then juggling a soccer ball, they recorded small bursts of electricity with every hit.

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Electricity generating fabric

Above: Schematic illustration shows the microfiber nanowire hybrid nanogenerator, which is the basis of using fabrics for generating electricity.

The researchers harvested energy from the environment by converting low-frequency vibrations into electricity. Those vibrations came from simple body movements, the beating of the heart or movement of the wind. They did so with zinc oxide nanowires that conduct the electricity. The zinc oxide nanowires are piezoelectric — they generate an electric current when subjected to mechanical stress. The diameter and length of the wire are 1/5,000th and 1/25th the diameter of a human hair.

Credit: Prof. Z.L. Wang and Dr. X.D.
Wang, Georgia Institute of Technology

A loudspeaker in a flag

Credit: Michigan State University

Researchers at Michigan State University have created an audio product that could be the key to manufacturing a foldable loudspeaker, a voice-activated security patch for computers or a talking newspaper. 

A FENG, or ferroelectret nanogenerator, is a material that converts mechanical energy into electrical energy. The team discovered that the same properties could also be used to create a microphone or loudspeaker. They demonstrated this by turning a MSU Spartans team flag into a loudspeaker.

Credit: Michigan State University

FENG is made of a silicone wafer, which is then fabricated with several layers of silver, polyimide and polypropylene ferroelectret. Ions are added so that each layer in the device contains charged particles.


Tiny Piezoelectric Generator Lights 100 LEDs With Flick Of A Finger

Researchers in South Korea have taken another step toward harvesting the energy in tiny movements and vibrations. They’ve built a piezoelectric generator that converts enough kinetic energy into electricity to briefly light more than 100 LED bulbs. 

Keon Jae Lee, an associate professor of materials science and engineering at The Korea Advanced Institute of Science and Technology, said his team’s work showed “a high-output performance of ~250 V from the slight mechanical deformation of a single thin plastic substrate.”

They claim they attained conversion efficiency 40 times higher than previous attempts. They are now working on stacking the thin-film generators to up power output so the units can make enough electricity to operate machines like implants and other small devices in inaccessible places.

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A Fabric That Delivers the Juice You Need

Concern and speculation about battery life had been building for months before yesterday’s launch of the Apple Watch. Up to a few days ago, when information started leaking in advance of the device’s release, rumors were flying that it wouldn’t last through a day’s normal usage before needing to be recharged.

The good news for Apple enthusiasts is that the company seems to have pushed energy efficiency to the point where the watch won’t bow out before the sun goes down. But what if this wearable tech, or the myriad others coming down the pipe, didn’t ever need to be plugged in to get its electron tanks topped off? What if the device could get what it needed by harvesting the energy in a user’s movements?

We’ve reported on a number of projects whose goal is to make generators that take advantage of the triboelectric effect, an electrical phenomenon where two different types of materials create a charge when they rub together. Imagine capturing the hundreds of volts generated when you walk across a carpeted floor in sneakers and throwing it into your phone battery for later use.

Now researchers in South Korea and Australia say they have built an energy-generating cloth that uses the triboelectric effect to generate power for wearable electronics.

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