Energy harvesting material could power wireless devices researchers claim

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Researchers in France have made a breakthrough in the development of energy harvesting materials which they claim could one day see them used as alternative power supplies for electronic devices.

The team, from France’s National Institute of Applied Sciences of Lyon (INSA de Lyon) has discovered a way to enhance the mechanical performance of a class of smart materials known as "electrostrictive polymers" by introducing a plasticizer.

The group's work centres largely on the piezoelectric effect, which refers to the accumulation of electric charge in certain crystalline solids without a symmetric center in response to an applied mechanical stress or strain.

Electrostrictive polymers can produce field-induced strain when exposed to an applied external electric field. "And this strain has a quadric -- equation described by the second degree -- relationship with the applied electric field," explained Xunqian Yin, lead author and a researcher at the INSA de Lyon.

In this case, "the electrostrictive polymers are non-piezoelectric in nature," said Yin. "But a pseudo-piezoelectric effect can be induced for electrostrictive polymers when they're exposed to a large applied bias DC electric field. As a result, the pseudo-piezoelectric effect was adopted for the mechanical energy harvesting via electrostrictive polymers."

The group studied the influences on mechanical energy harvesting of a variety of operating conditions, including large applied bias DC electric field, as well as the amplitude and frequency of applied external strain. They discovered that increasing the applied bias provides a way to improve the energy conversion efficiency.

In particular, when they worked with a plasticizer-modified "terpolymer," it offered improved mechanical energy harvesting performance, especially when imposed to the same force level, and it can be tapped to create highly sensitive force sensors.

"The modified terpolymer thin film can lead to piezoelectric active sensors, such as force sensors," said Yin." Combining these sensors with advanced fabrication technologies -- inkjet or 3D printing -- should make it easier to build a network of sensors."