COLLEGE PARK, Md. - A University of Maryland-led team of researchers has created a heat-to-electricity device that could someday harness the body’s heat to provide energy.
The UMD team transformed a piece of wood into a flexible membrane that generates energy from the same type of electric current (ions) that the human body runs on.
This energy is generated using charged channel walls and other unique properties of the wood’s natural nanostructures. A small temperature differential can be utilized to efficiently generate ionic voltage, as demonstrated in a
paper published March 25 in the journal Nature Materials.
Trees grow channels that move water between the roots and the leaves. These are made up of fractally-smaller channels, and at the level of a single cell, channels just nanometers or less across. The team has harnessed these channels to regulate ions.
The researchers used basswood, which is a fast-growing tree with low environmental impact. They treated the wood and removed two components – lignin, that makes the wood brown and adds strength, and hemicellulose, which winds around the layers of cells binding them together. This process gives the remaining cellulose its signature flexibility and converts the structure of the cellulose from type I to type II, which is a key to enhancing ion conductivity.
Exemplified by lightning storms, generating charge between two very different temperatures is easy. But for small temperature differences, it is more difficult. However, the team says they have succesfully tackled this challenge. Hu said they now have “demonstrated their proof-of-concept device, to harvest low-grade heat using nanoionic behavior of processed wood nanostructures.”
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ARTICLE
Modified wood makes batteries safer
Inspired by the structure of wood, engineers at the University of Maryland have used modified wood as a unique architecture for the negative electrode of a lithium (Li) metal battery.
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“The charged channel walls can establish an electrical field that appears on the nanofibers," says Tian Li, first author of the paper, "[This helps] effectively regulate ion movement under a thermal gradient.”
Li, who was named as one of
Forbes "30 Under 30" in Energy in 2018, said “We are the first to show that this type of membrane, with its expansive arrays of aligned cellulose, can be used as a high-performance ion selective membrane by nanofluidics and molecular streaming and greatly extends the applications of sustainable cellulose into nanoionics,” said Li, summing up their paper.
This latest work builds on, and adds to, extensive previous UMD research to develop novel and potentially high impact applications of modified wood.
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