Wood-Based Technology Turns Heat into Electricity

University of Maryland researchers have modified a piece of wood to turn it into a device that can generate electricity from body heat.

A team of researchers has used a natural and abundant resource—a piece of wood—as the basis for a new heat-based electricity-generating device. Engineers at the University Of Maryland (UMD) created the flexible device, which runs on ions and which they believe could one day use heat from the human body to generate energy.

An illustration shows the process that allowed researchers at the University of Maryland to modify basswood and fashion it into a device that can turn heat into electricity. (Image source: University of Maryland)  

Natural Microstructures

A team led by UMD materials scientists Liangbing Hu, Robert Briber, and Tian Li and mechanical engineer Siddhartha Das built the device based on natural nanostructures in the wood, using small channels that move water between roots and leaves in to regulate the wood’s ions, they said.

These channels allowed them to transform a piece of wood into a flexible membrane that generates energy from these ions, which also is the same type of energy on which the human body runs. With this new wood-based technology, researchers said that they can use a small temperature differential to efficiently generate ionic voltage.

Specifically, researchers used basswood, 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 to bind them together.

The removal of these elements left the remaining cellulose, which is inherently a flexible material. This process also served to turn the cellulose’s structure from type I to type II, a key to enhancing ionic conductivity, researchers said.

Generating an Electrical Signal

To create the device itself, the team bordered a membrane made of a thin slice of wood with platinum electrodes, and injected a sodium-based electrolyte the cellulose, said Li, first author of a paper published on the work in the journal Nature Materials. The construction regulates the ion flow inside the tiny channels and generates an electrical signal, she said.

“The charged channel walls can establish an electrical field that appears on the nanofibers and thus help effectively regulate ion movement under a thermal gradient,” Li explained.

Moreover, the crystal structure conversion of cellulose and separation of the surface functional groups allow the sodium ions in the electrolyte to flow into the aligned channels, she 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,” Li said.

The work is an extension of previous work by a team at UMD to develop novel and potentially high impact applications of modified wood. In previous research, the team created a “super” wood that is stronger than most metals, as well as experimented with using wood in place of glass for windows to regulate building temperature.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.

 

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