Wood-based Technology Creates Electricity From Heat

Researchers in the A. James Clark School of Engineering have created a heat-to-electricity device that runs on ions that could someday harness the body’s heat to provide energy.

Associate Professor Liangbing Hu and Professor Robert Briber, both of the Department of Materials Science and Engineering, and Siddhartha Das, an assistant professor of mechanical engineering, 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. With this new wood-based technology, they can use a small temperature differential to efficiently generate ionic voltage, as demonstrated in a paper published yesterday 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, which makes the wood brown and adds strength, and hemicellulose, which winds around the layers of cells binding them together. This gives the remaining cellulose its signature flexibility.

A membrane made of a thin slice of wood was bordered by platinum electrodes, with sodium-based electrolyte infiltrated into the cellulose. They regulate the ion flow inside the tiny channels and generate electrical signal.

“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,” said postdoctoral researcher Tian Li, the first author of the paper.