Wood-based flexible tech creates electricity from body heat

Scientists, including one of Indian origin, have transformed a piece of wood into a flexible membrane that generates power from the same type of electric current that the human body runs on.

This energy is generated using charged channel walls and other unique properties of the wood's natural nanostructures, according to researchers from University of Maryland in the US.

With the technology, researchers can use a small temperature difference to efficiently generate voltage.

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 nanometres or less across.

The team has harnessed these channels to regulate ions, according to the study published in the journal Nature Materials.

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 gives the remaining cellulose its signature flexibility. This process also converts the structure of the cellulose from type I to type II which is a key to enhancing ion conductivity.

A membrane, made of a thin slice of wood, was bordered by platinum electrodes, with sodium-based electrolyte infiltrated into the cellulose. The 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 nanofibres and thus help effectively regulate ion movement under a thermal gradient," said Tian Li, first author of the research.

Li said that the sodium ions in the electrolyte insert into the aligned channels, which is made possible by the crystal structure conversion of cellulose and by dissociation of the surface functional groups.

"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.