DR KEITH WHEELER/SCIENCE PHOTO LIBRARY
Wood is the new styrofoam. By stripping away all the filler material in wood, leaving just bare fibres, researchers have shown that the resulting “nanowood” material outperforms just about all existing insulators.
of the University of Maryland in College Park, led the team that developed nanowood. To make it, they expose wood to cheap, simple chemicals – sodium hydroxide, sodium sulphite and hydrogen peroxide. Together, these strip out the cell walls in wood, made up of lignin and hemicellulose, leaving just the skeletal nanofibres of cellulose.
It is the parallel arrangement of these surviving nanofibers that gives nanowood its unusual properties. Heat can’t travel easily across the fibres and is mostly reflected, not least because all the solid filler material in wood that would otherwise convey the heat is gone, replaced by poorly-conducting air.
And because the surviving fibres are parallel, they help to dissipate any heat that does penetrate, so it can’t become concentrated. This duality of heat conductance – stopping heat penetrating through in one direction and guiding away any that does in another – gives it a big edge over other insulators, says Hu.
“This really shows that nature has outperformed humankind, once again,” says
of Purdue University in West Lafayette, Illinois, whose work also focuses on producing
industrially useful products derived from wood
. “We just have to unlock her secrets.”
Lab tests showed that nanowood’s capacity to block heat from penetrating through from one side to the other is on a par with that of styrofoam, which is hundreds of times better at blocking heat than epoxy, wool and glass. But nanowood is also incredibly strong, withstanding loads of 13 Megapascals – equivalent to almost 2000 pounds per square inch.
The sample tested was only 15 centimetres long and 2 centimetres thick, but the researchers say it could be made in virtually any size or shape already obtainable with wood. Because the material is so versatile, it could be used to insulate entire buildings, tiny computing components, or engines in airplanes, spaceships and cars, says Hu.
It’s also extremely light and cheap to make – just $7 for the chemicals to make each square metre of it. But it also has the major ecological benefit that it’s made from ordinary, recyclable wood. “Wood stores rather than emits carbon dioxide,” says Hu, who has set up a spin-off company called Inventwood to commercialise the material.
“This work shows that with proper treatment, wood can become stronger and more insulating than commonly used insulation, such as fiberglass for houses, with the added benefits that it is non-toxic and sustainable,” Youngblood says.
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