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Ultra-thin sheets of wood modified with nanocrystals can work as a shield against electromagnetic waves.

Electrical devices such as phones, laptops and microwaves produce electromagnetic radiation, which can disrupt electrical circuits, harming performance or stopping devices from working.

To stop this happening, electrical components are often encased within protective conductive materials, such as copper and aluminium, which can absorb and reflect electromagnetic energy.

But researchers are always seeking more sustainable options for such jobs. Now, at the University of G枚ttingen in Germany and his colleagues have come up with a way to do the job effectively with wood.

They created a carbonised wood film by compressing half-a-millimetre-thick slices of wood under high pressure, before heating them at 1200掳C (2192掳F) in the presence of nitrogen. The researchers then treated the resultant layers in nitric acid, washed them and dried them.

Zhang and his colleagues then grew what are known as zeolitic imidazolate framework nanocrystals on the surface of the wood film to increase its conductivity and shielding ability.

To test how well the modified wood film worked, the researchers fired electromagnetic waves at it and measured the radiation passing through it. The substance could shield against roughly 46 decibels of the radiation at a thickness of just 140 micrometres, which is above the shielding effect required for commercial applications.

This is a higher shielding ability relative to its thickness and weight than any previous wood-derived shields.

鈥淭he result seems too good to be true,鈥� says at Northeastern University in Massachusetts. 鈥淏ut the data seems valid, they got this high level of shielding with such a thin material.鈥�

However, he isn鈥檛 sure that wood-derived shields for electromagnetic interference will take off in the mass markets. 鈥淎luminium foil works just as well and it can be easily recycled,鈥� says Sun.