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A bionic form of camouflage designed to reflect both visible and infrared light and mimic the appearance of leafy foliage could be used to hide technology such as surveillance equipment in forest settings.

“We wanted our device to mimic the way natural leaves look under different kinds of cameras, not just to the human eye,” says at the University of Science and Technology of China. He and his colleagues worked out how to do so by studying the internal structure of camphor tree () leaves.

Their material mimics the internal layers of the tree’s leaves. For instance, the top layer, equivalent to a leaf’s upper epidermis, is made from a compound of indium, tin and oxygen. This layer emits very little infrared light, so the material is difficult to detect with a thermal camera.

The material’s second layer, meanwhile, imitates a leaf’s mesophyll. This layer of tissue is studded with cells containing photosynthetic structures called chloroplasts, which give leaves their green colour. The researchers mimicked the mesophyll by mixing nanometre-sized particles into a rubbery, transparent plastic that scatters light to emit a green hue. Ye says this second layer makes the new material difficult to detect against a leafy background with conventional cameras.

The researchers made samples of the material and placed them in a tree, among leaves, before trying to detect the samples with a camera that could record light in many different wavelengths. They found there was only a tiny discrepancy – 5.3 per cent – between the way the material and the real leaves reflect visible light, meaning it blended in extremely well. The material also reflected less infrared light than natural leaves, making it difficult to detect using a thermal camera.

Ye says these properties may make the material a good choice for concealing sensors or other technologies in natural habitats.

But at the University of Central Florida says there are major hurdles to overcome first. Chanda points out that leaves change colour over time – particularly during autumn – so the material would have to adjust its appearance with the passing of the seasons. He says it is also possible that a super-sensitive infrared camera could detect the material based on the fact that it reflects less infrared light than the leaves around it. This might make a camouflaged object stand out as a patch of forest with an unusually low infrared signal.