It's usually one of the first science facts learned in elementary school: a tree is a natural insulator. For those who need a refresher, this means that the material generally doesn't conduct electricity very well. But although this information is fundamental, the research team added an asterisk to the rule: they concluded that after modifying the tree, it can conduct electricity. They can also be converted into natural transistors.
According to a recent article in the journal Proceedings of the National Academy of Sciences, engineers from Sweden's Linköping University have successfully crushed cork by first removing lignin, a natural binder found in wood, and other plants. After the lignin is removed through the cork, a network of water-bearing tubes called lumines remains. The remaining balsa preform can be immersed in a slurry containing an electrically conductive polymer. The result was a material capable of transporting water along with electrolytes through its lumen and a new natural transistor.
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Before balsa, the team tried to make conductive wood from other specimens, including birch and ash. However, these alternatives did not have the same degree of structural integrity after being immersed in the polymer solution, and they did not absorb the polymer properly. Additionally, the team found that, unlike other test options, balsa showed compositional versatility in all seasons.
But don't expect to see wooden transistors in the next iPhone. Compared to modern silicon transistors, the wooden strip version is much larger and slower. As New Scientist explains, a single fingernail-sized computer chip often contains billions of transistors, each of which can cycle on and off billions of times per second. For comparison: the length of a balsa transistor is about three centimeters. It also takes one second to turn off and about five seconds to turn back on.
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However, wooden transistors also show promise in other industries such as forestry and agricultural monitoring. Wooden ladders are also more durable than existing alternatives and can also be used to monitor plant resilience to climate change and other environmental issues. Looking ahead, the researchers told New Scientist they hope to one day grow wood samples with conductive polymers using different versions that penetrate the wood without the need to remove lignin.
