WScientists have developed a transistor made of balsa wood that has been made Conductive. According to the researchers, the conductive pathways of the wood are well suited for lining them with a conductive plastic and filling the cavities with a gel as an electrolyte. The group led by Isak Engquist from Linköping University in Norrköping (Sweden) is putting the transistor in the “Proceedings” the US National Academy of Sciences (“PNAS”).
“This wood-based device and proposed working principle demonstrates the possibility of incorporating active electronic functionality into wood, suggesting different types of bio-based electronic devices,” the study authors write. They demonstrate the usability of wood for electrical functions using a transistor – i.e. a switching element for controlling and amplifying currents or voltages. Such electronic components are now built into billions of smartphones and computers – albeit much smaller than Engquist and colleagues designed.
However, the group’s initial aim was to prove that it works in principle. The scientists chose balsa wood because of its high strength, low density and high permeability. In a chemical bath, they removed part of the wood component lignin to make the wood more porous. They let the conductive combi-plastic PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) run into the small wooden vessels, which settled on the vessel walls. As tests have shown, part of the plastic penetrates the wood.
Engquist’s team built the so-called field effect transistor from three small strips of conductive balsa wood: two wider ones as control electrodes and one narrower one as a channel between the current source and outlet. The researchers filled the cavities in the channel with a gel electrolyte in which electrons and ions can move. The strips lay on top of each other at a 90-degree angle and were separated from one another by a thin cellulose cloth. With a control current at a voltage of 2.5 volts, the current flow between the source and drain could be interrupted, allowing the transistor to do its job.
The researchers admit that their transistor is not very powerful and is quite slow: it can switch off the current flow in one second, but it takes about five seconds to turn it on. However, the scientists are confident that the device can be improved. They see potential for this in areas such as bioelectronics, bio-based electronics and plant electronics. “We expect that this device and its concept will be a stepping stone for the development of wood-based electrical components,” they write.
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