Researchers create transistor made of… wood

A group of researchers from Sweden have achieved something that seems straight out of a comic book: they have developed a transistorthe basic semiconductor component for every electronic device on the planet, made from wood. And yes, it is fully functional.

The novelty can pave the way for a more sustainable development for electronics, computing, infrastructure and whatever else you can imagine, but there are a number of caveats that we need to consider.

Yes, this is a transistor.

Yes, this is a transistor.

Photo: Thor Bakhed/Linköping University / Meio Bit

The transistor is one of the most important inventions of the 20th century, and many serious people put it at the top of the list (me too, but I don’t fit the “serious people” category). It is a component that has two main functions, blocking the passage of an electric current, or amplifying it. As an amplifier, it produces a higher intensity output, something easily exemplified by a microphone connected to a sound system.

As a switch, a transistor is used to determine when, and how many times, a current can pass through a circuit. Along with resistors and capacitors, transistors are the foundation for implementing Boolean logic in electronics, converting analog signals into conditionals, or simplifying binary math.

Transistors have become the cornerstone of modern computing, replacing the huge and less efficient thermionic tubes. Every electronic device uses concepts established by Julius Edgar Lilienfeld in 1926, but first demonstrated in 1947.

A transistor uses semiconductor material (obvious), the most used are silicon and germanium, but others can also be used; Needless to say, the bulk of semiconductor and transistor production is now in Asia, mainly China and Taiwan, and the collapse in the supply chain, caused by the Covid pandemic, has affected the entire consumer, industrial, infrastructure, etc. market. from the planet.

There are also a number of questions about the extraction of these and other rare minerals from Nature, which in many places violate basic human rights (such as the cobalt mines in Congo, the material used in lithium batteries), leading researchers to try their luck with other approaches, some curious.

Replica of the first working transistor, developed by John Bardeen and Walter Brattain at Bell Labs in 1947

Replica of the first working transistor, developed by John Bardeen and Walter Brattain at Bell Labs in 1947

Photo: Executive Office of the President of the United States/public domain / Meio Bit

Which brings us to the research of a mixed group of Swedish scientists, from the University of Linköping and the Royal Institute of Technology (KTH). The article describes the “organic” transistor using wood from the tree known as balsa wood (Ochroma pyramidale), native to the Americas, occurring from northern South America to Mexico. It is usually used in the production of ferries (hence the name) and model airplanes, but it was also used in the construction of fighter planes, such as the DH.98 Mosquito.

ecological transistor

Balsa wood is considered the lightest and least dense wood recorded, due to its organization. Its cellulose fibers resemble “combs”, which are filled with lignin, a macromolecule that gives rigidity to plants, which was removed, leaving empty spaces.

Next, the “combs” were filled with a plastic polymer called poly(3,4-ethylenedioxythiophene), or PEDOT:PSS, which has conductive capabilities. The set was then properly assembled, resulting in a wood-based semiconductor component.

In the tests, the scientists found that the passage of electric current through the transistor occurs without the component deteriorating; previous experiments did not work, because the models only allowed the transport of ions, but when these ran out, the semiconductor also stopped working.

wooden transistor diagram

wooden transistor diagram

Photo: Linköping University/PNAS / Meio Bit

Although a certain amount of buzz has formed around the research, raising the hypothesis of using wooden transistors to enable electronic controls in plants, or using the method to replace silicon, it is necessary to take it easy. The research transistor measures 3 cm in length, and those used in modern computing are measured in nanometers, where 1 nm = 0.000000001 m, or 1 billionth of a meter.

A modern processor, with billions of transistors, if it used the wooden one in the research, would have an area of ​​many kmtwo, which I think, would do away with the concept of portability. Not to mention that the frequency he is able to regulate was… 1 Hz. No GHz or MHz, not even KHz. A measly hertz. I think, I just think, that he wouldn’t run Crysis.

The search for efficient solutions to resolve the problem of the theoretical limit of silicon has become an arms race, with researchers today betting on graphene, or on other approaches to already established materials. The wood experiment is nowhere near designed for this scenario, and the researchers admitted they were moved by the Hacker Spirit, just to see if it could be done.

On the other hand, the research raises the possibility of using the technique in more limited and less demanding applications, both in computational power and in energy efficiency, with the bonus of being ecologically correct.

Bibliographic references

TRAN, VC, MASTANTUONI, GG, ZABIHIPOUR, M. et al. Electrical current modulation in wood electrochemical transistor. PNASVolume 120, Issue 18, 7 pages, April 24, 2023. Available here.

Source: Linkoping University

Researchers create transistor made of… wood

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