Un wooden electrochemical transistor balsa opens up the possibility of embedding sensors and other electronic devices in plants, which could help agriculture and forest management.
An electrical switch made of conductive wood it could become a basic element for future electronic devices incorporated in plants.
A new field of research: Electronic Plants
There is an emerging field of research called "Electronic Plants," where scientists are looking at different ways to send signals inside plants or to incorporate functionalities such as sensors into plants, he says. Isak Engquist from Linköping University in Sweden.
Engquist and his colleagues developed the wooden equivalent of a transistor – an electronic component that can increase electrical currents or act as a switch for electrical signals.
Operating characteristics and applicability
A single integrated circuit the size of a fingernail contains billions of tiny transistors made of semiconductor materials such as silicon. Each semiconductor transistor can turn on and off multiple times per second. Compared to silicon transistors, wooden transistors are significantly larger, each three centimeters long. Also, they have much slower switching speeds, which allow them to turn off in just about one second and start up in about five seconds.
But wooden transistors, it might prove more durable and biocompatible for certain electronic applications in agriculture or forestry, such as monitoring the resistance of plants to environmental stress and climate changes.
To create the wooden transistor, Engquist and his colleagues used a chemical process with heat to remove the "lignin" from the balsa wood. Lignin is a polymer typical of vascular plants with a three-dimensional, amorphous and complex structure. In plants, it serves as "cement" that gives resistance to stems, trunks and other plant structures.
They then immersed the wood in a liquid solution containing a conductive polymer, allowing the polymer to soak into the wood. This made it like the wood should be conductive, able to interact with electrolytes – chemical substances that conduct electricity when dissolved in water.
The researchers demonstrated and measured the operations of the wooden transistor during multiple switching tests. This represents an "exciting engineering possibility for using wood" as a scaffold "that can incorporate electrical materials into devices," he says. Tian Li from Purdue University in Indiana, who was not involved in the study.
The team initially tried several types of wood, including birch and ash. But raft proved to have the ideal characteristics for this approach, including maintaining its structural integrity after lignin removal and conductive polymer absorption.
As a future plan/study, the researchers could eventually grow conductive wood with the polymer already inside, says Engquist. This study could involve the use of different conducting polymers to penetrate the wood without the need to remove the lignin.
About balsa wood
Valued worldwide for its strong, yet light wood, the balsa tree is native to the tropical forests of South America. Over 95% of balsa wood comes from Ecuador, where it is cultivated in dense plantations.
Balsa trees grow incredibly fast, reaching almost 30 meters in less than 15 years, but they rarely live past 35. The balsa tree is a member of the Malvaceae family which contains species such as cotton (Gossypium hirsutum), cacao (Theobroma cacao) and okra (Abelmoschus esculentus).