Electronic Plants

Credit: Laboratory of Organic Electronics

Plants all around us are already an integral part of human life system supporting it (life system) in different ways. With the growing use of electronic devices in our daily lives, scientists and engineers are exploring ways to integrate the plants for their electronic functionality with human and electronic devices.  Plants are complex organisms that rely on the transport of ionic signals and hormones to perform necessary functions. However, plants operate on a much slower time scale making interacting with and studying plants difficult. Augmenting plants with electronic functionality would make it possible to combine electric signals with the plant's own chemical processes.

Research status

Efforts to introduce electronics in plants for the paper industry originated with the idea of  printed electronics on paper. Researchers at a university in Sweden have created analog and digital electronics circuits inside living plants. They have used the vascular system of living roses to build key components of electronic circuits. Researchers demonstrate that wires, digital logic, and even displays elements  fabricated inside the plants  could develop new applications for organic electronics and new tools in plant science. The research team tried to introduce conductive polymers through rose stems. Only one polymer, called PEDOT-S, successfully assembled itself inside the xylem channels as conducting wires, while still allowing the transport of water and nutrients.  They used the material to create long (10 cm) wires in the xylem channels of the rose. By combining the wires with the electrolyte that surrounds these channels researchers were able to create an electrochemical transistor, a transistor that converts ionic signals to electronic output. Digital logic gate function was also demonstrated using the xylem transistors. Scientists used methods common in plant biology  vacuum infiltration  to infuse another PEDOT variant into the leaves. The infused polymer formed "pixels" of electrochemical cells partitioned by the veins. Applied voltage caused the polymer to interact with the ions in the leaf, subsequently changing the color of the PEDOT in a display-like device  functioning similarly to the roll-printed displays. These results are early steps to merge the diverse fields of organic electronics and plant science.

Researchers at Linköping University in Sweden have also created analog and digital electronics circuits inside living plants. The group at the Laboratory of Organic Electronics (LOE), under the leadership of Professor Magnus Berggren, have used the vascular system of living roses to build key components of electronic circuits.

Science behind

It’s not exactly established where these voltages come from but there seems to be some signaling in trees, similar to what happens in the human body but with slower speed. Traditional electronics send and process electronic signals, while plants transport and handle ions and growth hormones. In organic electronics, based on semi-conductive polymers, both ions and electrons can serve as signal carriers. With the help of organic electronics it therefore becomes possible to combine electric signals with the plant’s own, as if translating the plant’s signals into traditional electronics.

Electrical power in trees

The electronic trees (e-trees) use L-systems to simulate growth. L-systems are very important in the field of complexity science because they are the basic algorithm for self-replicating systems. It is these self-replicating systems like those that are affectionately called A-life, in an explicit claim that they represent 'life'. Life is a complex phenomena and l-systems (and related algorithms) are a popular way to represent this complexity simply. However in A-life, there is often a larger claim that 'life is a formal property' rather than a property of the actual material. The tree-power phenomenon is different from the popular potato or lemon experiment, in which two different metals react with the food to create an electric potential difference that causes a current to flow. The custom circuit is able to store up enough voltage from trees to run a low-power sensor. A study found that plants generate a voltage of up to 200 millivolts when one electrode is placed in a plant and the other in the surrounding soil. The team sought to further academic research in the field of tree power by building circuits to run off that energy. They successfully ran a custom circuit solely off tree power.

The team next built a device that could run on the available power. The circuit is built from parts measuring 130 nanometers and it consumes on average just 10 nanowatts of power during operation. However, normal electronics are not going to run on the types of voltages and currents that we get out of a tree but the nanoscale is not just in size, but also in the energy and power consumption. Tree power is unlikely to replace solar power for most applications but the system could provide a low-cost option for powering tree sensors that might be used to detect environmental conditions or forest fires. The electronic output could also be used to gauge a tree’s health. A team of researchers at MIT (USA) is investigating whether energy generated from trees can power a network of sensors to prevent spreading forest fires. This team also claims that this technology opens the possibility of using trees as silent sentinels along the nation’s borders to detect smuggled radioactive materials. Also, adding sensors could save trees by providing better local climate data in fire prediction equipment.

Possible applications

Controlling and interfacing with chemical pathways in plants could pave the way to:

  • photosynthesis-based fuel cells
  • sensors and growth regulators
  • devices that modulate the internal functions of plants
  • develop applications for energy, environmental sustainability, and new ways of interacting with plants.
  • power plants- we can place sensors in plants and use the energy formed in the chlorophyll, produce green antennas, or produce new materials

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