Plants in their various forms are always an integral part to human life system supporting it (life system) in different ways. Plants are the primary source of food, providers of oxygen as they sequester carbon and regulate the ecosystem but technologically they synthesize materials and convert sunlight to chemical energy. Plants have non-speaking human like complex organisms that rely on the transport of ionic signals and hormones to perform necessary functions for them. However, plants operate on a much lower capacity and slower time scale thus making interacting with and studying plants difficult. Scientists are developing bio-electronic technologies that will enable to understand better how plants function and their biological processes. By functionalizing plants with electronic materials, scientists and technologists aim to push the boundaries of knowledge and understand better the interface between natural and artificial. Further, augmenting plants with electronic functionality might make it possible to combine electric signals with the plant’s own electrical signals based on their chemical processes. These technologies can be used as tools by plant biologists but can also find applications in agriculture and forestry with climate change and the increasing population. According to researchers, both analog and digital electronic circuits can be created inside the living plants (flowers, bushes and trees) with the use of semi-conductive polymers. Integrating electronics in plants can also play an important role towards bio-hybrid systems, plant optimization and monitoring. Research efforts are going on template electronics in plants, affect plants biochemistry with electronics, to make plants as parts of our technology. Laboratory stage studies on plant growth in a controlled environment and development, characterization and integration of electronic devices and materials in plants is underway.
Science behind
The various parts of a plant as: root, stem, leaves, and vascular circuitry are responsible for conveying the chemical signals as well as to regulate the growth and functions of a plant. From a certain viewpoint these features are said to be equivalent to the contacts, interconnections, wires of discrete and integrated electronic circuits and devices. Several attempts have been made so far to enhance plant functions with the use of electroactive materials but without any efforts to directly merge electronics with plant’s circuitry. The tree-power activity is totally different to 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 can be used to make it possible to store up enough voltage from trees to run a low-power sensor. Scientists have found that putting one electrode in a plant and the other in the surrounding soil, plants can generate a voltage of up to 200 millivolts. The research team wanted to advance their research in the field of power from tree by building circuits to run-off plant electric energy and successfully ran a custom circuit solely off tree power. It’s not exactly established so far from where the voltages in plants 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 can send and process electronic signals whereas plants transport and handle ions and growth hormones. In case of organic electronics based on semi-conductive polymers both ions and electrons can serve as signal carriers which makes it possible to combine electric signals with the plant’s own electrical signals as if translating the plant’s signals into traditional electronics. The manufacturing of analog and digital organic electronic circuits and devices in living plants has been reported. The four key components of a circuit (an energy source, a conductor (wire), an electrical load, and at least one controller) have been achieved using the xylem, leaves, veins, and signals of the plant as the pattern and integral part of the circuit elements and functions. With the help of integrated and distributed electronics in plants, we can imagine a range of applications including, energy harvesting from photosynthesis, precision recording and regulation of plant physiology and alternatives to genetic modification for plant optimization.
Research status
Bioelectronic devices for plant monitoring and optimization are the desired tools for plant biologists, agriculture and forestry. Bioelectronic devices, sensors and actuators, based on organic electronic and iontronic materials for plant interface are being designed and developed. Creation of plant bioelectronic devices will define new means for decoding and manipulating plant biology from the cellular level to the organism level. These devices will offer unique characteristics including dynamic control of physiology of plant and signal monitoring with high spatiotemporal resolution. These devices will be compatible with both wild type and genetically engineered plants. The goal is to develop technologies with a focus on understanding and enhancing plant responses to environmental stress. Efforts to introduce electronics in plants for the paper industry originated with the idea of printed electronics on paper. Researchers of a university in Sweden have created analog and digital electronic circuits inside living plants by using the vascular system of living roses to build key components of electronic circuits. Researchers have successfully demonstrated that wires, digital logic, and even displays elements when fabricated inside the plants can generate new applications for organic electronics and new tools in plant science. The research team tried to introduce conductive polymers through rose stems and 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 inside the plant. They have used the material to create long (10 cm) wires in the xylem channels of the rose. Researchers were able to create an electrochemical transistor (a transistor that converts ionic signals to electronic output) by combining the wires with the electrolyte that surrounds these channels. Further, the digital logic gate function was also demonstrated using the xylem transistors. Scientists used methods common in plant biology like vacuum infiltration to infuse another PEDOT variant into the leaves and then 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 change the color of the PEDOT in a display-like device. This is functioning similar process as in case of the roll-printed displays. Though, these results are simply the early steps to merge the diverse fields of organic electronics and plant science but will lead towards possible electronics plants in near future.
Power from tree
With the growing use of electronic devices in our daily lives, scientists and engineers are also exploring ways to integrate the plants for their electronic functionality with human and electronic devices. The research team has also built a device that could run on the available power from plant. The circuit built with parts measuring about 130 nanometers during operation consumes on average just 10 nanowatts of power. The normal electronics is not going to run on the types of currents and voltages getting out of a tree as the nanoscale is not just in size, but also in the energy and power consumption. Electric power to be extracted from plants (i.e., Tree power) is unlikely to replace solar power for most applications but the electronic output from plant bioelectronics system could provide a low-cost option for powering tree sensors that might be used to gauge a tree’s health, to detect environmental conditions or forest fires. Recently uncontrolled and devastating forest fires in USA has force research to think critically about the bioelectronics i.e., creating electronic plants. Thus, researchers team 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 the technology will open the possibility of using trees as silent sentinels along the nation’s borders to detect smuggled radioactive materials as well as to provide better local climate data towards fire prediction.
Possible applications
Creating electronic plants can become a reality with a new technique that creates in vivo electronic circuits. Controlling and interfacing with chemical pathways inside the plants could pave the way to various exotic applications as:
- photosynthesis-based fuel cells.
- sensors and growth regulators.
- devices that will be helpful to modulate the internal functions of plants.
- new ways of interacting with electronic plants will help to develop applications for energy and environmental sustainability.
- sensors employed in plants making use the energy formed in the chlorophyll will produce green antennas, or produce new materials.
