Swedish researchers create electronic circuits inside roses
22 November 2015
Researchers at Linköping University in Sweden have used the vascular system of living roses to create analogue and digital electronic circuits within them.
A group at the Laboratory of Organic Electronics (LOE) based at Linköping University in Sweden, under the leadership of Professor Magnus Berggren, has demonstrated wires, digital logic, and even display elements - fabricated inside the plants - that could develop new applications for organic electronics and new tools in plant science.
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. Controlling and interfacing with chemical pathways in plants could pave the way to photosynthesis-based fuel cells, sensors and growth regulators, and devices that modulate the internal functions of plants.
"Previously, we had no good tools for measuring the concentration of various molecules in living plants," says says Ove Nilsson, professor of plant reproduction biology and director of the Umeå Plant Science Center. "Now we'll be able to influence the concentration of the various substances in the plant that regulate growth and development. Here, I see great possibilities for learning more."
The idea of putting electronics directly into trees for the paper industry originated in the 1990s while the LOE team at Linköping University was researching printed electronics on paper. Early efforts to introduce electronics in plants were attempted by Assistant Professor Daniel Simon, leader of the LOE's bioelectronics team, and Professor Xavier Crispin, leader of the LOE's solid-state device team, but a lack of funding hindered these projects.
Thanks to independent research money from the Knut and Alice Wallenberg Foundation in 2012, Professor Berggren was able to assemble a team of researchers to reboot the project. The team tried many attempts at introducing conductive polymers through rose stems. Only one polymer - PEDOT-S - synthesised by Dr Roger Gabrielsson, successfully assembled itself inside the rose's xylem channels as conducting wires, while still allowing the transport of water and nutrients.
Dr Eleni Stavrinidou used the material to create long (10cm) wires in the xylem channels of the rose. By combining the wires with the electrolyte that surrounds these channels she was able to create an electrochemical transistor, a transistor that converts ionic signals into an electronic output. Using the xylem transistors she also demonstrated a digital logic gate function.
Dr Eliot Gomez 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. An applied voltage caused the polymer to interact with the ions in the leaf, subsequently changing the colour of the PEDOT in a display-like device - functioning similarly to roll-printed displays.
The aim of this work is to develop applications for energy, environmental sustainability, and new ways of interacting with plants. Professor Berggren envisions the potential for an entirely new field of research: "Now we can really start talking about 'power plants' - we can place sensors in plants and use the energy formed in the chlorophyll, produce green antennas, or produce new materials. Everything occurs naturally, and we use the plants' own very advanced, unique systems."