The idea of combining electronics and plants sounds like something you might see in a far-flung corner of Glastonbury festival, but it's actually been an area of research since the 1990s. Sceptical investors prevented the project from finding its feet at first, but in 2012 Magnus Berggren of Linköping University in Sweden rebooted the project with a new set of researchers. Their first results have been published in Science Advances today.
With the help of synthetic polymers, the team managed to use the vascular system of rose stems to build the basic parts of electronic circuits inside the plant. According to the paper, "The four key components of a circuit have been achieved using the xylem, leaves, veins, and signals of the plant as the template and integral part of the circuit elements and functions."
Berggren and his team experimented with different synthetic polymers to find one that could conduct an electrical current inside the plant. After many failed attempts, the team managed to find a synthetic polymer that could assemble itself into conducting wires up to 10 cm long inside the plant's xylem channel while still allowing the transport of water and nutrients to keep the plant alive.
So far the team has only got as far as using these conductive wires to light up ions in the leaves of the plants, but the implications of the technology go further. On seeing the conducting wires for the first time Berggren said in a phone call he was "basically breathless" to see how well it had worked.
"Now we can really start talking about power plants—we can place sensors in plants and use the energy formed in the chlorophyll [to power them], produce green antennae, or produce new materials," he said of the potential applications. "Everything occurs naturally, and we use the plants' own very advanced systems."
Berggren told me he is already thinking about ways to introduce some kind of biofuel cell system inside the plant, so they could convert solar energy into chemical energy and then convert the chemical energy into stored electrical energy.
"Right now we are trying to put electrodes into the leaves with enzymes that we connect to the electrodes," he said. "The sugar that is produced in the leaves is converted by the enzyme; they deliver a charge to the electrode and then hopefully we can collect that charge in a biofuel cell."
It's obviously early days, but Berggren is wistful about potential further developments. "The future will include using many different types of energy conversion systems," he said. "What percentage of that will be from plants I can't say but plant energy for sure opens up a completely novel way to harvest from the world around us."
"When we have tapped out resources from nature in the past we have always chopped it or burnt it," he added. "Maybe this could be a way of tapping energy from plants without having to kill them."