When you think of cyborgs, plants probably don't pop into your head. But it's time for that to change.
A team of researchers at the Laboratory for Organic Electronics at Linköping University in Sweden has managed to grow living roses with electronic circuits in their vascular systems. The research was published Friday in the journal Science Advances.
The team, led by Professor Magnus Berggren, sees several possibilities in the project, including the surveillance and regulation of plant growth, and the potential to tap into photosynthesis as a means of generating power.
The research isn't quite at that stage yet, but the team have been able to change the hue of a rose's leaves by applying an electrical current to the system. The breakthrough follows two years of research and development, and opens new avenues for studying what happens inside plants.
"Previously, we had no good tools for measuring the concentration of various molecules in living plants," said Ove Nilsson, co-author of the journal article and professor of plant reproduction biology at Umeå University's Umeå Plant Science Centre. "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 researchers are using the plant's own architecture and biology, but getting to that point was not as simple as running wires through the plant. Instead, the idea was to introduce conductive polymers into the plant's system. These were dissolved in water, and cut rose stems placed in the water to see if the polymer would be wicked up into the plant's xylem, the channel in a plant's stem that carries water to the leaves.
The team tried over a dozen different polymers that didn't work, either poisoning the plant, clogging the xylem, or both.
They eventually reached success with a polymer called PEDOT-S:H. When cut rose stems were placed in a PEDOT-S:H solution, they absorbed the material readily. Living plants also absorbed it, albeit more slowly, through their root systems. The polymer created a thin film inside the xylem, eventually forming a solid wire as long as 10cm, which the team used to create a basic transistor. The xylem could also continue to absorb water and other nutrients normally.
The team also sent another variant of PEDOT together with a nanocellulose into the rose's leaves. The cellulose forms a tiny, sponge-like 3D structure within the leaves, and the pockets in the sponge then fill with the polymer. This creates electrochemical cells, fed by electrolytes in the liquid in the leave. When an electrical current is applied, this slightly changes the hue of the leaf.
"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," Berggren said.
"As far as we know, there are no previously published research results regarding electronics produced in plants. No one's done this before."