The new research paves the way for storing and harvesting energy in plants.
The world already has human cyborgs—people like Neil Harbisson, who can hear color with an implant, or Moon Ribas, who can feel earthquakes through an online sensor stitched into her skin. Humans have also implanted their pets with tracking devices, which is just the beginning of animal cybernetics. So it’s only natural that researchers would want to see what happens when plants become bioelectronics devices, which is what researchers at Linköping University have done with their new “electronic flowers.”
The project started very slowly about 10 years ago, growing out of the university’s Laboratory of Organic Electronics in Linköping, Sweden. Housed in the Department of Science and Technology, the laboratory develops and studies devices based on organic electroactive materials.
One of the group’s researchers, assistant professor Daniel Simon, tells GOOD that the electronic flowers developed from a series of discussions about converging paper electronics with organic and plastic electronics on trees and plants.
In 2008, they initially considered combining the lab’s drug delivery technology with trees and other plants. They also thought it would be fun to try the “kids’ experiment” of taking celery or flowers and sucking up food coloring, but with conductive “inks” instead of food coloring. They tried it in 2008, and failed. The plants—tulips, at the time—died pretty quickly.
But in 2012, the lab succeeded in getting funding for the drug-delivery-to-plants project. Since then the researchers have been working on combining organic bioelectronic devices with developing root systems—research that is nearing publication.
“During the last 18 months, we decided to reboot the ‘conducting wood’ idea, and engaged a dedicated chemist (co-author Roger Gabrielsson), and two postdoctoral researchers (Eleni Stavrinidou and Eliot Gomez),” Simon says. “To our great surprise, it worked. We were able to use this particular conducting polymer system, PEDOT-S, to repeat the colored-celery experiment, only this time [with] the coloring aggregates in the water channels (xylem) to form conducting filaments.”
These xylem wires are what Simon, lead research Magnus Berggren, and others use to demonstrate conducting stems, and then transistors and logic circuits, inside the rose. “The electronics are templated by the living plant,” Simon explains.
They also tried getting conducting polymer material into the leaves. Simon explains that leaves have an open gas-exchange region on their underside (where oxygen and CO2 are processed), and the team was able to use a standard plant biology trick (vacuum infusion) to get their material into the leaves.
“By applying external electrodes, we could electrically address this infused conducting polymer,” he says. “The PEDOT conducting polymer we used has the property of changing color from light/transparent when addressed with positive voltage (i.e., when it’s oxidized) to dark blue when addressed with negative voltage (i.e., when it’s reduced). This is what we were able to show with the leaves.”
While Simon emphasizes that the color change is in itself not so dramatic (they won’t be decorating homes anytime soon), they did demonstrate significant electrical charge storage in the leaves.
“The color change is just our favorite way of evaluating this charge storage capacity,” he adds. “Lots of electrical charge storage right on top of where photosynthesis happens clearly paves the way for energy harvesting (and storage) directly in the leaves. Indeed, we’re already at work on this.”