Clever Watering Solution Turns Bean Plants Into Living, Growing Supercapacitors

A team of researchers at Linköping University, the Swedish University of Agricultural Sciences, the University of Bordeaux, and other institutions have developed a novel way to turn plant roots into energy storage for electronic circuits — by watering the plant with a special solution.

"We have previously worked with plants cuttings, which were able to take up and organize conducting polymers or oligomers," Eleni Stavrinidou, PhD, associate professor and principal investigator in the Electronics Plants Group of Linköping University, explains.

"However, the plant cuttings can survive for only a few days, and the plant is not growing any more. In this new study we use intact plants, a common bean plant grown from seed, and we show that the plants become electrically conducting when they are watered with a solution that contains oligomers."

In its latest experiments, the team watered the whole living plants with a trimer, ETE-S, which becomes polymerized by the plant itself — creating an electrically conductive layer of polymer on the roots, turning the whole root system into easily-accessible conductors.

The roots of the treated plant remained conductive for at least four weeks after treatment, and proved capable of storing energy — turning the plant into a living supercapacitor that used the roots as electrodes for charging and discharging.

"Supercapacitors based on conducting polymers and cellulose are an eco-friendly alternative for energy storage that is both cheap and scalable," Stavrinidou notes. "The plant develops a more complex root system, but is otherwise not affected: It continues to grow and produce beans."

The team's work, which showed an improvement in the amount of energy which could be stored of two orders of magnitude over previous work, has been published under open-access terms in the journal Materials Horizons.