Scientists at Sweden’s Linköping University have recently demonstrated how plant roots can be used as viable energy storage devices. The team’s experiment involved watering bean plants (Phaseolus vulgaris) with a special solution that made the roots electrically conductive, demonstrating the potential for creating biohybrid systems that combine biological processes with electronic functionality.

Dr Eleni Stavrinidou, Principal Investigator in the Electronic Plants Group at the university’s Laboratory of Organic Electronics, showed in 2015 that circuits can be integrated within the vascular tissue of roses. As reported by New Atlas, the researcher did this by dosing the plants with a conductive polymer called PEDOT. The polymer was absorbed by the plant’s vascular system to create electrical conductors that were used to form transistors. In a follow-up study, she demonstrated that a conjugated oligomer, ETE-S, could polymerize within the plant and create conductors capable of storing energy.

“We have previously worked with plants cuttings, which were able to take up and organize conducting polymers or oligomers,” says Stavrinidou. “However, the plant cuttings can survive for only a few days, and the plant is not growing anymore. 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 their most recent research, the scientists have used a bean plant capable of polymerizing the ETE-S oligomer, which was added to the watering solution. They then saw a conducting film of polymer forming on the roots of the plant, causing the complete root system to function as a network of readily accessible conductors. The roots remained electrically functional for more than four weeks.

The team then explored using the roots to store energy by building a root-based supercapacitor, with the roots functioning as electrodes during charging and discharging. The plant-based supercapacitor could store 100 times the energy of its previous systems. The researchers also found that the device could be reused multiple times since the process didn’t seem to affect the plants wellbeing. The plant develops a more complex root system, but is otherwise not affected: it continues to grow and produce beans,” says Stavrinidou.

The study’s findings pave the way for the development of sustainable energy storage innovations and contribute to our understanding of how we could bridge the communication gap between electronic and biological systems.

Study source: Materials Horizons: Biohybrid plants with electronic roots via in vivo polymerization of conjugated oligomers