Engineering news
The breakthrough could lead to turning plants into autonomous energy systems - distributed solar cells with energy storage, or sentinels - surveying their environment and signalling to people if something is wrong. It could also lead to harvesting energy from plants to power sensors and various types of switches, and to turning plants into fuel cells.
On a much bigger scale, the technology has the potential of powering the Internet of Things, with plants acting as the power supply of a distributed network for sensors.
The concept hopes to use plants to store energy more efficiently, releasing it swiftly on request. “Our results demonstrate that energy storage and wide-spread tapping out of electrical energy can be achieved in plants,” says Magnus Berggren, an organic electronics professor at Linköping University, and one of the authors. The idea opens up a whole new pathway towards new and green energy technology, he adds.
The team has put an electronic plastic material into the vascular system of a rose – effectively growing circuits inside it. The material then formed, slowly and spontaneously, long-range conducting wires and battery devices throughout the entire plant and within the stem of the flower.
"We have been able to charge the rose repeatedly, for hundreds of times without any loss on the performance of the device,” says Eleni Stavrinidou, assistant professor at the Laboratory of Organic Electronics. “The plant can, without any form of optimisation of the system, potentially power our ion pump, for example, and various types of sensors."
“I find the idea of plants producing electronic devices fascinating,” says George Malliaras, a bioelectrician at École des Mines de Saint-Étienne, who is not connected to the study. “Electronic devices are made in fabs and although there are examples of fabrication using self-assembly and biological templates, I think this work represents a bold step forward… [it] gets you dreaming. I can imagine producing rather complex devices by templating structures inside plants in a massively parallel fashion.”
Berggren says that his team’s aim is to come up with new technologies to interface and integrate within plants. For instance, the researchers hope to create bio-fuel cells that can convert the chemical energy of plants into electricity, turning the plant into a solar cell. “But one needs to store the energy efficiently over time to enable a later transfer of the electrical energy,” he says. The current study creates efficient and distributed energy storage devices in plants together with long-range electrical wires.
At the moment, the conductivity of the wires is somewhat low and the charge storage capacity is approximately less by a factor of 10 than would be for state-of-the-art engineered devices operating in optimal conductions, says Berggren.
Although he believes that the development is exciting, Malliaras argues that he is “not sure we fully realise where this idea can lead us. We need to first answer questions such as ‘if we get plants to store electrical energy, will they still produce food and oxygen?’”
The concept of integrating electronics in plants was first demonstrated in November 2015, but worked mainly in the stem of the rose. However, the team is now using a new organic electronic material, a conducting oligomer, that was synthesised by the chemist of the group, Roger Gabrielsson, and which can be distributed in every part of the vascular tissue of the plant, from stem to leaves and flowers.
“This material polymerises [forms longer conducting chains] in-vivo with the help of the plant and forms conducting wires along the water transport channels of the rose. The material doesn’t affect the physiological function of the plant,” says Stavrinidou.
While the development is "exciting," at this stage the researchers are "really only demonstrating the fundamental science, there is much more work to do before it can be shown to be reliable and commercially viable," says biomedical engineer David Martin of the University of Delaware.
"The true novelty is the integration of the novel organically conductive materials, and the ability to convert them into functional devices within the framework of the living plant. Given that plants are extremely efficient at converting sunlight into chemical energy, the ability to take advantage of this natural process to make interesting devices presents many opportunities for the future."
The results appear in the
Proceedings of the National Academy of Sciences (PNAS) journal.