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MIT researchers develop ink sensor that can predict droughts

Artist’s impression of the sensor comprised of conductive ink printed across a stoma.
Betsy Skrip
Artist’s impression of the sensor comprised of conductive ink printed across a stoma.

Researchers at the Massachusetts Institute of Technology say they have a sensor that can predict droughts. With the same technology, they can also get your plant to water itself.

Michael Strano, a chemical engineering professor at MIT and a senior author of a study about the technology in the journal “Lab on a Chip,” said he and his team have created a “light-conductive ink” sensor that, when applied to the leaf of a plant, creates a circuit that can generate real-time information about the water levels in a plant.

This information could then warn farmers when their crops are in need of water before they start to wilt, the typical indicator of water-stress, Strano said.

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“We don’t have many ways of detecting if a plant is under water-stress, and you don’t want an indication that your plant is under water-stress when it’s dying,” he said in a telephone interview Tuesday afternoon. “One of the most useful ways of using this sensor is to design more stress-tolerant crops.”

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The sensor, which is actually a special ink developed in Strano’s lab, is applied to the surface of a plant’s leaf over microscopic pores called stomata, Strano said.

There are millions of these pores on each leaf, and they open and close to allow water to evaporate through them, he said. They open in response to light and close in darkness.

“People already knew that stomata respond to light, to carbon dioxide concentration, to drought, but now we have been able to monitor it continuously,” Volodymyr Koman, an MIT post-doctoral researcher and a lead author on the paper, said in a statement from the university Wednesday. “Previous methods were unable to produce this kind of information.”

When the ink is printed on the surface of a leaf, it forms a circuit that can be broken by the opening of a stoma.

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“The ink forms a very tiny wire that is on the leaf,” Strano said. “When the stomata pore is closed, it connects both sides of the conducting ink. When it opens, it breaks the circuit.”

By measuring this opening and closing over a few days, under normal and dry conditions, the researchers were able to tell when a plant is experiencing water-stress because the stomata open more slowly and close more quickly when the plant needs to retain water, the university said.

“What we show in the paper is that this can be used to predict drought,” Strano said.

An arguably less important way to put the sensor to use is by having it trigger a mechanism that automatically waters a plant when it shows signs of distress, Strano said.

“If there was a compelling need to, we could actually build this,” he said. “I could have a high school student build that.”

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Strano is working with a large agricultural producer to put the sensors to use on crops, the university said.

“It could have big implications for farming, especially with climate change, where you will have water shortages and changes in environmental temperatures,” Koman said.

Alyssa Meyers can be reached at alyssa.meyers@globe.com. Follow her on Twitter @ameyers_.