Spinach is a fine addition to the dinner table, but scientists at MIT have been developing technology that would give the delicious leaves a completely new life—as a way to raise the alarm about dangerous chemicals in the groundwater.
In a paper published today in Nature Materials, MIT scientists explain how they successfully embedded spinach leaves with carbon nanotubes that enable them to detect certain chemicals and then wirelessly send a message to a handheld device. The implants are made using a technique called "vascular infusion:" the scientists paint the underside of a leaf with nanotubes, which are absorbed into the plant's fibers. It's one of the first instances of embedding electronic systems in living plants, an emerging scientific field called plant nanobionics.
In a research study led by MIT chemical engineering professor Michael Strano and graduate student Min Hao Wong, the spinach leaves were implanted with nanotubes that emit fluorescent light when they detect a class of chemicals called nitroaromatics—which can be founded in explosive devices—in their water. A $35 credit-card-sized Raspberry Pi computer attached to an infrared camera then reads the light signals and then send a message to an electronic device to notify a human of the chemicals' existence. Most smartphone cameras currently filter out infrared light, but if they didn't, the researchers say these devices could read the plants' light signals too.
Because of plants' extensive root network and ability to constantly pull groundwater into their leaves, they make for natural chemical analysts. "Plants are very environmentally responsive," Strano says in a statement. "They know that there is going to be a drought long before we do. They can detect small changes in the properties of soil and water potential. If we tap into those chemical signaling pathways, there is a wealth of information to access."
Two years ago, Strano and MIT postdoc Juan Pablo Giraldo were able to strengthen plants' ability to photosynthesize and act as sensors for the chemical nitric oxide, a pollutant that erodes the ozone layer. Since then, they've created nanotubes that can detect hydrogen peroxide, the explosive TNT, and the nerve gas sarin in groundwater, testing them on a laboratory plant Arabidopsis thaliana, commonly called the thale cress.
The latest study proves that their technique can be applied to any living plant. Wong is now commercializing the science through a company founded in 2015, Plantea, using the technology to create real-time organic sensors that monitor plant health. Maybe in the future, our vegetable gardens will double as chemical detectors.