For millennia, mankind has known that spinach is a leafy green vegetable that qualifies as “good for you” according to legions of mothers and as poison to millions of kids. (God help you if you ever had to eat the slimy green horror that is canned spinach. Popeye is not enough to make that okay.) Now MIT engineers announced a breakthrough in the heretofore unknown art of bomb-detecting spinach. These spinach plants were capable of detecting “nitroaromatic compounds” in groundwater to which they were exposed. TNT is short for “tri-nitro-toluene,” which is a nitroaromatic, but so is the RDX in C-4, which we’re still making (we quit making TNT in the 80s).
The plants were developed by chemical engineering professor Michael Strano’s lab at MIT. The lab has previously developed carbon nanotubes that can be used as sensors to detect a wide range of target molecules, including hydrogen peroxide, TNT, the nerve gas sarin, and even dopamine. They get into the plant by being painted onto the undersides of the leaves, from where the nanotubes are conveyed into the mesophyll — the inside layer of leaves, where most photosynthesis happens. When the target molecule binds to a polymer wrapped around the nanotube, it alters the nanotube’s fluorescence properties.
To read the signal when the plants pick up nitroaromatics, researchers shine a laser onto the leaves, which induces them to release light in the near IR. The wavelength of the light depends on whether the nanotube complexes have bound to their targets.
“This setup could be replaced by a cell phone and the right kind of camera,” Strano said. “It’s just the infrared filter that would stop you from using your cell phone.” In fact, the team used a Raspberry Pi CCD camera with the infrared filters removed.
I immediately imagine “smart shrubs” that could know if explosives had even brushed past. Or “smart salads” that can somehow tell you more about a salad than that it is good for you.
“These sensors give real-time information from the plant. It is almost like having the plant talk to us about the environment they are in,” says coauthor and graduate student Min Hao Wong. “In the case of precision agriculture, having such information can directly affect yield and margins.”
With the smart spinach ceiling cracked, who knows what other culinary creations await us? Perhaps we could design some kind of Stingray-detecting squash? Cancer-diagnosing cauliflower? Actually, scrap those. I’ll settle for lima beans that actually taste like food.