To read the signal, the researchers shine a laser onto the leaf, prompting the nanotubes in the leaf to emit near-infrared fluorescent light. This can be detected with a small infrared camera connected to a Raspberry Pi, a $35 credit-card-sized computer similar to the computer inside a smartphone. The signal could also be detected with a smartphone by removing the infrared filter that most camera phones have, the researchers say.
“This setup could be replaced by a cell phone and the right kind of camera,” Strano says. “It’s just the infrared filter that would stop you from using your cell phone.”
Using this setup, the researchers can pick up a signal from about 1 meter away from the plant, and they are now working on increasing that distance.