Spinach is no longer just a super food. By embedding spinach leaves with carbon nanotubes, MIT engineers have transformed spinach plants into sensors that can detect explosives and wirelessly relay that information to a handheld device similar to a smartphone.
This is one of the first demonstrations of engineering electronic systems into plants, an approach that the researchers call “plant nanobionics.”
In this case, the plants were designed to detect chemical compounds known as nitroaromatics, which are often used in landmines and other explosives.
When one of these chemicals is present in the groundwater sampled naturally by the plant, carbon nanotubes embedded in the spinach leaves emit a fluorescent signal that can be read with an infrared camera.
The camera can be attached to a small computer similar to a smartphone, which then sends an email to the user.
The finding is published in Nature Materials.
Plants are ideally suited for monitoring the environment because they already take in a lot of information from their surroundings.
In the new study, the researchers embedded sensors for nitroaromatic compounds into the spinach leaves.
Using a technique called vascular infusion, which involves applying a solution of nanoparticles to the underside of the leaf, they placed the sensors into a leaf layer known as the mesophyll, which is where most photosynthesis takes place.
They also embedded carbon nanotubes that emit a constant fluorescent signal that serves as a reference.
This allows the researchers to compare the two fluorescent signals, making it easier to determine if the explosive sensor has detected anything.
If there are any explosive molecules in the groundwater, it takes about 10 minutes for the plant to draw them up into the leaves, where they encounter the detector.
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.
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.
The researchers suggest that this approach holds great potential for engineering not only sensors but also many other kinds of bionic plants that might receive radio signals or change color.
Citation: Wong MH, et al. (2016). Nitroaromatic detection and infrared communication from wild-type plants using plant nanobionics. Nature Materials, published online. DOI:10.1038/nmat4771.
Figure legend: This Knowridge.com image is credited to Christine Daniloff/MIT.