Spinach Photo Prints

Some people like spinach in their salads. Others would prefer it if it never gets near their fork. Still, other folks, like [Almudena Romero], use it for printing pictures, and they’re the folks we’ll focus on today.

Anthotypes are positive images made from plant dyes that fade from light exposure. Imagine you stain your shirt at a picnic and leave it in the sun with a fork covering part of the stain. When you come back, the stain not sheltered by cutlery is gone, but now you have a permanent fork shape logo made from aunt Bev’s BBQ sauce. The science behind this type of printmaking is beautifully covered in the video below the break. You see, some plant dyes are not suitable for light bleaching, and fewer still if you are not patient since stains like blueberry can take a month in the sun.

The video shows how to make your own plant dye, which has possibilities outside of anthotype printing. Since the dye fades in sunlight, it can be a temporary paint, or you could use samples all over your garden to find which parts get lots of sunlight since the most exposed swatches will be faded the most. Think of a low-tech UV meter with logging, but it runs on spinach.

If the science doesn’t intrigue you, the artistic possibilities are equally cool. All the pictures have a one-of-a-kind, wabi-sabi flare. You take your favorite photo, make it monochrome, print it on a transparent plastic sheet, and the ink will shield the dye and expose the rest. We just gave you a tip about finding the sunniest spot outdoors, so get staining.

Anthotype printing shares some similarities with etch-resist in circuit board printing processes, but maybe someone can remix spinach prints with laser exposure!

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Sensing Danger With Spinach

Do you need more proof that we’re living in the future? A group of MIT engineers have found a way for spinach, aka Popeye’s favorite short-term strength booster, to send potentially lifesaving emails regarding explosives in the area.

As the team outlined in a paper published in 2016, the field of plant nanobionics uses nanotechnology to enhance the natural abilities of plants and make them do new tricks. Here’s how this one works: the roots of the spinach plants absorb nitroaromatic compounds such as picric acid from the groundwater, and these transpire up through the stem and into the leaves along with water and other nutrients. When the compounds reach the leaves, they accumulate in the plants’ mesophyll — the inner tissue of the leaves.

A pair of sensors made of single-walled carbon nanotubes are built into the leaves. One sensor is engineered to detect nitroaromatic compounds using near-infrared fluorescent emission, and the other is used as a reference signal. As the the compounds build up in the mesophyll, the IR signal gets stronger. This change is detected by a camera, which triggers an email alert to the researchers within a matter of minutes. After running the experiments with a fancy-pants indium-gallium-arsenide camera, the researchers were able to duplicate the results using a Raspberry Pi and a CCD camera module with the infrared filter removed.

Plants have an ear to the groundwater like none other and absorb a lot of information about the environment around them, so the researchers believe that detecting explosive materials is only the beginning — they could also be harbingers of pollution and other environmental concerns.

Even if there is no threat of landmines in the vicinity, weeds are a problem everywhere. There’s a Raspberry Pi-based solution for those, too.