Wearable sensors for plants measure water use in crops

By Warren Miller, contributing writer

Technology has insinuated itself into almost every nook and cranny of life on Earth, but it can’t possibly help make plants grow faster and more efficiently, can it? Thanks to a tiny “plant tattoo sensor” developed at Iowa State University, it really can. The diminutive graphene sensor, when taped to the leaves of corn plants, can collect information such as how long it takes water to migrate from the roots to the leaves, providing farmers and agriculturists with information necessary to breed crops that use water more efficiently.

In order to make high-performance, cost-effective sensors, the ISU research team came up with a process whereby small, circular indentations are created on a polymer block via 3D printing or a more traditional molding technique. The indentations are then filled with liquid graphene and allowed to settle. After the graphene has solidified into the shape of the indentations, engineers lay a strip of tape along the row of indentations and then pull it away with the graphene sensors now attached to the sticky surface. The sensors themselves can be as small as five-millionths of a meter thick, meaning that it would take a stack of 20 of them to be as wide as a human hair.

Iowa State University researchers have developed these “plant tattoo sensors” to take real-time, direct measurements of water use in crops. Image source: iastate.edu.

The sensors used on the corn plant like the one pictured above are made of graphene oxide, a material that reacts measurably when in contact with water vapor. The U.S. Department of Agriculture and Food Research Initiative has recently invested nearly half-a-million dollars in grant money to fund further research into studying the rate at which water migrates through corn plants, and members of the ISU research team have been granted an option to commercialize the water sensor technology.

“The most exciting application of the tape-based sensors we’ve tested so far is the plant sensor,”said Liang Dong, associate professor of electrical and computer engineering at ISU and co-developer of the technology. “The concept of wearable electronic sensors for plants is brand new. And the plant sensors are so tiny that they can detect transpiration from plants, but they won’t affect plant growth or crop production.” Dong and his team also believe that the sensors could be modified to detect the presence of disease in plants or to measure their level of chemical infiltration from pesticides.

Perhaps sensors could even survive the harvesting process for some larger items. Could the same sensor then be used to track the temperature and humidity of every orange, avocado, or banana? Once on the shelf, could your smartphone determine the quality grade, origin, and other information? Maybe after a couple of days, a sale price would kick in.

Agriculture, however, is just one realm in which technology like this could be applied. In a paper published in last December’s issue of Advanced Materials Technologies, the researchers claim that the sensors could be used for a variety of purposes, such as gathering medical diagnostic information from hospital patients or checking the structural integrity of buildings or bridges. It doesn’t seem too far-fetched to think that the technology could one day monitor anything with a surface that you can stick a piece of tape to.