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As an Iowa State University plant scientist, Patrick Schnable is working with low-cost, graphene-based sensors that can be attached to plants. The technology measures the time it takes for two kinds of corn plants to move water from their roots, to their lower leaves, and then to their upper leaves. The information gathered will provide new types of data to researchers and farmers.
“With a tool like this, we can begin to breed plants that are more efficient in using water,” he says. “That’s exciting. We couldn’t do this before. Once we can measure something, we can begin to understand it.”
Dubbed the plant sensor tattoo, the technology was developed by Liang Dong, an Iowa State associate professor of electrical and computer engineering, to make these water measurements possible. Seval Oren, a doctoral student in electrical and computer engineering, also helped develop the sensor-fabrication technology. Schnable, along with Halil Ceylan, a professor of civil, construction, and environmental engineering, assisted in testing applications of the sensors.
exciting technology for researchers
First discovered in 2004, graphene is made from honeycomb sheets of carbon just one atom thick. Its properties are exciting researchers because they are strong and stable, thin, almost completely transparent, extremely light, and an amazing conductor of electricity and heat.
“We’re trying to make sensors that are cheaper and still high performing,” Dong says.
To do that, the team developed a process for fabricating intricate graphene patterns on tape. The first step, Dong explains, is creating indented patterns on the surface of a polymer block, either with a molding process or with 3-D printing. Engineers apply a liquid graphene solution to the block, filling the indented patterns. They use tape to remove the excess graphene and then take another strip of tape to pull away the graphene patterns, which creates a sensor on the tape.
The process can produce precise patterns as small as 5 millionths of a meter wide. Making the patterns so small, Dong says, increases the sensitivity of the sensors.
“This fabrication process is simple. You just use tape to manufacture these sensors. The cost is cents,” he says.
In plant studies, the sensors are made with graphene oxide, a material very sensitive to water vapor. “The presence of water vapor changes the conductivity of the material, which can be quantified to accurately measure transpiration from a leaf,” explains Dong.
Successfully tested in lab and pilot field experiments, a three-year, $472,363 grant from the USDA’s Agriculture and Food Research Initiative will support more field-testing of water transport in corn plants. Michael Castellano, an Iowa State associate professor of agronomy, and William T. Frankenberger, professor in soil science, will lead the project. Dong and Schnable will serve as co-investigators.
going to market
The Iowa State University Research Foundation has applied for a patent on the sensor technology.
It has also granted an option to commercialize the technology to EnGeniousAg, an Ames, Iowa, start-up. It was founded by Dong, Schnable, Castellano, and James Schnable, an assistant professor of agronomy and horticulture at the University of Nebraska-Lincoln, a collaborator on another Iowa State sensor project that sparked the creation of the company.
“The concept of wearable electronic sensors for plants is brand new,” says Dong. “The most exciting application of the tape-based sensors we’ve tested so far is the plant sensors. The plant sensors are so tiny they can detect transpiration from plants, but they won’t affect plant growth or crop production.”
That’s not all the sensors can do.
They could also open new doors for a wide variety of other applications, including sensors for biomedical diagnostics, for checking the structural integrity of buildings, and for monitoring the environment. After some modifications, the sensors could be used for testing diseases or pesticides in crops.
• Liang Dong
• Patrick Schnable