3D Printing Used to Develop Sensors That Measure Plants’ Use of Water

Plants don’t talk, so humans can only observe to see how well they’re doing or how they’re reacting to their treatment and environment. But researchers at Iowa State University have developed a way for people to better understand the invisible processes that are happening within plants – and perhaps breed more efficient plants in the future.

Tiny graphene sensors, which the researchers are calling “plant tattoo sensors,” are being taped to the leaves of plants, looking quite a bit like tattoos indeed. The sensors transmit data to the researchers about how quickly plants are moving water from their roots to their leaves and then releasing the water into the air.

“With a tool like this, we can begin to breed plants that are more efficient in using water,” said plant scientist Patrick Schnable. “That’s exciting. We couldn’t do this before. But, once we can measure something, we can begin to understand it.”

The research was documented in a paper entitled “High-Resolution Patterning and Transferring of Graphene-Based Nanomaterials onto Tape toward Roll-to-Roll Production of Tape-Based Wearable Sensors,” which you can access here.

The graphene-on-tape technology has already been used for other applications such as smart gloves, flexible mechanical sensors and sensor arrays.

“We’re trying to make sensors that are cheaper and still high performing,” said Liang Dong, Associate Professor of Electrical and Computer Engineering.

The first step in the process is to use either molding or 3D printing to create indented patterns on the surface of a polymer block. A liquid graphene solution is then applied to the block, filling in the indented patterns. The excess graphene is removed with tape, and then another strip of tape is used to lift away the graphene patterns, creating a strip of sensors on the tape. The process can create patterns as small as five millionths of a meter wide, or one-twentieth the width of a human hair. According to Dong, the smaller the sensors are, the more sensitive they are.

It sounds easy, and it is – and it’s also inexpensive, fulfilling the researchers’ goal of making cheap, high-performing sensors.

“This fabrication process is very simple,” Dong said. “You just use tape to manufacture these sensors. The cost is just cents.”

For the plant tattoos, graphene oxide is used because of its sensitivity to water vapor. The presence of water vapor changes the material’s conductivity, which can be used to measure transpiration, or the release of water vapor, from the leaf. The plant sensors have been successfully tested in lab and pilot field experiments, and a new three-year, $472,363 grant from the U.S. Department of Agriculture’s Agriculture and Food Research Initiative will allow for more field testing of water transport in corn plants.

The Iowa State University Research Foundation has applied for a patent on the technology, and granted an option to commercialize the technology to EnGeniousAg, a startup formed by several of the researchers.

“The most exciting application of the tape-based sensors we’ve tested so far is the plant sensor,” Dong said. “The concept of wearable electronic sensors for plants is brand new. And the plant sensors are so tiny they can detect transpiration from plants, but they won’t affect plant growth or crop production.”

The technology could be used for many other applications, however, including sensors for biomedical diagnostics, checking the structural integrity of buildings, monitoring the environment or testing crops for diseases or pesticides.

Authors of the paper include Seval Oren, Halil Ceylan, Patrick S. Schnable and Liang Dong.

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[Source: Iowa State University]