美國愛荷華州立大學的研究人員已經開發出這些“植物紋身傳感器”，可以及時直接測量農作物的用水量。 這些是傳感材料是以石墨烯做出來的，怎麼有點像蕨類孢子
Engineers
make wearable sensors for plants, enabling measurements of water use in crops
Iowa State University plant scientist Patrick
Schnable quickly described how he measured 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.
This was no technical,
precise, poster talk. This was a researcher interested in working with new,
low-cost, easily produced, graphene-based, sensors-on-tape that can be attached to plants and can provide new kinds 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 said. "That's exciting. We couldn't do this before. But,
once we can measure something, we can begin to understand it."
The
tool making these water measurements possible is a tiny graphene sensor that
can be taped to plants - researchers have dubbed it a "plant tattoo
sensor." Graphene is a wonder material. It's a carbon honeycomb just an
atom thick, it's great at conducting electricity and heat, and it's strong and
stable. The graphene-on-tape technology in this study has also been used to
produce wearable strain and pressure sensors, including sensors built into
a "smart glove" that measures hand movements.
Researchers
describe the various sensors and the "simple and versatile method for
patterning and transferring graphene-based nanomaterials" to create the
flexible sensors in a paper featured on the cover of the December 2017 issue of
the journal Advanced Materials Technologies.
The
research has been primarily supported by the Faculty Scholars Program of Iowa
State's Plant Sciences Institute.
Liang
Dong, an Iowa State associate professor of electrical and computer engineering,
is the lead author of the paper and developer of the technology. Seval Oren, a
doctoral student in electrical and computer engineering, is a co-author who
helped develop the sensor-fabrication technology. Co-authors who helped test
applications of the sensors are Schnable, director of Iowa State's Plant Sciences
Institute, a Charles F. Curtiss Distinguished Professor in Agriculture and Life
Sciences, the Iowa Corn Promotion Board Endowed Chair in Genetics and the Baker
Scholar of Agricultural Entrepreneurship; and Halil Ceylan, a professor of
civil, construction and environmental engineering.
"We're trying to make sensors that are cheaper and still high performing," Dong said.
To
do that, the researchers have developed a process for fabricating intricate
graphene patterns on tape. Dong said the first step 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.
Then they take another strip of tape to pull away the graphene patterns,
creating a sensor on the tape.
The
process can produce precise patterns as small as 5 millionths of a meter wide -
just a twentieth of the diameter of the average human hair. Dong said making
the patterns so small increases the sensitivity of the sensors.
(The
process, for example, produced a detailed image of Iowa State's Cyclone mascot
that was less than 2 millimeters across. "I think this is probably the
smallest Cyclone," Dong said.)
"This
fabrication process is very simple," Dong said. "You just use tape to
manufacture these sensors. The cost is just cents."
In
the case of 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, and that can be quantified to accurately measure
transpiration (the release of water vapor) from a leaf.
The
plant sensors have been successfully tested in lab and pilot field experiments,
Dong said.
A
new three-year, $472,363 grant from the U.S. Department of Agriculture'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. Co-investigators include Dong and Schnable.
The
Iowa State University Research Foundation has applied for a patent on the
sensor technology. The research foundation has also granted an option to
commercialize the technology to EnGeniousAg - an Ames startup company
co-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 establishment of
the company (and Patrick Schnable's son).
"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."
But
that's not all the sensors can do. The technology could "open a new
route" for a wide variety of applications, the authors wrote in their
paper, including sensors for biomedical diagnostics, for checking the
structural integrity of buildings, for monitoring the environment and, after
appropriate modifications, for testing crops for diseases or pesticides.
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