Cheap Sensors for Smarter Farmers From This Year
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Cheap sensors for smarter farmers from this year just go to show we are truly living in an era of smart agriculture. At this year’s ARPA-E Summit many technologies were showcased, especially from the farming sector. This included sensors for crops and farmlands which enable farmers to monitor plant and soil conditions almost in real-time, similar to how we monitor our health using smart devices.

The two devices that caught the eyes of the experts were a 3D printed biodegradable soil sensor and the other is a zero-power infrared sensor detecting a plant’s thirst.

3D Printed Biodegradable Soil Sensor
A 3-D printed, biodegradable soil sensor created at the University of Colorado, Boulder

3D Printed Biodegradable Soil Sensor

The 3D printed biodegradable soil sensor checks moisture and nitrogen levels. According to Gregory Whiting one of the lead investigators of the team working on sensors from the University of Colorado, Boulder, said, “Agriculture is a pretty cost constrained industry. 3D-printed sensors allow farmers to place many sensors throughout their large farmlands—often hundreds of acres—without spending a ton of money.”

Farmers will be able to monitor soil conditions in greater detail, depending on various factors such as how the sun hits the ground, the amount of water or the fertilizer needed could vary patch by patch.

Sensors have been expensive in the past for farmers, especially in large quantities and hence the plan did not prove to work effectively. While the new sensors are cheap, farmers will be able to collect data from their farms without having to worry about the variability.

Zero-power infrared sensor detecting a plant’s thirst

Zero-power infrared sensor detecting a plant's thirst
A conceptual vision of a smart farm that could employ the Northeastern University zero-power and low-cost sensor nodes in a crop field. Each wireless sensor node is used for non-contact water stress detection in plants. VAGGEESWAR RAJARAM/NORTHEASTERN UNIVERSITY

This sensor, developed by Matteo Rinaldi and his team at Northeastern University, shines infrared light on the leaves of a plant. The sensor reads the reflected light to tell if the plant is dehydrated or not.

Rinaldi has used the idea of infrared light in his earlier project where it was used to detect exhaust fumes from cars. He modified the detection range to match the reflection signal from the moisture of plant leaves instead of the exhaust fumes, making it possible to use the tech for agriculture. According to Antea Risso, a graduate student working on this project, “Whatever changes in reflectance [are] depending only on water stress of the plant and nothing else. So, it’s quite reliable.”

According to Risso, it can be challenging to work with soil sensors as the soil quality may differ even in a single farm, the sensors need to be calibrated accordingly which can take a lot of time.

While in the case of plant sensors they only need to be calibrated by the plant type, which makes it easy to use compared to soil sensors. He further said reading moisture levels directly from the plant assesses its health more accurately, which is ultimately what the farmers care about.

Having said that, it is not easy to mass produce sensors, but the new biodegradable sensors use materials such as Zinc and Wood, though it gives rise to a new issue, What if the sensor degrades before the job is done?

To fix this problem Whiting and his team used beeswax or soy wax casing, which offers protective wax casing. It ensures moisture and nitrogen sensing parts made from Zinc to operate properly for the desired amount of time. It is the few months the crop requires to fully grow and by the end of it the casing will break down and the sensors will degrade.

silicon chip with micromechanical photoswitches
The silicon chip hosts hundreds of plasmonically enhanced micromechanical photoswitches.RUBY WALLAU/NORTHEASTERN UNIVERSITY

The soil sensor’s signals are transmitted via long-range RFID and collected using drone or farm equipment with a reader attached. The team is currently working in a greenhouse testing their soil sensors. Whiting says it is weird to build electronics made of zinc, wood, and wax but it’s cool and they plan to move out to a field by 2022.

As far as the plant sensor is concerned, the signal with the right wavelength is absorbed by the nanoplasmonic absorbers designed and engineered by Rinaldi’s team. This increases the temperature of the device causing it to bend and turn on the power switch, as the switch is expected to be used sparingly, Rinaldi is confident the sensors will last for 10 years without the need to change batteries.

The prototype of the plant sensor has been tested by the team in a lab environment. According to Rinaldi by the end of this year, the team will test a portable prototype in an actual field. They are also taking steps to commercialize the technology.

Rinaldi in partnership with Zhenyun Qian, a research assistant professor at Northeastern, co-founded Zepsor Technologies, look forward to bring the

Risso said, “There are a lot of precision-oriented agriculturists [who] are very, very interested in this. So, we are hoping to test it sooner with their collaboration.”

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