Drones are already used by farmers to soar over large fields and monitor crop health, temperature, and humidity. But these machines consume so much power to fly that they cannot travel very far without needing a charge.
Currently, engineers at the University of Washington have designed a sensing system that is sufficiently small to ride aboard a bumblebee. Since insects can fly on their own, the package just requires a miniature rechargeable battery that could endure for seven hours of flight and then charge while the bees get back to their hive at night. The research team presented their findings online and in person at the ACM MobiCom 2019 conference.
“Drones can fly for maybe 10 or 20 minutes before they need to charge again, whereas our bees can collect data for hours,” said senior author Shyam Gollakota, an associate professor in the UW’s Paul G. Allen School of Computer Science & Engineering. “We showed for the first time that it’s possible to actually do all this computation and sensing using insects in lieu of drones.”
So instead of drones, the insects are the solution to the power issue, nevertheless, this method has its own set of difficulties: Firstly, insects cannot carry a lot of weight. Secondly, GPS receivers, which function well for helping drones state their positions, use up too much power for this application. To develop a sensor package that could be positioned on an insect and sense its location, the team had to look into both matters.
We decided to use bumblebees because they’re large enough to carry a tiny battery that can power our system, and they return to a hive every night where we could wirelessly recharge the batteries. For this research, we followed the best methods for care and handling of these creatures.
Vikram Iyer, Study Co-Author and Doctoral Student, Department of Electrical and Computer Engineering, UW
Earlier, other research teams have fitted bumblebees with simple “backpacks” by supergluing small trackers, like radio-frequency identification (RFID) tags, to them to trail their movement. For these types of experiments, scientists put a bee in the freezer for a couple of minutes to slow it down before they glue on the backpack. When they are done with the experiment, the team takes off the backpack using a similar process.
These earlier studies, however, only involved backpacks that merely tracked bees’ locations over short distances—around 10 inches—and did not carry anything to study the environment around the insects. Here, Gollakota, Iyer and their team developed a sensor backpack that rides on the bees’ backs and weighs 102 mg, or around the weight of seven grains of uncooked rice.
“The rechargeable battery powering the backpack weighs about 70 milligrams, so we had a little over 30 milligrams left for everything else, like the sensors and the localization system to track the insect’s position,” said co-author Rajalakshmi Nandakumar, a doctoral student in the Allen School.
As bees do not publicize where they are flying and because GPS receivers are extremely power-hungry to ride on a small insect, the team came up with a technique that does not use any power to localize the bees. The scientists installed multiple antennas that aired signals from a base station across a specific area. A receiver in a bee’s backpack uses the strength of the signal and the angle difference between the base station and the bee to triangulate the insect’s position.
To test the localization system, we did an experiment on a soccer field. We set up our base station with four antennas on one side of the field, and then we had a bee with a backpack flying around in a jar that we moved away from the antennas. We were able to detect the bee’s position as long as it was within 80 meters, about three-quarters the length of a football field, of the antennas.
Anran Wang, Study Co-Author and Doctoral Student, Paul G. Allen School of Computer Science and Engineering, UW
Next, the researchers added a series of small sensors—monitoring temperature, light intensity, and humidity—to the backpack. That way, the bees could gather data and log that information together with their location, and finally compile information about the entire farm.
“It would be interesting to see if the bees prefer one region of the farm and visit other areas less often,” said co-author Sawyer Fuller, an assistant professor in the UW Department of Mechanical Engineering. “Alternatively, if you want to know what’s happening in a particular area, you could also program the backpack to say: ‘Hey bees, if you visit this location, take a temperature reading.'”
Then after the bees have completed their day of foraging, they get back to their hive where the backpack can upload any data it gathered via a technique called backscatter, through which a device can share information by reflecting radio waves conveyed from a nearby antenna.
Presently, the backpacks can only store approximately 30 kilobytes of data, so they are restricted to carrying sensors that produce small amounts of data. Furthermore, the backpacks can upload data only when the bees get back to the hive. The team would ultimately like to build backpacks having cameras that can live stream information about plant health back to farmers.
Having insects carry these sensor systems could be beneficial for farms because bees can sense things that electronic objects, like drones, cannot. With a drone, you’re just flying around randomly, while a bee is going to be drawn to specific things, like the plants it prefers to pollinate. And on top of learning about the environment, you can also learn a lot about how the bees behave.
Shyam Gollakota, Senior Author and Associate Professor, Paul G. Allen School of Computer Science and Engineering, UW
Living IoT: A Flying Wireless Platform on Live Insects