A team of researchers at the University of Washington have developed ultra-compact wireless sensors, weighing just 98 milligrams each, designed for deployment from microminiature drones — or, unusually, on the backs of moths.
"We have seen examples of how the military drops food and essential supplies from helicopters in disaster zones. We were inspired by this and asked the question: Can we use a similar method to map out conditions in regions that are too small or too dangerous for a person to go to," explains senior author Associate Professor Shyam Gollakota. "This is the first time anyone has shown that sensors can be released from tiny drones or insects such as moths, which can traverse through narrow spaces better than any drone and sustain much longer flights."
The team's "insect-scale" sensor weighs just 37mg, less than a 20th of the weight of a jellybean, and is paired with a 68mg battery to make a 98mg device capable of running for over a year on a single charge at a transmission rate of 10-50 packets per hour — and the signal can be picked up at distances of up to 1km (around 0.6 miles).
That the sensor can operate for so long from its tiny battery is impressive enough, but it's the team's deployment plan that really surprises: Attaching the sensors to a 28mm-wide microminiature drone and triggering an airdrop via Bluetooth — meaning the drone never actually has to land, and that the sensor can survive despite falling from heights up to 22mm onto a hard surface.
If that weren't enough, the team also proved that it's possible to deploy the same sensors using a biological delivery system: Manduca sexta, a common moth. The sensors were attached to the moths using a magnetic pin surrounded by a thin coil of wire, and following the deployment transmission the pin is released and the sensor falls — rotating, as it does, to generate drag and slow its descent to a terminal velocity of 11 miles per hour.
The team's work has been published as part of the 26th Annual Conference on Mobile Computing and Networking (MobiCom '20) under closed-access terms. The next step: A system for collecting the expired sensors from the field for refurbishment or recycling.