Mark wearing sensor backpack

Moths could be used to airdrop sensors into danger zones

Image credit: Mark Stone/University of Washington

Engineers at the University of Washington have created a sensor system which can be carried to its destination by a small drone or flying insect, before being dropped safely on the ground.

There are many locations which are difficult for researchers to study due to the danger involved in reaching and exploring them, such as scenes of natural disasters.

Now, researchers have developed a solution: a tiny sensor which can be carried on a small flying body and dropped from a great height.

“We have seen examples of how the military drops food and essential supplies from helicopters in disasters zones. We were inspired 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?” said 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.”

While industrial-size drones use grips to carry their payloads, this tiny sensor is held using a magnetic pin surrounded by a thin coil of wire. To release the sensor, a command can be sent via Bluetooth to create a current in the coil and generate a magnetic field. This causes the pin to pop out of place and loosen the sensor.

The sensor system is just 98mg: small and light enough to ride on the back of a flying insect.

It was designed such that its heaviest part (the battery) is in one corner. This structure causes it to rotate around this corner (to 'flutter') as it falls, generating additional air resistance and limiting its terminal velocity. It can fall 22m (the equivalent of the sixth floor of a building) without breaking. Once on the ground, it can collect data for almost three years.

The researchers demonstrated the system by attaching it to a 28mm-wide drone and a tobacco hawk moth, finding that the sensors suffered no damage upon impact after landing on a tiled floor.

The researchers suggest that this system could be used to create a network of sensors within a study area; for instance, they could use drones or flying insects to scatter them across a forest or farm for monitoring. Although they will first focus on developing a mechanism to recover sensors after they reach the end of their battery life, the engineers plan to eventually replace the battery with a solar cell.

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