A robotic drone that can fly through air and land on water has been developed to collect environmental samples and monitor water quality in difficult environments.

The Multi-Environment Dual Robot for Underwater Sample Acquisition - Medusa for short - was developed at Imperial College London and tested at the Empa and Eawag research institutes in Switzerland. The researchers say the unique design means it can be quickly deployed in the aquatic environment and has successfully monitored water in lakes for signs of microorganisms and algal blooms, which can pose hazards to human health.

It could also be used to monitor indicators of climatic shifts, like temperature changes in Arctic seas.

"Medusa is unique in its dual-robot design, with a flight component that reaches difficult-to-access areas and a diving component that monitors water quality," said Professor Mirko Kovac, principal investigator, and director of the Aerial Robotics Lab at Imperial and head of the Robotics Centre at Empa. "Our drone considerably simplifies robotic underwater monitoring by performing challenging tasks which would otherwise require boats."

The researchers have tested MEDUSA in laboratory environments at Imperial College and Empa, and in field environments including lakes in Switzerland.

The drone flies using remotely controlled multi-rotors - lift-generating blades that gyrate around a central vertical mast like helicopter blades. Using multi-rotors means Medusa can travel long distances carrying significant loads, fly over obstacles, and manoeuvre through difficult terrain.

The craft can access hard-to-reach aquatic locations, before landing on the water and deploying its tethered underwater pod - with attached camera and sensors - to depths up to 10 meters. The drone operator remotely adjusts the pod's depth and three-dimensional position in the water using buoyancy control and jets.

The user is guided throughout the operation by real-time video and sensor feedback from the pod. Once water samples are taken, the drone recoils the tether to reunite with the pod before taking off and flying back to the operator.

While the underwater pod design capability is new, the aerial drone design is industry standard, meaning Medusa systems can be easily constructed and deployed using existing operational guidelines.

Climate clues

Ecologists typically use boats to reach and monitor aquatic areas, but Medusa could help reduce the risk to humans of travelling to challenging aquatic locations. This could be particularly useful in the Arctic Ocean, where changes in ocean temperatures, acidity, salinity, and currents can offer critical clues about the global climate crisis.

Kovac said, "We have much to learn from the Earth's water: by monitoring ecological parameters we can identify trends and understand the factors affecting water quality and the health of the ecosystem in a changing climate. Medusa's unique ability to reach difficult places and collect aquatic images, samples and metrics will be invaluable for ecology and aquatic research and could support our understanding of local climate in difficult-to-access environments like the Arctic."

The next round of testing will involve developing shape-shifting metamorphic drones within the newly approved ERC Consolidator grant, called ProteusDrone, with international partners at Empa. The research was supported by UK Research & Innovation's Engineering & Physical Sciences Research Council.