Swiss researchers develop drone that collects samples from tree branches

Increasingly, ecologists are using traces of genetic material to map and monitor biodiversity. Living organisms leave this material, also known as environment DNA (eDNA), in the environment. Now, these traces allow researchers to find out in which areas certain species occur. Obtaining samples from water or soil is easy, but it is different for foliage, for example. This leaves many species without a trace in poorly surveyed areas.

This is why researchers at ETH Zurich and the Swiss research institute WSL are developing an autonomous drone that can land on tree branches and take samples. “Researchers have already tested their device on seven tree species. In the samples, they found DNA from 21 different groups of organisms,” ETH Zurich said in a press release.

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Flexible branches

The drone is equipped with adhesive strips. When the plane lands on a branch, material from the branch sticks to these strips. Researchers can then extract, analyse and assign DNA to genetic matches of different organisms in the laboratory using database comparisons. But not all branches are the same: they vary in thickness and elasticity. Branches also bend and rebound when a drone lands on them. Programming the aircraft so that it can still autonomously approach a branch and remain stable on it long enough to take samples was a big challenge for the roboticists.

“Landing on branches requires complex control,” explains Stefano Mintchev, professor of environmental robotics at ETH Zurich and WSL. “Initially, the drone does not know how flexible a branch is, so the researchers fitted it with a force-sensitive cage. This allows the drone to measure this factor on the spot and include it in its flight manoeuvre,” he says.