For more than a hundred years, quadcopters have been built according to the same basic principle. Four arms, each with a propeller, extend from a rigid central body. This design is ideal for precise, agile flight, but it has one major weakness—the drones are highly sensitive to unexpected contact with their surroundings. If they bump into a wall or another obstacle, they can become destabilized or even break apart.

Researchers at ETH Zurich hope to solve this problem with a new structural design. Their FlexiQuad drone features a soft, ring-shaped frame without a central body. The rotors, batteries and control module are evenly distributed along the frame. This design allows the drone to deform on impact, thereby absorbing some of the collision energy.

FlexiQuad was developed by Luca Girardi and Stefano Mintchev, then a professor at ETH Zurich, at the Environmental Robotics Lab. Girardi is currently conducting research at the Mobile Robotics Lab at ETH Zurich, while Mintchev has since taken up a professorship in agricultural robotics at the University of Bonn. The pair has filed a patent application for FlexiQuad, and the invention has been nominated for this year’s Spark Award.