# ETH Zurich builds FlexiQuad, a soft-frame quadcopter prototype that survives 25 km/h collisions

- Published: 2026-11-04 23:50 UTC
- Section: Sky & Space › Drones
- Tags: FlexiQuad, ETH Zurich drone, soft-frame quadcopter, collision-tolerant drone, flexible drone frame, Environmental Robotics Laboratory, Luca Girard, Stefano Mintchev, drone prototype, Spark Award
- URL: https://realtech.media/news/rt-d6c347f9fb0b1a7b09f7220a_eth_zurich_builds/

**The ETH Zurich prototype has a ring-shaped soft frame with no central body, reaches 80 km/h and kept flying after deliberate impacts at up to 25 km/h.**

![ETH Zurich builds FlexiQuad, a soft-frame quadcopter prototype that survives 25 km/h collisions](https://sgzwpqqelzmajkcubgkl.supabase.co/storage/v1/object/public/rt-media/2026/11/bba1da2873bc4246.jpg)
*Project Kei, Wikimedia Commons, CC BY-SA 4.0*

Researchers at ETH Zurich have built FlexiQuad, a quadcopter prototype with a soft ring-shaped frame and no central body, according to DEV.UA, citing Tech Xplore. The rotors, batteries and control module are distributed evenly along the frame. The drone was developed by Luca Girard and Stefano Mintchev at the Environmental Robotics Laboratory of ETH Zurich. The authors have filed a patent application, and the project was nominated for the Spark Award [1].

## Soft ring frame instead of a rigid body

For more than a century, quadcopters have followed one basic layout: four arms with propellers extend from a rigid central body. This layout suits precise flight, but it is sensitive to unplanned contact, and even a minor hit against a wall can destabilize or destroy the aircraft [1].

In FlexiQuad the frame deforms on impact and absorbs most of the collision energy. The frame is not flexible in every direction. Girard says the team drew on birds and insects, and on how stiff their wings are in different directions. The frame bends easily in the horizontal plane, where deformation is needed, and stays rigid vertically, so the rotors can transmit thrust efficiently [1].

The design is modular and inexpensive: the body materials cost less than 15 Swiss francs. The flat frame elements fold compactly when disassembled, and Girard transported one of the prototypes in an ordinary suitcase [1].

## Test results and open problems

According to Girard, the drone reaches 80 km/h, and its linear and angular acceleration is comparable to that of rigid drones. In tests, FlexiQuad deliberately flew into obstacles at up to 25 km/h. The frame deformed briefly, which reduced the load, and the drone continued flying. The same flexibility is used for handling cargo: the drone carried a soft first-aid kit and lifted a load heavier than itself [1].

The authors name possible uses in confined spaces: inspecting ship ballast tanks and other hard-to-reach structures, scouting inside collapsed buildings by squeezing through narrow openings, and taking measurements in dense forests where branch collisions are a risk [1].

Before leaving the laboratory, FlexiQuad needs reliable orientation and autonomous navigation. After a collision, vibrations of the flexible frame blur the camera images, which complicates the work of the sensors. The researchers took insect reflexes as inspiration: the drone is currently being trained to stabilize itself after an impact using onboard motion sensors, and only then to return to autonomous flight. The team is also studying whether the frame's own vibrations and deformations could serve as an additional feedback channel for the flight control system [1].

## Sources

1. [DEV.UA](https://dev.ua/news/u-shveitsarii-stvoryly-hnuchkyi-dron-shcho-ne-boitsia-zitknen-1793782496)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-d6c347f9fb0b1a7b09f7220a_eth_zurich_builds/