In a striking shift from conventional robotics, researchers at EPFL in Switzerland have unveiled tiny, fish-safe aquatic robots designed not only to monitor water quality but also to become part of the food chain once their job is done.
Shaped like miniature motorboats and just 5 cm long, the robots are built from freeze-dried fish feed pellets, making them entirely edible and biodegradable. Once deployed, these tiny scouts scoot across water surfaces without batteries, using a natural propulsion method that mimics insect motion.
Inside each 1.43-gram robot lies a chamber of citric acid and baking soda, sealed with a hydrogel plug. Topped with non-toxic propylene glycol, the device activates when water seeps in, triggering a reaction that releases CO? gas.
This gas gently expels glycol from the back, lowering surface tension and propelling the robot forward using the Marangoni effect, a trick nature borrowed from water striders.
Designed by Professor Dario Floreano and PhD student Shuhang Zhang, the bots can carry sensors to record pH levels, temperature, or pollutants — either wirelessly transmitting data or storing it for later.
After fulfilling their mission, the robots absorb water, sink, and break down, becoming edible for aquatic life. Even if not consumed, every component is non-toxic and fully degradable.
The team envisions additional uses in fish farming, where these bots could deliver medicated feed. Future improvements aim to address the one non-edible component: the sensors.
“Edible materials with targeted nutritional profiles and function have barely been considered,” said Floreano, “but they open up a world of opportunities for human and animal health.”
The findings were published in Nature Communications.
