The research, which was published in Nature Communications, introduces a small, boat-shaped robot powered by entirely edible components. By mimicking the Marangoni effect — the same surface tension trick used by water-walking insects — the robot zips across the water using a simple chemical reaction involving citric acid and baking soda. The reaction releases carbon dioxide, pushing a biodegradable fuel, propylene glycol, into the water and creating a surface tension gradient that propels the robot forward.
The result is an agile, non-toxic device that not only poses no harm to aquatic life, but actually benefits it. The robot’s outer shell is crafted from high-protein fish food, offering structural support during operation and becoming nourishment for aquatic animals at the end of its life cycle.
“Conventional aquatic robots often rely on plastics and electronics, which can be harmful if deployed at scale in natural ecosystems,” said EPFL PhD student Shuhang Zhang. “We’ve replaced those with edible, biodegradable components, making our robot safe for wildlife and even beneficial.”
The robot measures just 5 cm and operates autonomously for several minutes. Its simplistic design eliminates the need for onboard electronics; instead, researchers manipulate its movement using asymmetrical fuel channels that cause it to veer left or right. This pseudo-random motion is ideal for dispersing fleets of the robots to monitor water quality or deliver nutrients.
The team envisions equipping the robots with biodegradable sensors to collect data on temperature, pH levels, and pollutants. These sensors could either be read remotely or retrieved after the robot’s deployment.