Scientists at Switzerland's École Polytechnique Fédérale de Lausanne (EPFL) have created a groundbreaking environmental monitoring solution that addresses two critical challenges: reducing electronic waste and minimizing ecosystem disruption during water quality assessment.
The 5-centimeter boat-shaped robots, developed by a team led by Professor Dario Floreano and PhD student Shuhang Zhang, are made entirely from biodegradable and edible materials. Their bodies consist of commercial fish feed pellets ground into powder, mixed with a biopolymer binder, and freeze-dried into shape. To enhance nutritional value, the researchers formulated the outer structure with 30% higher protein content and 8% lower fat content than standard fish pellets.
What makes these robots truly innovative is their propulsion system, which requires no electronics or batteries. The devices utilize the Marangoni effect—the same phenomenon some aquatic insects use to move across water surfaces. A chemical reaction between citric acid and sodium bicarbonate in a small chamber produces carbon dioxide gas, which forces non-toxic propylene glycol fuel out through a channel. This expelled fuel reduces water surface tension, propelling the robot forward at speeds of up to three body lengths per second for several minutes.
The EPFL team envisions deploying these robots in large numbers across bodies of water. Each would be equipped with biodegradable sensors to collect data on water pH, temperature, pollutants, and microorganisms. Rather than precisely controlling their movement, the researchers have created 'left-turning' and 'right-turning' variants by altering the fuel channel's asymmetric design, allowing the robots to disperse naturally across water surfaces.
"While the development of miniature swimming robots for natural environments has progressed rapidly, these typically rely on plastics, batteries, and other electronics, which pose challenges for mass deployment in sensitive ecosystems," explains Zhang. "In this work, we show how those materials can be replaced by completely biodegradable and edible components."
The research, published in Nature Communications in May 2025, represents the latest advancement in the burgeoning field of edible robotics. It builds on EPFL's previous work with edible soft actuators, fluidic circuits, and conductive inks, all part of the EU-funded RoboFood consortium launched in 2021 with €3.5 million in funding.