A research team has developed a fully biodegradable, edible aquatic robot capable of monitoring water environments and safely decomposing without leaving behind waste—an innovation that merges soft robotics with ecological responsibility.
Study: Edible aquatic robots with Marangoni propulsion. Image Credit: Black Salmon/Shutterstock.com
Published in Nature Communications, the study presents a small, fish-food-based robot that moves autonomously using Marangoni propulsion—a method driven by surface tension gradients—and operates without electronic components or traditional motors. Once deployed, it can perform targeted tasks such as delivering nutrients or medications to aquatic life before naturally breaking down in the environment.
Addressing a Persistent Problem in Environmental Robotics
Aquatic micro-robots are increasingly used for sensing, intervention, and monitoring in water systems. However, their widespread adoption raises environmental concerns due to the use of synthetic materials, plastics, and embedded electronics. These components not only risk polluting ecosystems but also pose ingestion hazards to aquatic species if robots are lost or abandoned.
To address these issues, the researchers in this study have designed a robot using edible, non-toxic materials that eliminate the need for post-use retrieval. The materials were selected to be both mechanically functional and ecologically compatible, ensuring safe degradation in natural settings.
Material Selection and Manufacturing Process
The researchers constructed the robot's hull using freeze-dried commercial fish feed, combined with edible binders like gelatin. The mixture was molded, frozen, and then freeze-dried to create a lightweight, buoyant structure that could float on water while maintaining its form.
Motion was achieved through a simple actuator: a gelatin-glycerol hydrogel chamber filled with citric acid and sodium bicarbonate. Once submerged, the chemical reaction generated carbon dioxide, building pressure inside the chamber. This pressure pushed out a small amount of propylene glycol—a non-toxic, food-safe surfactant—creating motion via the Marangoni effect.
Crucially, all components were food-grade and biodegradable. No electronics, plastics, or toxic fuels were involved.
Results: Contained, Controlled, and Compostable
In controlled lab tests, the robot moved consistently across water at speeds between 0.034 and 0.098 meters per second. Propulsion could last up to 69 seconds, depending on material composition. Design variations in the actuator also allowed for predictable turning behavior, demonstrating basic control over the robot’s trajectory without requiring any onboard electronics.
Of the three surfactants tested (ethanol, lecithin, and propylene glycol), propylene glycol struck the best balance between propulsion force and environmental safety. Although less energetic than ethanol, it offered significantly lower toxicity and greater stability during operation.
Gelatin-based hulls also performed well in water resistance and mechanical strength, outperforming alternative starch- or flour-based versions. While hydrophobic additives were initially tested to reduce water absorption, they weakened structural integrity and were ultimately excluded.
Beyond safe degradation, the robot’s materials offered a nutritional bonus. The final structure was composed of about 77 % protein with low fat content, making it suitable as a supplemental feed for fish or other aquatic animals.
This dual-purpose design, robot and food, offers compelling use cases in aquaculture, where robots could be used for monitoring or medication delivery and then serve as a resource rather than a pollutant.
Conclusion
Although this was a proof-of-concept study with manually fabricated prototypes, the results point to scalable possibilities. Automating the manufacturing process could reduce variability and support broader deployment of similar biodegradable systems in real-world environments.
More broadly, the work presents a viable model for how robotics can be integrated into sensitive ecosystems without creating new forms of waste. Rather than persisting in the environment, these robots are designed to fulfill a specific function and then simply disappear; an idea with significant implications for environmental monitoring and sustainable design.
Journal Reference
Zhang, S., Kwak, B., Zhu, R., Pankhurst, M., Zhang, L., Boom, R. M., & Floreano, D. (2025). Edible aquatic robots with Marangoni propulsion. Nature Communications, 16(1). DOI:10.1038/s41467-025-59559-8. https://www.nature.com/articles/s41467-025-59559-8
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.