What is it about?

Many robots work well in one environment but lose efficiency when moving between land and water. We developed AdaptBot, a soft robot that can change its shape passively when the environment changes. On land, it keeps its fins folded and rolls like a wheel. When it enters water, a fast-swelling hydrogel expands and deploys the fins, allowing the robot to paddle more effectively. A light-powered artificial muscle drives the robot, while a ratcheting transmission converts the muscle’s back-and-forth motion into forward movement. With this design, AdaptBot can roll, climb, tow loads, and swim across land, water, and transition zones. After the fins deploy in water, its swimming speed increases by 780%.

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Why is it important?

Future robots may need to operate in complex environments such as wetlands, shorelines, disaster sites, or other unstructured terrains where conditions change rapidly. Most adaptive robots require sensors, electronics, multiple actuators, and active control to change shape. AdaptBot shows a different strategy: the environment itself can trigger useful shape change. By combining responsive materials with mechanical design, the robot uses water exposure to deploy fins and improve swimming performance without adding a separate motor or control system for adaptation. This work suggests a pathway toward simpler, lighter, and more energy-efficient soft robots that can adapt across multiple environments.

Perspectives

This paper is especially meaningful to me because it is my first first-author research paper. I was excited by the idea that a robot does not always need more electronics or more complex control to become more adaptive. Instead, materials and mechanisms can be designed so that the environment directly helps the robot change its body and improve performance. I hope this work encourages more designs that combine soft materials, mechanical intelligence, and bioinspired principles to build robots capable of moving through complex real-world environments.

Shukun Yin
California Institute of Technology

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This page is a summary of: Amphibious passive adaptation in untethered soft robots, Proceedings of the National Academy of Sciences, April 2026, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2532988123.
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