Armored caterpillars offer robot designers lessons in crossing slippery glass

Animals have long been one of the primary sources of inspiration for robotics researchers. This is because they rely on sophisticated biological mechanisms and locomotion strategies that could be artificially reproduced in robots to equip them with desired capabilities.

Caterpillars, the wormlike larvae that later develop into butterflies or moths, have also attracted the attention of many roboticists. Their elastic bodies and their ability to stick onto many types of surfaces allow them to move in complex natural environments and squeeze through narrow openings.

Caterpillars adapt their movements based on what they are crawling on, as they might not always adhere perfectly to each surface. Researchers at the University of Naples Federico II and the University of Palermo recently assessed how well caterpillars moved on wood, steel, slate and glass, observing how they coped with more challenging conditions.

The team improved a mathematical model introduced in one of their previous papers, which represents the body of caterpillars as masses connected by springs. Guided by the model, they then fitted real caterpillars with artificial armor to increase their body stiffness and added weights to improve friction and adhesion.

The results of the team's experiments led to the identification of strategies that could allow robots to attach themselves and move on various materials. Their paper, published in the Journal of the Royal Society Interface, may guide the development of new nature-inspired soft crawling robots.

"Building on previous studies, this work employs a crawling model that represents the body as spring-linked masses, interacting with the environment via threshold-based adhesion and Winkler-like springs," wrote Mario Argenziano and his colleagues in their paper.

Observing caterpillars crawling on distinct surfaces

Argenziano and his colleagues built on their previously introduced model of caterpillar crawling. They tested the model's predictions experimentally by observing caterpillars from the species Pieris brassicae as they crawled on wood, steel, slate and glass.

"Our results highlight a strong correlation between substrate roughness and crawling performance," wrote the authors. "While caterpillars seamlessly adapt their movement to predominant surface patterns, they struggle on smooth surfaces like glass—where microscale asperities are insufficient for proleg grip—confirming that adequate adhesion is crucial to trigger and sustain movement."

Based on their initial observations and using their mathematical model, the researchers then developed artificial armor that would increase the stiffness of the caterpillars' bodies. They then fitted caterpillars with the armor, adding separate weights to increase friction and adhesion. They found that the armor and weights improved the insects' ability to crawl on smooth glass.

"Driven by the model's insights on these physical constraints, we explored how crawling mechanics could be artificially enhanced," wrote the authors. "Through proof-of-concept experiments, we equipped larvae with artificial armor to increase body stiffness and additional masses to improve effective friction and adhesion, allowing them to cross non-walkable glass surfaces."

Inspiring new crawling soft robots

The team's experiments yielded insights that could be useful for the development of caterpillar-inspired and other crawling robots. Most notably, they demonstrated that achieving a balance between body elasticity and the ability to adhere to surfaces is an essential aspect of effective crawling.

"These findings validate the model's predictive accuracy, envisioning possible novel design criteria for bioinspired soft crawlers capable of adapting movements in complex habitats," wrote the authors.

The mathematical model developed by Argenziano and his colleagues and the crawling principles they uncovered could prove useful for the development of soft robots that can effectively move on various surfaces and terrains. Future studies could try to reproduce the properties of the artificial armor created by the team in robotic systems.

Written for you by our author Ingrid Fadelli, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

Publication details

Mario Argenziano et al., Allowing caterpillar locomotion on any substrates: towards hybrid soft robots design, Journal of the Royal Society Interface (2026). DOI: 10.1098/rsif.2026.0288.

Who's behind this story?

Ingrid Fadelli

Freelance journalist with BSc Psychology and MA International Journalism. Covers AI, robotics, neuroscience, and astrophysics since 2018. Full profile →

Gaby Clark

MA in English, copy editor since 2021 with experience in higher education and health content. Dedicated to trustworthy science news. Full profile →

Robert Egan

Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

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