The Robot That Thinks With Its Legs

A soft-bodied robot built from elastic tubes and powered by nothing but air can walk, hop, and swim, all without a computer, a sensor, or a single line of code. Its creators at the AMOLF research institute in Amsterdam published their results in Science in May 2025, and the details are worth slowing down for.

The robot's legs are soft tubes connected to a shared air supply. When air flows through a tube, it creates a travelling kink, a ripple of pressure that makes the tube oscillate. On its own, each leg flails unpredictably. But connect several legs together and something unexpected happens: the movements synchronise. No instruction tells them to. The physics of shared air pressure does the work. The legs fall into step, and the robot walks.

It walks fast, too. The robot covers 30 body lengths per second. A Ferrari, relatively speaking, manages about 20. The inspiration, fittingly, is not cutting-edge engineering but those wobbling inflatable tube figures you see flapping outside car dealerships. The same physics that makes them wiggle turns out to be surprisingly useful when harnessed properly.

What makes this more than a novelty is what happens when the environment changes. If the robot hits an obstacle, it reorients itself. Drop it into water, and its gait shifts spontaneously from an in-phase hop to an alternating swimming stroke. No software decides this. The robot's body, interacting with the medium around it, produces a different movement automatically. Sea stars coordinate hundreds of tube feet the same way, using local feedback and body dynamics rather than a centralised brain.

The team built two versions. The first had four legs and received air through a hose. The second, lighter version had two legs and carried its own battery-powered pump. That smaller model drew just 0.12 watts and ran for half an hour on a single charge.

How to discuss this with your kids

Start with the inflatable tube men. Most children have seen them outside shops and car dealerships, flailing about in the wind. Tell them scientists looked at that same wobbly physics and thought: what if we could make that useful? That is the story of this robot in one sentence.

Then ask the question the researchers themselves grappled with: if something has no brain, no sensors, and no code, but it can walk, dodge obstacles, and switch to swimming when it hits water, is it a robot? There is no tidy answer, which is exactly why it is worth discussing. It sits right on the boundary between a machine and something that behaves like a creature.

For children who like building things, the deeper point lands well. Most robotics stories are about adding complexity. This one asks how much you can do with almost nothing, if you understand the physics well enough. The hardest problems are not always solved by making something more complicated. Sometimes they are solved by understanding something simple more deeply.

Watch it in action

AMOLF has short video clips of the robot walking, dodging obstacles, and switching from land to water: amolf.nl/news/this-soft-robot-thinks-with-its-legs. For a version curated for younger viewers, The Kid Should See This has a good video presentation.

Source: Comoretto, A. et al., "Physical synchronization of soft self-oscillating limbs for fast and autonomous locomotion," Science (2025). Also reported by New Atlas and NewsForKids.net, AMOLF