Brainless robot created that runs and swims is powered solely by air

A wheezing pump, a length of elastic tubing, and a spark of curiosity have produced a machine that challenges every textbook rule of robotics. Instead of lines of code, this soft robot contraption runs on nothing more than air pressure and the shape of its own body.

Lead author Alberto Comoretto and his colleagues at the Dutch research institute AMOLF built the two‑pound device and watched it trot across a lab bench, clamber over a book, then slip into a tank and paddle like a terrier.

Johannes Overvelde, also at AMOLF, helped show that the simple rig adjusts its movements to ground or water without a single transistor.

Rethinking control with airflow

A conventional robot relies on a digital controller that measures, decides, and commands, yet every loop burns power and time.

The AMOLF machine outsources all that work to the physics of its pneumatic limbs, shaving the response delay to milliseconds and the parts list to a pump and four valves.

Each limb is a hollow silicone tube bent into a soft knee; steady airflow makes a kink race down the length, relax, then reappear at the top, yielding a rhythmic kick.

That self‑oscillation reaches 300 hertz, far faster than earlier soft robot walkers that topped out near three hertz.

Because the tubes all share one air line, a pressure change in one leg tugs on the others the way a common spring links a row of metronome clocks. The result is limb synchronization that emerges for free; nothing has to calculate a gait.

On carpet, the legs stiffen against drag, so all four strike the ground in phase and the robot bounds forward.

Drop it into water and drag vanishes, the phase slips to an alternating pattern, and the same body now swims.

This soft robot teaches itself

Comoretto first noticed the effect while pinching an air hose and hearing it sing. High‑speed video revealed a kink that chased its own pressure wave, a tiny version of the flapping “Fly Guy” inflatable figures invented for the 1996 Atlanta Olympics.

Those roadside mascots seem chaotic, yet their thrashing follows the same feedback loop of pressure, bend, and release.

By constraining the tubing length, wall thickness, and bend angle, the team turned that loop from a dance into a motor.

The engineers printed a rigid backbone that fixes the tubes at just the right tilt so gravity pushes each foot down as the kink passes. They tuned flow rate, not software, to swap between a walk, a rapid bound, and an in‑place shuffle.

“We were super excited because we saw this self‑sustaining, periodic, asymmetric motion,” said Comoretto, recalling the moment he realized the hose was alive with possibility. His excitement grew when the limbs copied one another without his help.

Robot walks, then swims

A tangle of hoses limited the first tests, so the group trimmed the design to two legs and mounted the pump onboard.

Flow dropped from fifteen standard liters per minute to under one, and the power draw plunged to just 0.12 watts for the pair.

That thrift let the robot carry a cellphone‑size lithium battery and operate for half an hour on a charge. Two photodiodes wired to a relay gave it a crude sense of phototaxis, letting it scuttle toward a flashlight beam the way a moth seeks a porch lamp.

“Now when it hits a wall, it starts to turn left. If it lands in water, it starts to swim backwards. We didn’t come up with that – it just happens,” Overvelde said.

When an acrylic wall blocked its path, the oscillations skewed, the body veered left, and the machine sidestepped the obstacle without ever “knowing” the wall existed. 

In a fish‑tank trial the legs flipped phase to mimic a dog paddle, propelling the chassis three body lengths in ten seconds.

That speed rivals centimeter‑scale amphibious bots that need magnets, heaters, or onboard microcontrollers to achieve similar feats.

Less power, more motion

Pumps still dominate the weight budget, so the researchers are experimenting with thin membranes that act as passive valves, squeezing each tube rhythmically with the exhaust of its neighbor.

If successful, the pump could shrink to a thumbnail and the battery to a coin cell.

A second project fits the same limbs around a silicone sac to form a soft artificial heart that pulses in sync with blood pressure. Overvelde argues that a medical implant should “just work” and never wait for a firmware patch.

Beyond toys and demos

The study hints at a new class of devices that swap silicon intelligence for embodied intelligence, the control wisdom stored in shape and material.

That principle echoes through biology, where spinal reflexes and tendon elasticity free the brain to plan instead of micromanage.

Industrial pick‑and‑place arms built of rigid links may soon share floors with soft grippers that tune their own squeeze by airflow alone.

Search‑and‑rescue robots could crawl through rubble without risking an electrical short, then swim across a flooded basement with the same actuators.

The approach also answers a thorny sustainability question. Electronic waste from motors and circuit boards grows yearly, yet a pump, a hose, and recyclable elastomer leave a smaller footprint.

Soft robots built for space

Critics note that air systems struggle at high altitudes and in vacuum, but the authors see hybrid designs that mix compressed gas with chemical gas generators for space exploration.

Further studies will map the equations that govern phase shifts and resonance, letting engineers dial up climbing or burrowing gaits on demand.

Soft robotics has progressed from floppy toys to lab curiosities to practical tools in less than fifteen years.

By proving that simple physics can orchestrate complex motion at hundreds of beats per second, the Dutch team has nudged the field toward everyday utility.

The next milestone is reliability, measured not in hours but in years, because nobody wants to babysit a rescue robot or swap out a heart pump every season.

As Comoretto’s accidentally singing tube showed, sometimes the path to long life begins with a sound, not a spreadsheet.

The study is published in Science.

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