Robot climbs walls using heated gecko-inspired adhesive

Robot climbs walls with heated gecko feet

A four-legged robot can slowly climb walls made of steel, glass, aluminum, and rough wood. Its feet use a gecko-inspired adhesive that sticks more strongly when heated and releases when cooled.

The research, published in the journal Matter, demonstrates a new method for reliable robotic adhesion. Unlike suction cups or magnets, this approach works on a variety of smooth and slightly rough surfaces.

How the thermal adhesive works

The robot's adhesive pads are made from a soft polymer embedded with expandable microspheres. When heated to about 70°C (158°F), the microspheres expand, creating a rough surface texture that grips onto microscopic bumps on a wall.

Cooling the pad to around 10°C (50°F) causes the microspheres to contract. This makes the surface smooth again, breaking the adhesive bond and allowing the foot to detach cleanly. The cycle repeats for each step.

This heating and cooling process is a direct mimic of a gecko's climbing technique. "A gecko controls adhesion by changing the contact area between its feet and the surface," said senior author Michael Bartlett. "We do the same thing, but we use temperature to control that roughness and contact."

The climbing robot's design

The prototype robot is relatively small, weighing just 0.6 kilograms (about 1.3 pounds). It uses four articulated legs, each equipped with one of the thermal adhesive pads.

A control system coordinates the movement and temperature of each foot in a careful sequence:

• One foot heats up and presses against the wall to stick.
• The robot shifts its weight onto that foot.
• The opposite foot cools down and detaches to take the next step.

This slow, deliberate gait allows the robot to climb vertically and even transition from a floor to a wall. Its current speed, however, is only about 0.7 millimeters per second.

Advantages over other climbing methods

The thermal adhesive system solves several problems common in climbing robots. Suction cups fail on rough or porous surfaces and require constant energy to maintain a vacuum. Magnets only work on ferromagnetic materials like steel.

Gecko-inspired dry adhesives have been explored before, but they often struggle with detachment. The new thermal method provides a clear, controlled signal for when to stick and when to release.

"The main challenge with gecko adhesives is disengaging them. They want to stay attached," said Bartlett. "We found that by controlling temperature, we can engage and disengage the adhesion very well."

Future applications and challenges

The researchers see potential for this technology in inspection and maintenance robots. These machines could climb the hulls of ships, the sides of storage tanks, or the exterior of buildings to perform tasks.

Significant hurdles remain before practical deployment. The robot's speed must be greatly increased, and the system needs to be tested on dirty or wet real-world surfaces, not just clean lab materials.

The team also aims to make the technology more energy-efficient. Currently, the heating and cooling process consumes a lot of power relative to the robot's small size and slow movement.

Despite these challenges, the project marks a step toward versatile climbing robots. By borrowing and modifying a proven technique from nature, engineers are creating machines that can access spaces humans cannot.