A 70-Gram Suction Disc Inspired by Lamprey Mouths Can Lift 850 Times Its Own Weight

Beijing Institute of Technology Press Co., Ltd

The lamprey is nobody's idea of a charismatic animal. Jawless, eel-shaped, and parasitic, it attaches to other fish by clamping its circular mouth onto their bodies and holding on, sometimes for weeks. But that mouth is an engineering marvel: a soft lip creates a seal, a muscle pump generates vacuum, and a ring of horny teeth physically interlocks with whatever surface it contacts. Now a team at Peking University has translated that triple-threat adhesion strategy into a robotic device weighing just 70 grams.

Where conventional suction fails

Traditional suction cups have a fundamental problem, or rather two of them. Underwater, flowing water can breach the seal and break adhesion. On rough surfaces in air, microscopic gaps between the cup and the surface prevent a proper vacuum from forming. Either environment alone is challenging; transitioning between them is nearly impossible for conventional designs.

"Traditional suction cups easily fail underwater due to fluid washing, or they lose their vacuum seal on rough surfaces," said Junzhi Yu, the study's corresponding author and a professor at Peking University. The team needed a single mechanism that could handle both problems simultaneously.

Soft lip, smart core

Their solution combines a flexible silicone lip, similar to the lamprey's, with a core made of shape-memory polymer (SMP). The SMP is the key innovation. When a built-in heater warms it to just above 33 degrees Celsius, the material transitions from rigid to rubbery. Activating vacuum suction while the SMP is soft pulls the material deep into the microscopic crevices and pores of whatever surface it contacts, creating a precise impression of the texture. When the heater turns off, the SMP cools and hardens, locking itself into the surface like a key molded to fit a specific lock.

This hybrid approach decouples adhesion strength from continuous vacuum maintenance. Even if the vacuum system fails or air leaks through rough surface irregularities, the physical interlocking of the hardened SMP maintains the grip.

Testing across six orders of magnitude

The laboratory results are striking in their range. The 70-gram device generated enough pull-off force to stably support loads exceeding 850 times its own weight in both air and water. On highly rough surfaces where pure-vacuum suction cups failed entirely, the bio-inspired disc maintained adhesion. Air retention time nearly tripled compared to conventional designs, while underwater retention time increased by up to 540%.

But the more impressive demonstration was the device's versatility across object types. In dry tests, it handled objects spanning six orders of magnitude in mass: from a fragile 0.01-gram microelectronic chip to an 11.4-kilogram desk. It adapted to irregular everyday items and industrial tools like wrenches and hammers. Underwater, it gripped smooth metal coins, naturally porous red bricks, scallop shells, and large conches with complex three-dimensional curves.

Crossing the air-water boundary

The most demanding test involved a cross-media demonstration. A robotic arm equipped with the suction disc grabbed a bionic manta ray robot in air, submerged it entirely into a water tank, released it to swim, then reattached to the wet robot underwater and lifted it back into air. The system adapted to the air-water interface transition without modification or recalibration.

This kind of cross-media operation is exactly what existing adhesion technologies struggle with. An underwater suction system and an in-air suction system face different physics, and designing for one typically compromises performance in the other. The lamprey-inspired approach, by combining vacuum, conformable sealing, and mechanical interlocking, sidesteps that tradeoff.

The biology behind the engineering

The lamprey's solution evolved over hundreds of millions of years. These ancient fish are among the most primitive living vertebrates, yet their attachment mechanism is sophisticated enough to have persisted largely unchanged since before dinosaurs existed. The biological system uses three complementary strategies: a deformable oral disc that conforms to surfaces, negative pressure generated by a piston-like tongue muscle, and keratinous teeth that physically grip irregular substrates.

The engineering replica preserves this functional hierarchy while substituting materials. Silicone replaces the soft oral tissue. The SMP replaces the teeth, with the advantage that it can conform to any surface rather than relying on fixed tooth geometry. An active vacuum pump replaces the tongue muscle.

What the device cannot yet do

Several limitations constrain practical deployment. The SMP heating and cooling cycle takes time, meaning rapid attachment and release on rough surfaces is slower than with a simple vacuum cup. The device has been demonstrated only in laboratory settings with controlled conditions; how it performs in murky water, on biofouled surfaces, or under sustained ocean currents remains untested. The 33-degree Celsius activation temperature works well in temperate conditions but could be problematic in very hot environments where ambient temperature approaches the SMP transition point.

The device's long-term durability, particularly of the SMP after repeated heating cycles and mechanical deformation, has not been characterized in the published work. And while 850 times the device's weight is impressive for a 70-gram prototype, scaling the technology to industrial loads will introduce new engineering challenges.

The research team envisions integration into robotic platforms for deep-sea resource exploration, marine engineering maintenance, and amphibious emergency rescue operations. But the path from a laboratory demonstration to a field-ready tool involves bridging gaps in environmental testing, durability validation, and manufacturing scalability.