Science1 publisher2 min readPublished
Cuttlefish suckers gripped stiffer plates harder than softer ones in a Wageningen pull test
Wageningen biomechanists found microscopic pillars on the rim of a cuttlefish sucker, then measured how hard dissected arms clung to plates of varying roughness and stiffness in a water tank. Plate stiffness is what moved the reported forces.
The Scientist · Science desk
What happened
- Biomechanists at Wageningen University & Research tested how suckers from the common cuttlefish grip rough and uneven surfaces, and published the work in Journal of the Royal Society Interface.
- They bought freshly caught cuttlefish from local fisheries, dissected the arms, glued each one to a glass slide and set it at the bottom of a small water tank with the suckers facing up.
- A custom-built automated indenter pressed plates of varying roughness and softness onto the suckers and recorded the force needed to pull each plate away again.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- constraint An engineer copying these forces is copying a passive seal, since muscle activation in a living animal never entered the measurement.
- capability Designers weighing a textured seal now have a quantity to compute, water crossing the rim, instead of only a micrograph of pillars to imitate.
- contradiction The cuttlefish-beats-octopus framing rests on prior suction-pressure work, and this experiment cannot arbitrate it, so a gripper spec justified by that ranking is leaning on evidence collected elsewhere.
A sucker holds because the water beneath it sits at lower pressure than the water outside, and that difference produces the force pinning it to a surface [2]. The rim decides how long the difference survives. The Wageningen group built a mathematical model of leakage, the movement of water across the rim of a sucker, and the model agreed with the experiments qualitatively, reproducing the overall pattern seen in the tests [12].
The pillars are the reason the study exists. "This study came about from looking at a cuttlefish's suction cup under the microscope, where we noticed it had these microscopic pillars all over the suction cup rim," said Guillermo Javier Amador, the paper's senior author [3]. "These structures, known as papillae, confused us, since we normally think of suction cups having very smooth rims to ensure that a secure seal is formed. However, we realized that cuttlefish use their suction cups to stick to their prey, which typically have very rough skins," he said [4].
"We made artificial substrates that varied in roughness and stiffness based on what the cuttlefish are known to attach to in the wild (like crabs, shrimp or fish)," said Brett Klaassen van Oorschot, a co-first author [11]. The suckers came away harder from stiffer plates than from softer ones [10]; the roughness half of the design is where the papillae hypothesis sat [9][6].
The claim that gets cuttlefish suckers noticed is that they generate greater suction pressures than octopus suckers do [2]. That comparison comes from earlier work. Klaassen van Oorschot said most biological sucker research "has been on octopus and clingfish" [5], and no octopus sucker went into this indenter [14]. Ranking a cuttlefish against an octopus on rough, stiff prey would take a different experiment.
The account of the work does not report the measured forces or the number of arms tested [15]. It does say the observations suggest papillae help the suckers attach [13]. I would treat that as a lead worth following and not yet a design rule, because a model that matches the shape of a curve cannot size a rim [16]. "We were really interested in quantifying this observation and testing the hypothesis that their papillae play a role in suction," Klaassen van Oorschot said [6].
What to watch
- Whether the Journal of the Royal Society Interface paper reports the pull-off forces and sample sizes absent from the public summary.
- Whether the leakage model is later fitted to measured magnitudes.
- A moulded rim carrying papillae-like pillars, measured against a smooth rim on the same rough, stiff plates.