The remora is a fascinating fish, not least because of a strong suction cup-like structure on the back of its head, allowing it to latch onto larger animals for protection and transport. Now researchers at the New Jersey Institute of Technology (NJIT) have designed a remora-inspired suction cup that’s far more adhesive than the real thing.
Evolution has crafted quite an intricate design for the remora's suction cups. They’re surrounded by a fleshy ring that forms a tight seal, while the inside contains rows of ridges called lamellae, which are lined with toothy tissue called spinules. This structure creates friction that holds the fish firmly onto its host, even with strong drag as they move through the water
The researchers from NJIT and the University of Akron set out to mimic this natural wonder with a new type of suction cup. Looking at the evolutionary history of the fish, the team noticed that modern remora have more lamellae than their ancestors, suggesting that more makes for a better grip. So they put that idea to the test.
The researchers 3D printed various versions of their suction cup, with different numbers of lamellae. These were then tested underwater, measuring the shear force and time it took to pull the discs off of silicon surfaces. These surfaces were also varied in smoothness – 100-grit, 180-grit and 350-grit.
Sure enough, the more lamellae, the stronger the disc’s adhesive ability. The team found a sweet spot between nine and 12 – the latter, for example, was able to withstand 27 newtons of force for 50 seconds. That makes it about three times stronger than a regular remora’s disc latching onto a shark. The disc itself weighed just 45 g (1.6 oz).
The team found that discs with less than six lamellae weren’t able to adhere at all. And interestingly, this is exactly how many have been found on 32 million year-old fossils of remora ancestors.
“The beauty behind the remora’s adhesive mechanism is that biological tissues inherently do most of the work,” says Brooke Flammang, lead researcher on the study. “The most significant aspect of this research is that our robotic disc relies completely on the fundamental physics driving the adhesive mechanism in remoras, allowing us to determine biologically relevant performance and gain insight into the evolution of the remora’s disc. This was previously not possible with past designs that required a human operator to control the system.”
The research was published in the journal Bioinspiration and Biomimetics.
Source: NJIT
