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Study of remoras may lead to new adhesives

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February 22, 2013

A group of remoras, freeloading off a bull shark (Photo: Shutterstock)

A group of remoras, freeloading off a bull shark (Photo: Shutterstock)

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If you’ve seen even a few minutes of any documentary on sharks, then chances are you’ve seen a remora. They’re the smaller fish that hitch rides on sharks by sucking onto them. Not only are the remoras able to achieve a seal against their hosts’ rough, sandpaper-like skin, but they also don’t appear to harm that skin in the process. Researchers from the Georgia Tech Research Institute are now studying how the remoras manage this, in hopes of applying their findings to the development of next-generation adhesives.

Remoras are thought to latch onto sharks for three main reasons – it’s easier than swimming that same distance themselves, predators aren’t too likely to approach them with their toothy host nearby, and they get to eat the food scraps that the shark creates while tearing into unfortunate sea creatures.

They’re able to hold on not by using their mouths, but with a sucker on their back. That structure is actually a dorsal fin, that through the course of evolution has flattened. It has a lip of fleshy tissue around its perimeter to create a seal against the shark skin, but it also has an oval disk in the middle, made up of rows of louvered plates known as lamellae.

Each lamella, in turn, incorporates rows of tooth-like structures called spinules. The scientists noted that the spacing between the spinules was very similar to the spacing of the scales of the mako shark, allowing the spinules to non-destructively fit between those scales. This, needless to say, allows for excellent adhesion between the two – that said, remoras are also pretty good at sucking onto other things, such as sea turtles.

An enlarged 3D rapid prototype of a lamella (top) and a remora's adhesive disk (bottom)

An enlarged 3D rapid prototype of a lamella (top) and a remora's adhesive disk (bottom)

If the remoras need to exert physical effort to maintain their hold, then the practicality of an adhesive based on their lamellae might be quite limited. By dissecting and examining the muscle tissue around the suction disk, however, the scientists discovered that the fish utilize a passive form of adhesion – they just latch on and relax. In fact, it’s likely that drag created by the passing water causes the spinules and scales to mesh together more firmly.

Lead scientists Jason Nadler and Allison Mercer, along with their colleagues, are now looking into human applications for what they’ve learned. “We are not trying to replicate the exact remora adhesion structure that occurs in nature,” said Nadler. “We would like to identify, characterize and harness its critical features to design and test attachment systems that enable those unique adhesive functions. Ultimately, we want to optimize a bio-inspired adhesive for a wide variety of applications that have capabilities and performance advantages over adhesives or fasteners available today.”

More specifically, it has been suggested that such an adhesive could be used to create bandages that don’t cause pain or leave behind residue when they’re removed, to attach sensors in marine or military environments, as a replacement for surgical clamps, and as a means of helping robots climb vertical surfaces. Interestingly, some or all of those applications have also been suggested for adhesives based on porcupine quills and gecko feet.

Source: Georgia Tech Research Institute

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
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