Shark skin has always fascinated everyone, from fishermen to physicists. And it's not hard to see why: these creatures are capable of swimming at incredible speeds that no Olympic swimmer could ever dream of matching. The credit goes to their scales, which evolved into tiny three-dimensional anvil-shaped structures called denticles.
But how exactly do denticles make sharks so hydrodynamic? Until now, no one had been able to find out for sure. But now, thanks to a groundbreaking study, the mystery has finally been revealed. And the truth is even more incredible than previously thought.
Mission Impossible
Studying shark denticles is a bit like trying to understand how an alien spaceship works. They are structures so small (less than half a millimetre) and complex that reproducing them in the laboratory is a titanic undertaking. And analyzing them directly on the shark's skin is even more difficult, because once removed from the fish, the skin loses its special properties.
In short, it's like having a magical object in your hands that stops working as soon as you touch it. A puzzle that has driven scientists crazy for decades, forcing them to settle for simplified structures or inconclusive experiments.
The engine of science, however, never stops. With patience, curiosity and creativity, researchers have continued to search for the Holy Grail of denticles: the secret to their effectiveness.
Denticles, the anvil and the wave
Benjamin Savino e Wen Wu, two physicists from the University of Mississippi, asked themselves: what if instead of experimenting with real denticles, we simulated them on the computer? No sooner said than done, the two created a virtual model. Precisely "that" shark skin covered with anvil-shaped denticles, complete with support pillars and hammer heads fitted together. Find the complete study here.
A masterpiece of biomimetic engineering, which allowed researchers to understand for the first time the operating mechanism and fluid flow around these structures. Surprise: the denticle heads don't just reduce friction, they actively inject fluid into the protected space beneath them, creating a sort of reverse wave.
This “wave effect” is the key to everything. Because it generates a propulsive thrust in the direction of motion, like a tiny hydrodynamic motor integrated into the skin. A discovery that has left researchers speechless, and which could revolutionize the way we design ships and submarines.
Sharks, the secret of the back
The surprises don't end there. Savino and Wu discovered another crucial detail: Denticles work best when placed on a curved surface, like the back of a shark.
It is there that the ideal pressure gradient is created to inject the fluid into the protected space and generate the reverse thrust. A mechanism so effective that sharks may have purposely evolved humps on their skin to make the most of it.
Prosaic summary: the shark is full of micro hydrodynamic devices, the result of millions of years of evolution. An engineering lesson that nature put under our noses, and that we are only now starting to understand.
Hi-tech sharks
What can we humans do with this knowledge? Well, the applications are potentially endless. Think ships and submarines clad in artificial denticles, capable of hurtling through the water with unprecedented efficiency. Or hi-tech swimming suits that will transform athletes into Olympic "sharks".
Of course, there is still a lot of work to do. We need to understand how to keep the serrations clean from marine fouling, and how to best integrate them into the curved surfaces of our vehicles. But the path is clear, and the goal is within reach.
Because ultimately, evolution is the greatest engineer of all time. And sharks are its most hydrodynamic creatures, perfected over millions of years of swimming.
Copying them is not cheating, but paying homage to their mastery.
