BBC Future

Nature's Tricks

Woodpecker inspires cardboard bike helmet

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  • Head case
    Industrial designer Anirudha Surabhi created the Kranium bike helmet following a cycling accident that left him with concussion. (Copyright: Anirudha Surabhi)
  • Impact zone
    Surabhi was then studying at the Royal College of Art in London and was looking for an end of year thesis project. (Copyright: Anirudha Surabhi)
  • Bird and beak
    He turned to the anatomy of a woodpecker for inspiration, as the bird has various adaptations that protect it from repeated blows. (Copyright: SPL)
  • Cushion the blows
    In particular, he wanted to recreate the bird’s spongy cartilage, which acts as a shock absorber between the skull and the beak. (Copyright: Anirudha Surabhi)
  • Paper weight
    Surabhi recreated this layer out of various materials, before eventually settling on a corrugated cardboard – which is both strong and lightweight. (Copyright: Anirudha Surabhi)
  • Hat collapse
    If the person wearing the hat is involved in a crash, the material’s hexagonal air pockets collapse to absorb the impact. (Copyright: Anirudha Surabhi)
  • Testing times
    Laboratory tests show on the helmet shows the liner absorbs three times as much force as standard polystyrene helmets. (Copyright: Anirudha Surabhi)
  • Flying in
    The helmets are now in production and will be available from January in the UK and Japan, and summer in the US. (Copyright: Anirudha Surabhi)
The way a woodpecker is able to protect itself from long bouts of head banging influences the design of radical new head protection.

If ever there were a creature that seemed destined to suffer from concussions, it would be the woodpecker. It pounds its head at into tree trunks 12,000 times per day, at speeds of 6 to 7m/s. And yet, despite this frequent, high speed head banging, the birds experience no brain damage. Not a lick.

Luckily for the woodpecker, evolution has handed it a variety of anatomical adaptations that protect its head during all that hammering. And soon, we humans may also be able to keep concussions at bay using the woodpecker’s time-tested methods.

Industrial designer Anirudha Surabhi has created the new, super-strong Kranium bike helmet, which protect cyclists’ heads by mimicking features of the woodpecker’s distinctive anatomy.

Surabhi’s interest in building a better bike helmet is personal. Several years ago, he was riding his bike through Notting Hill in London when he had an accident. He was wearing a helmet but still ended up in the hospital with a concussion. “My fall wasn’t really that bad,” Surabhi says. “It was a minor fall, but still my helmet cracked.” 

At the time, Surabhi was doing a master’s degree in design at the Royal College of Art, and he just happened to be looking for an idea for his final solo project. He decided to try to build a better bike helmet - and to take inspiration from nature.

Researchers have discovered that woodpeckers have a variety of anatomical adaptations that protect their brains from injury. For instance, woodpeckers have a hyoid bone that is different from that of other birds. Normally, this y-shaped bone runs along the bottom of the mouth and to the back of the skull. But in many varieties of woodpecker, this bone is extra long, wrapping all the over the top of the skull. It acts as a natural seatbelt, keeping the brain from jostling around during impact.

But what caught Surabhi’s eye was another protective feature of woodpecker anatomy. “The woodpecker is one of the only birds on the planet where the beak and the skull are not joined together,” Surabhi says. The base of the beak and the skull are separated by a bit of flexible, spongy cartilage, which acts as a shock absorber and helps cushion repeated blows.

Racing ahead

Surabhi decided to try and recreate this kind of spongy layer and use it to line the inside of a bike helmet. He started building versions of this structure out of every material he could think of - glass, rubber, cork, carbon fiber - and put each of his 150 samples through laboratory crash tests. The material needed to be strong, able to protect the human brain from grave injury, but also lightweight.

The winner, it turned out, was a lining made out of material that isn’t commonly seen in bicycle helmets: cardboard. But not just any cardboard; Surabhi designed a special dual density cardboard with an internal honeycomb structure.

"Hexagonal elements exist all over nature and they provide protection from impact in almost all directions." says Surabhi.
The structure of the material is not quite the same as that used by woodpeckers. Their cartilage also has air pockets and voids, but they are distributed in a way that Surabhi says was hard to replicate using mass manufacturing. The hexagonal honeycomb structure, in addition to being strong, is also relatively straightforward to produce.

To construct the liner, Surabhi laser-cut individual ribs out of this honeycomb board and assembled them into an interlocking, helmet-shaped lattice. He intentionally designed this lattice to have more “give” than a standard polystyrene foam liner; in this event of a crash, this flex in the helmet helps to soften the blow. The air pockets inside each individual rib do the rest of the work—in a collision, the air-filled cells collapse, absorbing the rest of the impact and protecting the wearer’s head.

According to laboratory tests, the Kranium liner absorbs three times as much force as polystyrene helmets, and, because 90% of the liner is air, it’s also 15% lighter. 

What’s more, the liner, which is made of recycled paper, is also more eco-friendly than polystyrene, which is a petroleum-based product and is not biodegradable. Though Surabhi says his primary goal was to create a safer helmet, “the fact that it’s green and recyclable, is just a plus.” (Surabhi also dips the liners in a waterproof solution to keep them from degrading when exposed to sweat or rain.)

Surabhi is now working with a variety of companies to bring Kranium liners and helmets to market. The first helmets, he says, will be available for purchase in the UK and Japan in mid-January. Germany and Italy should see their own versions later this spring and customers in the US may be able to buy Kranium products by the end of the summer. He’s also received a major vote of confidence from Force India, a Formula 1 team that has asked Surhabi to design helmets for its pit crew.

So while we may not bash our heads into trees 12,000 times a day, in the future, we might just owe our brain health to creatures that do.


