New 3D-printed cycling helmet could be ‘safer, lighter and more comfortable’, but researchers admit design still needs more comprehensive testing

“With further development, this technology could lead to a new generation of bicycle helmets that are safer, more comfortable and more customisable.”

That is the claim of University of Gothenburg researchers who have this month unveiled an “innovative” new helmet design made with 3D-printed “auxetic metastructures” that offer “better protection” and come in lighter than current products.

Not got a clue what an auxetic metastructure is? Don’t worry, we’ll get to that in a second. Although maybe we should temper the claims of the paragraphs above by also mentioning now that the study concludes by admitting that, while testing and numerical simulation results do currently “meet the standard requirements”, any further implementation will necessitate “a comprehensive testing protocol”.

This should include, the academics admit, “testing multiple helmets under repeated impacts at varying angles and velocities and across a range of environmental temperatures, adhering to the relevant standard”. So we’re not at the finished product just yet, even if Mohsen Mirkhalaf (an associate professor of mechanics and physics of materials at the University of Gothenburg) and his team are confident we could be at some point in the not-so-distant future.

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So, back to the question on everybody’s lips — what is an auxetic metastructure and why is it relevant for what I put on my head when I go for a bike ride?

Thankfully the paper — ‘Design, optimization and additive manufacturing of an innovative bike helmet using auxetic metastructures’, published in the International Journal of Solids and Structures — offers the diagram below to demonstrate the concept but, in short, it refers to the design of the helmet whose “honeycomb” shock-absorbing material is designed in “special geometric patterns that behave differently under impact conditions compared to conventional foam liners”.

We’ve seen this sort of thing before, for example the Hexr helmet which used a 3D printed honeycomb construction that independent testing says performs 26 per cent better than the average lid. 

Then there was Bontrager’s WaveCel tech with its layers that “move independently and flex until the cell walls crumple and then glide, actively absorbing direct and rotational energy and redirecting it away from your head”.

We put these examples to Mirkhalaf and asked what exactly the difference was between their idea and the already established products, something he said was down to the use of an “auxetic metastructure”, coming back to the earlier diagram comparing it to other ‘honeycomb’ designs.

“Auxetic metastructures have been shown to offer enhanced energy absorption capabilities compared to conventional structures,” he said. “This is highly relevant for a helmet and helps to develop safer helmets because they can absorb impact energy better.

“When exposed to energy from an impact, the liner material contracts, and this improves the absorption of impact energy, which means lower risks of injuries to a cyclist’s head in an accident,” Mirkhalaf explains, the process seeing nine design structures with the suggested dimensions created and subsequently simulated through helmet impact tests.

“We used a specific design optimisation method to identify the best possible geometric configuration to minimise crash forces. The geometry of the material structure is a key factor.”

The designs’ impact tests were carried out on a flat and kerbstone anvil, the paper concluding that “both the experimental test and the numerical simulation results meet the standard requirements”, which demonstrates the auxetic liner “is able to effectively absorb and dissipate energy, providing adequate protection to the wearer”.

Naturally, as this is just the initial design for a helmet liner, there is plenty more work to be done to produce a final helmet which would, of course, then need the “comprehensive testing” the researchers admitted would be necessary. They suggest the next step would be to manufacture their design using a TPU material and the helmet shell using a PETG material with a 3D printer.

You would then need all the finishings, such as the strap, and the whole thing constructed, the researchers noting that due to the geometry and angle of the liner, there would be “no need to use glue for the connection”.

Because of the subject matter the headline act is always going to be the safety claims, Mirkhalaf and his team suggesting the design has “the potential to enhance energy absorption and reduce the risk of head injuries” and their findings can “provide valuable insights” for helmet manufacturers, researchers, and regulatory bodies.

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However, he also sees performance and comfort gains too, with potential for lighter, more comfortable and more customisable helmets thanks to the material and 3D-printing involved, which means designs could be customised to an individual’s head shape and benefit users who struggle to find a comfortable lid that works for them.

“The knowledge of auxetic metastructures that expand laterally when stretched has been around for almost 40 years. However, development of different metastructures has exploded due to the advancements in 3D-printing technology,” Mirkhalaf said.

“With further development, this technology could lead to a new generation of bicycle helmets that are safer, more comfortable and more customisable. Although 3D-printing technology currently is more expensive than mass-produced foam liners, costs are expected to fall as the technology becomes more widely used. In the future, it may even be possible to have personalised helmets printed on demand, ensuring that each rider receives the best possible protection.”

It has been a news-heavy week for helmet tech. On Monday, we brought you a look at British brand Venete’s aH+1, an inflatable helmet that is said to deflate to 10 per cent of its inflated size, making it more compact than a laptop when stored. 

It will set you back £350, including the pump, and Venete says it meets full EU and UK certification standards, although many of the figures cited in its study relate solely to linear risk. Our review will be going live shortly.