18-05-2025
World's smartest shell? New armor material reacts in real time to crashes and impacts
Nature has spent millions of years building better protection.
Think of a turtle's shell, the hard outer shell of a crab, or the shiny inside of a seashell. These aren't just for show.
They help animals survive by spreading out force, soaking up impacts, and bending instead of breaking.
Now, engineers are using those same ideas to create a new kind of man-made material.
Inspired by seashells in particular, they've built a layered synthetic material that doesn't just take a hit but adapts to it.
Each layer is designed to react differently, and all the layers work together to soften the blow.
The new study, led by civil and environmental engineering professor Shelly Zhang from the University of Illinois Urbana-Champaign and professor Ole Sigmund from the Technical University of Denmark, shows how this material could one day make things like car bumpers or wearable protection much smarter and safer.
A practical way forward might seem simple: just copy how natural protective layers work.
But the researchers chose to go a step further. Instead of reverse-engineering nature, they developed a method to program individual layers to work together under stress.
One natural material in particular stood out: nacre, or mother-of-pearl. Found inside seashells of mollusks like oysters and abalones, nacre is made of microscopic layers that make it both hard and surprisingly tough.
Scientists have long admired it for how well it absorbs force without cracking.
Inspired by nacre's toughness, they designed synthetic layers that respond in a coordinated, adaptive way.
'We landed on the idea to design multilayered materials with each layer being capable of exhibiting different properties and behaviors,' Zhang said.
This collective behavior marks a shift from earlier approaches that treated layers as isolated or static.
In this new design, the layers actively collaborate, changing how force travels through the material.
Buckling is what happens when a material suddenly bends or collapses under pressure, like when a metal can crumples under too much force.
In most cases, it signals failure. But here, the researchers use it as a controlled response.
Depending on the impact, the synthetic layers buckle in stages. This staggered response helps spread out the force and absorb more energy than traditional shock-absorbing materials.
'This work was born out of a discussion with my collaborator, Professor Sigmund, about how we already can achieve some very extreme behaviors, but there's always a physical limit or upper bound that single materials can achieve, even with programming,' Zhang said.
'That led us to consider what kind of engineering could enable some of the crazy material behaviors needed in real life. For example, extreme buckling behaviors could help dissipate energy for things like car bumpers.'
The researchers didn't just assign properties to each layer. They programmed the micro-level connections between them, creating a material that acts like a single, intelligent unit.
'Our new framework presents several advantages over existing methodologies for nonlinear stress-strain responses,' Zhang said.
'It optimizes nacre-like multiple layers along with their interconnections in a continuum setup, which significantly expands the design space compared to similar work involving a single-layer setup or lattice structures.'
When the team built physical prototypes, the materials didn't behave exactly as the models predicted. But the researchers saw that as useful.
'The discrepancy we found is something that will always happen in real life,' Zhang said.
'But we can harness this information to intentionally program the sequence of the buckling of each of the individual cells in assembly, store some information inside, and then later we can decode the information. It was fascinating to capture this discrepancy and for it to end up providing information needed to improve the work.'
Zhang says large-scale manufacturing is still a hurdle. But the core idea is already a breakthrough. 'I think it works the same for materials,' she said.
'When different materials collectively work together, they can do things that are much more impactful than if they do things individually.'
The study findings are published in the journal Science Advances.
