Science News

Bones inspire new synthetic materials

Thu, 6th Feb 2014

Harriet Johnson

Scientists have copied the structure of bone to create a strong yet Microarchitecturelight synthetic material.

Making something strong but light is a holy grail of engineering and technical development. Technical foams have gone some of the way to achieving this, yet do not have the strength comparable with bulk materials such as steel.

The natural world has solved many mechanical problems through adaption and evolution, although it can take millions of years to get it right.

Not wanting to wait this long, researchers in Germany have looked at how bones achieve a winning combination of strength and low weight.

Bone is composed of tiny particles that work like nanosized building blocks that organise themselves into a minute framework. This structure leaves small gaps between the particles, making the material light.

Using 3D laser printing, Jens Bauer and his team, publishing in the Proceedings of the National Academy of Sciences journal, have been able to replicate bone microarchitecture in ceramics and create synthetic materials which, for their weight, are stronger than any natural or man-made materials. 

Surprisingly, the smaller something is, the stronger it is. You may be able to snap a credit card in half once, but try to break the remaining half and it will be much harder. Because the internal framework - or microarchitecture - of the bone is so small, it is much harder to crush.

The team tried many different patterns for their framework. Taking further inspiration from natural mechanics, the honeycomb pattern was found to provide the strongest structure, with a performance equivalent to high-strength steels. 

However it will be a while yet before we see these new materials in use, as Jens Bauer explained "it is in the experimental stage ... the little cubes you see in the paper, it takes one hour to make one of those [to] produce a sample an inch by an inch would take weeks or years" he added, due to the small size "some first applications could be cushions for microelectronical devices or for filtration in microfluidics".

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It is not necessarily new to incorporate air into a structure.  Your basic foam is essentially air + polystyrene.  Some of the lightest materials are Aerogel, aerographite. and metallic microlattice.

3D Printing may allow creating very custom engineering structures.  For example one might design a hard, dense shell, covering a loose webbing, and potentially even add strand orientation for expected stress patterns.  Of course one may also be able to engineer non-printing methods to merge a shell over a lattice structure.

Honeycombs are strong structures, and it sounds like there may be a benefit of miniaturizing the honeycomb size.

As far as bone...  would it be possible to engineer osteoblasts and osteoclasts to maintain your artificial structure?
CliffordK, Thu, 13th Feb 2014

As one of our most common building materials, iron is strong, but also very dense.

It's not commercially available at present, but some forms of carbon (like diamond, carbon nanofibers and graphene) are strong, but much lower density than iron. evan_au, Sat, 15th Feb 2014

As has been done for many years in building aircraft wings. Several light aircraft use a GRP shell over styrofoam to give a more continuous contour than you can get with conventional ribs, and simple model planes use self-skinned polyurethane which is virtually crashproof.

The real fun trick, however, would be to design a material as intelligent as bone, which responds to stress by increasing its local rigidity.

Which is why we use it to make lattice frameworks which we infill with insulating materials like wood, brick, concrete foam,  etc. The joy of steel is that it isn't brittle and can be joined by screwing or welding sheets and girders. These techniques are much easier to apply in the field (literally) than laying up fiber reinforcements and carefully degassing and annealing the resin bonding material round them, and steel doesn't suffer catastrophic local failure if you drill or cut it after assembly.  alancalverd, Sat, 15th Feb 2014

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