New bone-like material is lighter than water but as strong as steel

Feb 03, 2014 by Akshat Rathi, The Conversation
Lighter, stronger, better. Credit: Jens Bauer

Materials shape human progress – think stone age or bronze age. The 21st century has been referred to as the molecular age, a time when scientists are beginning to manipulate materials at the atomic level to create new substances with astounding properties.

Taking a step in that direction, Jens Bauer at the Karlsruher Institute of Technology (KIT) and his colleagues have developed a bone-like material that is less dense than water, but as strong as some forms of steel. "This is the first experimental proof that such materials can exist," Bauer said.

Material world

Since the Industrial Revolution our demand for has outstripped supply. We want these materials to do many different things, from improving the speed of computers to withstanding the heat when entering Mars' atmosphere. However, a key feature of most new materials still remains in their strength and stiffness – that is, how much load can they carry without bending or buckling.

All known materials can be represented quite neatly in one chart (where each line means the strength or density of the material goes up ten times):

The line in the middle at 1000kg/m3 is the density of water – all materials to its left are lighter than water and those on the right are heavier. No solid material is lighter than water unless it is porous. Porous materials like wood and bone exhibit exquisite structures when observed under a microscope, and they served as inspiration for Bauer's work.

Credit: Jens Bauer/PNAS

For many years, material scientists have thought that some empty areas on the compressive strength-density chart should be filled by materials that theory predicts. Computer simulations could be used to indicate an optimum microstructure that would give a material the right properties. However, nobody had tools to build materials with defined patterns at the scale of a human hair.

With recent developments in lasers and 3D printing, however, a German company called Nanoscribe started offering lasers that could do just what Bauer wanted. Nanoscribe's system involves the use of a polymer that reacts when exposed to light and a laser that can be neatly focused on a tiny spot with the help of lenses.

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A drop of a honey-like polymer is placed on a glass slide and the laser is turned on. A computer-aided design is fed into the system and the slide carefully moves such that the laser's stationary focus touches only those points where the material is to be made solid. Once complete, the extra liquid is washed away, leaving behind materials with intricate internal structures.

However, these materials on their own are not as strong as Bauer wanted. So he coats them with a thin layer of alumina (aluminium oxide) before subjecting them to stress tests. Based on the tests, he was able to improve the theoretical models he used to design the of the materials. Their results were just published in the Proceedings of the National Academy of Sciences.

Even though alumina layers increase the density of these materials, all of them remain lighter than water. Bauer's strongest material has a specific honeycomb internal structure and is coated with a 50 nanometre-thick (billionth of a metre) layer of alumina. It beats all natural and man-made materials that are lighter than 1000kg/m3, being able to withstand a load of 280MPa (mega pascals is a unit of measuring pressure), which makes it as strong as some forms of steel.

There are limitations. Nanoscribe's system can only make objects that are tens of micrometres in size. "One of their newer machines can make materials in the milimetre-range, but that's about it for now", Bauer added. But that is not enough for any real-life application.

However, there have been rapid improvements in all the areas this work relies on: 3D printing, new polymers and laser technology. That means we may soon have a suite of new, super lightweight for everything from skis to aircraft parts. If nothing else, Bauer's work shows that we are definitely in the molecular age.

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Argiod
3.3 / 5 (4) Feb 03, 2014
Some day I could see a variation of this tech being used to print new bones and joints, custom designed to exactly duplicate the original bone or joint (using MRI or other scanning technique to get a 3-D image that can be 'printed' in situ...) directly into the body... for a perfect fit.
Star Trek replicator tech, anyone?
TheGhostofOtto1923
4 / 5 (4) Feb 03, 2014
Some day I could see a variation of this tech being used to print new bones and joints, custom designed to exactly duplicate the original bone or joint (using MRI or other scanning technique to get a 3-D image that can be 'printed' in situ...) directly into the body... for a perfect fit.
Star Trek replicator tech, anyone?
Well I can see it too because I have a computer.
http://phys.org/n...one.html
http://www.lunenf...anadians

-Aw youre just trolling arent you?
210
5 / 5 (2) Feb 03, 2014
"...Aw youre just trolling arent you?..."

IT IS getting hard to tell isn't it Ghostly one...!? I had to give you a five for just sayin'
Moebius
5 / 5 (1) Feb 04, 2014
The future of 3D printing is to eventually be able to put any atom anywhere and build things atom by atom making perfect structures. The only limit on what atoms we can use and how big we can build things with this tech will be economic.
Ralph
5 / 5 (2) Feb 04, 2014
You wrote, "No solid material is lighter than water unless it is porous." That just isn't true. For example, the density of ordinary solid candle wax is about 900 kg/m^3.
ahaveland
not rated yet Feb 06, 2014
It would be stronger if the all the rods were concave instead of convex and the nodes 'blobby', and especially if tetrahedral like diamond, though that may increase its density.
sirchick
1 / 5 (1) Feb 08, 2014
The future of 3D printing is to eventually be able to put any atom anywhere and build things atom by atom making perfect structures. The only limit on what atoms we can use and how big we can build things with this tech will be economic.


Building atom by atom for 3D printing would surely take for ever for something on the scale of human bones, but for computer technology it makes sense...

For bones would it not be better to carve the shape out with laser precision ?