Based on the nanostructure of the sea urchin spines, team develops cement that is significantly more fracture-resistant

November 30, 2017, University of Konstanz
Sea urchin spines. Credit: University of Konstanz

Sea urchin spines are made mostly of calcite, but the spines are much more durable than this raw material alone. The reason for their strength is the way that nature optimises materials using a brick wall-style architecture. A research team headed by Professor Helmut Cölfen successfully synthesised cement at the nano-level according to this "brick and mortar" principle. During this process, macro-molecules were identified that take on the function of mortar, affixing the crystalline blocks to each other on the nano-scale, with the blocks assembling themselves in an ordered manner. The aim is to make cement more durable. The study's results are published in the 1 December 2017 issue of Science Advances.

"Our cement, which is significantly more fracture-resistant than anything that has been developed thus far, provides us with completely new construction possibilities," Cölfen says. A pillar made of this cement could be built 8,000 metres high, or ten times as high as the current tallest building in the world, before the material at its base would be destroyed by its weight. Normal steel, which has a value of 250 megapascals, could only reach 3,000 metres in height.

In nanoscience, brick wall-style architecture can be compared to the work of a mason: Each layer of brick that is laid is held in place by mortar. The guiding principle is to layer hard, then soft, hard, then soft materials. This is exactly the principle nature uses to make sea urchin spines so resilient. When force is applied to the brittle calcite, its crystalline block does crack, however, the energy is then transferred to a soft disordered layer. Since this material has no cleavage planes to tear, it prevents further cracking. A thin section of sea urchin spine reveals this structural principle: Crystalline blocks in an orderly structure are surrounded by a softer amorphous area. In the sea urchin's case, this material is calcium carbonate.

Bending experiment on elastic cement in a scanning electron microscope, enlarged 2,000 times Bar-shaped micro-structure precision-cut from nano-structured cement using an ion beam, bends under the pressure of a micro-manipulator without breaking (micro-manipulator left in the picture). Credit: Dr Zhaklina Burkhard

Mussel shells or bones are constructed in much the same way. "Our goal is to learn from nature," says Helmut Cölfen. The researcher has been honoured numerous times for his trailblazing results in the field of crystallisation, with, for example, the 2013 Academy Prize from the Berlin-Brandenburg Academy of Sciences and Humanities. Bionics or biomimetics is the term used for employing natural phenomena to inspire technical developments.

Cement itself has a disordered structure—each component sticks to all the others. This means that in order for cement to truly profit from the increased stability provided by brick and mortar construction, its structure will have to be reorganised at the nano-level. Helmut Cölfen describes the process as "encoding fracture-resistance at the nano-level." In this case, it means identifying a material that bonds only with cement nanoparticles and nothing else in the cement. About ten negatively charged peptide combinations were identified that both adhere to and bond materials well.

In collaboration with the University of Stuttgart, the team was able to use an ion beam under an electron microscope to cut a bar-shaped micro-structure out of the nanostructured cement that was three micrometers in size. This micro-structure was then bent using a micro-manipulator. As soon as it was released, the micro-structure returned to its original position. Mechanical values could be calculated based on the elastic deformation of the micro-structure. Based on these calculations, the optimised achieved a value of 200 megapascals. By comparison: Mussel shells, which are the gold standard in fracture-resistance, reach a value of 210 megapascals, which is only slightly higher. The concrete commonly used today has a value of two to five megapascals.

Micro-manipulator bending a cement microbar. Credit: University of Konstanz

See urchin spines and mussel shells are made of calcite, because large quantities of calcium are available in water. Helmut Cölfen explains: "People have much better construction materials than calcite. If we succeed in designing the structures of materials and reproduce nature's blueprints, we will also be able to produce much more fracture-resistant materials—high-performance inspired by nature."

Explore further: Technique offers advance in testing micro-scale compressive strength of cement

More information: Andreas Picker et al, Mesocrystalline calcium silicate hydrate: A bioinspired route toward elastic concrete materials, Science Advances (2017). DOI: 10.1126/sciadv.1701216

Related Stories

X-rays reveal why sea urchins are no easy prey

February 14, 2012

( -- The spine of a sea urchin is 99.9% chalk, a very common material forming tiny crystals that are very hard but easy to break apart. Scientists have now discovered how these marine animals use chalk or lime ...

Natural mother of pearl structure, synthetic replication

August 19, 2016

Biomaterials play a crucial role in the development of future high-performance materials. A naturally occurring example of such biomaterial, the mollusk shell, guides chemical replication processes in laboratories. Due to ...

How to make stronger, 'greener' cement

September 25, 2014

Concrete is the world's most-used construction material, and a leading contributor to global warming, producing as much as one-tenth of industry-generated greenhouse-gas emissions. Now a new study suggests a way in which ...

Sea urchin spines could fix bones

March 22, 2017

More than 2 million procedures every year take place around the world to heal bone fractures and defects from trauma or disease, making bone the second most commonly transplanted tissue after blood. To help improve the outcomes ...

Recommended for you

X-ray triggered nano-bubbles to target cancer

July 16, 2018

Innovative drug filled nano-bubbles, able to be successfully triggered in the body by X-rays, have been developed by researchers, paving the way for a new range of cancer treatments for patients.

Smart window controls light and heat, kills microorganisms

July 13, 2018

A new smart window offers more than just a nice view—it also controls the transmittance of sunlight, heats the interiors of buildings by converting solar radiation into heat, and virtually eliminates E. coli bacteria living ...

Quantum dot white LEDs achieve record efficiency

July 12, 2018

Researchers have demonstrated nanomaterial-based white-light-emitting diodes (LEDs) that exhibit a record luminous efficiency of 105 lumens per watt. Luminous efficiency is a measure of how well a light source uses power ...

How gold nanoparticles could improve solar energy storage

July 12, 2018

Star-shaped gold nanoparticles, coated with a semiconductor, can produce hydrogen from water over four times more efficiently than other methods—opening the door to improved storage of solar energy and other advances that ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.