The importance of geometry in materials...

3-D-printed “gyroid” models such as this one were used to test the strength and mechanical properties of a new lightweight material. Credit: Melanie Gonick/MIT

MIT researchers have found a way to create 3D objects with 2D layers of graphene. Graphene is like a sheet one carbon atom thick, as thin as it gets, so we may say it is a 2D object (it is not alone, scientists have managed to create a few other 1-atom thick layers compounds).

Moving from a 2D structure to a 3D structure is not easy at all! Hence the interest for the result obtained at MIT.

The result is a material that is 10 times stronger than steel with a density that is just 4.6% of steel.

What is really interesting in this research is that the strength is not 100% depending on the material used (graphene), rather it is the result of the geometry used in the structure of the object. This is not surprising if you think that a thin sheet of paper is so easy to crumple. However if you roll the sheet into a tube that same sheets gets much stronger!

The researchers modelled on a computer the interactions among molecules and turned out a specific geometry that yields exceptional strength. The resulting object is also full of "empty" space so that overall its density is extremely low.

By using specific pressure and heat they have couched graphene to assemble into this kind of structures, known as gyroids. 

They demonstrated the crucial role of the geometry in the structure by using a 3D printer to create a prototype. Surprisingly, they also demonstrated (watch the video) that the thinner the walls forming the structure are, the more strength it has, which is clearly counterintuitive. 

A true discovery? Well, actually ... no! It turns out that Mother Nature has already created these kinds of structures in corals and diatoms (microscopic shells living in the sea). Yet, finding a process to replicate this is a great success!

Author - Roberto Saracco

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