3D printed ceramics, inspired by nature
Robocasting can produce strong components with intricate internal structures
3D printing (also known as additive manufacturing) is advancing by leaps and bounds, and has been used to make everything from customised prosthetics to a concrete bridge. Behind the scenes it is revolutionising rapid prototyping, and there’s even a 3D printer on the International Space Station. Sub-micron 3D printing now offers a fantastic level of control, and produces items with remarkable properties, but is a slow process that is impractical for manufacturing larger objects.
For some time, scientists have known about the remarkably complex internal structures of natural materials such as bone, wood and mother-of-pearl, which give them resistance to cracks and fractures. Replicating these structures with traditional manufacturing methods is impossible, but recent research published in Scientific Reports has demonstrated that 3D printing can be used to produce bio-inspired structures in a reasonable timeframe.
The 3D printing technique used by the researchers is called robocasting, in which a paste is extruded through a computer-controlled nozzle, building up objects layer by layer. Although, to date, most development has focused on 3D printing with polymers and metals, robocasting can be used to ‘print’ with a wide range of materials, including graphene, bioactive and ferroelectric materials, and ceramics.
A key feature of these experiments was the high percentage of ceramic material in the printed objects, achieved using alumina platelets. Controlling both the composition of the ceramic paste and the shear forces in the nozzle, the researchers were able to print ceramic components with incredibly complex microstructures that offered resistance to cracks and fractures in three dimensions. The researchers used X-ray tomography on the I13-2 beamline to quantify platelet alignment in the nozzle. They found the mechanical properties of the printed objects to be comparable to engineering materials such as carbon fibre reinforced epoxy composites (CFRP).
Lead author of the paper, Ezra Feilden, says that “this research has demonstrated that very promising mechanical properties can be achieved when experimenting with just one structure inspired from natural materials. With many thousands of natural structures to choose from, there may be undiscovered opportunities to create materials with greatly improved mechanical properties using the techniques developed in this work.”
The strong and lightweight components produced via this method will be of interest across a wide range of industries, from aerospace and automotive to bioengineering. Further work will focus on producing more complex internal structures, exploring different materials for the printing pastes, and improving strength even further (e.g. by the addition of reinforcing fibres).
Feilden, E et al. 3D Printing Bioinspired Ceramic Composites, Scientific Reports 7.1 (2017).