Biomimicry in 3D printing?

New rotational 3D printing method developed by Harvard researchers allows engineered composites to mimic nature.

When you really think about it, tree limbs and bones don’t break as often as you might expect them to. Natural composite materials such as wood and bone are low in weight and density, yet are strong and sturdy. This is often due to complex and diverse arrangements of fibers within a system. While humans have fabricated increasingly complex composite materials throughout history, achieving the same kind of intricate microstructures and mechanical benefits as those found in nature is a challenge.

Researchers at Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS, Cambridge, MA, US) have come up with a new 3D printing method inspired by natural composites. The idea was to achieve the best arrangement of short fibers at each location of the part being printed.

“Being able to locally control fiber orientation within engineered composites has been a grand challenge,” says Jennifer A. Lewis, senior author of the study and Hansjorg Wyss Professor of Biologically Inspired Engineering at Harvard SEAS. “We can now pattern materials in a hierarchical manner, akin to the way that nature builds.”

The team’s paper, published in February in the Proceedings of the National Academy of Sciences, calls the method “rotational 3D printing.” The process uses a nozzle capable of varying rotation speeds relative to the printing speed to control the fiber orientation within a polymer matrix – resulting in materials optimized for stiffness, strength and damage tolerance. 

While Lewis’ team worked to create carbon fiber-epoxy composites, the method could have far-reaching applications. The rotating nozzle concept could theoretically be used with any material extrusion printing method including direct ink writing, fused filament fabrication (FFF) and thermoplastic additive manufacturing. Different fillers – carbon, glass, metallic or ceramic – as well as different matrix combinations can be used yield a range of properties in the printed objects.

Nature is a tough act to follow, but by following her lead this advancement in additive manufacturing takes engineered composites yet another level of complexity and versatility – it will be exciting to see how it is used. 

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