Novel 3-D Printing Technique Mimics Nature, Can Produce High-Performance Composites Like Wood, Bones, Shells and Teeth

Image courtesy of Lewis Lab/Harvard SEAS

The work, described in the journal PNAS, was carried out in the Lewis lab at Harvard. Collaborators included then-postdoctoral fellows Brett Compton (now Assistant Professor in Mechanical Engineering at the University of Tennessee, Knoxville), and Jordan Raney (now Assistant Professor of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania); and visiting PhD student Jochen Mueller from Prof. Kristina Shea’s lab at ETH Zurich.

“Rotational 3D printing can be used to achieve optimal, or near optimal, fiber arrangements at every location in the printed part, resulting in higher strength and stiffness with less material,” Compton said. “Rather than using magnetic or electric fields to orient fibers, we control the flow of the viscous ink itself to impart the desired fiber orientation.”

Compton noted that the team’s nozzle concept could be used on any material extrusion printing method, from fused filament fabrication, to direct ink writing, to large-scale thermoplastic additive manufacturing, and with any filler material, from carbon and glass fibers to metallic or ceramic whiskers and platelets.

Image courtesy of Lewis Lab/Harvard SEAS

The technique allows for the 3D printing of engineered materials that can be spatially programmed to achieve specific performance goals. For example, the orientation of the fibers can be locally optimized to increase the damage tolerance at locations that would be expected to undergo the highest stress during loading, hardening potential failure points.

“One of the exciting things about this work is that it offers a new avenue to produce complex microstructures, and to controllably vary the microstructure from region to region,” Raney said. “More control over structure means more control over the resulting properties, which vastly expands the design space that can be exploited to optimize properties further.”

“Biological composite materials often have remarkable mechanical properties: high stiffness and strength per unit weight and high toughness. One of the outstanding challenges of designing engineering materials inspired by biological composites is control of fiber orientation at small length scales and at the local level,” said Lorna J. Gibson, Professor of Materials Science and Engineering at MIT, who was not involved in the research. “This remarkable paper from the Lewis group demonstrates a way of doing just that. This represents a huge leap forward in the design of bio-inspired composites.”

The Harvard Office of Technology Development has protected the intellectual property relating to this project.

Previously, Lewis has conducted groundbreaking research in the 3D printing of tissue constructs with vasculature, lithium-ion microbatteries, and the first autonomous, entirely soft robot.

Other contributors to the paper include Thomas Ober from Harvard SEAS and Kristina Shea from ETH Zurich.

The research was supported by the Office of Naval Research and GETTYLAB.