Harvard researchers have drawn inspiration from natural cellular structures to 3D print materials with independently tunable macro-and microscale porosity using a ceramic foam ink.
The new approach spearheaded by researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), the Wyss Institute for Biologically Inspired Engineering at Harvard University, and MIT, represents an important step toward the scalable fabrication of architected porous materials.
“By expanding the compositional space of printable materials, we can produce lightweight structures with exceptional stiffness,” said Jennifer Lewis, Hansjorg Wyss Professor of Biologically Inspired Engineering at SEAS.
The ceramic foam ink used by the Lewis Lab contains alumina particles, water, and air.
“Foam inks are interesting because you can digitally pattern cellular microstructures within larger cellular macrostructures,” said Joseph Muth, a graduate student in the Lewis Lab. “After the ink solidifies, the resulting structure consists of air surrounded by ceramic material on multiple length scales. As you incorporate porosity into the structure, you impart properties that it otherwise would not have.”
By controlling the foam’s microstructure, the researchers tuned the ink’s properties and how it deformed on the microscale. Once optimized, the team printed lightweight hexagonal and triangular honeycombs, with tunable geometry, density, and stiffness.
“This process combines the best of both worlds,” said MIT Professor Lorna Gibson.“You get the microstructural control with foam processing and global architectural control with printing. Because we’re printing something that already contains a specific microstructure, we don’t have to pattern each individual piece. That allows us to make structures with specific hierarchy in a more controllable way than we could do before.”
Muth intoned that it was now possible to make multifunctional materials, in which many different material properties, including mechanical, thermal, and transport characteristics, can be optimized within a structure that is printed in a single step.
While the team has focused on a single ceramic material for this research, they contend that printable foam inks can be made from many materials, including other ceramics, metals, and polymers.
Image, excerpts and video credits: Harvard SEAS