Ceramic foam inks used to control the structure of 3D printed materials

Researchers are looking towards nature to help develop a new method to 3D print materials.

Harvard and MIT researchers 3D printed lightweight hexagonal and triangular honeycombs (pictured here), with tunable geometry, density, and stiffness using a ceramic foam ink. Image courtesy of James Weaver/Wyss Institute

A collaboration between the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), the Wyss Institute for Biologically Inspired Engineering at Harvard University, and MIT have led researchers to 3D print materials with independently tunable macro-and microscale porosity using a ceramic foam ink.

When first exploring this concept, the team examined the architectural features of a blade of grass, which supports its own weight, can stand up to wind pressure and bounce back after being bent. A blade of grass is able to do these things due to its hollow, tubular macrostructure and porous, cellular microstructure.

The team believes that by replicating these mechanical properties they will be able to fabricate lightweight structural materials, thermal insulation or tissue scaffolds.

The ceramic foam ink being used in the process 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 and first author of the paper. “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 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 and senior author of the paper. Lewis is also a Core Faculty Member of the Wyss.

The team was able to control the foam’s microstructure by exploring how it deformed on the microscale and tuned the ink’s properties accordingly. They were then able to print lightweight hexagonal and triangular honeycombs, with tunable geometry, density, and stiffness.

This process really enables the best of both worlds. According to Lorna Gibson, the Matoula S. Salapatas Professor of Materials Science and Engineering at the Massachusetts Institute of Technology, who coauthored the paper, “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.”

The team primarily explored using a single ceramic material for this research; however, printable foam inks can be made from many materials, including other ceramics, metals, and polymers.

The research is published in the Proceedings of the Natural Academy of Science.

www.seas.harvard.edu