Feb 7, 2017 | By Benedict

Using a ceramic foam ink, scientists from Harvard and MIT have developed a new method for 3D printing materials with independently tunable macro-and microscale porosity. The technique could be used to 3D print lightweight structural materials, thermal insulation, and tissue scaffolds.

Some of the best inspiration for engineering and design can be found in nature—whether it’s bats engendering new drones or shrimp inspiring football helmets. A group of top research scientists has now found inspiration in grass, whose tubular macrostructure and porous microstructure makes it robust enough to withstand strong winds and frequent compression. Seeking to replicate these properties in a 3D printed material, the Harvard and MIT scientists developed a new 3D printing technique that uses a ceramic foam ink to create materials with independently tunable macro-and microscale porosity.

The researchers, who come from the Wyss Institute for Biologically Inspired Engineering at Harvard University, the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), and MIT, believe that their new 3D printing technique could be used for a variety of purposes, including the fabrication of lightweight structural materials, thermal insulation, or tissue scaffolds. Their findings have been published in the journal Proceedings of the Natural Academy of Science.

“By expanding the compositional space of printable materials, we can produce lightweight structures with exceptional stiffness,” said Jennifer A. Lewis, Sc.D., a Core Faculty member of the Wyss Institute who is also the Hansjörg Wyss Professor of Biologically Inspired Engineering at SEAS and senior author of the paper. Lewis is the Founder and Chief Scientific Advisor at 3D printer developer Voxel8, whose Developer’s Kit 3D printer can be used to print embedded electronics.

The ceramic foam ink used to 3D print the grass-inspired materials contains alumina particles, water, and air. By controlling the microstructure of the ink, the researchers were able to alter the its properties, changing the way it deformed on the microscale. Lightweight porous honeycombs, triangular and hexagonal, were then 3D printed with different configurations of geometry, density, and stiffness.

“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.”

Lorna Gibson, Ph.D., the Matoula S. Salapatas Professor of Materials Science and Engineering at the Massachusetts Institute of Technology and coauthor of the paper, said that the new ceramic foam ink 3D printing technique “combines the best of both worlds,” since it offers both microstructural control (via foam processing) and global architectural control (via 3D printing). “Because we’re printing something that already contains a specific microstructure, we don’t have to pattern each individual piece,” Gibson said. “That allows us to make structures with specific hierarchy in a more controllable way than we could do before.”

The researchers say that the new 3D printing method allows them to create multifunctional materials whose material properties can be finely tuned, while printing can be completed in just one step. Excitingly, there is also room for development of the technique, since other printable foam inks besides ceramic ones—metals, polymers etc.— could also be used.

“This work represents an important step toward the scalable fabrication of architected porous materials,” said Lewis.

Posted in 3D Printing Materials

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