Researchers at Harvard and MIT have 3D printed lightweight porous honeycombs with tunable stiffness, geometry, and density using a ceramic foam ink.

3D printing offers a new level of control over structures for everything from engines to buildings. However, researchers are now using the same approach to potentially fabricate tissue scaffolds, lightweight structural materials, and thermal insulation.

For this, researchers from Wyss Institute for Biologically Inspired Engineering at Harvard University, the Harvard John A. Paulson SEAS, and MIT are working together.

The researchers were inspired by nature to develop a new method to 3D print materials with independently tunable macro and microscale porosity. To do this, they used ceramic foam ink.

Although often overlooked, grass is the inspiration behind this new idea. Even though it has limited design materials, it can support its weight. It also regularly resists strong winds and recovers after being stood on. The reason behind this is its porous microstructure and hollow macrostructure.

Jennifer Lewis, Sc.D., is a Core Faculty member of the Wyss Institute and the Hansjörg Wyss Professor of Biologically Inspired Engineering at SEAS. She is also senior author of the paper. She adds: “By expanding the compositional space of printable materials, we can produce lightweight structures with exceptional stiffness.”

Mimic Nature’s Cellular Architectures with Ceramic Foam

Joseph Muth is a graduate student in the Lewis Lab and author of the paper. He  said:

“Foam inks are interesting because you can digitally pattern cellular microstructures within larger cellular macro-structures. 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.”

The researchers would tune the ink’s properties by controlling the foam’s microstructure. They could then control how it deformed on the microscale.

After this optimization, they 3D printed lightweight honeycombs, as you can see in the video above. The result is that these structures have tunable geometry, density, and stiffness.

By printing something which already has a specific microstructure determined, the researchers cut out the need to pattern each piece. This allows the researchers to make structures with specific hierarchy in a more controllable way than before.

Muth adds: “We can now 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.”

For this project, the team focused on just one ceramic material for printing. However, printable foam inks can be made from many other materials such as polymers, metals, and ceramics.

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

The research was supported by the Harvard Materials Research Science and Engineering Center National Science Foundation. Want to read more? The research is published in the Proceedings of the Natural Academy of Science.

Source: WYSS Institute