Scientists from Harvard University and MIT used a ceramic foam ink to develop their method, with allows for the 3D-printing of materials with independently tunable macro-and microscale porosity, they said. Their approach has a number of applications and can be used to fabricate lightweight structural materials, thermal insulation, or tissue scaffolds, among others.
The team was inspired by natural cellular structures and their ability to have remarkable structural capabilities despite being limited in design, according to researchers. For example, grass can support its own weight, resist strong winds, and recover even after being compressed, characteristics that are due to a combination of its hollow, tubular macrostructure and porous, or cellular, microstructure.
Harvard and MIT researchers used 3D printing to fabricate lightweight hexagonal and triangular honeycombs (pictured) with tunable geometry, density, and stiffness using a ceramic foam ink. Their approach could be used to fabricate lightweight structural materials, thermal insulation, or tissue scaffolds. Foam ink can be made from a number of materials aside from ceramic, including metal or polymer. (Source: James Weaver/Wyss Institute)
Inspired by this, researchers worked with a ceramic foam ink comprised of alumina particles, water, and air, controlling its microstructure to tune the ink’s properties and how it deformed on the microscale, said Jennifer Lewis, a professor of biologically inspired engineering at Harvard’s John A. Paulson School of Engineering and Applied Sciences and senior author of a paper about the work published in the journal Proceedings of the National Academy of Sciences. Once they optimized the ink, the team printed lightweight hexagonal and triangular honeycombs, with tunable geometry, density, and rigidness, she said.
“By expanding the compositional space of printable materials, we can produce lightweight structures with exceptional stiffness,” Lewis said. “This work represents an important step toward the scalable fabrication of architected porous materials.”
Researchers chose to use a foam ink because the material makes it possible to digitally pattern cellular microstructures within larger cellular macrostructures, said Joseph Muth, a graduate student studying with Lewis in her lab.
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“After the ink solidifies, the resulting structure consists of air surrounded by ceramic material on multiple length scales,” he said. “As you incorporate porosity into the structure, you impart properties that it otherwise would not have.”
Foam inks also are flexible in the type of materials from which they can be developed. Though the team used only a single ceramic material for the ink used in the research, it’s possible to make printable foam inks from other ceramics, as well as metals and polymers, Muth said.
The research shows how 3D printing can be used 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,” he added.
Harvard’s Office of Technology Development has filed a patent application for the method the team developed and is currently considering how to commercialize the research.