Multimaterial 3D printhead paves way for printed wearables, electronics
The "active" 3D printhead mixes viscoelastic inks using a rotational impeller inside a microscale nozzle (see image below) allowing – for the first time, say the researchers – both composition and geometry to be controlled simultaneously during printing. This differs from most mixing approaches, which passively converge streams of thin, flowing fluids into a single channel resulting in imprecise diffusive mixing.
The "active" 3D printhead mixes complex inks using an impeller rotating at a constant rate inside a microscale nozzle, allowing heterogeneous materials to be printed in three dimensions. (Credit: Wyss Institute at Harvard University)
Unlike such previous approaches, the new multimaterial printhead is also able to handle thicker, high-viscosity fluids like gels. This opens the way for flexible printing platforms that could potentially be able to seamlessly switch between printing both flexible and rigid materials, as well as multiple inks of varying conductivity and resistivity used to create electrical circuits.
"[This] latest technical advance enables fabrication of objects composed of different types of materials that are absolutely required for optimal function, yet could not be integrated seamlessly into a single unitary object with 3D printing in the past," says Donald Ingber, M.D., Ph.D., a Professor of Bioengineering at Harvard’s School of Engineering and Applied Sciences (SEAS), and Founding Director of the Wyss Institute for Biologically Inspired Engineering at Harvard.
In demonstrations, the research team showed that the printhead’s active mixing approach could seamlessly print silicone rubber into gradient architectures comprising soft and rigid regions, which could find potential application in areas like flexible electronics, wearables, and soft robotics. The printhead was also shown to be able to print reactive materials, such as two-part epoxies, as well mix conductive and resistive inks on demand, for potential embedding of electrical circuitry inside 3D printed objects.
The same team also recently designed another printhead that is able to rapidly switch between multiple inks within a single nozzle. This eliminates the printing errors that often occur with other printheads during the start-and-stop process of switching materials and aligning multiple nozzles.
"Together, these active mixing and switching print heads provide an important advance for multi material 3D printing," says lead researcher Jennifer A. Lewis, a Core Faculty Member at the Ways Institute and the Hans Ways Professor of Biologically Inspired Engineering at SEAS. "They allow one to programmable control both materials composition and structure at the micro scale, opening new avenues for creating materials by design."
For more, see the paper published in the Proceedings of the National Academy of Sciences: Active mixing of complex fluids at the micro scale
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