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.
"[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