Novel active mixing and switching printheads enable 3D printing of complex fluids and gels

Three dimensional printing is revolutionizing the production of new devices and structures, including soft robots, flexible electronics and engineered tissue replacements, but advances have been challenged by the inherent complexity of integrating multiple materials. Now, breaching the next frontier in 3D printing, Jennifer A. Lewis, Sc.D., has designed new systems to actively mix and print concentrated viscoelastic inks that, for the first time, allow for the simultaneous control of composition and geometry during printing.

A new “active” 3D printhead, developed by Wyss Core Faculty member Jennifer Lewis, mixes complex inks using a rotational impeller inside a microscale nozzle, allowing heterogeneous materials to be printed in three dimensions.

Lewis is a Core Faculty member at the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Hansjörg Wyss Professor of Biologically Inspired Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS).

The goal of integrating different material and structural properties within printed objects has demanded the invention of new, flexible printing platforms. For example, to print a functional “wearable” device including its electronic components, a 3D printer would need to seamlessly transition from the flexible material that moves with the wearer’s joints to the rigid material that holds the electronic components. It would also need to embed electrical circuitry with multiple inks of varying conductivity and resistivity, precisely switching between them. And, it would be ideal to do all of this inside one continuous print job with active mixing of complex fluids.

But until now, most mixing approaches are passive, so that two streams of fluids converge into a single channel where they undergo diffusive mixing. This method works well with thin, flowing fluids with low-viscosity, but is ineffective with thicker, high-viscosity fluids like gels, especially in small volumes over short periods of time.Read more

Source: Wyss Institute, Harvard University