Morphing nozzle allows 3D printing of custom fibre-filled composites

The nozzle offers the means for 3D-printing fibre-filled composites: materials made up of short fibres which have enhanced properties compared with traditional 3D printer parts, such as strength or electrical conductivity. These properties are based on the orientations of the fibres, which has previously been difficult to control during the manufacturing process.

“When 3D printing with the morphing nozzle, the power lies on their side actuators, which can be inflated like a balloon to change the shape of the nozzle, and in turn, the orientations of the fibres,” said Professor Ryan Sochol, a mechanical engineer at the University of Maryland.

The nozzle was built using 3D printing technology known as PolyJet Printing. This allowed them to 3D-print the nozzle with flexible materials for the inflatable side actuators and shape-changing central channel, while the outer casing and access ports were built from rigid materials.

The researchers set their sights on so-called “4D printing” applications. Professor David Bigio explained: “4D printing refers to the relatively new concept of 3D-printing objects that can reshape or transform depending on their environment.”

In this case, they focused on how printed parts swell when submerged in water and whether they could alter that behaviour using the morphing nozzle.

Recent advances in 4D printing rely on materials capable of both anisotropic expansion (asymmetric swelling) and isotropic expansion (swelling identically in all directions). However, switching between these properties has previously required printing with multiple materials.

“What was exciting was discovering that we could cause a single printed material to transition between anisotropic and isotropic swelling just by changing the nozzle’s shape during the 3D printing process,” said lead author Connor Armstrong.

In one potential application, the team of researchers is exploring using the nozzle in biomedical scenarios in which bulk-printed objects could reshape in the presence of certain stimuli from the body. They are also in discussions with US Department of Defence laboratories to use the nozzle to support the production of weapons for military systems.

The nozzle’s shape-changing ability could have other applications in 3D printing, such as to customise the elastic, thermal, magnetic, and electrical properties throughout an object.

“By providing researchers with an accessible way to 3D-print fibre-filled composite materials with on-demand control of their fibre orientations, and thus their ultimate performance, this work opens the door for new applications of 3D printing that harness these unique material properties and the distinctive capabilities they enable,” Sochol said.