Engineers at the University of Maryland (UMD) created the ‘morphing’ nozzle, which offers new ways of printing fibre-filled composites. The materials are made of short fibres that boost properties over conventional printed parts, such as enhanced strength or electrical conductivity.
The challenge, the researchers said, is that these properties are based on the orientations of the short fibres – something that was previously difficult to control during the printing process.
“When 3D printing with the morphing nozzle, the power lies in 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 UMD mechanical engineer Ryan Sochol.
To demonstrate their new approach, the researchers focused on ‘4D printing’ applications – creating 3D printed objects that can reshape or transform depending on their environment.
“In our work, we looked at how printed parts swelled when submerged in water, and specifically, if we could alter that swelling behaviour using our morphing nozzle,” said co-author David Bigio.
Recent advances in 4D printing rely on materials capable of both ‘anisotropic’ expansion – swelling more in one direction than another – as well as ‘isotropic’ expansion, swelling identically in all directions. Switching between these conditions has typically required researchers to print with multiple, different materials, however.
“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.
“Importantly, the nozzle's ability to morph and to even up the score in terms of swelling properties is not limited to 4D printing,” said co-author Noah Todd. “Our approach could be applied for 3D printing many other composite materials to customise their elastic, thermal, magnetic or electrical properties."
To build the morphing nozzle itself, the team used a different 3D printing technology known as polyjet printing. This multi-material inkjet-based approach allowed the researchers to 3D print their nozzle with flexible materials for the inflatable side actuators and the shape-changing central channel, and rigid materials for the outer casing and the access ports.
The team is exploring the use of the new technique to bulk-print biomedical objects that could change shape within the body. The team is also in discussions with the US Department of Defence about using the morphing nozzle to support the production of weapons.
The research was published in Advanced Materials Technologies.
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