This 3D Printer DNGE "Ink" Delivers Flexible Devices Without Mechanical Joints

"The beauty of our approach," says EPFL's Esther Amstad, "is that anyone with a standard bioprinter can use it."

EPFL researchers have come up with a novel elastomer-based "ink" for 3D printing functional devices that are flexible yet lack bulky mechanical joints — suggesting that it could be an ideal way to created soft actuators, sensors, and wearables.

"Elastomers are usually cast so that their composition cannot be changed in all three dimensions over short length scales. To overcome this problem, we developed DNGEs: 3D-printable double network granular elastomers that can vary their mechanical properties to an unprecedented degree," explains Esther Amstad, head of EPFL's Soft Materials Laboratory and corresponding author on the paper. "The beauty of our approach is that anyone with a standard bioprinter can use it."

Using an off-the-shelf CELLINK BIO X 3D printer, PhD student Eva Baur used the DNGE "ink" to print a prototype finger-like device that mixed rigid "bones" and soft "flesh" — and which deformed in a planned and predetermined manner, proving its potential as a manipulator for soft robotics.

The team's ink is created by extracting elastomer microparticles from oil-in-water emulsion drops and then suspending them in a precursor solution. As the microparticles absorb the elastomer compounds in the solution, they swell before being turned into an ink compatible with unmodified 3D bio-printers. As the structure is printed, the precursor is polymerized — making the object rigid. A combination of the microparticle and precursor elastomeric networks gives the material its tunable flexibility and toughness.

The team suggests that the DNGE ink could be used for sensors, soft robotic manipulators, and even in healthcare — delivering devices for motion-guided rehabilitation, guides for surgery, or tunable prosthetics. The lab's next step, says Amstad: integrated active elements, including electrical connections, into the printed devices.

The team's work has been published in the journal Advanced Materials under open-access terms.

Main article image courtesy of Titouan Veuillet.

Gareth Halfacree
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