Engineers develop gallium alloy paste to 3D print soft robotics

Gallium alloys have low toxicity, good conductivity, plus they're inexpensive and "self-healing", making them great for complex structures.

0 March 6, 2018

Additive manufacturing is expanding its reach into many new industries. However, this technology is somewhat limited by the number of materials it is able to work with.

Engineers at Oregon State University (OSU) have developed a new method to enable the use of 3D printable gallium alloys.

OSU researchers printed structures up to 10 millimeters high and 20 millimeters wide. Photo courtesy of Oregon State University.

Gallium alloys have low toxicity and good conductivity, plus they’re inexpensive and “self-healing”, making them an excellent candidate for 3D printing complex structures.

With this development, the team is moving towards being able to rapidly manufacture flexible computer screens and other stretchable electronic devices, including soft robots.

In order to do this, researchers put nickel nanoparticles into the liquid metal, galinstan, to thicken it into a paste with a consistency suitable for additive manufacturing. The team used sonication — the energy of sound — to mix the nickel particles and the oxidized gallium into the liquid metal.

For this study, researchers printed structures up to 10 millimeters high and 20 millimeters wide.

“The runny alloy was impossible to layer into tall structures,” said Yiğit Mengüç, assistant professor of mechanical engineering and co-corresponding author on the study. “With the paste-like texture, it can be layered while maintaining its capacity to flow, and to stretch inside of rubber tubes.”

The team was able to demonstrate the discovery’s potential by 3D printing a very stretchy two-layered circuit whose layers weave in and out of each other without touching.

“Liquid metal printing is integral to the flexible electronics field,” said co-author Doğan Yirmibeşoğlu, a robotics Ph.D. student at OSU. “Additive manufacturing enables fast fabrication of intricate designs and circuitry.”

Yirmibeşoğlu believes the future is very bright and this discovery makes it easy to imagine developing soft robots that are ready for operation, that will just walk out of the printer.

The gallium alloy paste demonstrates several features new to the field of flexible electronics.

“It can be made easily and quickly,” adds co-corresponding author Uranbileg Daalkhaijav, Ph.D. candidate in chemical engineering. “The structural change is permanent, the electrical properties of the paste are comparable to pure liquid metal, and the paste retains self-healing characteristics.”

Future work will explore the exact structure of the paste, how the nickel particles are stabilized, and how the structure changes as the paste ages.

Findings were recently published in Advanced Materials Technologies.

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