Novel 3D-printable alloy for flexible devices, soft robots

Scientists have developed a novel alloy that can be used to 3D-print components for computer screens and stretchable electronic devices, and soft robots.
The advance by researchers at Oregon State University in the US also paves the way toward the 3D printing of tall, complicated structures with a highly conductive gallium alloy.
Researchers put nickel nanoparticles into the liquid metal, galinstan, to thicken it into a paste with a consistency suitable for additive manufacturing.
"The runny alloy was impossible to layer into tall structures," said Yigit Menguc, assistant professor at OSU.
"With the paste-like texture, it can be layered while maintaining its capacity to flow, and to stretch inside of rubber tubes," said Menguc.

"We demonstrated the potential of our discovery by 3D printing a very stretchy two-layered circuit whose layers weave in and out of each other without touching," he said.

Gallium alloys are already being used as the conductive material in flexible electronics; the alloys have low toxicity and good conductivity, plus they're inexpensive and "self-healing" - able to attach back together at break points.
However, prior to the modification developed at OSU, which used sonication - the energy of sound - to mix the nickel particles and the oxidized gallium into the liquid metal, the alloys' printability was restricted to two-dimensional.

For the study published in the journal Advanced Materials Technologies, scientists printed structures up to 10 millimetres high and 20 millimetres wide.
"Liquid metal printing is integral to the flexible electronics field," said Dogan Yirmibesoglu, PhD student at OSU.
"Additive manufacturing enables fast fabrication of intricate designs and circuitry," said Yirmibesoglu.
The field features a range of products including electrically conductive textiles; bendable displays; sensors for torque, pressure and other types of strain; wearable sensor suits, such as those used in the development of video games; antennae; and biomedical sensors.
"It's easy to imagine making soft robots that are ready for operation, that will just walk out of the printer," said Yirmibesoglu said.

The gallium alloy paste demonstrates several features new to the field of flexible electronics, added co-corresponding author Uranbileg Daalkhaijav, PhD candidate at OSU.