A Four-Dimensional Conductive Gel Could Revolutionize 3D-Printed Electronics — Just Ask This Spider

Researchers from North Carolina State University, Northwestern Polytechnical University, Tianjin University, the Xi'an University of Science and Technology, the Taiyuan University of Technology, and the National University of Singapore have developed a 3D-printable highly-conductive metallic gel, which can be used to create 3D electronic devices at room temperature — including a shape-shifting spider-bot.

"3D printing has revolutionized manufacturing, but we're not aware of previous technologies that allowed you to print 3D metal objects at room temperature in a single step," claims Michael Dickey, professor at NCSU and co-corresponding author of the paper detailing the new gel. "This opens the door to manufacturing a wide range of electronic components and devices."

The team's gel is based on a solution of copper particles, each a few microns in size, suspended in water and mixed with an indium-gallium metal alloy which remains liquid at room temperature. As the mixture is stirred, the copper sticks to the liquid metal — forming a "network" of metallic gel within the water.

"This gel-like consistency is important, because it means you have a fairly uniform distribution of copper particles throughout the material," Dickey explains. "This does two things. First, it means the network of particles connect to form electrical pathways. And second, it means that the copper particles aren't settling out of solution and clogging the printer."

The metallic gel can be printed using an unmodified 3D printer nozzle, the team says, and retains its shape when printed — hardening as the mixture dries at room temperature. Adding heat during the drying process, though, unlocks new capabilities through predictable structural deformation — allowing the shape of the printed object to be controlled post-printing.

"Ultimately, this sort of four-dimensional printing — the traditional three dimensions, plus time – is one more tool that can be used to create structures with the desired dimensions," Dickey claims. "But what we find most exciting about this material is its conductivity."

"Because the printed objects end up being as much as 97.5 per cent metal, they are highly conductive," Dickey continues. "It's obviously not as conductive as conventional copper wire, but it's impossible to 3D print copper wire at room temperature. And what we've developed is far more conductive than anything else that can be printed. We're pretty excited about the applications here."

The team's work, which includes a "conductive spider" sculpture which lifts itself into a three-dimensional structure after having been printed as a flat object, has been published in the journal Matter under open access terms; Dickey claims to be interested in "working with industry partners" to bring the technology to market.