Conductive metallic gel that prints 3D objects at room temperature

A new highly conductive metallic gel that can help print 3D solid objects at room temperature in a single step has been developed for the first time by researchers at North Carolina State University. The breakthrough could lead to the manufacturing of new types of electronic components and devices.

As reported in the journal Matter [Xing et al. Matter (2023) DOI: 10.1016/j.matt.2023.06.015], the team produced their metallic gel by suspending a solution of micron-scale copper particles in water, before a small amount of an indium-gallium alloy was added. The mixture was then stirred together, which allowed the liquid metal and copper particles to adhere to each other to form a metallic gel ‘network’ within the aqueous solution.

A gel-like consistency was crucial as it ensures relatively uniform distribution of copper particles throughout the material. This also meant the network of particles could connect to form electrical pathways, as well as stopping the copper particles from settling out of solution and clogging the printer. The gel can be printed with a standard 3D printing nozzle and retains its shape on being printed. When dried at room temperature, the 3D object is even more solid while still maintaining its shape.

When heat was applied to the printed object during drying, the alignment of the particles affected how the material dries, with rapid drying causing structural deformation. As this deformation is predictable, it is possible to make a printed object change shape after printing by controlling the pattern of the printed object and the amount of heat it is exposed to. This kind of programmed shape change is known as ‘4D printing’ as 3D-printed structures change shape with respect to time in response to external stimulus.

Since the printed objects are as much as 97.5% metal, they are highly conductive, much more so than anything else that can be printed. To demonstrate, the team printed a conductive spider that lifts and assembles its own body from an initially flat shape. As co-corresponding author Michael Dickey told Materials Today, “The main significance is that we can print metal parts at room temperature that have excellent electrical conductivity and decent mechanical properties. As a consequence, it is possible to print metal parts in a very simple manner.”

The ability to 3D print metals could have many applications, including electronic devices and even structural materials due to the attractive properties of metals. The researchers now hope to gain a better understanding of the mechanical properties of the printed parts, identify better metal combinations to develop parts with a range of properties, and to find industry partners to explore potential applications.

“The main significance is that we can print metal parts at room temperature that have excellent electrical conductivity and decent mechanical properties. As a consequence, it is possible to print metal parts in a very simple manner.”Michael Dickey