Revolutionary Metallic Gel Unleashes Shape-Shifting and Conductivity in 3D Printing

Scientists Unveil Breakthrough: Conductive Metallic Gel Facilitates Room Temperature 3D Printing, Empowering Shape Alterations

A cutting-edge metallic gel has been developed by researchers, boasting remarkable electrical conductivity and the ability to fabricate three-dimensional (3D) solid objects at ambient temperatures. This groundbreaking technique, known as “4D printing,” introduces shape-shifting capabilities to printed structures as the gel dries, with time serving as the fourth dimension. In an impressive demonstration, a metallic spider was printed at room temperature utilizing this metallic gel, seamlessly assembling and solidifying into its final 3D configuration through the power of 4D printing. Image credit: Michael Dickey, NC State University.

In a significant advancement, scientists have successfully engineered a conductive metallic gel for 3D printing solid objects at room temperature. By combining copper particles with an indium-gallium alloy, this gel transitions into a solid state upon drying and exhibits controllable shape modifications when subjected to heat—an innovation aptly termed four-dimensional (4D) printing. The resulting objects showcase exceptional electrical conductivity, laying the foundation for an array of electronic components and devices.

Remarkably, researchers have accomplished the elusive feat of printing 3D metal objects at ambient temperatures in a single step, a capability that has eluded previous technologies, as explained by Michael Dickey, co-corresponding author of the study and the distinguished Camille & Henry Dreyfus Professor of Chemical and Biomolecular Engineering at North Carolina State University. He states, “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. This opens the door to manufacturing a wide range of electronic components and devices.”

To create the metallic gel, the scientists initiate the process with a solution containing copper particles suspended in water at the micron scale. Subsequently, they introduce a minute quantity of an indium-gallium alloy, which remains in a liquid state at room temperature. These components are then meticulously combined through stirring.

During the stirring process, the liquid metal and copper particles intertwine, forming a network-like metallic gel within the aqueous solution. This gel-like consistency plays a crucial role by ensuring a relatively even distribution of copper particles throughout the material. Dickey explains, “This does two things. First, it means the network of particles connects to form electrical pathways. And second, it means that the copper particles aren’t settling out of solution and clogging the printer.”

The resulting gel can be printed using a conventional 3D printing nozzle, retaining its intended shape during the printing process. Upon drying at room temperature, the 3D object further solidifies while preserving its form.

However, applying heat during the drying phase introduces intriguing possibilities. The alignment of particles significantly affects the drying behavior of the material. For instance, if a cylindrical object is printed, its sides contract more than the top and bottom during drying. Although the process of drying at room temperature is slow enough to prevent structural alterations in the object, the rapid drying induced by heat—such as placing it under an 80-degree Celsius heat lamp—can cause predictable deformations. By skillfully controlling the pattern and heat exposure of the object during drying, users can induce shape changes in the printed object after its fabrication, harnessing the power of 4D printing.

Dickey emphasizes, “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. But what we find most exciting about this material is its conductivity.”

With the printed objects consisting of up to 97.5% metal, their conductivity is remarkably high. Although not on par with conventional copper wire, which exhibits the highest conductivity, the ability to 3D print copper wire at room temperature remains impossible. In comparison, the developed metallic gel exhibits significantly greater conductivity than any other printable material. The potential applications stemming from this innovation are genuinely promising.

Dickey expresses enthusiasm regarding potential collaborations with industry partners to explore various applications. Furthermore, he welcomes discussions with potential collaborators to steer future research endeavors.

The research paper titled “Metallic Gels for Conductive 3D and 4D Printing” was published on July 5 in the journal Matter.

Reference: “Metallic Gels for Conductive 3D and 4D Printing” by Ruizhe Xing, Jiayi Yang, Dongguang Zhang, Wei Gong, Taylor V. Neumann, Meixiang Wang, Renliang Huang, Jie Kong, Wei Qi, and Michael D. Dickey, 5 July 2023, Matter.
DOI: 10.1016/j.matt.2023.06.015

Ruizhe Xing, a former visiting scholar at NC State affiliated with Northwestern Polytechnical University and Tianjin University, serves as the first author of the paper. The co-corresponding authors are Dickey from NC State, Renliang Huang, and Wei Qi from Tianjin University. The paper’s co-authors include Jiayi Yang, a former visiting scholar at NC State who is now at Xi’an University of Science and Technology; Dongguang Zhang, a former visiting scholar at NC State who is currently at Taiyuan University of Technology; Wei Gong, a former visiting scholar at NC State who is now at the National University of Singapore; Taylor Neumann, a former Ph.D. student at NC State; Meixiang Wang, a postdoctoral researcher at NC State; and Jie Kong from Northwestern Polytechnical University.

The study received support from the National Natural Science Foundation of China under grant number 52203101 and from the China Scholarship Council under grant number 201906250075.

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