At a Glance
- Caltech scientists have developed a new 3D printing method called HIAM, which enables the manufacture of intricate metal alloys with micro-scale precision and custom chemical compositions.
- The process utilizes a 3D-printed hydrogel scaffold that is infused with metal salts, burned to remove organic matter, and heated in hydrogen to form a pure alloy.
- This technique produces a unique hierarchical microstructure containing tiny, unreduced oxide nano-inclusions that get trapped within the metal as it forms.
- These embedded features reinforce the material, elevating the hardness of the resulting copper-nickel alloys by up to four times compared to their bulk counterparts.
- This work demonstrates a novel pathway for tailoring the mechanical properties of alloys by controlling their microstructure, with potential applications in aerospace and medicine.
Scientists at the California Institute of Technology have developed a revolutionary 3D printing technique that enables the creation of custom metal alloys with unprecedented control over their composition and internal structure. Published in the journal Small, this new method yields materials, such as a copper-nickel alloy, that are up to four times stronger than their conventionally produced counterparts. The breakthrough promises to reshape metallurgy, opening the door to advanced materials for specialized applications, from mechanically robust medical stents to lightweight and durable components for satellites.
The technique, called hydrogel-infusion additive manufacturing, or HIAM, begins with the 3D printing of a scaffold made from a squishy polymer resin called a hydrogel. This gel-like structure is then soaked in a liquid solution containing the desired metal salts, such as those of copper and nickel, infusing the scaffold with metal ions. Next, the structure is heated in a process called calcination, which burns away the organic gel, leaving behind a delicate structure of metal oxides. The final, innovative step, known as reductive annealing, heats the material in a hydrogen environment, which pulls oxygen out of the oxides to form water vapor, leaving a solid, pure metallic alloy in the precise shape of the original 3D-printed scaffold.
“The composition can be varied in whatever manner you like, which has not been possible in traditional metallurgy processes,” says Julia R. Greer, a professor at Caltech and leader of the research team, in a university press release. This fine-tuned control over the alloy’s recipe and the unique manufacturing steps result in a special internal structure, or microstructure. The HIAM process creates extremely tiny metal crystals, or grains, and traps minuscule oxide particles, called nano-inclusions, within the final alloy. These features act as internal reinforcement, significantly disrupting the ways a material would typically bend or break.
This new understanding of how to build stronger metals challenges long-held beliefs. The researchers found that the size of its metal grains not only determines the material’s strength but is also heavily dependent on its exact chemical composition, which influences the density of the strengthening nano-inclusions. This work provides a powerful new pathway for scientists to design and characterize alloys from the nano-scale up, tuning their properties to create superior materials for the 21st century.
References
- Fesenmaier, K. & California Institute of Technology. (2025, August 1). Bringing metallurgy into the 21st century: Precisely shaped metal objects provide unprecedented alloy control. Phys.Org; California Institute of Technology. https://phys.org/news/2025-08-metallurgy-21st-century-precisely-metal.html
- Tran, T. T., Gallivan, R. A., & Greer, J. R. (2025). Multiscale microstructural and mechanical characterization of cu–ni binary alloys reduced during hydrogel infusion‐based additive manufacturing(Hiam). Small, e01320. https://doi.org/10.1002/smll.202501320
