Cross-section of a copper-infused hydrogel. Credit ALCHEMY EPFL (CC BY-SA)
A new 3D printing approach has been used to create intricate metal and ceramic structures which could be used for sensors, biomedical devices and other devices which require strong, lightweight and complex materials.
“Our work not only enables the fabrication of high-quality metals and ceramics with an accessible, low-cost 3D printing process, it also highlights a new paradigm in additive manufacturing where material selection occurs after 3D printing, rather than before,” says Daryl Yee, head of the Laboratory for the Chemistry of Materials and Manufacturing at École Polytechnique Fédérale de Lausanne, Switzerland.
The approach uses a standard ‘vat photopolymerisation’ 3D printing technique to cure a light-sensitive hydrogel resin with laser or ultraviolet light into the desired structure.
The blank hydrogels are then immersed in metal salt solutions for 60 minutes at 65°C to allow metal ions to infuse and permeate the structure. The ions are then converted into metal-containing nanoparticles by a precipitating agent.
“The infusion-precipitation cycle is then repeated multiple times to increase the mass of metal-containing nanoparticles in the hydrogel composite,” the authors of the study explain.
After 5 to 10 of these growth cycles, a final heating step burns away the remaining hydrogel and sinters the metal-containing nanoparticles together to form a metal or ceramic object in the shape of the original 3D printed hydrogel.
In a paper presenting the technique in the journal Advanced Materials, the researchers created strong and intricate ‘gyroid lattice’ structures out of metal – iron, silver, and copper – and strontium hexaferrite (SrFe12O19) ceramic.
A large (1.3 x 1.0 cm) iron gyroid. Credit: ALCHEMY EPFL (CC BY-SA)
“Our materials could withstand 20 times more pressure compared to those produced with previous methods, while exhibiting only 20% shrinkage versus 60-90%,” says PhD student and first author Yiming Ji.
These large shrinkages limit scalability because they require impractically large polymer templates.
“In addition, the significant shrinkages of these large templates are frequently accompanied by significant warping, which limit the utility of the final metal parts,” the authors write.
The new approach produced lattices which remained nearly flat after thermal treatment.
“While warping can sometimes be tolerated in lattice structures, it becomes highly detrimental in planar or tubular structures,” the researchers add.
They used the new infusion-precipitation to produce tiny, flat iron gears and tubular stents which retained their shape well.
Structures fabricated using the new infusion-precipitation approach, including (a) cm-scale iron gyroid lattice and (b) stents, and (c) mm-scale iron gears, (d) mm-scale silver gyroid, and (e) strontium hexaferrite gyroid with (f) iron oxide powder used to visualise the magnetic field around it. Credit: Ji et al 2025, Advanced Materials https://doi.org/10.1002/adma.202504951
“The reduced warping achieved with our process broadens the range of parts that can be fabricated,” they write.
“These stents and gears are representative of critical components used in biomedical and mechanical devices, underscoring the immediate potential of our technology for manufacturing non-lattice-based industrial-relevant parts.
“Beyond structural metal parts, our technology can also be applied to fabricate functional ceramics. To demonstrate this, we fabricated 3D gyroid structures out of hard-magnetic strontium hexaferrite.”
While the repeated infusion and precipitation cycles make the method more time consuming than other 3D printing techniques used for converting polymers to metals, Yee says they are already working to bring the total processing time down by using a robot to automate these steps.