The concept aims to power the production of unique sensors, biomedical devices, or energy conversion and storage components.

Scientists at the Ecole Polytechnique Fédérale de Lausanne, in Switzerland, have created dense, high-strength structures by injecting hydrogel with metal salts of various minerals like iron and copper. Early results show materials 20-times stronger with much less shrinkage than earlier methods.

As novel a concept as "cultivating metal" sounds like, it's actually been done before, but challenges presented themselves which could not be overcome in these previous experiments.

They involved vat photopolymerization—a type of 3D printing that sees pouring a light-reactive liquid resin into a container and then solidifying specific areas with a laser or ultraviolet light to create a shape. However, because this method only works with light-sensitive polymers, its practical uses are limited.

Daryl Yee, who leads the Laboratory for the Chemistry of Materials and Manufacturing at EPFL's School of Engineering, said these earlier approaches have major flaws.

"These materials tend to be porous, which significantly reduces their strength, and the parts suffer from excessive shrinkage, which causes warping," he told his university press.

To address these issues, Yee and his team have introduced a new approach described in their paper published in Advanced Materials. Instead of hardening a resin already mixed with metal compounds, the researchers first 3D print a framework using a simple water-based gel known as a hydrogel. They then soak this "blank" structure in metal salts, which are chemically converted into tiny metal-containing nanoparticles that spread throughout the gel. Repeating this process multiple times allows them to create composites with very high metal content.

After 5–10 of these "growth cycles," the remaining hydrogel is removed through heating, leaving behind a dense metal or ceramic object that precisely matches the shape of the original printed gel. Because the metal salts are added only after printing, the same hydrogel template can be used to make a variety of different metals, ceramics, or composite materials.