A new bone-like metal foam can ‘heal’ at room temperature

For 6,000 years, humans have been making things from metal because it’s strong and tough; a lot of energy is required to damage it. The flip side of this property is that a lot of energy is required to repair that damage. Typically, the repair process involves melting the metal with welding torches that can reach 6,300 degrees Fahrenheit.

two side-by-side closeup images of metallic bone — The strut-and-gap internal structure of a metallic foam reduces its weight while maintaining its strength, but makes it impossible to repair with traditional methods, which would melt that structure away. In the new technique, electrochemistry adds new metal just to the broken struts, reconnecting them and “healing” the damage. (Image: Pikul Research Group)

Penn Engineers have developed a way to repair metal at room temperature. They call their technique “healing” because of its similarity to the way bones heal, recruiting raw material and energy from an external source.

The study was conducted by James Pikul, assistant professor in the Department of Mechanical Engineering and Applied Mechanics and Zakaria Hsain, a graduate student in his lab.

Beyond the energy costs associated with the current process of repairing metal by melting it to a more pliable form, there are some metal components where such a repair strategy is not even an option. For example, melting removes the intricate internal structure of metallic foams, which are metals made with internal pockets of air. This arrangement of struts and gaps reduces the material’s weight while maintaining its overall strength.

While exploring ways to repair such porous metals, Pikul and Hsain looked at existing “self-healing” materials, which are generally made from relatively soft polymers and plastics.