Self‐Healing Materials from Electronically Integrated Microscopic Robots

Biological materials heal, learn, and adapt thanks to the collective work of tiny agents acting at their microscale. Extensive research in robotics has tried to duplicate this scheme in a synthetic system, yet in their current centimeter‐scale forms, the constituent robots are too large and too few, especially when compared to their biological inspiration. Here, this study shows a new type of high‐stiffness, low‐density material made entirely from robots of submillimeter dimensions. To bear load, these hundred‐micrometer robots directly grow metal onto their bodies and bond together under the control of on‐device microelectronics. The resulting aggregates achieve some of the lowest densities of any material and toughness/elastic moduli approaching the fundamental limits for metallic foams. Going beyond static properties, this study shows that robots can be used to actively repair the material microstructure, restoring stiffness and toughness following compressive fatigue. Broadly, these results clear the way for a new breed of programmable materials with bulk properties that can be rationally tuned over several orders of magnitude through the actions of robots too small to see with the naked eye.