Self-Assembly and Self-Healing in a Metallic Foam Made of Electroplating Microrobots

Metallic electrodeposition is an attractive technique for both the synthesis and healing of high-performance porous metals, a result of the high room temperature mobility of metal ions in aqueous solution. Typically, a desired morphology is achieved by growing metal within the interstices of an inverted lattice or on the surface of a sacrificial scaffold, driven by a globally applied plating voltage. However, by instead rationally directing metal deposition at specific sites in a material, enhanced structural complexity and intelligent healing could be achieved. To demonstrate, we present a proof-of-concept materials platform where assembly and healing are driven locally by electronically integrated electroplating microrobots. The robots deposit metal on their bodies using electronic signals, which form bonds between neighbors via the merging of growth fronts. Through this mechanism, hundreds of robots self-assemble into an ultra-low density macroscopic metallic foam, with toughness and elastic moduli approaching the fundamental limits reported in the literature. We show that robots can autonomously repair damage to the material microstructure via electrodeposition, 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.

This work was supported by the Army Research Office (ARO YIP W911NF-17-S-0002) and the Air Force Office of Scientific Research (AFOSR FA9550-21-1-0313).