  Herein, self-healing small-scale swimmers capable of autonomous propulsion
and on-the-fly structural recovery are described. The new strategy
instantaneously restores the functionality of the swimmer after it has suffered
severe damage. Incorporation of magnetic microparticles in strips along with
the printed functional body layers (consisting of conductive carbon,
low-density hydrophobic polymer and catalytically active metal) results in
rapid reorientation and reattachment of the moving damaged catalytic tail to
its complimentary broken static body piece. Such magnetic alignment and
attraction restores the original swimmer structure and propulsion behavior,
independent of user input, displaying healing efficiencies as high as 88
percent. Modeling of the magnetic fields and simulations of various swimmer
configurations are used to study the magnetic force field distribution around
the swimmers. The influence of the damage position and pattern of multiple
magnetic healing strips is examined and their influence upon healing efficiency
is compared. Owing to its versatility, fast recovery, simplicity, and
efficiency, the new on-the-fly self-healing strategy represents an important
step towards the development of new classes of robots that can regain their
functionality in situations of extreme mechanical damage where repair is not
possible or challenging.
