Exhaustive scratching and healing test.
As shown in Movie S4
, a PDMS rod with a diameter of around 1 mm is attached to a clock hand to repeatedly scratch an r-GO/oil-coated wire, at the same spot, once every minute. Every scratch removes a small piece of the coating, which repeatedly heals until there is insufficient amount of r-GO/oil left to form a complete coverage on the wire. For the wire (1.02 mm in diameter) shown in the photo, the coating sustained 180 scratches. Unhealable damage on the coating becomes visible after 240 scratches.