You don’t always need to use metals to build robots. Scientists from UVM and Tufts have managed to build robots from repurposed living cells scraped from frog embryos. Xenobots can move toward a specific target and heal themselves after cut.
As Michael Levin explains:
You look at the cells we’ve been building our xenobots with, and, genomically, they’re frogs. It’s 100% frog DNA—but these are not frogs. As we’ve shown, these frog cells can be coaxed to make interesting living forms that are completely different from what their default anatomy would be