https://techcrunch.com/2022/09/21/these-autonomous-wireless-robots-could-dance-on-a-human-hair/

The competition to create ever smaller, ever better robots is a fierce one, and Cornell University is out front now with a set of bots small enough to sit on a human hair, but that can move on their own using nothing but light as a power source.

Now, you may remember a similarly small machine from a few months ago, sitting proudly on the rim of a penny. Small, yes — but calling it a robot isn’t quite accurate. It was a tiny machine, for sure, but it operated through being repeatedly heated and cooled, leading it to expand and contract its legs.