The robot, equipped with a solar panel–like energy harvester and four wheels, is about the size of a penny, weighs as much as a raisin and can move about the length of a bus in an hour on a cloudy day.


The robot, equipped with a solar panel–like energy harvester and four wheels, is about the size of a penny, weighs as much as a raisin and can move about the length of a bus in an hour on a cloudy day.