Of all the exotic space-age materials you can use to build a robot, we never thought bubbles would be a viable option. But researchers at the University of Hawaii have done just that with a microscopic robot creation made from a single bubble controlled by a laser.
In lab experiments the bubbles were created in a saline solution and controlled with a 400 mW infrared laser that was shone onto its inner surface. As the fluid surrounding the bubble was heated by the laser, it automatically moved to the cooler side which resulted in the bubble being pushed towards where the laser was targeted. And while the bubble microrobot's capabilities are limited, they can be very useful as microscopic bulldozers, pushing and positioning other tiny particles and structures with remarkably fine control and accuracy.
Because all you need to create a bubble is a needle full of air, building a small army of bubblebots in a given solution is incredibly cheap. And multiple bubbles can be controlled independently by different lasers, which could in theory allow them to be organized into more complex machines and mechanisms as needed. But we're mostly hopeful for a future where millions of these microrobots will automatically scrub us clean in a luxurious robo-bubble bath.