The RoboBee learns to launch itself out of the water

The RoboBee, a millimeter-wide flying robot platform from Harvard’s Wyss Institute, has been gaining improvements for years. The latest trick of this diminutive robo-creature is to dive into the water, then emerge and blast itself upwards^[1] using a strange and clever mechanism for a safe landing nearby.

The issue was that, while a robot may be able to fly in the air and swim in the water (as the RoboBee can^[2]), transitioning between them is the tricky part. At that size, the resistance of water on its lower parts is considerable, and can hamper takeoff (the robot already has to be careful not to flap too fast under water because the wings might break off).

First, in order to get the robot past the surface tension of the water, another physical barrier we generally don’t need to worry about at our size, the team attached four little “buoyant outriggers” — floaties. These help bring it to the surface.

But there, with only so much power coming from its tiny wings, the RoboBee may very easily find itself stranded. How could they create a single powerful upward impulse that gets it free and clear, where it can resume effective flapping?

The solution arrived at by grad student Elizabeth Farrell Helbling, Yufeng Chen, and the rest of the team was to use gas. Of course, a robot that can fit in a thimble can’t carry much. So why not make it on the fly, so to speak?

In addition to its little water wings, the RoboBee has a little electrolytic plate that splits water into hydrogen and oxygen, then mixes them together for an easily combustible mixture. Once there’s enough, a tiny spark plug fires off and...