Robot bees can now dive in and out of water using tiny combustible rockets

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Harvard’s robot bees have really evolved over the years. The RoboBee project was first unveiled in 2013, when the bots were only capable of takeoff and flying. Since then, they’ve been modified to stick to surfaces and swim underwater, and now their creators say they’re able to dive in and out of water — a big achievement for a tiny robot bee.

Getting out of the water is usually pretty easy for humans, but it’s a challenge for anything as small as an insect. The RoboBee weighs just 175 milligrams (that’s 14 times lighter than a cent), and at this size, surface tension is like extra strong gravity: it’s 10 times the robot’s weight, and three times its lifting power. “The force from surface tension feels like an impenetrable wall,” said Harvard professor of engineering Robert Wood in a press release. Imagine that next time you’re getting out of the bath.

To solve this problem, researchers from Harvard’s outfitted the RoboBee with a tiny combustible rocket, giving it the oomph needed to break the water’s surface tension. Gas fills a chamber in the RoboBee’s interior, it’s lit by an internal spark, and woosh, it shoots out of the water. Or, as it’s described in a paper published in the journal Science Robotics today: “The robot [assumes] a ballistic trajectory.”

What’s cleverest about this system is that it actually uses the water itself as fuel. A pair of tiny electrolytic plates convert the liquid into oxyhydrogen, a violently explosive gas. (And if you’re wondering why we don’t use this sort of gas more often, it’s because it costs a lot of energy, in the form of electricity, to produce.)