We've been following the exploits of Harvard's tiny Robobee for a few years now, from its first controlled flight, then learning to swim and perch, and rising out of the water with style. Until recently, it's been powered via a wire tether, but researchers have cut the cord by installing teeny solar panels on the little robotic insect.

Robobee's first solo flight actually happened in August last year, but has only just been described in a paper published in the journal Nature. Graduate student Elizabeth Farrell Helbling, Ph.D and postdoctoral fellow Noah T. Jafferis have both been working on the Robobee project for six years, and for this demonstration it underwent some modifications.

"The change from two to four wings, along with less-visible changes to the actuator and transmission ratio, made the vehicle more efficient, gave it more lift, and allowed us to put everything we need on board without using more power," said Jafferis.

The smallest commercially-available solar panels – weighing just 10 mg – are reported unable to harvest enough energy from sunlight to enable tether-free flight, so the researchers simulated the equivalent of about three Suns using halogen lights.

The PV cells sit 3 cm above the wings and are connected to an electronics panel that hangs below Robobee. The little flyer needs around 120 mW of power to stay in the air, and the job of this hanging panel is to convert low-voltage from the solar array into enough power to control the actuators.

All in, the modified Robobee tips the scales at just 259 mg, making it much lighter than a paperclip. It's not the first tiny robot to fly untethered, but it is reported to be the lightest.

The first flight was brief and basically just up, up and away, heading straight for the lights. Until the researchers panicked and killed the lights, allowing Robobee to be safely caught by its Kevlar safety harness. The next step will be to add onboard steering and control systems. The video below has more.

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