To be a fly on the wall, an observer must be ubiquitous, unobtrusive and quiet. What if, instead, the observer was just a tiny fly-sized robot, independently powered, able to travel like its insect inspiration? That’s one possibility from the long line of work on the RoboBee series of miniature flying machines, the latest of which recently flew independently under its own photovoltaic power.

RoboBee is a long-running project of the Harvard Microrobotics Lab and the Wyss Institute for Biologically Inspired Engineering. The end goal is ultimately controlled swarms of insect-sized flying machines, with visions of these swarms performing everything from plant pollination to surveillance. These are ambitious aims, and all have been hindered to this point by a fundamental constraint on the form: the robots are too small to carry batteries.

Much of the flight design uses a tethered power supply, allowing the designers to craft Piezoelectric motors that expand and contract as electrical current passes through the muscle-like membranes. This created wings that could flap and propel the robot upward, but it wasn’t until recently that the robot could do it on its own power supply.

RoboBees are smaller than any drone currently employed by the U.S. military, minute enough to make the palm-sized Black Hornet feel gargantuan. Without a sensor payload, it’d be a novelty, but the military has already invested in cheap, expendable sensor-carrying drone gliders for tasks such as meteorological data collection. Should this power supply enable RoboBees to support a meaningful sensor package, they could be used in a similar fashion, scattered as sensors that can flap their way into a new position.

Holding six solar power cells on a stick, and with a second set of wings, the vehicle successfully flew under its own power, even if only for the briefest of moments. The researchers’ documentation of their project was published in scientific journal Nature June 26, appearing under the title “Untethered flight of an insect-sized flapping-wing microscale aerial vehicle.”

The whole RoboBee weights 259 milligrams, or less than a paperclip, and under special lights was able to generate enough lift to support an additional payload of 70 mg, which could be used for lightweight sensors, control electronics, or larger power supply in the future. Fitting sensors to a craft the small is likely a challenge, but also essential for the promise of the device.

There is also the small matter that, even using photovoltaic cells, the robot needs an alien sun to fly.

“The Robobee X-Wing needs the power of about three Earth suns to fly, making outdoor flight out of reach for now,” stated the summary from Harvard’s School of Engineering and Applied Sciences. “Instead, the researchers simulate that level of sunlight in the lab with halogen lights.”

Should the sensors exist, and the device become capable of outdoor flight, microrobotics could become a ubiquitous part of modern life, performing functions alongside insects and relaying sensor information back as an unseen intelligence platform.

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Kelsey Atherton blogs about military technology for C4ISRNET, Fifth Domain, Defense News, and Military Times. He previously wrote for Popular Science, and also created, solicited, and edited content for a group blog on political science fiction and international security.