Harvard Engineering researchers have developed an insect-sized flying vehicle with four flapping wings that is the lightest so far to achieve sustained, if very brief, untethered flight.
The 90-gram vehicle along with electronics that include a photovoltaic array and a signal generator weighs a total of 259 milligrams and consumes just 120 milliwatts of power, but matches the thrust efficiency of a bee in flight.
Called the RoboBee, its weight is less than a paper clip, but it has a wingspan of 3.5 cm and a height of about 6 cm. It is powered by six solar cells that each weigh about 10 mg.
It could eventually be deployed for environmental exploration or search and rescue missions, the researchers said. One day it might perform in a swarm, with sensors, lightweight batteries and improved circuitry to take longer flights.
One of the researchers, Prof. Robert Wood of Harvard School Engineering and Applied Sciences, said the project was several decades in the making including six years of recent intensive work. He called the concept of powering flight “something of a Catch-22 as the tradeoff between mass and power becomes extremely problematic at small scales where flight is inefficient.”
The other researchers on the project are Noah Jafferis, E. Farrell Helbling and Michael Karpelson.
It takes less power to fly the RoboBee than it would to light a single light on a string of LED Christmas lights, according to a YouTube video showing the robot in action. Compared to earlier versions the latest model has a better transmission ratio and improved piezoelectric actuators and an additional pair wings.
It took the equivalent of three Suns to deliver enough energy to the solar array, which the team achieved with indoor testing under halogen lights. A bill of materials shows RoboBee included transformers, switches, an input capacitor, diodes, resistors, a microcontroller and circuit board.
The robot is not finished, partly because it “flies only for just under a second before veering off out of view,” according to Kenny Breuer, a researcher in the School of Engineering at Brown University, in Nature.
Eventually, lighter batteries could be developed to replace the solar panels along with improved small-scale electronics and communications. “The controlled flight of tiny robots seems within our grasp,” Breuer said.
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