Harvard's RoboBee now perches on overhanging surfaces to preserve power

The RoboBee can now stick to almost any surface during flight to save energy(Credit: Harvard Microrobotics Lab/Harvard University)

When the insect-sized RoboBee first took flight in 2012, its developers were unable to keep it aloft for more than a few seconds at a time. These days, the tiny drone is so adept at flying that researchers are actively bringing it down to rest. In the latest exhibition of their flying microbot, Harvard researchers have demonstrated the RoboBee's newfound ability to land on surfaces during flight, a neat trick that allows it save power and remain in action for longer periods of time.

The researchers behind the RoboBee imagine that one day swarms of the tiny robots will work together in search and rescue operations, to monitor crops and even carry out espionage missions. An ability to fly for longer would be very useful for these purposes, as it would for most drone applications, for that matter.

Around the size of a paper-clip, the RoboBee is crafted from flat layers of laser-cut carbon fiber and weighs about 80 mg. Through a set of piezoelectric actuators it flaps gossamer-like plastic wings back and forth at 120 beats per second, but in its current form it is powered from an external source by way of a wire tether.

As the researchers work to develop an untethered RoboBee, they are looking at their creation from every angle to work out how to minimize its power requirements. This led them back to their original inspiration in nature, where creatures like bats, birds and butterflies will perch during flight to conserve energy.

"A lot of different animals use perching to conserve energy," says Kevin Ma, a co-author of the new study. "But the methods they use to perch, like sticky adhesives or latching with talons, are inappropriate for a paperclip-size microrobot, as they either require intricate systems with moving parts or high forces for detachment."

The team overcame this problem by introducing electroadhesion, the very same phenomenon that causes balloons to stick to ceilings after you rub them on your hair. But where a balloon loses its grip after a while as the opposite charges dissipate, the researchers were able to devise a system that allows the RoboBee to stick to vertical and overhanging surfaces for as long as it pleases.

They attached an electrode patch and a foam mount to absorb shock on impact. When a charge is delivered to the electrode patch, it enables the robot to stick to just about any surface including glass, wood and leaves. To hold its place, the patch requires around 1,000 times less power than if the RoboBee was to be left hovering. And when it comes time to take off again, simply cutting the power supply from the patch causes the robot to detach.

"The use of adhesives that are controllable without complex physical mechanisms, are low power, and can adhere to a large array of surfaces is perfect for robots that are agile yet have limited payload – like the RoboBee," says Robert Wood, senior author of the study. "When making robots the size of insects, simplicity and low power are always key constraints."

Currently RoboBee can only perch on vertical and overhanging surfaces as the patch is fitted to its top surface, but researchers plan on tweaking the design so it can plant itself anywhere.

The research was published in the journal Science and you can see the RoboBee show off its new maneuver in the video below.

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