New flying robots can hitchhike on birds, butterflies

Harvard scientists have developed flying microrobots that can use static electricity to perch on bats, birds or butterflies to conserve energy in long-duration flights.
"Many applications for small drones require them to stay in the air for extended periods," said Moritz Graule, who conducted the research as a student at Harvard University.
"Unfortunately, smaller drones run out of energy quickly. We want to keep them aloft longer without requiring too much additional energy," said Graule.
"A lot of different animals use perching to conserve energy, 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," said Kevin Ma, from Harvard.

The team turned to electrostatic adhesion - the same basic science that causes a static-charged sock to cling to a pants leg or a balloon to stick to a wall.
"In the case of the balloon, however, the charges dissipate over time, and the balloon will eventually fall down," said Graule.

"In our system, a small amount of energy is constantly supplied to maintain the attraction," he said.
The RoboBee, pioneered at the Harvard Microrobotics Lab, uses an electrode patch and a foam mount that absorbs shock.
The entire mechanism weighs 13.4 mg, bringing the total weight of the robot to about 100mg - similar to the weight of a real bee.

The robot takes off and flies normally. When the electrode patch is supplied with a charge, it can stick to almost any surface, from glass to wood to a leaf. To detach, the power supply is simply switched off.
"One of the biggest advantages of this system is that it doesn't cause destabilising forces during disengagement, which is crucial for a robot as small and delicate as ours," said Graule.
The patch requires about 1,000 times less power to perch than it does to hover, offering to dramatically extend the operational life of the robot.
Reducing the robot's power requirements is critical for the researchers, as they work to integrate onboard batteries on untethered RoboBees.

"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," said Robert Wood, Professor at the Wyss Institute for Biologically Inspired Engineering at Harvard University.
"When making robots the size of insects, simplicity and low power are always key constraints," Wood said.
The research was published in the journal Science.