Insects can be remarkably acrobatic and resilient in flight. Those traits help them navigate the aerial world, with wind gusts, obstacles, and general uncertainty. Researchers have developed insect-sized drones with similar dexterity and resilience. The aerial robots are powered by a new class of soft actuator that allows them to withstand the physical travails of real-world flight. The robots could one day aid humans by pollinating crops or performing machinery inspections in cramped spaces.
Typically, drones require wide open spaces because they’re neither nimble enough to navigate confined spaces nor robust enough to withstand collisions in a crowd. Very small drones require a fundamentally different construction than larger ones. Large drones are usually powered by motors, which lose efficiency as they shrink in size. For insect-sized drones, the alternative has been to employ a small, rigid actuator built from piezoelectric ceramic materials. While piezoelectric ceramics allowed the first generation of tiny robots to take flight, they’re quite fragile. And that’s a problem when you’re building a robot to mimic an insect — foraging bumblebees endure a collision about once every second.
The team designed a more resilient tiny drone using soft actuators instead of hard, fragile ones. The soft actuators are made of thin rubber cylinders coated in carbon nanotubes. When voltage is applied to the carbon nanotubes, they produce an electrostatic force that squeezes and elongates the rubber cylinder. Repeated elongation and contraction cause the drone’s wings to beat nearly 500 times per second, giving the drone insect-like resilience. The drones can be hit when they are flying and recover and can also perform aggressive maneuvers like somersaults in the air. The drones weigh 0.6 grams or approximately the mass of a large bumblebee. The drone looks a bit like a tiny cassette tape with wings, though the team is working on a new prototype shaped like a dragonfly.
Because of the soft actuators’ inherent compliance, the robot can safely run into obstacles without greatly inhibiting flight. This feature is well-suited for flight in cluttered, dynamic environments and could be very useful for any number of real-world applications. A key step toward those applications will be untethering the robots from a wired power source, which is currently required by the actuators’ high operating voltage.
The mini drones could navigate complex machinery to ensure safety and functionality; for example, when inspecting a turbine engine. The drone needs to move around an enclosed space with a small camera to check for cracks on the turbine plates. Other potential applications include artificial pollination of crops or completing search-and-rescue missions following a disaster.