Sunlight-powered hovering of an ultra-light micro aerial vehicle

The limited flight duration presents a significant obstacle to the widespread application of micro aerial vehicles (MAVs)^1-3, especially for ultra-lightweight ones weighing less than 10 grams, generally having a flight endurance of no more than 10 minutes^1,4. Sunlight power^5-7 is a potential alternative to improve the endurance of ultra-light micro aerial vehicles, but owing to the restricted payload capacity of the vehicle and low lift-to-power efficiency of traditional propulsion systems, previous studies can not achieve untethered flight or sustaining hovering of MAVs powered by natural sunlight ^8,9. To address the challenges, here we present a novel electrostatic-driven propulsion system with ultra-low power consumption (137 mW) and high lift-to-power efficiency (30.7 g·W^-1) to realize the first sunlight-powered hovering of a micro aerial vehicle (with a total lift-to-power efficiency of 7.4 g·W^-1) under natural sunlight conditions (920 W·m^-2). The vehicle mainly consists of an electrostatic-driven propulsion system and an ultra-light kilovolt power system, with a total mass of 4.21 g, which is 1/600 of the existing lightest sunlight-powered aerial vehicle capable of hovering⁶. The sunlight-powered aerial vehicle we present is the first micro aerial vehicle to achieve untethered flight and sustained hovering under natural sunlight conditions (as opposed to artificial light sources ^8,10 and wireless radiofrequency¹¹).