Researchers have unveiled a drone they’ve dubbed the CoulombFly. This innovative aerial vehicle’s design is as unusual as its functionality. It combines solar cells, a voltage converter, and an electrostatic motor to power a helicopter-like propeller. The system is meticulously engineered to balance efficiency with minimal weight.
Despite its incredible features, there are considerable limitations: the drone lacks onboard control hardware and cannot navigate directed flights, making it susceptible to drifting if used outdoors. Furthermore, many of its components are quite delicate. However, the drone’s design allows for miniaturization, with a prototype weighing a mere 9 milligrams.
A significant part of this development was the shift from traditional electromagnetic motors to a lightweight electrostatic motor. Unlike conventional motors that use metal coils, the CoulombFly’s motor operates through charge attraction and repulsion. The motor comprises a stationary inner ring of charged plates called the stator and a rotating ring of 64 plates. When the plates in the outer ring are charged, they interact with the stator plates, creating motion through a process of attraction and repulsion.
This motor, while large relative to the drone’s size, is highly efficient. The system, when coupled with a 10-centimeter eight-bladed propeller, can generate a maximum lift of 5.8 grams, guiding the design parameters for other components.
Solar power is harnessed through a thin gallium arsenide film, known for its high efficiency but high cost. The solar cells, while effective, generate a relatively low voltage, necessitating a high-voltage power converter. The researchers opted for a lightweight design with a series of voltage converters, weighing just 1.13 grams and stepping up voltage from 4.5 V to 9.0 kV, albeit with a modest efficiency of 24 percent.
In testing, conducted by opening a window on a sunny day in Beijing, the CoulombFly successfully hovered for over an hour. The drone required just over half a watt to stay aloft, achieving a lift-to-power efficiency of 7.6 grams per watt. Focusing solely on the motor, the efficiency soared to over 30 grams per watt. The researchers are optimistic about further optimizations, including enhancing motor torque, propeller lift, and solar cell integration.
The CoulombFly also features a miniaturized version, only 8 millimeters high and weighing 9 milligrams, which generates a milliwatt of power and spins its propeller at over 15,000 rpm. Despite its impressive performance, it lacks the necessary control hardware to maneuver and is kept in place within controlled environments to prevent drifting.
However, future iterations could potentially incorporate additional hardware if further optimizations are achieved.
