Insect-scale aerial vehicles are useful tools for communication, environmental sensing and surveying confined spaces. However, the lack of lightweight high-power-density batteries has limited the untethered flight durations of these micro aerial vehicles. Wireless power transmission using radiofrequency electromagnetic waves could potentially offer transmissivity through obstacles, wave-targeting/focusing capabilities and non-mechanical steering of the vehicles via phased-array antennas. But the use of radiofrequency power transmission has so far been limited to larger vehicles. Here we show that a wireless radiofrequency power supply can be used to drive an insect-scale flapping-wing aerial vehicle. We use a sub-gram radiofrequency power receiver with a power-to-weight density of 4,900 W kg–1, which is five times higher than that of off-the-shelf lithium polymer batteries of similar mass. With this system, we demonstrate the untethered take off of the flapping-wing micro aerial vehicle. Our RF-powered aircraft has a mass of 1.8 g and is more than 25 times lighter than previous radiofrequency-powered micro aerial vehicles.

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Piezoelectric actuation is a promising principle for insect-scaled robots. A major concern while utilizing a piezoelectric actuator is energy loss due to its parasitic capacitance. In this paper, we propose a new concept to recover the charge stored in the parasitic capacitance; it requires only three additional lightweight passive components: two diodes and a resistor. The advantages of our concept are its small additional mass and simple operating procedure compared with existing charge recovery circuits. We provided a guideline for selecting a resistor using a simplified theoretical model and found that half of the charge can be recovered by employing a resistor that has a resistance sufficiently larger than the forward resistance of the additional diode. In addition, we experimentally demonstrated the concept. With a capacitive load (as a replacement for the piezoelectric actuator), it was successfully observed that the proposed concept decreased the power consumption to 58% of that in a circuit without charge recovery. Considering micro aerial vehicle (MAV) applications, we measured the lift-to-power efficiency of a flapping wing piezoelectric actuator by applying the proposed concept. The lift force was not affected by charge recovery; however, the power consumption was reduced. As a result, the efficiency was improved to 30.0%. We expect that the proposed circuit will contribute to the advancement of energy-saving microrobotics.