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Untethered Microrobots Driven by kV-Level Capacitive Actuators via Mechanical Electrostatic Inverters

Several microrobots driven by capacitive actuators have shown excellent performance because of the high power density and low working current of the actuators. However, these capacitive actuators need high alternating working voltage (hundreds or thousands of volts), which results in heavy and bulky inverter circuits and increases the difficulty of achieving untethered movements for microrobots. In this work, we report a novel and lightweight mechanical electrostatic inverter based on the self-excited electrostatic vibration for untethered crawling microrobots driven by piezoelectric actuators (working under 300 volts) and dielectric elastomer actuators (working under 3600 volts), respectively. The electrostatic inverter, consisting of just two electrodes and a conductive cantilever, is integrated into the body of the microrobots to generate a high alternating voltage from 200 to 10000 volts, and its weight is in milligram scale (16.2 mg--96.7 mg). Powered by onboard capacitors, two untethered microrobots worked continuously for 3 s--6 s and moved at a maximum speed of 18--41 mm/s. The work provides another scheme for designing untethered microrobots driven by capacitive actuators with high working voltage up to thousands of volts.