A Novel Electrostatic Comb Actuator Based on Self-Excited Oscillation for Insect-Scale Microrobots

The self-excited electrostatic actuator is a novel actuation scheme that utilizes the electrostatic force induced self-excited oscillation to convert the input dc signals to sustained oscillations of microstructures. Due to a simple oscillating structure or bulky electrode structure, it remains challenging for existing self-excited electrostatic actuators to achieve both high output power and power density. This article presents a new comb configuration for the self-excited electrostatic actuator, which combines a comb oscillating structure with a lightweight electrode structure to achieve both high output power and power density. Utilizing the design of common electrodes, the new comb actuator eliminates the need for additional insulating mediums between adjacent electrode pairs and reduces the number of electrodes by half. With identical materials and structural dimensions (including electrodes and oscillating structure), the comb actuator exhibits a maximum increase of 47.0% in power density compared with the previous comb actuator with the same actuation cells. Furthermore, the power of the comb actuator can be magnified easily by increasing the actuation cells. Via the comb actuator, a crawling microrobot (10 mm, 88 mg) is developed, successfully demonstrating tethered locomotion on a plastic board. These findings present an innovative actuation scheme for insect-scale microrobots.