Soft Electromagnetic Actuator and Oscillator

Abstract

Abstract Soft actuators are critical for enabling soft robots, medical devices, and haptic systems. Many soft actuators, however, require power to hold a configuration and rely on hard circuitry for control, limiting their potential applications. In this work, the first soft electromagnetic system is demonstrated for externally‐controlled bistable actuation or self‐regulated astable oscillation. This novel bellows‐shaped actuator uses liquid metal encased in silicone as a compliant conductor that is capable of force generation, integrated sensing, and self‐reconnecting. In the bistable configuration, the actuator can hold positions with no power. By utilizing a unique soft kinking mechanism, the actuator can generate feedback for self‐regulated oscillation. The construction, sensing, and feedback mechanisms for this actuator are first discussed. Then, the force output, thermal performance, and dynamics are characterized. The bistable version has a stroke of 6 mm and can compress/expand with only 15 W of power for 30 ms. The astable version has a stroke of 3 mm and can oscillate at 27 Hz with 18 W of power. Several applications are demonstrated including bistable crawling, hopping, pulsing, and swimming. By adding a 20 V battery, self‐regulated astable vibrational locomotion is also demonstrated. Overall, this work shows how these actuators and oscillators can bridge the gap between conventional and soft robots.