Analysis of resonant characteristics of microwave actuators at different frequencies

Microwave-based wireless driving have garnered significant attention due to their penetration capability, selective heating, and medium heating properties. In multi-microwave actuator systems, selective control of actuators using microwave frequencies has emerged as a promising approach. Understanding the resonance mechanism of microwave actuators is key to implementing frequency-based control strategies for microwave driving. Herein, we analyzed the resonance condition of flexible microwave actuators composed of SMA springs and passive wires. We demonstrate the response characteristics of standalone SMA springs and the influence of passive wires on the SMA spring in a microwave field. We then analyzed the wire's equivalent antenna model and resonant length. We also evaluated the effects of SMA spring coil numbers and passive wire lengths on the actuator's resonant state at different frequencies (2.4 GHz, 4 GHz, and 5.9 GHz) and developed an equivalent model for the actuator. Our research provides insights for designing microwave actuators with different frequency responses and establishes a foundation for developing complex microwave robotic systems.