Hygroscopic Actuator Optimization

Design a passive, multi-stage hygroscopic actuator capable of generating a predictable linear displacement of at least 5mm when transitioning between 30% and 80% relative humidity. You must characterize the material fatigue limit across 50 cycles and provide a mathematical model representing the force-displacement curve of your composite structure. Success is measured by the repeatability of the stroke length and the minimization of hysteresis during the dehumidification phase.