The dynamic behavior of a liquid-vapor phase change actuator has been investigated. A modular liquid-vapor phase change actuator was designed and fabricated. The actuator consists of a cavity filled with a two-phase fluid bounded on the bottom by a thin membrane into which heat is added and on the top by a cover slip which is displaced by the expansion of the vapor. A parametric study of geometric and operation parameters was conducted. A lumped parameter mathematical model of the actuator was developed to predict the dynamic behavior of the actuator. The model was validated against measured data. Based on the parameter study, actuators with smaller bubbles experienced higher heat loss. Thicker actuators were associated with higher thermal inertia. Thermal inertia, as well as heat losses, had a major effect on the dynamic behavior of the actuator. The model showed that faster response times and higher sensitivity can be achieved if the thermal inertia and heat loss coefficient values are reduced. Time constants less than 2.5 ms and displacement sensitivity higher than 30 m/W are feasible.