Structural modeling of unencapsulatedionic polymer metal composite (u-IPMC) actuators that are used for flapping the insect scale-flapping wing of micro air vehicles (FMAV) in dry environmental conditions is carried out. Structural modeling for optimization of design parameters for retention of water,maximize actuation performance and to study the influence of water activity on the actuation characteristics of u-IPMC is exploredfor use in FMAV. The influence of equivalent weight of Nafion polymer, cations, concentration of cations, pre-treatment procedures on retention of water of u-IPMCs and on actuation parameters, flapping angle, flexural stiffnessandactuation displacement are investigated. IPMC designed with Nafion having equivalent weight 900-1100,pre-heated at 300C and with sodium as the cations is promising for optimum retention of water and actuation performance. The actuation parameters while in operation in dry and humid environment with varying water activity can be tuned to desirable frequency, deflection, flap angle and flexural stiffness by changing the water activity and operational temperature of the environment. © 2017 Techno-Press, Ltd.