On the geometrical and mechanical multi-aspect optimization of PPy/MWCNT actuators

Polypyrrole (PPy) conducting polymers as one of the most well-known actuation materials have shown numerous applications in a variety of fields such as biomedical devices as well as biomimetic robotics. This study investigates the multiobjective optimization of a PPy/MWCNTs actuator through an electrochemomechanical model. The multilayer actuator is composed of a PVDF layer, as the core membrane and an electrolyte reservoir, as well as two one layer of a conjugated polymer and one layer of multiwalled carbon nanotubes deposited on each side of the PVDF layer. In order to obtain the optimum values for each decision variable (i.e., geometrical and electrochemical), the two main outputs of the bending actuator, the tip displacement and blocking force, have been mathematically modeled and formulated as the objective functions. A multiobjective optimization algorithm is applied to simultaneously maximize the blocking force and tip displacement generated by the actuator. Furthermore, a range for each design variable is defined within which none of the objective functions of the film-type actuator dominates the other one while they are both kept within an acceptable range. The results obtained from the mathematical model are experimentally verified. Moreover, in order to determine the performance of the fabricated actuator, its outputs are compared with their counterparts of a neat PPy actuator.