Effect of electrolyte storage layer on performance of PPy-PVDF-PPy microactuators

Trilayer electroactive conducting polymer actuators comprising of two active polymer layers separated by an electrolyte storage layer in between are capable of working in air. Ions are shuttled between the two active layers via the middle inactive layer during electrochemical switching, which leads to a bending motion like the bending of a cantilever beam under a load. Performance of these types of cantilevered actuators greatly depends on the middle electrolyte storage layer, which holds electrolyte and eliminates the necessity of an external electrolyte reservoir, as required by their predecessors. In this paper, we used different types of poly(vinylidene fluoride) (PVDF) films as an electrolyte reservoir and compared bending displacement performance of the actuators made from such PVDF films. The results indicate that the thickness of the PVDF layer has significant effect on the tip displacement of the actuators. With a reduction in the PVDF thickness, the bending stress generated by the actuator decreases while the free tip displacement increases. Several types of PVDF thin films were also compared. As expected, porous PVDF thin films retained more liquid electrolyte and produced larger actuation than non-porous films of the same thickness. It was also found that addition of the electrolyte salt directly to the PVDF film during its spin casting increased the film conductivity and actuation tip displacement.