Performance Of Ionic Polymer-metal Composite Actuators Research Articles

Ex-situ temperature and humidity aging effect on the tensile behavior of Nafion N117 membrane used in Ionic Polymer–Metal Composite actuators

Nafion N117 is a kind of polymer electrolyte membrane widely used as the ion exchange material in Ionic Polymer–Metal Composite (IPMC) actuators. The mechanical properties of N117 have a great effect on the performance of IPMC actuators. During the manufacturing of IPMC, the procedure includes heating/annealing, and soaking/drying. The membrane is very sensitive to temperature and humidity conditions, so we believe that returning to the initial conditions, irreversible variation of the mechanical properties has occurred during these treatments. This paper focuses on the effect of thermal and hygroscopic treatments on the mechanical responses of the Nafion N117 membrane. The results obtained from this study showed that no matter the thermal or hygroscopic treatments applied, it would decrease the elastic modulus and yielding stress. Furthermore, this decreasing was mainly showed in the intermolecular response. We also found the treated specimens regardless of thermal and hygroscopic treatments showed a sharp transition from elastic to plastic behavior.

Effect of nucleation time on bending response of ionic polymer–metal composite actuators

An autocatalytic electro-less plating of nickel is attempted to replace an electroless impregnation-reduction (IR) method in ionic polymer–metal composite (IPMC) actuators to reduce cost and processing time. Because nucleation time of Pd–Sn colloids is the determining factor of overall processing time, we used the nucleation time as our control parameter. To optimize nucleation time and investigate its effect on the performance of IPMC actuators, we analyzed the relationship between the nucleation time, interface morphology and electrical properties. The optimized nucleation time was 10h. The trends of the performance and electrical properties as a function of nucleation time were attributed to the fact that the Ni penetration depth was determined by the minimum diffusion length of either Pd–Sn colloids or reducing agent ions. The Ni-IPMC actuators can be fabricated less than 14h processing time without deteriorating performance of the actuators, which is comparable to Pt-IPMC prepared by IR method.

Preparation and performance of IPMC actuators with electrospun Nafion ®–MWNT composite electrodes

A new ionic polymer actuator was prepared with Nafion ®-117 membrane and electrodes made of an electrospun Nafion ®/multiwalled carbon nanotube (MWNT) web. The surfaces of composite electrodes were ion-beam coated with gold layers of 2–3 μm thickness to reduce the surface resistance. The composite electrodes offer several advantages over conventional platinum electrodes prepared via electroless plating process, i.e. flexibility, simple processability in large scales, and batch-to-batch reproducibility. The new ionic polymer–metal composite (IPMC) actuators showed a rapid and large bending motion. Under an applied potential of 3 V dc, the maximum horizontal displacement ( δ max) measured at the tip of IPMC strip (cantilever length: 20 mm) was 16.7 mm, the tip velocity in the initial linear region was 10.5 mm/s, 88% of the δ max was reached within initial 5 s, and the generated strain% was 0.79 (13.6 mm, 7.2 mm/s, 85%, and 0.88, respectively for a conventional Nafion ®–IPMC made via the electroless plating of platinum). It was noted that the energy efficiency of strain was over 10 times higher than that of the conventional Nafion ®–IPMC. And the crack formation of metal electrode after repeated bending deformation significantly reduced with the introduction of relatively flexible electrode assembly into the IPMC architecture. The remarkable improvements in its performance were considered to be due to the efficient quantum chemical and double-layer electrostatic effects in a charge injection model, induced by the good dispersion of MWNTs through a typical electrospinning technique.