Electromechanical Evaluation of Ionomeric Polymer-Metal Composites Using Video Analysis

Abstract

Ionomeric Polymer-Metal Composites (IPMC) are smart materials whose electromechanical behavior depends on the electrical stimulus intensity, membrane hydration level, and ionic migration. This paper investigates the effects of the voltage, relative humidity, and counterion type (Li + and K + ) on a Nafion-based IPMC performance. Instrumentation capable of applying an electrical stimulus and measuring the electromechanical response was developed. The ionic conductivity was obtained using Electrochemical Impedance Spectroscopy. Complementary SEM analyses were performed before and after actuation cycles. The IPMC performance improved when the electrical stimulus was 5.00 V, RH = 90%, and Li + was used. The IPMC-Li sample is an excellent candidate to be used as an actuator since it exhibited fast actuation movement, considerable displacement, and no evident back-relaxation. However, its mechanical performance decreased over time because of a progressive increase in platinum electrode crack density and dehydration. The video analysis technique is an efficient, effective, and low-cost technique.

PI Controller for IPMC Actuators Based on Nafion®/PT Using Machine Vision for Feedback Response at Different Relative Humidities

“…Therefore, to avoid any sample hydration level variation during the tests, the IPMC was kept in a closed chamber, controlling the RH continuously for 120 minutes to achieve osmotic equilibrium and kept constant until the end of test 23 .…”

“…The ionic transport mechanisms are related to the actuator hydration level 17 . Saccardo et al 23 analyzed the variation in the magnitude of the impedance (|Z|) as a function of RH using Impedance Spectroscopy. At low frequencies, it was observed that the ionic response of the material dominates it.…”

“…This ionic movement causes an internal pressure gradient, leading to a spatially nonuniform mass accumulation, which causes the device to bend 18 (Figure 1b). Therefore, several factors influence mechanical performance, such as the dependence on the operating environment (temperature and humidity) [19][20][21][22] , counterion type 23 , polymeric membrane dimensions (especially the thickness), and electrode physical properties 24 .…”

“…Other phenomena are also observed, such as backrelaxation (drawback associated with water counter diffusion, which causes the IPMC to shift in the opposite direction after maintaining a bias for a while) 23,31 , electrolysis (a reaction that splits water into hydrogen and oxygen) 32 , hysteresis (tendency to conserve their properties in the absence of the stimulus that generated them) 33 , and highly uncertain 34 . In other words, these devices have variations and instabilities in electromechanical performance, exhibiting nonlinearities and time-varying behaviors 35 .…”

Improving the swelling, mechanical, and electrical properties in natural rubber latex/carbon nanotubes nanocomposites: Effect of the sonication method

“…In the elastomeric field, conductive rubber composites (CRC) are gaining importance by combining the above‐mentioned characteristics with their unique strain properties 1,2 . The rubbers' high flexibility allows, for example, the replacement of metallic electrodes in devices that are subjected to repeated actuation cycles, such as in ionomeric polymer–metal composites (IPMCs), 3,4 whose conventional electrodes degrades over time 5–7 . Other applications include biomimicry, 8 capacitors, 9 electrochemical sensors, 10 biomedicine, 11 and flexible electronics 12 …”