High-Performance Hybrid (Electrostatic Double-Layer and Faradaic Capacitor-Based) Polymer Actuators Incorporating Nickel Oxide and Vapor-Grown Carbon Nanofibers

Abstract

The electrochemical and electromechanical properties of polymeric actuators prepared using nickel peroxide hydrate (NiO2·xH2O) or nickel peroxide anhydride (NiO2)/vapor-grown carbon nanofibers (VGCF)/ionic liquid (IL) electrodes were compared with actuators prepared using solely VGCFs or single-walled carbon nanotubes (SWCNTs) and an IL. The electrode in these actuator systems is equivalent to an electrochemical capacitor (EC) exhibiting both electrostatic double-layer capacitor (EDLC)- and faradaic capacitor (FC)-like behaviors. The capacitance of the metal oxide (NiO2·xH2O or NiO2)/VGCF/IL electrode is primarily attributable to the EDLC mechanism such that, at low frequencies, the strains exhibited by the NiO2·xH2O/VGCF/IL and NiO2/VGCF/IL actuators primarily result from the FC mechanism. The VGCFs in the NiO2·xH2O/VGCF/IL and NiO2/VGCF/IL actuators strengthen the EDLC mechanism and increase the electroconductivity of the devices. The mechanism underlying the functioning of the NiO2·xH2O/VGCF/IL actuator in which NiO2·xH2O/VGCF = 1.0 was found to be different from that of the devices produced using solely VGCFs or SWCNTs, which exhibited only the EDLC mechanism. In addition, it was found that both NiO2 and VGCFs are essential with regard to producing actuators that are capable of exhibiting strain levels greater than those of SWCNT-based polymer actuators and are thus suitable for practical applications. Furthermore, the frequency dependence of the displacement responses of the NiO2·xH2O/VGCF and NiO2/VGCF polymer actuators were successfully simulated using a double-layer charging kinetic model. This model, which accounted for the oxidization and reduction reactions of the metal oxide, can also be applied to SWCNT-based actuators. The results of electromechanical response simulations for the NiO2·xH2O/VGCF and NiO2/VGCF actuators predicted the strains at low frequencies as well as the time constants of the devices, confirming that the model is applicable not only to EDLC-based actuator systems but also to the fabricated EDLC/FC system.

Ordered and Active Nanochannel Electrode Design for High‐Performance Electrochemical Actuator

“…In order to promote the actuation performance, electrochemically active materials such as metal oxides, conducting polymers, and heteroatoms doping were introduced, which could improve the electrochemical activity of carbon materials and thus enhance device performance in many applications, including capacitors, lithium ion batteries, and electrocatalysts . In the field of electrochemical actuators, Asaka's group reported the method of adding metal oxide nanoparticle (RuO 2 and NiO 2 ) into nanocarbon materials, and the actuation deformation was enhanced by the faradic capacitance that captured extra electron for more cation accommodation. Wallace et al reported polypyrrole and polypyrrole/CNT based electrochemical actuator where polypyrrole generated large redox process to uptake more ion in electrode, resulting in an increase of actuation strain levels.…”

Ruthenium oxide–carbon-based nanofiller-reinforced conducting polymer nanocomposites and their supercapacitor applications

“…Terasawa et al [49] presented the incorporation of metal oxide particles such as RuO 2 , NiO 2 , MnO 2 , or IrO 2 [50] with carbon materials. 1 wt% of RuO 2 into multi-walled carbon nanotubes (MWCNTs) electrode can increase the C sp from 30 to 80 F/g.…”

Soft parallel manipulator fabricated by additive manufacturing

“…In electric double layer charging and discharging process, there is no electrochemical reaction and there is only accumulation of charge at the electrode/electrolyte interface whereas in faradic reaction the charge takes part in the oxidation or reduction reactions of the polymer [41]. There are attempts to improve the actuation by using both processes by combining electrochemically active PEDOT:PSS and inactive components such as carbonbased materials together in electrode preparation [41,42]. Physically it is rather complicated to measure or separate the charge contributed by each of the processes but through simulation, we separate and provide the charge contribution by each process providing new insights in the underlying kinetics in the PEDOT:PSS printed actuators fabricated in this work.…”