Superior performance of PEDOT:Poly(4-styrenesulfonate)/vapor-grown carbon fibre/ionic liquid actuators exhibiting synergistic effects

- This paper describes new actuators with PEDOT:PSS/vapor-grown carbon fibre/ionic liquid structures.
- These improvements are attributed to be obtained from simultaneous EDLC and FC mechanisms.
- The PEDOT:PSS polymer helps to increase the specific capacitance, strain, and maximum generated stress values.
- These films may have significant potential as actuator materials for wearable energy conversion devices.
- A double-layer charging kinetic model was developed to account for the oxidation and reduction reactions of PEDOT:PSS.

This paper describes new actuators with poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/vapor-grown carbon fibre/ionic liquid (PEDOT:PSS/VGCF/IL) structures, as an alternative to those incorporating single-walled carbon nanotubes (SWCNTs). These devices show superior strain performance compared to those using SWCNTs in place of VGCFs or poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF(HFP)) instead of PEDOT:PSS. These improvements are attributed to be obtained from simultaneous electrostatic double-layer (EDLC) and faradaic capacitor (FC) mechanisms. The electrode in the new actuator system represents an electrochemical capacitor composed of an EDLC and an FC, since PEDOT:PSS (used as a substitute for PVdF(HFP)) acts as both an FC and a base polymer. In addition, the VGCF skeleton increases the electroconductivity of the device and provides an EDLC effect. The functioning mechanism of this device therefore differs from those of conventional actuators, which act solely as EDLC units. The PEDOT:PSS polymer helps to increase the specific capacitance, strain, and maximum generated stress values compared to those obtained with a conventional actuator. Surprisingly, the synergistic effect from the combination of the PEDOT:PSS and VGCFs is much greater than the enhancement achieved by combining PEDOT:PSS and SWCNTs. For this reason, these new, flexible and robust films may have significant potential as actuator materials for wearable energy conversion devices. A double-layer charging kinetic model was developed to account for the oxidation and reduction reactions of PEDOT:PSS, and this model is similar to that previously proposed for PEDOT:PSS/SWCNT/IL actuators. The model was successfully applied to simulate the frequency-dependent displacement response of the actuators.

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