Nanocomposite electrodes using highly conductive sub-millimetre-long single-walled carbon nanotubes pasted with PEDOT:PSS and high-performance actuators

Abstract

We describe new nanocomposite electrodes and actuators using highly conductive single-walled carbon nanotubes (<1 mm in length) fabricated using the ‘super-growth’ method (SG-SWCNT) pasted with poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and combined with electrostatic double-layer capacitors (EDLCs) and faradaic capacitors (FCs). The electromechanical/chemical properties of the SG-SWCNT/PEDOT:PSS/ionic liquid (IL) electrode and actuator were compared with those of the SG-SWCNT/IL electrode and actuator. The SG-SWCNT/PEDOT:PSS/EMI[C(CN)3] electrode (volume resistivity; 4.26 Ω cm, surface resistivity; 0.55 Ω/sq. and conductivity; 235 S/cm) was a more conductive electrode than the equivalent SG-SWCNT/EMI[C(CN)3] electrodes (36.0 Ω cm, 2.37 Ω/sq. and 28.0 S/cm). This is thought to be a result of the synergy between SG-SWCNT and PEDOT:PSS. The maximum strain of the SG-SWCNT/PEDOT:PSS/EMI[B(CN)4] actuator ranged from 0.39% to 1.88%, which is approximately 1.6–7.5 times larger than that of the SG-SWCNT/EMI[B(CN)4] actuator. The actions of the hybrid actuators differed from those of the SG-SWCNT/IL actuators, which function only as EDLC units. A kinetic model featuring double-layer charging successfully simulated the frequency-dependent displacement responses of both types of actuators. The use of a PEDOT:PSS polymer promotes higher conductivity, specific capacitance, and strain, which is thought to originate in synergy between SG-SWCNT and PEDOT:PSS. Thus, flexible robust films that exploit this synergy are likely to be useful as actuator components in energy conversion and wearable devices.