Conducting polymer actuators are being investigated for a number of applications. Both linear contracting/expanding and bending type actuators can be constructed that utilise the redox-induced volume changes in the conducting polymer. Improved actuator performance has been demonstrated by modifications to our helix-tube design. The pitch of the helix and bundling the actuators have increased the strain and force generated. Short-term improvements to the strain were also generated using new dopants, but cycle life was poor in this case. Further studies on the mechanism of actuation have continued to focus attention on the influence of the elastic modulus on the actuation strain. Surprising results have been obtained from polythiophene actuators that show an increased strain and increased work-per-cycle with an increasing applied load in isotonic operation. The observations were explained by an increase in modulus during the contraction cycle of the actuation. Preliminary studies show how the change in modulus can be conveniently measured using an in situ mechanical technique.
The phase inversion technique was used to produce polyaniline (PAn) actuators with different geometries that cannot be obtained by PAn cast from N-methyl-2-pyrrolidinone (NMP) solution in a conventional way. PAn was cast and coagulated in a water bath forming films and tubes with or without a platinum (Pt) wire helix as an interconnect. PAn was doped with hydrochloric solution (HCl, 1 M) (PAn/HCl) or methanesulfonic acid (MSA, 1 M) (PAn/MSA). In nitric acid (HNO3, 1 M) aqueous electrolyte, the actuation strain of PAn/HCl was 0.9% which increased to 2.0% and 2.7% for the tubes without and with the Pt helix, respectively. The Pt helix helped prevent the IR drop along the actuator. Comparing with NaNO3 (1 M) aqueous electrolyte, the use of HNO3 aqueous electrolyte gave better actuation stability where at least 100 cycles were observed and the final actuation strain was determined by the size of dopant. Change of coagulation bath from water to NMP (30% w/w)/water resulted in subtle difference in the Young’s modulus of PAn/MSA in oxidized and reduced states. PAn prepared by phase inversion technique is porous by nature, consequently it is brittle and exhibits a low actuation stress (0.3 - 0.4 MPa).
Smart fabrics are those with electronic devices embedded in the material structure. Metallic fibres are not compatible with a comfortable fabric and flexible fibres with electronic capabilities are desired. Polyaniline (PANi) and carbon nanotubes (CNTs) show potential for application in different electronic devices such as conductive yarn, sensor, actuator, battery, capacitor and diode. The development of fibres from these materials can be considered as potentially useful for the manufacturing of smart fabric which embedded non metallic electronic devices. This paper describes the influence of CNT addition on the electronic, mechanical of PANi-CNT composite fibre which was fabricated by a wet spinning process. PANi(EB)-nanotube (SWNT, DWNT)- dimethyl propylene urea (DMPU) composite spinning solution have been prepared by an ex-situ process. The size distribution of nanotubes has been characterized by zeta sizer. Furthermore the rheological study has been conducted for optimization of PANi/CNT weight ratio to produce solutions with suitable fluidity for spinning process. In spite of the great impact of nanotubes on the mechanical and electrical properties of PANi composite fibre, the structure of the composite is far from ideal and it can be proposed that by proper ex-situ and in-situ solution preparation and processing techniques further improvements in properties are possible.