Free-standing films made of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) were
prepared by casting water dispersion of its colloidal particles. Specific surface area, water vapor sorption, and electroactive
polymer actuating behavior of the resulting films were investigated by means of sorption isotherm, and
electromechanical analysis. It was found that the non-porous PEDOT/PSS film, having a specific surface area of 0.13 m2
g-1, sorbed water vapor of 1080 cm3(STP) g-1, corresponding to 87 wt%, at relative water vapor pressure of 0.95. A temperature rise from 25 to 40 °C lowered sorption degree, indicative of an exothermic process, where isosteric heat of sorption decreased with increasing water vapor sorption and the value reached 43.9 kJ mol-1, being consistent with the heat of water condensation (44 kJ mol-1). Upon application of 10 V, the film underwent contraction of 2.4% in air at 50% relative humidity (RH) which significantly increased to 4.5% at 90% RH. The principle lay in desorption of water vapor sorbed in the film due to Joule heating, where electric field was capable of controlling the equilibrium of water vapor
The combination of electrical and hygroscopic nature of conducting polymers provided an insight into the development of a new class of electro-driven actuators or artificial muscle systems that worked in ambient air. The electrochemically synthesized polypyrrole films underwent quick and intensive bending in air as a result of a dimensional change due to the sorption of water vapor from one side of the film. Furthermore, an application of electric field caused contraction of the film in air. The dimensional change of the polypyrrole film under the electric field was expressed by two processes: one was the contraction due to the desorption of water vapor and the other was the thermal expansion of polymer chains both caused by Joule heating. The degree of contraction attained 1.2% under 2 V, where the initial speeds of contraction and elongation of the film were 4.4 and 1.8%/min, respectively. Under loading conditions, the power density increased with increasing load and the value attained 0.78 W/kg (6 μW) under the load of 60 g (4 MPa). Under isometric conditions, when dc 2 V is applied to the film under the thermostatic conditions (25°C, 50% RH), the film generated contractile stress repeatedly in response to the applied voltage. The stress reached 6.1 MPa, which was 4 orders of magnitude larger than its own weight and nearly 20 times that of skeletal muscle in animals. The generated stress under 2 V increased to 8.9 MPa upon stretching the film by 1%, which could be associated with the Young's modulus of the film rose due to the desorption of water vapor that plasticized polymer chains. The work capacity of the film increased as the applied voltage became higher and reached 48.2 kJ/m3 at 3 V, while the energy efficiency, defined as the ratio of work capacity to the electric energy, was the order of 10-3%.
We have been studying the Chemical Oxygen-Iodine Laser (COIL) Thermal Image Marker System to the far field objects. This system can mark the distinguishable thermal image on the far field objects with the laser beam of the COIL to guide the Imaging Infrared homing air vehicle to the object marked thermal image with pinpoint accuracy. For the development of this system the study of the COIL resonator is the main task to meet the generation of the required high quality laser beam.
Therefore, first we made two kinds of the experiments. One is to generate the distinguishable thermal image mark (TIM) on the object with stable resonator of the 13 kW output COIL system in the near field. Another is to improve the laser beam quality with the unstable resonators of the COIL system in the low gain condition. Then we studied the high power unstable resonator design for this system with the numerical simulation based on its experimental data and the two-dimensional Fresnel-Kirchhoff integration method with partially coherent scalar electric field. Finally we made the numerical far field TIM generation to verify the TIM generation with the laser beam of the studied high power unstable resonator. The result of simulation shows the fine TIM generation.
The result of the experiment and the resonator design study shows that it is possible to realize the good thermal image mark, the good quality laser beam and the promising unstable resonator for the COIL Thermal Image Marker System.