Advances in Science and Technology Vol. 79

Abstract: Poly(vinyl chloride) (PVC) has been found to be actuated by applying dc electric field, accompanying colossal strain on the anode surface, particularly when plasticized with large amount of plasticizer [1]. We call the plasticized PVC as PVC gel for convenience in this paper. The deformation has been explained only phenomenologically. However, impedance spectroscopy revealed recently the some fundamental mechanism of the actuation, that is, the deformation depends on the dielectric nature of the materials. The colossal increase of dielectric constant was induced in the gel in the low frequency range. The dependency is strongly depends on the nature of the plasticizer and its content. The phenomena observed as electrical actuation of the PVC gels were (1) Creep deformation on the anode surface, (2) Creep induced bending motion, (3) Tacking to the anode, (4) Contractile deformation, and (5) Vibrational motion by dc electric field application. Creep deformation and the excellent transparency of the gel can be utilized for focus controllable lens. Tacking force can be applied various in combination with bending deformation. Bending actuator has been successfully applied micro-finger actuator and passed for hundreds thousands times continuous operation. In this paper, we will introduce not only the various features of the actuation, but also will get into the some detailed mechanism of the deformation.

Abstract: One of the major obstacles associated with the synthesis of conducting polymer nanoparticles in water is their unstable nature, which is traditionally overcome through the use of soft or hard templates. Such methods use expensive surfactants, often in large amounts, and require the removal of the template, which adds complexity, expense, and environmental hazard. This study explores a facile, one-pot synthesis of stable polypyrrole and polyaniline nanospheres in water that uses ozone as the oxidant. Multiple variables were investigated in order to study the mechanism of this reaction, including monomer concentration, ozone exposure time, reaction temperature, pH, and the solvent system. Particle size measurements revealed that the size of the nanospheres, ranging from 50 nm to 500 nm in diameter, can be controlled via these reaction conditions. These self-stabilizing nanospheres were also characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and zeta potential.

Abstract: Artificial muscles based on conducting polymers, fullerene derivatives, carbon nanotubes, graphenes or other carbon derivative molecular structures are electrochemomechanical actuators. Electrochemical reactions drive most of the volume variation and the concomitant actuation. So under flow of a constant current, any working or surrounding variable influencing the reaction rate will be sensed by the muscle potential, or by the consumed energy, evolution during actuation. Experimental results and full theoretical description will be presented. The muscle potential is a well defined function of: driving current, volume variation (external pressure or hanged masses), temperature and electrolyte concentration. While working artificial muscles detect any change of whatever of those variables by changing either its potential or its consumed energy evolution. Experimental changes fit those predicted by the theoretical description. Only two connecting wires contain, simultaneously, actuating (current) and sensing (potential) signals. Those constitute new feedback intelligent and biomimetic devices opening new technological borders and mimicking natural muscles/brain communication.

Abstract: Thin metal films are not commonly used electrodes for dielectric elastomer actuators as it is a common presumption that they are too stiff to allow large actuated strains. However, using thin metal film electrodes can improve reliability due to their ability to self heal, as shown from their use in metalized plastic film capacitors. Typically, from literature, actuated area strains do not exceed 10% when using thin, un-patterned, metal films formed by sputtering. However, in this present work, large actuated area strains of up to 50% have been demonstrated. This was accomplished by using thin silver film electrodes formed by electroless deposition, and it has been noticed that micro-cracks were present in such electrodes. In this paper, micro-cracks in thin silver electrodes are studied and compared against sputtered silver electrodes. This includes the study of the manner in which they affect the magnitude of actuated strain and the repeatability of the actuator. It has been found that the cracks have helped to improve actuated strain, yet did not affect repeatability, as the cracks did not propagate in subsequent activations. Instead, the cracked electrodes had reached a sort of “steady-state”

Abstract: This presentation discusses how biopolymers such as chitosan and ionic polymer metal composites (IPMCs) can be combined by intercalation and co-polymerization to form a new nanocomposite with actuation, energy harvesting and sensing capabilities and yet have medical healing and diagnostics capabilities. Described are chitosan and ionic polymeric networks containing conjugated ions that can be redistributed by an imposed electric field and consequently act as distributed nanosensors, nanoactuators and artificial muscles. The presentation briefly discusses the manufacturing methodologies and the fundamental properties and characteristics of such chitosan/ionic polymers as distributed nanosensors, nanoactuators and artificial muscles. It will further include descriptions of the basic materials' typical molecular structures. An ionic model based on charge dynamics of the underlying sensing and actuation mechanisms is also presented. Intercalation of chitosan biopolymer and ionic polymers such as perfluorinated sufonic ionomers and subsequent chemical plating of them with a noble metal by a REDOX operation is also reported and the properties of the new product are briefly discussed.

Abstract: Among the broad class of electro-active polymers, dielectric elastomer actuators represent a rapidly growing technology for electromechanical transduction. In order to further develop this applied science, the high driving voltages currently needed must be reduced. For this purpose, one of the most promising and adopted approach is to increase the dielectric constant while maintaining both low dielectric losses and high mechanical compliance. In this work, a dielectric elastomer was prepared by dispersing functionalised carbon nanotubes into a polyurethane matrix and the effects of filler dispersion into the matrix were studied in terms of dielectric, mechanical and electro-mechanical performance. An interesting increment of the dielectric constant was observed throughout the collected spectrum while the loss factor remained almost unchanged with respect to the simple matrix, indicating that conductive percolation paths did not arise in such a system. Consequences of the chemical functionalisation of carbon nanotubes with respect to the use of unmodified filler were also studied and discussed along with rising benefits and drawbacks for the whole composite material.

Abstract: Adhesion between two surfaces may be strongly improved by chemical crosslinking of the interfaces. Polydimethylsiloxane (PDMS) is a widely used polymer that has received considerable attention due to its unique properties, such as relatively low price, biocompatibility, flexibility, high thermal stability, and outstanding dielectric properties. The excellent performances of PDMS elastomers enable the realization of pneumatic, electromagnetic, and thermal actuators. In this work, two-layered PDMS films were adhered together by different mixtures of crosslinkers. The double-layered films were investigated by rheology and microscopy. The objective of this work was to create adhesion of two layers without destroying the original viscoelastic properties of the PDMS films.

Abstract: Actuators from conducting IPNs architecture are described. The electroactive materials are based on several PEO/elastomer IPNs as solid polymer electrolytes in which the conducting polymer Poly(3,4-ethylenedioxythiophene) (PEDOT) is gradually dispersed, i.e. its content decreases from the outside towards the centre of the film. Influence of the electrolyte on the actuation properties has been studied. Moreover, the effect of actuator thickness has been investigated. It is shown that the decrease of the thickness leads to fast response systems presenting large deformations at frequencies above 100 Hz.

Abstract: IPMC actuators suffer because of a large number of influencing factors that do not allow adequate open loop working conditions and they require the use of controlling strategies. IPMC controllers can be designed by using suitable device models. Here a non integer order transfer function is used to model IPMC actuators. In the present paper the IPMC model is scaled as a function of the actuator length and the control law has been parameterized according to this physical parameter