Electroactive Polymers

Boron doped and undoped Poly(vinyl) alcohol/Zirconium-yttrium acetate (PVA/Zr-Y) nanofibers were prepared by electrospinning using PVA as a precursor. The effect of boron doping was investigated in terms of solution properties, morphological changes and thermal properties. The effect of boron doping on calcined yttria stabilized zirconia (YSZ) fibers were evaluated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy analysis. XRD
analysis revealed varying amounts of monoclinic and tetragonal zirconia present in the undoped fibers calcined at 800oC. The average crystallite sizes of the undoped YSZ were increased from 9.28 to 22.79 nm with calcining temperature increasing from 250 to 800 °C. The crystallite size was enhanced with boron doping. The systematic evolution of morphological features in the spun and the processed fibers were employed by scanning electron microscopy.

In the present paper the analysis of the leg movements of mechanical spider robot has been done. A mechanical spider is an eight leg robot which works on klann’s mechanism and can be used at bumpy roads, hilly area or any type of surfaces. Engineering specifications and requirements for the design of an artificial mechanism are the main objective of this paper.As fantastic as this idea may seem, recent developments in electroactive polymers (EAP) may one day make such bionics possible.As this technology continues to evolve, novel mechanisms that are biologically inspired are expected to emerge.In recognition of the need for cooperation in this multidisciplinary field, there is a series of international forums that are leading to a growing number of research and development projects and to great advances in the field. In this paper, the field of EAP as artificial muscles will be reviewed covering the state of the art, the challenges and the vision for the progress in future years.

In this study, grafted gelatin with oligoaniline (GelOA) was synthesized and then mixed with Poly (vinyl alcohol) (PVA). Several scaffolds with different ratio of PVA/GelOA were electrospun to fabricate electroactive scaffolds. GelOA was characterized using Fourier-transform infrared spectroscopy (FTIR); moreover, nanofiber properties were evaluated by differential scanning calorimetry (DSC), thermogravi-metric analysis (TGA), and scanning electron microscope (SEM) analyses. Nanofibers diameter was decreased with aniline oligomer increment form 300 to 150 nm because of the hydrophobic nature of the aniline oligomer. Aniline oligomer electroactivity was studied using cyclic voltammetry, which exhibited two redox peaks at 0.4 and 0.6. Moreover, aniline oligomer enhancement resulted in melting point increasing from 220°C to 230°C because of the crystallinity increment. To assess the biocompatibility of nanofibers, cell viability and cell adhesion were tracked using mesenchymal stem cell (MSCs). It was revealed that the presence of aniline oligomer leads to enhancing the conductivity, thermal properties and lowering the degradation rate and drug release. Among of different scaffolds, sample with high content of GelOA shows better behavior in physical and biological properties. Accumulative drug releases under

Dielectric elastomers are a class of electro-active polymers (EAPs) which have great potentials to be used in smart composites. These materials with compliant electrodes are converters of electrical energy to mechanical energy in order to produce external load and strain with good efficiency. Electrode materials should typically have good compliancy so that undergo large strain alongside the film, without producing any additional stress and constraint for the actuator. In the present study, the effect of 4 different electrode materials (graphite filled silicone oil, silver filled grease, graphite powder and electrically conductive silicone rubber) on the performance of dielectric elastomer actuators has been studied. The principle of operation, the method of fabrication and test method of planar actuators are discussed. We have also studied the effects of different driving voltages and different prestrain values on the actuator response. Experimental results showed that electrical conductivity, material compliancy, and compatibility with substrate in the electrode materials are some of the important parameters affecting the actuator performance.

The nonverbal expression of the emotions, especially in the human face, has rapidly become an area of intense interest in computer science and robotics. Exploring the emotions as a link between external events and behavioural responses, artificial intelligence designers and psychologists are approaching a theoretical understanding of foundational principles which will be key to the physical embodiment of artificial intelligence.

Ionic polymer-metal composites (IPMCs) are electroactive materials that bend under an applied electric field. Existing work has typically dealt with the control of IPMC actuators themselves. In this paper we investigate the stabilization of an inverted pendulum on a cart using an IPMC actuator. Different from the traditional setting of cart- pendulum systems, we require that the voltage on the IPMC actuator stay close to zero, to prolong the actuator life and reduce power consumption. A state-space model is developed for the system, based on which an LQR controller together with an observer is designed. The proposed control scheme is able to stabilize the inverted pendulum for the entire duration of the experiment (five minutes). These results indicate that IPMC actuators hold potential for more sophisticated control applications.

Myelination of Schwann cells (SCs) is critical for the success of peripheral nerve regeneration, and biomaterials that can promote SCs' neurotrophin secretion as scaffolds are beneficial for nerve repair. Here we present a biomaterials-approach, specifically, a highly tunable conductive biodegradable flexible polyurethane by polycondensation of poly(glycerol sebacate) and aniline pentamer, to significantly enhance SCs' myelin gene expression and neurotrophin secretion for peripheral nerve tissue engineering. SCs are cultured on these conductive polymer films, and the biocompatibility of these films and their ability to enhance myelin gene expressions and sustained neurotrophin secretion are successfully demonstrated. The mechanism of SCs' neurotrophin secretion on conductive films is demonstrated by investigating the relationship between intracellular Ca 2þ level and SCs' myelination. Furthermore, the neurite growth and elongation of PC12 cells are induced by adding the neurotrophin medium suspension produced from SCs-laden conductive films. These data suggest that these conductive degradable poly-urethanes that enhance SCs' myelin gene expressions and sustained neurotrophin secretion perform great potential for nerve regeneration applications.

Thermoelectrochemical cells are a promising new technology for harvesting low-grade waste heat. The operation of these cells relies on a redox couple within an electrolyte, which is most commonly water-based, and improvement of these materials is a key aspect of the advancement of this technology. Here, we report the gelation of aqueous electrolytes containing the K 3 Fe(CN) 6 /K 4 Fe(CN) 6 redox couple using a range of different polymers, including polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (Cmc), polyacrylamide (PAAm), and two commercial polyurethane-based polymers: HydroMed D 640 and HydroSlip C. These polymers produce quasi-solid-state electrolytes with sufficient mechanical properties to prevent leakage, and allow improved device flexibility and safety. Furthermore, the incorporation of various ionic liquids within the optimized hydrogel network is investigated as a route to enhance the electrochemical and mechanical properties and thermal energy harvesting performance of the hydrogels.

A novel method of fabrication of gadolinia doped bismuth oxide nanoceramic via the sol-gel technique is reported. Their thermal, structural and morphological properties are described by measurements of Differential Thermal Analysis/Thermal Gravimetry, X-ray Powder Diffraction and Scanning Electron Microscopy. The samples have stable high ion conductive face centered cubic δ-phase nanocrystalline structure. The electrical measurements of the nanoceramic powders were carried out in the temperature range of (689-1091 K) using 4-point probe technique. There is a transition between two distinct regions at 720 °C, which can be attributed to the order-disorder transition. This observation is supported by the differential thermal analysis measurements. The experimental results show that the value of conductivity increases with increasing temperature over linear parts characterized by two different activation energies. The conductivity data over whole measured temperature range were fitted the Arrhenius plot and it shows two linear regions with different slopes which correspond to low-temperature range (689-975 K) and high-temperature range (999- ersus q/kT plot as 1.25 eV and 2.81 eV for low-temperature range and high-temperature range, respectively.

A facile and low cost synthesis of Ni(OH)2 nanobelts (NBs) modified electroactive poly(vinylidene fluoride) (PVDF) thin films with excellent dielectric properties has been prepared via in situ formation of Ni(OH)2 NBs in PVDF matrix. Formation and
morphology of the NBs are confirmed by UV-Visible spectroscopy and Field emission scanning electron microscopy respectively. A remarkable improvement in electroactive β
phase nucleation (~82%) and dielectric constant (ε ~ 3.1 x 106 at 20 Hz) have been observed in the nanocomposites (NCs). The interface between the NBs and the polymer matrix plays a
crucial role in the enhancement of electroactive β phase and the dielectric properties of the thin films. Strong interaction via hydrogen bond between Ni(OH)2 NBs and PVDF matrix is
the main reason for enhancement β phase crystallization and improved dielectric properties.
The NC thin films can be utilized for potential applications as high energy storage devices like supercapacitors, solid electrolyte batteries, self-charging power cells, piezoelectric
nanogenerator, thin film transistors and sensors.

A simple ellipsometric technique is traditionally used for investigating the non-linear optical effects in poled polymer matrices. Upon writing a hologram in a low glass-transition-temperature photorefractive polymer composite, the chromophores are oriented in situ by the formed space-charge field. This way, the orientation of the chromophores gives us information about the latter one. We show how simple transmission ellipsometry can reproduce the results of the standard four-wave-mixing technique, yielding the quantitative determination of the space-charge field. Besides, this technique offers high sensitivity at low poling fields. This method is simple, easy-adjustable, and non-erasing, i.e. ideally suited to complement traditional holographic methods.

ABSTRACT Reconfigurable lens is biomimetic as it mimics human eye and is a transparent actuating material that can change its curvature in the presence of external stimuli. Focus tunable, adaptive lenses provide several advantages over traditional lens assemblies in terms of compactness, cost, efficiency and flexibility. To further improve the simplicity and compact nature of adaptive lenses, we present lens system which makes use of an inline, transparent electro active polymer actuator. This paper reports the preliminary development we have achieved in reconfigurable lens systems made with cellulose nanocrystals (CNC) using the principle of Kerr effect. Preparation of the hydrophobic CNC solution as well as the optical properties of the lens has been discussed. This soft gel actuator was analyzed by measuring the electric birefringence in the pulse field of constant and sinusoidal voltage based on the use of modulation of elliptic light polarization.

Dielectric elastomers are a class of electro-active polymers (EAPs) which have been used for smart structures, such as muscle-like actuators. These materials with compliant electrodes are transducers of electrical to mechanical energy, with extremely large strain and good efficiency. A thorough understanding of the physics underlying the nature of different electrode materials can help modify actuator response. The objective of this paper is to investigate the effect of 4 different electrodes (graphite powder, carbon filled grease, silver filled grease and electrically conductive silicone rubber) on the performance of dielectric elastomer actuators. The principle of operation, the method of fabrication and test method of planar actuators are discussed. Effects of different driving voltages and different prestrain values on the actuator response have been studied. Electrical conductivity under strain, electrode surface uniformity and mechanical compatibility with substrate, as the mo...

NASA is seeking to reduce the mass, size, consumed power, and cost of the instrumentation used in its future missions. An important element of many instruments and devices is the actuation mechanism and electroactive polymers offer an effective alternative to current actuators. In this study, two families of electroactive polymer materials were investigated, including bending ionomers and longitudinal electrostatically driven elastomers. These materials were demonstrated to effectively actuate manipulation devices and their performance is being enhanced in this on-going study. The recent observations are reported in this paper, which also include cryovac tests at conditions that simulate Mars environment. Tests at T equals -140 degree(s)C and P approximately 1 Torr, which are below Mars conditions, showed that the bending actuator was still responding with a measurable actuation displacement. Analysis of the electrical characteristics of the ionomer showed that it is a current driven material rather than voltage driven. Measurements of transient currents in response to a voltage step shows a time constant on the order of few seconds with a response speed that is enhanced with the decrease in drive voltage. The ionomer main limitation is its requirement for being continuously moist. Tests showed that while the performance degrades as the material becomes dry, its AC impedance increases, reaching an order of magnitude higher than the wet ionomer. This response provides a gauging indication of the material wetness status. Methods of forming the equivalent of a skin to protect the moisture content of the ionomer are being sought and a limited success was observed using thick platinum electroding as well as when using polymeric coating.