Chatchai Putson

Modeling and experimentation on an electrostrictive polymer composite for energy harvesting

The harvesting of energy from ambient environments is an emerging technology with potential for numerous applications, including portable electronic devices for renewable energy. Most of the current research activities refer to classical piezoelectric ceramic materials, but more recently the development of electrostrictive polymers has generated novel opportunities for high-strain actuators. At present, the investigation of using electrostrictive polymers for energy harvesting (a conversion of mechanical to electrical energy) is beginning to show potential for this application. This paper discusses the development of a model that is able to predict the energy harvesting capabilities of an electrostrictive polymer composite (EPC). An equivalent electrical scheme has been developed by using the model of current that was recently developed by our group. After the validation of the model on a macroscopic level, an empirical relationship was established to predict the value of power from the electrostriction coefficient, the dielectric permittivity, and the compliance of the material. Finally, results indicated that the dielectric permittivity was the crucial parameter for energy harvesting.

Electrostrictive energy conversion in polyurethane nanocomposites

Electrostrictive polymers have demonstrated an ability to convert mechanical energy into electrical energy and vice versa. This energy conversion has been exploited in an extensive range of applications, including sensors and actuators. Recently, electrostrictive polymers have been investigated as electroactive materials for energy harvesting. The present work aims at establishing an analytical modeling based on electrostrictive equations for predicting a current that can be obtained from the first flexural mode of a beam which was attached by the electrostrictive polymers. The study was carried out on polyurethane films, either without filler or filled with nanosized SiC or a carbon nanopowder. Experimental measurements of the harvested current have been compared to the theoretical behavior predicted by the proposed model. A good agreement was observed between the two sets of data, which consequently validated that the modeling can be used to optimize the choice of materials. It was also shown that the i...

Effects of copper filler sizes on the dielectric properties and the energy harvesting capability of nonpercolated polyurethane composites

Nonpercolated composites based on polyurethane (PU) filled with low concentrations copper (Cu) powders of varying sizes were studied as electrostrictive materials for mechanical energy harvesting. The dispersion of the fillers within the polymeric matrix was investigated by scanning electron microscopy, and results showed a relatively homogeneous dispersion for the microsized fillers and the existence of agglomerates for their nanosized counterparts. Differential scanning calorimetry measurements displayed that there occurred no interaction between the polymeric matrix and the microsized fillers whereas the nanosized fillers slightly enhanced the glass transition of the soft segments of PU and significantly affected the recrystallization temperature. The dependence of the dielectric properties of the composites as a function of the filler volume fraction and filler size was investigated over a broad range of frequencies, showing an increase in the permittivity when fillers were used. This increase was more pronounced for the composites containing nanosized fillers. The measurement of the harvested current and of the harvested power also demonstrated an enhancement of the energy harvesting capability when nanofillers were employed. From the experimental data, it appeared that the electrostrictive coefficient Q was not proportional to the inverse ratio of the permittivity and the Young modulus for the studied composites. Finally, analytical modeling of the harvested current and of the harvested energy offered an accurate description of the experimental data.

Analysis of AC-DC conversion for energy harvesting using an electrostrictive polymer P(VDF-TrFE-CFE)

Harvesting systems capable of transforming unused environmental energy into useful electrical energy have been extensively studied for the last two decades. The recent development of electrostrictive polymers has generated new opportunities for harvesting energy. The contribution of this study lies in the design and validation of electrostrictive polymer- based harvesters able to deliver dc output voltage to the load terminal, making the practical application of such material for self-powered devices much more realistic. Theoretical analysis supported by experimental investigations showed that an energy harvesting module with ac-to-dc conversion allows scavenging power up to 7 μW using a bias electric field of 10 V/μm and a transverse strain of 0.2%. This represents a power density of 280 μW/cm3 at 100 Hz, which is much higher than the corresponding values of most piezo-based harvesters.

Electrostrictive polymer composite for energy harvesters and actuators

Abstract Polymers have attractive properties when compared with inorganic materials: they are lightweight, inexpensive, pliable, and easily processed and manufactured. They can be configured into complex shapes and their properties can be tailored according to demand. With the rapid advances in materials used in science and technology, various substances embedded with intelligence at the molecular level are being developed. A type of electroactive polymer known as electrostrictive has shown considerable promise for a variety of applications, such as actuation with a strain thickness of 15% for an electric field of 10 V/μm. Polyurethane-based nanocomposite films were prepared by incorporating a carbon black nanopowder (C) into the polymer matrix. Electric field-induced strain measurements revealed that a loading of 1 vt% C (volume percentage of carbon black nanopowder) increased the strain level by a factor of 2.5 at a moderate field strength (10 V/μm). Moreover, another application for this material concerned the harvesting of mechanical energy, which constitutes an attractive alternative to the strict reliance on traditional batteries with limited lifetimes. For instance, an effective conversion from the mechanical-to-electric domains of 2.3 μW/cm3, under a transverse vibration level of 0.25% at 100 Hz, has been demonstrated for nylon. The final results indicated that the dielectric constant was a crucial parameter for energy harvesting.

Interface Polarization Effect on Dielectric and Electrical Properties of Polyurethane (PU)/Polyaniline (PANI) Polymer Composites

In this study conductive polymer composites of polyurethane (PU)/polyaniline (PANI) below the percolation threshold were prepared by using solution casting. The dispersion of the conductive PANI fillers within the PU matrix was investigated by scanning electron microscopy (SEM). The SEM results showed a relatively homogeneous dispersion of the PANI fillers within the polymeric matrix. The effects of filler concentration on the dielectric and electrical conductivity depend upon the interface between conductive filler and matrix. Dielectric properties and ac conductivity of polymer composites have been investigated at different frequencies (102 - 105 Hz). The results show that the dielectric constant, dielectric loss and the electrical conductivity are strongly dependent on the frequency. The dielectric constant and dielectric loss decreased, whereas electrical conductivity increased with increasing frequency. In addition, the dielectric constant and conductivity increase when concentration of PANI increased. Differential scanning calorimetry (DSC) presented an enhanced the glass transition temperature (Tg) of the polymer composite with increasing PANI fillers. A correlation of Tg and the interface polarization between the PANI fillers and PU matrix on dielectric properties was proposed.

Electrostrictive Energy Conversion of Polyurethane with Different Hard Segment Aggregations

This work reported the electrostriction of polyurethane (PU) with different aggregations of hard segments (HS) controlled by dissimilar solvents: N,N-dimethylformamide (DMF) and a mixture of dimethyl sulfoxide and acetone denoted as DMSOA. By using atomic force microscopy and differential scanning calorimetry, the PU/DMSOA was observed to have larger HS domains and smoother surface when compared to those of the PU/DMF. The increase of HS domain formation led to the increase of transition temperature, enthalpy of transition, and dielectric constant (0.1 Hz). For the applied electric field below 4 MV/m, the PU/DMSOA had higher electric-field-induced strain and it was opposite otherwise. Dielectric constant and Young’s modulus for all the samples were measured. It was found that PU/DMF had less dielectric constant, leading to its lower electrostrictive coefficient at low frequency. At higher frequencies the electrostrictive coefficient was independent of the solvent type. Consequently, their figure of merit and power harvesting density were similar. However, the energy conversion was well exhibited for low frequency range and low electric field. The PU/DMSOA should, therefore, be promoted because of high vaporizing temperature of the DMSOA, good electrostriction for low frequency, and high induced strain for low applied electric field.

Ambient Energy Harvesting Using Electrostrictive Polymer Composite

The possibility of recycling ambient energies with miniature electrical generators instead of using batteries with limited lifespan has stimulated important research efforts over the past years. Integration of such miniature generators is mainly envisioned into low power autonomous systems, for various industrial or domestic applications. Advances in the field of new smart materials have suggested the investigation of their capabilities as energy converters. One of the most promising types of new materials is represented by electrostrictive polymer composites, belonging to the family of electro-active polymers. In fact the few microgenerators developed are often rigid structures that can perturb the application or the environement. Thus, our objective is to create a flexible, non-intrusive scavenger using electro-active polymers. We report in this paper an analytical model which, predict the energy produced by a simple electroactive membrane, and some promising experimental results.

Electrostriction of Natural Rubber Latex/Carbon Black Nanocomposites

The purpose of this paper is to investigate an electrostrictive behavior of natural rubber (NR) and NR composites filled with carbon black (CB) nanopowders below percolation threshold. These NR elastomers present advantageous features such as a high productivity, elasticity, and ease of processing. In addition, such materials also exhibit the high induced strain and low young modulus for electrostrictive materials that can be used as actuators and energy harvesting. The NR and all composites were prepared by using solution casting method. The electrostrictive property of the composites was evaluated at low electric field (E 5 MV/m) by measuring the electric field induced strain Sz with the photonic displacement apparatus. The surface morphology of the samples was observed by the atomic force microscopy (AFM) and their electrical properties were analyzed as function of concentration and frequency in a range of 102105 Hz. The results show that the dielectric constant and the dielectric loss decrease when the frequency was increased. Moreover, the dielectric constant and the electrical conductivity strongly increase with increasing the CB contents, relate to interfacial charge distribution. While the dielectric loss slightly increases with increasing filler concentration. The electrostriction coefficient tended to increase with a higher CB loading. In comparison at CB 1 wt%, it was found that the electrostriction coefficient of NR composites is approximately 7 times larger than the pure NR. The NR nanocomposites thus seem to be very attractive for low frequency electromechanical applications.

Compliant Natural Rubber Latex Electrodes for Electrostrictive Polyurethane Actuation

Improvement of the electrostrictive polymer with natural rubber (NR) compliant electrodes can potentially offer advantages for enhancement electromechanical efficiency of elastomer actuators. The NR elastomers are capable of advantageous features such as a high productivity, elasticity, and ease of processing. In this work, the NR composites filled with carbon black (CB) nanopowders at high conductivity was used as compliant electrodes on polyurethane electrostrictive polymer. The compliant NR composites electrodes were fabricated by using spin coating technique. The morphology of the NR composites was observed by the scanning electron microscope (SEM). The mechanical, electrical and electromechanical properties of NR composites were investigated. The electric field-induced strain of sample with compliant NR composites electrodes, and comparison with metallic electrodes was determined by using the photonic displacement apparatus. The results show that the thickness strain of polyurethane electrostriction with compliant NR was higher that with metal electrodes, depending not only on compliance between sample and electrodes, but also good conductivity and adhesion of electrodes. Correlation of the electromechanical properties and the mechanically coupled in stretching and compressing to volume incompressibility of polymer are also discussed.