Intelligent textiles are predicted to see a surprising development in the future. The consequence of this revived interest has been the growth of automobile industry and the improvement of innovative methods for the incorporation of electrical and thermal features into textiles materials. In the present work, the development of a smart stretchable heating device integrated into a car-seat headrest has been identified as a target application. The need for smart conductive materials is becoming increasingly apparent, but they still represent a great challenge for the heating textile area, particularly in additive manufacturing. Polymer-based composites reinforced with copper and carbon powders, attractive as advanced coatings, seems to be good solutions to this issue. Such composites are now acquainted as ideal materials for electronic device engineering and fabrication, thanks to their excellent electrical and thermal conductivities while maintaining suitable mechanical compliance. For easier process and integration, an extrusion 3D printer is employed to achieve thin films coated on the surface of the textile substrate. The developed heater device consists of two principal copper electrodes (so-called power bus), and one heating resistor made of carbon composites designed in different configurations. Finite element models (FEM) are developed to predict the heating behavior of the tested fabric substrates under different pattern suggestions. Experimental measurements via a thermal camera are in consistent with the numerical solutions. It is pointed out that the design optimization based on an adequate tuning of the pattern’s parameters allows to solve inevitable matters in terms of temperature regularity and overheating effect.
This paper reports on a novel measurement method to characterize piezoelectric thin layer (~ 20 μm) through a four-point bending (4PB) setup. Polymer-based piezoelectric composite is directly screen printed onto the surface of host structure, which is assimilated to an instrumented steel substrate. Because of electromechanical coupling properties, a voltage signal can be generated through the piezoelectric sensor when subjected to mechanical strain in its film plane. As the typically sensor layer is very thin in comparison to the underlying substrate, the mechanical properties of the whole system are mainly determined by the characteristics of the steel-type material. Furthermore, the piezoelectric layer properties strongly depend on underlying substrate, electrodes, and the processing route of the layered sensor structure. Therefore, the method developed here enables to reliably extract characteristics such as the effective piezoelectric behavior of the thin composite. In combination with a strain gage coated onto the back side of the substrate, the developed setup allows the determination of the effective piezoelectric sensitivity. The homogeneous strain distribution in the sensing layer is verified by finite element simulations. Furthermore, analytical model is investigated to predict the mechanical behavior of the 4PB structure. The results demonstrate that the developed sensing setup is capable to provide a direct strain/stress measurement instead of traditional techniques through interpolation, and thus offers an efficient method for on-line and in situ structural health monitoring of bearing.
Based on Coulomb forces, electrostatic attraction is a type of actuation that can find many applications for electroactive devices. Electroactive polymers (EAP) are electric responsive materials with specific mechanical and electrical properties that make them promising for an efficient use of this phenomenon. This paper reports on the identification and experimental validation of Figures of Merit (FoM) of electro-adhesion effect for a normal and tangential solicitation. These actuation possibilities are suitable for different kinds of displacement (linear or circular motion) and modulation of shape-shifting designs including origami structures. Several EAP are used to determine the accuracy of experimental benchmarks for the evaluation of these different FoM. The results demonstrate that the developed experimental benchmarks are able to provide accurate values in a range of electric field of [0-5] V/μm. For higher electric fields, different events can occur, at both macroscopic and microscopic scales, leading to a slight decrease of expected performances.
Piezoelectric composites play an important role in the field of sensors. However, composites with randomly dispersed fillers are not efficient, especially when compared to electroactive polymers. Via dielectrophoresis technique we developed composites with fillers, spherical and fiber-shaped, arranged in columnar structures through the thickness of the material. The chosen matrix is thermosetting polydimethylsiloxane, known for its flexibility and biocompatibility, while the fillers are NaNbO3 and BaTiO3. The designed sensors are extremely efficient and comparable to electroactive polymers, and are suitable to be integrated in medical devices, such as smart catheters and bio-scaffolds.
It is well know that ZnO based polymer composite attract enormous research interests, especially in applications of sensor/actuator devices as well as energy harvesting systems. In this study, a PDMS polymer filled with ZnO microparticles were synthesized and its piezoelectric behavior was observed while varying the ZnO concentration, the dielectrophoretic alignment process, and the poling condition. A real-time observation of particles movement under an alternating (AC) field was achieved in non-cured composites through a digital microscopy. Several processing parameters including amplitude and frequency of the applied electric field was investigated to determine the best configuration of dielectrophoretic manipulation. Simulation and experiment results revealed that the alignment process of the particles improved the poling effect caused by the directionality of the network structures. Owing to the high ZnO/ZnO connectivity, the aligned composites give raise to significantly enhanced dielectric and piezoelectric properties with respect to those randomly dispersed. The dielectric permittivity and piezoelectric response of composites increase with an increasing ZnO volume fraction as well. Finally, a 2D finite element model (FEM) was developed to predict the dielectric constant and the piezoelectric coefficient of the ZnO material. Simulation was in good agreement with the experiment results, confirming that a well-designed network structure of the composite would be a viable approach to improve the piezoelectric performance.
LiveMetaOptics presented the Exo-life finder (ELF) telescope combined with the hybrid dynamic structure of live and light active mirror named as “Live-mirror”. Recently we reported the idea of active optical surface correction using the advantage of an electromechanical stimulator to deform mirror surface in a significant correction scale. An effort to develop a conventional electroactive polymer (EAP) actuator through Live-mirror application has been taken the new approach, assembling EAP actuator via additive manufacturing or 3D printing technology. The approach of next-generation mirror leaned on 3D printing technological advancement is able to unlock the principles of a potentially new actuator manufacturing technique. Full 3D print of modified EAP was formulated with plasticized terpolymer for an active layer and terpolymer/CB composite for printed electrodes. Though rudimentary of electroactive polymer, the full-printed actuator could transfer its transversal stress or shear force to shape the mirror surface under low applied electric fields. We described here as well creating multilayer structures with capabilities well beyond those of the individual actuator components. Our various configurations of printed actuators could achieve glass surface deformation in a range of 50 nm to 2 µm considering the maximum glass deformation. As a result of material modification coupled with 3D printing technology, we can increase productivity while enabling a mass and cost reduction and an increase of the parts functionality in terms of the real application.
The novelty of correcting optical mirrors surface in a few microns of the desired precisely-shaped are supported by electroactive polymer actuating/sensing devices. The P(VDF-TrFE-CFE) terpolymer with the 10 % DINP plasticizer has field as EAP which showed 10 times higher in longitudinal strain with respect to the neat one and the increase of total axial strain from 0.4 % - 3.0 % with the multilayer sample 1 to 8 layers respectively. The actuator stack was integrated to the mirror in order to prove the concept of adaptive mirror which is able to reach to goal of a few micron mirror deformation.
Electro-active polymers (EAPs) such as P(VDF-TrFE-CTFE) was demonstrated to be greatly promising in the field of flexible sensors and actuators[1]. The advantages of using EAPs for smart electrical devices are due to their low cost, elastic properties, low density and ability to be manufactured into various shapes and thicknesses. In earlier years, terpolymer P(VDF-TrFE-CTFE), attracted many researchers due to its relaxor-ferroelectric property that exhibits high electrostriction phenomena[2]. Although their attractiveness, this class of materials still owns the main technological constrain of high electric fields required for their actuation (≥ 30 V/μm, about), which inevitably leads to high level of leakage current and thus short life-time[3]. This paper will demonstrate that an alternative approach is possible. Working on the pure terpolymer P(VDF-TrFE-CTFE) matrix, dedicated electro-thermal treatments are introduced in the film fabrication process in order to limit the conduction mechanisms at high electric fields. Reduction in high-voltage leakage current of 80% are achieved for a wide range of actuation electric fields (up to 90 V/μm), and a 4-fold extension in timeto-breakdown are measured for actuation electric field of 40 V/μm
Electro-active polymers (EAPs) such as P(VDF-TrFE-CTFE) was demonstrated to be greatly promising in the field of flexible sensors and actuators[1], but their low dielectric strength driven by ionic conductivity is main concern for achieving high electrostrictive performance. The well-known quadratic dependence of applied electric field on strain response as well as mechanical energy density highlights the importance of improving EAPs electrical breakdown while reducing the leakage current. This paper demonstrates that by controlling processing parameters of polymer synthesis and fabrication procedure, it is possible to drastically increase the electrical breakdown and decrease the ionic conductivity, giving rise to an enhancement in breakdown voltage of around 64% and a reduction in leakage current intensity of 73% at 30V/μm. Effect of polymer crystallinity, molecular mass, as well as crystallization temperature on leakage current were also investigated..
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