Interfacial treatment effects on behavior of soft nano-composites for highly stretchable dielectrics

We investigate the influence of interfacial treatment on the matrix–filler interaction using a melt mixing process to fabricate robust and highly stretchable dielectrics. Silicone oil and silane coupling agent are studied as possible solutions to enhance the compatibility between the inorganic fillers and polymer matrix. Morphology, thermomechanical and dielectric behavior of the prepared specimens are studied. Results show that specimens filled with silicone oil coated particles have promising dielectric and thermal properties. The mechanical properties reveal a stiffness enhancement by 67% with a high strain at break of 900%. The relative permittivity of the specimens prepared with silicone oil increased by 45% as observed from the dielectric analysis

Enhanced Polymer Nanocomposites for Condition Assessment of Wind Turbine Blades

Damages in composite components of wind turbine blades and large-scale structures can lead to increase in maintenance and repair costs, inoperability, and structural failure. The vast majority of condition assessment of composite structures is conducted by visual inspection and non-destructive evaluation (NDE) techniques. NDE techniques are temporally limited, and may be further impeded by the anisotropy of the composite materials, conductivity of the fibers, and the insulating properties of the matrix. In previous work, the authors have proposed a novel soft elastomeric capacitor (SEC) sensor for monitoring of large surfaces, applicable to composite materials. This soft capacitor is fabricated using a highly sensitive elastomer sandwiched between electrodes. It transduces strain into changes in capacitance. Here, we present a fabrication method for fabricating the SEC. Different surface treatment techniques for the nanoparticles are investigated and the effects on the mechanical and the electrical properties of the produced film are studied. Results show that using melt mixing fabrication method was successful at dispersing the nanoparticles without using any surface treatment, including coating the particles with PDMS oil or the use of Si-69 coupling agent. Yet, treating the surface would result in increasing the stiffness of the matrix as well as improving the interaction between the filler particles and the matri

Electrical breakdown of an acrylic dielectric elastomer: Effects of hemispherical probing electrodes size and force

© 2016 The Author(s). Dielectric elastomers are widely investigated as soft electromechanically active polymers (EAPs) for actuators, stretch/force sensors, and mechanical energy harvesters to generate electricity. Although the performance of such devices is limited by the dielectric strength of the constitutive material, the electrical breakdown of soft elastomers for electromechanical transduction is still scarcely studied. Here, we describe a custom-made setup to measure electrical breakdown of soft EAPs, and we present data for a widely studied acrylic elastomer (VHB 4905 from 3M). The elastomer was electrically stimulated via a planar and a hemispherical metal electrode. The breakdown was characterized under different conditions to investigate the effects of the radius of curvature and applied force of the hemispherical electrode. With a given radius of curvature, the breakdown field increased by about 50% for a nearly 10-fold increase of the applied mechanical stress, while with a given mechanical stress the breakdown field increased by about 20% for an approximately twofold increase of the radius of curvature. These results indicate that the breakdown field is highly dependent on the boundary conditions, suggesting the need for reporting breakdown data always in close association with the measurement conditions. These findings might help future investigations in elucidating the ultimate breakdown mechanism/s of soft elastomers

A novel approach to tunable diffractive transmission gratings based on dielectric elastomer actuators

Dielectric elastomer actuators (DEA) of poly-styrene-ethylene-butadiene-styrene (SEBS) and commonly used VHB4910 tape were studied for voltage tunable optical transmission gratings. A new geometry is proposed, in which the grating is placed in an area without electrodes, permitting for light transmission through the device. Experiments were performed to implement surface relief gratings on DEA films from pattern masters made from holographic recorded gratings. Since the actuation strain of the DEA depends strongly on the boundary conditions, the desired voltage-controllable deformation of the grating can be achieved by choosing suitable manufacturing parameters. Conditions were found permitting a shift of up to 9 % in a 1 ?m grating. A model based on independently measured material parameters is shown to describe the optical behavior

Soft Conductive Elastomer Materials for Stretchable Electronics and Voltage Controlled Artificial Muscles.

Block copolymer elastomer conductors (BEC) are mixtures of block copolymers grafted with conducting polymers, which are found to support very large strains, while retaining a high level of conductivity. These novel materials may find use in stretchable electronics. The use of BEC is demonstrated in a capacitive strain sensor and in an artificial muscle of the dielectric elastomer actuator type, supporting more than 100% actuation strain and capacity strain sensitivity up to 300%

Optical transmission gratings tuned by electro active polymers

Dielectric elastomer actuators (DEA) of poly-styrene-ethylene-butadiene- styrene (SEBS) and poly-acrylic VHB4910 were studied for voltage tunable optical transmission gratings. A new geometry is proposed, in which the grating is placed in an area without electrodes, permitting for light transmission through the device. Experiments were performed to implement surface relief gratings on DEA films from pattern masters made from holographic recorded gratings. Since the actuation strain of the DEA depends strongly on the boundary conditions, the desired voltage-controllable deformation of the grating can be achieved by choosing suitable manufacturing parameters. Conditions were found permitting a relative change up to 8.5 % in a 1 m grating. A model based on independently measured material parameters is shown to describe the optical behavior

Tunable diffractive optical elements on various electro active polymers

An innovative approach for voltage-tunable optical gratings based on dielectric elastomer actuators (DEAs) using electro active polymers is presented. Sinusoidal surface gratings, holographically written into azobenzene containing films, are transferred via nanoimprinting to DEAs of different carrier materials. We demonstrate that the surface relief deformation depends on the mechanical and geometrical properties of the actuators. The tested DEAs were made using commercially available elastomers, including a tri-block copolymer poly-styrene-ethylene-butadiene-styrene (SEBS), a silicone polydimethylsiloxane rubber (PDMS) and commonly used polyacrylic glue. The polyacrylic glue is ready to use, whereas the SEBS and the PDMS precursors have to be processed into thin films via different casting methods. The DEA material was pre-stretched, fixed to a stiff frame and coated with stretchable electrodes in appropriate designs. Since the actuation strain of the DEA depends strongly upon the conditions such as material properties, pre-stretch and geometry, the desired voltage-controllable deformations can be optimized during manufacturing of the DEA and also in the choice of materials in the grating transfer process. A full characterization of the grating deformation includes measurements of the grating pitch and depth modulation, plus the change of the diffraction angle and efficiency. The structural surface distortion was characterized by measuring the shape of the transmitted and diffracted laser beam with a beam profiling system while applying an electro-mechanical stress to the grating. Such surface distortions may lead to decreasing diffraction efficiency and lower beam quality. With properly chosen manufacturing parameters, we found a period shift of up to 9 % in a grating with 1 ?m pitch. To describe the optical behavior, a model based on independently measured material parameters is presented

Electrically tunable polymer DFB laser

Soft optical components based on flexible polymers or fluids can be coupled to electroactive polymer artificial muscles for monolithically integrated optical elements with voltage controlled properties. A flexible polymer distributed feedback (DFB) dye laser is combined with an electroactive dielectric elastomer actuator to afford continuous voltage-controlled wavelength shift

Enhanced Polymer Nanocomposites for Condition Assessment of Wind Turbine Blades

Damages in composite components of wind turbine blades and large-scale structures can lead to increase in maintenance and repair costs, inoperability, and structural failure. The vast majority of condition assessment of composite structures is conducted by visual inspection and non-destructive evaluation (NDE) techniques. NDE techniques are temporally limited, and may be further impeded by the anisotropy of the composite materials, conductivity of the fibers, and the insulating properties of the matrix. In previous work, the authors have proposed a novel soft elastomeric capacitor (SEC) sensor for monitoring of large surfaces, applicable to composite materials. This soft capacitor is fabricated using a highly sensitive elastomer sandwiched between electrodes. It transduces strain into changes in capacitance. Here, we present a fabrication method for fabricating the SEC. Different surface treatment techniques for the nanoparticles are investigated and the effects on the mechanical and the electrical properties of the produced film are studied. Results show that using melt mixing fabrication method was successful at dispersing the nanoparticles without using any surface treatment, including coating the particles with PDMS oil or the use of Si-69 coupling agent. Yet, treating the surface would result in increasing the stiffness of the matrix as well as improving the interaction between the filler particles and the matrixThis proceeding is published as Saleem, H., M. Thunga, M. Kollosche, M. Kessler, and Simon Laflamme. "Enhanced polymer nanocomposites for condition assessment of wind turbine blades." In Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2013, vol. 8694, p. 86940A. International Society for Optics and Photonics, 2013. DOI: 10.1117/12.2009856. Posted with permission.</p

Soft Conductive Elastomer Materials for Stretchable Electronics and Voltage Controlled Artificial Muscles.

Block copolymer elastomer conductors (BEC) are mixtures of block copolymers grafted with conducting polymers, which are found to support very large strains, while retaining a high level of conductivity. These novel materials may find use in stretchable electronics. The use of BEC is demonstrated in a capacitive strain sensor and in an artificial muscle of the dielectric elastomer actuator type, supporting more than 100% actuation strain and capacity strain sensitivity up to 300%