Electrothermal actuators (ETAs) are novel active materials that can generate different kinds of motions by thermal
expansion induced from Joule heating. The degree of expansion, which influences the deformation and response force, is
determined by the coefficient of thermal expansion (CTE) of the material. In order for the material to be activated, it is
necessary to create conductive network for Joule heating to take place. As a result, one of the most common methods for
creating ETAs is to insert high electrical and thermal conductive filler into the matrix, which allows for fast and uniform
heat distribution though out the material, thus initiate the actuation. In this study, we present the characterization results
of newly developed ETA composites that has ultra-low activation voltage requirement (9V). To create the novel ETA
composites, polydimethylsiloxane (PDMS) is coated to conductive networks which are constructed from high electrical
conductive fillers such as carbon nanotubes. The actuation performance of the novel ETA composites is characterized in
terms of the conductive network distribution, CTE, heat capacity, change in thermal gradient, and its actuation
Dielectric materials are commonly known as electrical insulators that can be polarized under strong electrical field. Currently, emerging dielectric research interests are focusing on nanoparticles mixed polymer based composites, since such materials demonstrated an astonishing increase in dielectric performance when compared to neat polymer matrix, due to the exponential increase in the interfacial area between the nanoparticles and polymer. Such findings infer that particle dispersion plays a critical role for the overall dielectric performance. In this study, we present a continuous manufacturing process consists of extrusion and stretching for Poly(vinylidene fluoride)/silane-treated titanium dioxide (PVDF/silane-treated TiO2) flexible organic/inorganic polymer nanocomposites and the experimental result. Our results show that melt blending process is able to break down both silane treated and untreated micro-size TiO2 agglomerates with extremely well dispersion in PVDF matrix. Follow-up studies and characterizations indicated that the material performances such as dielectric constant and dielectric loss are either similar or surpass the sample prepared via solvent casting and the effects of silane treatment are also discussed. A number of methods was used to characterize the composites, including AFM for dispersion verification and dielectric spectroscopy for dielectric analysis.
In this paper, we present the next generation of polymer based composite foam material fabricated from poly(vinylidene fluoride) (PVDF) and graphene nano-platelets (GNPs) as secondary fillers. We discovered that such composite material has thermoelectric properties and has the potential to be used in energy harvesting applications. The samples were fabricated though melt blending methods, which is a cheaper, simpler process and can be easily scaled up to industrial level for mass production. Our results indicate that melt blending processes can produce either similar or superior results compared to traditional solvent casting methods. In addition, we utilized a novel batch foaming method and successfully created closed-cell structure for the composite material. Our results also show that the thermal conductivity of PVDF/GNP foam samples have approximately an order of magnitude drop compared to solid samples, which is desired for thermoelectric materials. Furthermore, we observed a change in the electrical conductivity threshold of the GNP fillers after foaming. We report a Seebeck coefficient of 217 μV/K for 15 wt% GNP/PVDF foam samples, which is approximately 10 times higher than values reported previously.