electric fi elds (above 50 V mm − 1 ), which poses the greatest obstacle to their practical application.When an electric fi eld is applied across a fi lm thickness, a fi lm of electrostrictive materials is compressed in the longitudinal direction, and spreads in the lateral planar direction. Unlike piezoelectricity, which has a linear relationship with applied fi eld, this electrostriction behavior demonstrates that the total thickness strain, s z has a quadratic relationship with the applied electric fi eld ( E ), as delineated by the following equation:where R 33 represents the sensitivity of the strain response of a material to the applied electric fi eld.In general, the electric actuation of dielectric elastomers is driven by the two mechanisms of Maxwell stress and a true electrostrictive effect, as illustrated in Figure 1 . [ 13 , 14 ] The electrostriction of a dielectric elastomer is usually dominated by Maxwell stress, which is caused by the Coulomb interaction between oppositely charged compliant electrodes, expressed as Equation 2 . Electric Actuation of Nanostructured Thermoplastic Elastomer Gels with Ultralarge Electrostriction Coeffi cientsElectrostriction facilitates the electric fi eld-stimulated mechanical actuation of dielectric materials. This work demonstrates that introduction of dielectric mismatched nanodomains to a dielectric elastomer results in an unexpected ultralarge electrostriction coeffi cient, enabling a large electromechanical strain response at a low electric fi eld. This strong electrostrictive effect is attributed to the development of an inhomogeneous electric fi eld across the fi lm thickness due to the high density of interfaces between dielectric mismatched periodic nanoscale domains. The periodic nanostructure of the nanostructured gel also makes it possible to measure the true electromechanical strain from the dimensional change monitored via in situ synchrotron small angle X-ray scattering. The work offers a promising pathway to design novel high performance dielectric elastomers as well as to understand the underlying operational mechanism of nanostructured multiphase electrostrictive systems.

Without any contact with electrodes, nanostructured elastomers can electrically actuate, as reported by Sang Ouk Kim, Chong Min Koo, and co‐workers . The cover image illustrates the electric actuation of nanostructured materials, dominated by a true electrostriction mechanism. The degree of surface polarization on the interface between mismatched dielectrics is expressed by the surface color of the dispersion phases.

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Electromechanical properties of poly (vinylidenefluoride-co-trifluoroethylene) (P(VDFTrFE))/carbon nanotube (CNT), P(VDF-TrFE)/graphene (Gr) composites were investigated. The P(VDF-TrFE) composites with conductive fillers had the enhanced electromechanical strain response, which was affected by filler concentration but also by filler type. The strain was increased with the filler concentration. P(VDF-TrFE))/Gr composites had the higher strain response than the P(VDF-TrFE)/CNT composites at the same filler concentration level.