Fibers capable of generating axial contraction are commonly seen in nature and engineering applications. Despite the broad applications of fiber actuators, it is still very challenging to fabricate fiber actuators with combined large actuation strain, fast response speed, and high power density. Here, we report the fabrication of a liquid crystal elastomer (LCE) microfiber actuators using a facile electrospinning technique. Owing to the extremely small size of the LCE microfibers, they can generate large actuation strain (~60 percent) with a fast response speed (<0.2 second) and a high power density (400 watts per kilogram), resulting from the nematic-isotropic phase transition of liquid crystal mesogens. Moreover, no performance degradation is detected in the LCE microfibers after 106 cycles of loading and unloading with the maximum strain of 20 percent at high temperature (90 degree Celsius). The small diameter of the LCE microfiber also results in a self-oscillatory behavior in a steady temperature field. In addition, with a polydopamine coating layer, the actuation of the electrospun LCE microfiber can be precisely and remotely controlled by a near-infrared laser through photothermal effect. Using the electrospun LCE microfiber actuator, we have successfully constructed a microtweezer, a microrobot, and a light-powered microfluidic pump.

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Polymer composites with high dielectric permittivity and thermal conductivity are highly desired due to their potential applications in a wide range of electronic and electrical industries. In this study, the composite consisting of poly(vinyliene fluoride) (PVDF), Al, and carbon nanotubes (CNTs) was prepared. The investigation of the dielectric properties and thermal conductivities of the ternary composites while comparing with the Al/PVDF binary composites indicates that the addition of 1.0 wt% CNTs in the Al/PVDF clearly improved the dielectric permittivity due to enhanced interfacial polarization of filled matrix, whereas the dissipation factors still remained at acceptable low level owing to the insulating alumina shell and the isolation effect of Al on CNTs in the matrix. Moreover, the hybrid Al/CNTs particles obviously enhanced the thermal conductivity of the composites due to the more heat conductive pathways formed in the matrix from the CNTs bridging effect between the Al particles.

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Epoxy (EP) resin based nanocomposites with aluminum (Al) nanoparticles were prepared by solution method, with ultrasonic assisted dispersion followed by hot-pressing methods. The dielectric permittivity, loss tangent, conductivity, and electric modulus of the nanocomposites were investigated by dielectric spectroscopy measurements in a wide frequency range from 1 to 10 7 Hz at temperatures from 2208C to 2008C. For all samples, the dielectric permittivity, dissipation factor, and electric conductivity increase with increasing temperature due to enhanced chain mobility above glass transition temperature (T g ) . Broadband dielectric spectroscopy shows the multiple dielectric processes in the Al/epoxy nanocomposites corresponding to interfacial polarization (IP), a-relaxation, and ionic conductivity, respectively. IP is detected at low frequencies and high temperatures. A primary a-relaxation process is found at near T g at the middle frequencies and the intermediate dipolar effect (IDE) is presented at high frequencies. The mechanisms responsible for dielectric relaxation, conductivity process, and electric modulus response have been discussed in detail.