Hualing Chen

Tunable actuation behavior of ionic polymer metal composite utilizing carboxylated carbon nanotube-doped Nafion matrix

In this study, we propose to neutralize the relaxation deformation of Nafion-ionic polymer metal composite (IPMC) by slow anode deformation of Flemion-IPMC caused by carboxyl groups (–COOH). Carboxylated carbon nanotubes (CCNT) as –COOH carriers were doped into a Nafion matrix. By adjusting the doping content from 0 wt% to 10 wt%, an IPMC with constant steady-state deformation has been achieved at a critical CCNT content of 2 wt%. Moreover, the increasing rate of the slow anode deformation with the CCNT content is tunable, which is found to be 2.26 mm s−1 %−1.

Viscoelastic performance of dielectric elastomer subject to different voltage stimulation

Dielectric elastomer (DE) is capable of giant deformation subject to an electric field, and demonstrates significant advantages in the potentially application of soft machines with muscle-like characteristics. Due to an inherent property of all macromolecular materials, DE exhibits strong viscoelastic properties. Viscoelasticity could cause a time-dependent deformation and lower the response speed and energy conversion efficiency of DE based actuators, thus strongly affect its electromechanical performance and applications. Combining with the rheological model of viscoelastic relaxation, the viscoelastic performance of a VHB membrane in a circular actuator configuration undergoing separately constant, ramp and sinusoidal voltages are analyzed both theoretically and experimentally. The theoretical results indicated that DE could attain a big deformation under a small constant voltage with a longer time or under a big voltage with a shorter time. The model also showed that a higher critical stretch could be achieved by applying ramping voltage with a lower rate and the stretch magnitude under sinusoidal voltage is much larger at a relatively low frequency. Finally, experiments were designed to validate the simulation and show well consistent with the simulation results.

Performance investigation on dissipative dielectric elastomer generators with a triangular energy harvesting scheme

In this letter, a theoretical framework describing an energy harvesting cycle including the loss of tension (LT) process is proposed to investigate the energy harvesting performance of a dielectric elastomer generator (DEG) with a triangular energy harvesting scheme by considering material viscosity and leakage current. As the external force that is applied to the membrane decreases, the membrane is relaxed. When the external force decreases to zero, the condition is known as LT. Then the membrane undergoing LT can further relax, which is referred to as the LT process. The LT process is usually ignored in theoretical analysis but observed from energy harvesting experiments of DEGs. It is also studied how shrinking time and transfer capacitor affect the energy conversion of a DEG. The results indicate that energy density and conversion efficiency can be simultaneously improved by choosing appropriate shrinking time and transfer capacitor to optimize the energy harvesting cycle. The results and methods are expected to provide guidelines for the optimal design and assessment of DEGs.

Effect of constrained fibers on electromechanical actuation of charge-controlled dielectric elastomers

As is known, electromechanical deformation of voltage-controlled dielectric elastomers (DEs) is significant but is susceptible to pull-in and snap-through instabilities, while the large stable deformation can be achieved by spraying charge on DE surfaces, i.e. , charge-controlled DEs. In this article, we investigate the effect of constrained fibers on electromechanical actuation of charge-controlled DEs by involving two special deformation modes: uniaxial tension and pure shear state. The coupled effects between the geometrical sizes and the mechanical tensile force of the charge-controlled DEs are also explored. The research results indicate that, different from voltage-controlled DEs, the electromechanical stretch of charge-controlled DEs with constrained fibers does not always show a beneficial merit with respect to that of the charge-controlled DEs without constrained fibers.