Soft and highly stretchable, yet conductive elastomers are essential in development of next generation electronic devices. However, electrical conductivity and mechanical stretchability are normally mutually exclusive properties since good conductors are rigid, and stretchable materials are inherently soft. Furthermore, maintained conductivity at high elongation is difficult to achieve because of the particle break-up due to the imposed large mechanical stresses on the percolated conductive fillers in contrast to much lower stresses on the soft and compliant elastomer matrix. Herein, a novel, simple, and effective preparation method is presented for fabricating highly stretchable conductive elastomers, consisting of multi-walled carbon nanotubes (MWCNTs) as a conductor and poly(dimethylsiloxane) (PDMS) as a soft matrix. As a result of the preparation method, stretch-enhanced conductivity is observed due to the prepared “hairy” particles effectively constructing further conductive pathways upon elongation. The “hairy” structures result from entrapped MWCNTs uniformly dispersed into low-molecular weight silicone polymers that are lightly crosslinked before being introduced into a silicone network resulting from silicone polymers of longer length to create a so-called heterogeneous bimodal network. Through the advanced, yet simple, mixing procedure followed by curing of the silicone matrix, it is possible to prepare conductive MWCNT/PDMS elastomers that can be elongated up to 200%. The prepared system shows high initial conductivity of 0.038 S m⁻¹ with 2.6 phr (parts per hundred rubber) MWCNTs and constant conductivity throughout the 160% deformation range. The prepared MWCNTs/PDMS composite composes a new class of stretchable conductive materials with potential applications in next generation electronics.

In order to improve the vibration suppression effect of the flexible beam system, active control based on soft piezoelectric macro-fiber composites (MFCs) consisting of polyimide (PI) sheet and lead zirconate titanate (PZT) is used to reduce the vibration. The vibration control system is composed of a flexible beam, a sensing piezoelectric MFC plate, and an actuated piezoelectric MFC plate. The dynamic coupling model of the flexible beam system is established according to the theory of structural mechanics and the piezoelectric stress equation. A linear quadratic optimal controller (LQR) is designed based on the optimal control theory. An optimization method, designed based on a differential evolution algorithm, is utilized for the selection of weighted matrix Q. Additionally, according to theoretical research, an experimental platform is built, and vibration active control experiments are carried out on piezoelectric flexible beams under conditions of instantaneous disturbance and continuous disturbance. The results show that the vibration of flexible beams is effectively suppressed under different disturbances. The amplitudes of the piezoelectric flexible beams are reduced by 94.4% and 65.4% under the conditions of instantaneous and continuous disturbances with LQR control.

A novel piezoelectric generator based on soft piezoelectric film consisting of a polyimide (PI) sheet and lead zirconate titanate (PZT) is proposed to generate electric energy under the operating conditions of low-frequency and small-amplitude vibration. The theoretical model and working principle of the piezoelectric generator are discussed in detail. Using ANSYS software, a finite element analysis of the static and modal characteristics of the piezoelectric generator is carried out. Further, the output of the prepared piezoelectric generator is investigated by a home-made experimental platform. Results show that the transient excitation voltage of the generator increases with the increase in load resistance, and the continuous excitation voltage increases first and then remains almost stable. The maximum continuous power produced by the piezoelectric generator is about 4.82 mW. Furthermore, the continuous excitation voltage and power are in accordance with the simulation values when the load resistances are 20 kΩ and 25 kΩ, respectively.

The interphase region widely exists in polymer-based nanocomposites, which affects the dielectric properties of the nanocomposites. General models, such as the Knott model, are often used to predict the dielectric constant of nanocomposites, while the model does not take the existence of interphase into account, which leads to a large deviation between the predicted results and the experimental values. In this study, a developed Knott model is proposed by introducing the interphase region and appropriately assuming the properties of the interphase. The modeling results based on the developed model are in good agreement with the experimental data, which verifies the high accuracy of the development model. The influence of nanoparticle loading on the effective volume fraction is further studied. In addition, the effects of the polymer matrix, nanoparticles, interphase dielectric and thickness, nanoparticle size and volume fraction on the dielectric properties of the nanocomposites are also investigated. The results show that polymer matrix or nanoparticles with a high dielectric and thick interphase can effectively improve the dielectric properties of the materials. Small size nanoparticles with high concentrations are more conducive to improving the dielectric properties of the nanocomposites. This study demonstrates that the interphase properties have an important impact on the dielectric properties of nanocomposites, and the developed model is helpful to accurately predict the dielectric constant of polymer-based nanocomposites.

A developed model for estimating the dielectric permittivity of BaTiO ₃ –polymer nanocomposites is proposed by considering the influence of the interphase.