Interfacial polarization contributes significantly to the electric displacement of polymer nanocomposites and results in large energy density.

Stretchability is critical to wearable devices to afford a large amplitude strain. Herein, a uniformly nanoscale copper layer was successfully deposited onto the surface of a knitted fabric by a facile electroless deposition (ELD) approach for the construction of stretchable electrodes that had low and stable resistivity. A polymerized dopamine layer was pre-decorated onto the fiber surface for capturing a Pd2+ catalyst that was also partially reduced to nanoparticles by polydopamine. This process improved the electrical conductivity and stability. As a result, an initial surface resistivity R 0 as low as ∼0.32 Ω sq–1 (σ ≈ 2.83 × 105 S m–1) and a stretched R of ∼2.0 Ω sq–1 (R/R 0 ≈ 6) under 500% tensile strain were obtained. Prolonging the ELD process led to better mechanical performance and electrical conductivity of the as-made fabrics. The deformation mechanism of such e-fabrics was particularly emphasized on the “contact junction shift” principle, providing a reconstruction of the conductive networks under a large amplitude strain. Finally, two electronic prototypes with such e-fabric elements demonstrated great mechanical and chemical stability as well as washing fastness. This was the first report about the e-fabric with such high stretchability, which enabled it to be integrated efficiently with garments as a stretchable electrode or as an element of a physiotherapy device to afford perspiration evaporation and large-area stretchability and to minimize discomfort.

3D printing technology has been widely used in various fields, such as biomedicine, clothing design, and aerospace, due to its personalized customization, rapid prototyping of complex structures, and low cost. However, the application of 3D printing technology in the field of non-pneumatic tires has not been systematically studied. In this study, we evaluated the application of potential thermoplastic polyurethanes (TPU) materials based on FDM technology in the field of non-pneumatic tires. First, the printing process of TPU material based on fused deposition modeling (FDM) technology was studied through tensile testing and SEM observation. The results show that the optimal 3D printing temperature of the selected TPU material is 210 °C. FDM technology was successfully applied to 3D printed non-pneumatic tires based on TPU material. The study showed that the three-dimensional stiffness of 3D printed non-pneumatic tires is basically 50% of that obtained by simulation. To guarantee the prediction of the performance of 3D printed non-pneumatic tires, we suggest that the performance of these materials should be moderately reduced during the structural design for performance simulation.

Stretchable transparent electrodes (STEs) based on silver nanowires (AgNWs) have received considerable attention for a variety of flexible and wearable electronic/optoelectronic devices. Up to now, most efforts have focused on optimizing the STEs composed by a single AgNW conductive network. On the contrary, the structure−performance correlations of STEs formed by a hybrid percolative network which comprises the AgNW and a second conductive nanomaterial have rarely been discussed. In this work, we fabricated hybrid-type STEs by selecting three kinds of carbon nanotubes (CNTs) with different diameters to pair with three types of AgNWs with variable length-to-diameter ratios. The size effect of building blocks of the nine combinations on the optical, electrical, and mechanical properties of resultant STEs was thoroughly investigated. The results reveal that AgNWs and CNTs with smaller diameters are beneficial to achieve hybrid electrodes with a high transmittance and low haze. AgNWs with larger length-to-diameter ratios contribute hybrid STEs with lower sheet resistance by adding a suitable amount of CNTs. Importantly, the smaller differences in diameters of AgNWs and CNTs lead to more effective capillary-force-induced welding, which boosts both the conductivity and stretchability of STEs. An optimized AgNW/CNT hybrid electrode demonstrated a transmittance of 66.4% and a haze of 11.0% at a sheet resistance of 8.70 Ω sq. −1 which could endure a uniaxial tensile strain as large as 490%, while its resistance increased only 46.9% after experiencing 1000 cycles of 50% tensile strain. Alternating current electroluminescent devices based on such AgNW/ CNT hybrid STEs were also successfully developed, showing uniform and stable patterned luminescence.

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By means of a die-drawing technique in the rubbery state, the effect of the orientation of the microstructure on the dielectric properties of polypropylene (PP)/multiwalled carbon nanotube (MWCNT) nanocomposites was examined in this study. The viscoelastic behavior of the PP/MWCNT nanocomposites with MWCNT weight loadings ranging from 0.25 to 5 wt % and the dielectric performance of the stretched PP/MWCNT nanocomposites at different drawing speeds and drawing ratios were studied to obtain insight into the influences of the dispersion and orientation state of the MWCNTs and matrix molecular chains. A viscosity decrease (ca. 30%) of the PP/MWCNT-0.25 wt % (weight loading) melt was obviously due to the free volume effect. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction were adopted to detect the orientation structure and the variation of crystal morphology of the PP/MWCNTs. Melting plateau regions, which indicated the mixed crystallization morphology for the stretched samples, were found in the DSC patterns instead of a single-peak for the unstretched samples. We found that the uniaxial stretching process broke the conductive MWCNT networks and consequently increased the orientation of MWCNTs and molecular chains along the tensile force direction; this led to an improvement in the dielectric performance.

Additive manufacturing is a promising technology that can directly fabricate structures with complex internal geometries, which is barely achieved by traditional manufacturing. However, the mechanical properties of fused deposition modeling (FDM)‐printed objects are inferior to those of conventionally manufactured products. To improve the mechanical properties of the printed products, a series of novel thermoplastic polyurethanes with self‐healing properties, intrinsic photothermal effects, and excellent printability are designed and synthesized by introducing dynamic oxime–carbamate bonds and hydrogen bonds into the polymer chains. On‐demand introduction of near‐infrared (NIR) irradiation, direct heating, and sunlight irradiation enhances interfacial bonding strength and thus improve the mechanical properties of the printed product. Additionally, mechanical anisotropy of the printed products can be sophistically manipulated by regulating the self‐healing conditions. Support‐free printing and healing of damaged printed products are also achieved owing to the self‐healing properties of the material. Moreover, the as‐prepared materials exhibit shape‐memory properties NIR irradiation or direct heating effectively triggers shape‐memory recovery and demonstrates their potential in 4D printing by printing a man‐like robot. This study not only provides a facile strategy for obtaining high‐performance printed products but also broadens the potential applications of FDM technology in intelligent devices.