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The development of triboelectric nanogenerators (TENGs) can convert mechanical energy into electricity and bring new prospect for energy crisis. Improving tribo-charge surface density and contact area are two pivotal factors to enhance the output performance of TENG. However, improving the charge density and manipulating surface structure cannot be achieved simultaneously and complicated fabrication procedures may limit application of TENG. In this work, an environment friendly TENG based on bacteria cellulose film fabricated via facile vacuum filtration method was reported. In the presence of modifications, high dielectric particles BaTiO3were introduced into BC nanofiber film to improve the dielectric constant as well as construct micro-nano structure at the same. With the combination of the enhancement of dielectric constant and surface structure of BC nanofibers layer, the open voltage of 181 V, the short current of 21 μA, and transfer charge of 76.6 nC was achieved at a frequency of 2 Hz and a peak force of 42 N with the optimized film consisting of 13.5 vol% BaTiO3particles. Additionally, a peak power density of 4.8 W/m2was achieved when connecting with the resistance in series. Moreover, the TENG showed excellent stability and can harvest the mechanical energy by human motion. This work gives a better understanding of the triboelectricity produced by the TENG from the point of materials and provides a feasible and effective way to enhance the output performance of TENG from the material itself as well as surface modification.

Switchable materials have attracted enormous interest due to their promising applications in important fields such as sensing, electronic components, and information storage. Nevertheless, obtaining multifunctional switching materials is still a problem worth investigating. Herein, by incorporating (Rac-, L-, D-2-amino-1-propanol) as the templating cation, we have obtained (Rac-, L-, D-HTMPA)CdCl3(HTMPA = 1-hydroxy-N, N, N-trimethyl-2-propanaminium). We have adopted a chiral chemistry strategy that causes (Rac-HTMPA)CdCl3in the central symmetric space to crystallize in the chiral space group. Based on the modulation of the homochiral strategy, (L-, D-HTMPA)CdCl3shows a dual phasic transition at 269 and 326 K and a switchable second-harmonic generation response. In addition, (L-, D-HTMPA)CdCl3is chiral switchable material to exhibit stable dual dielectric and second-harmonic generation (SHG) switches. This work provides an approach to exploring multifunctional chiral switchable materials.

The sea valve is a critical unit in the seawater pipelines onboard. Its mainly used to control and adjust the flux of seawater. In the practical use, the vibration and sound level of a kind of valve is proved to be too high to maintain the acoustic performance of ships.In this paper, the three-dimensional geometry and CFD model of a typical sea valve is established.Then the flow fields inside the valve, flow characteristics, drag reduction characteristics and noise characteristics were analyzed, as well as the fluid-solid coupling response between the flow field and the valve structure. Based on the analysis, two optimum schemes are proposed in order to improve the flow characteristics of the flow field and reduce vibration and noise level of this type of sea valves. The calculated results show that two optimum schemes both can improve the hydrodynamic and noise characteristics, and the scheme two is relatively better.

Triboelectric nanogenerators (TENGs), a promising energy harvesting technology, have been rapidly developed in past few years. However, the specific structure and complicated preparation method greatly limited their mechanical flexibility as well as their potential applications. In this work, a novel and effective strategy to fabricate all-in-one triboelectric nanogenerator(TENG) was reported. The as-mentioned TENG was based on rubber/carbon nano-fiber composites achieved by supercritical carbon dioxide foaming process, which is environmentally friendly and suitable for mass production. Under the optimal condition, 91 V of the open voltage, 2.87 μA of short current and 40 nC of transferred charge was obtained, while this structure contributed to about 10-fold enhancement to transferred charge compared with the single-layer structured TENG at the same area of 4 cm2. The flexible silicone rubber based TENG can collect complex mechanical energy, such as stretching, twisting, bending and compressing. Moreover, when being pasted on soles, it can harvest the mechanical energy from human motion and the outputs can also be regarded as sensing signals which can be used to analyze the gait and sense the motion. This work provides a feasible and effective way to prepare an all-in-one TENG with high outputs, which can bring potential for the industrialized production and widespread application.