The ocean, with its highly variable and complex meteorological conditions, harbors enormous renewable resources. Triboelectric nanogenerators (TENGs), which possess unique advantages, show exciting prospects in water wave energy collection. How to design and optimize TENGs to cover all characteristic water wave energies and achieve efficient energy utilization is emergent. In this paper, we carefully designed and fabricated a columnar multi-layer sliding TENG (CMLS-TENG) that can harvest water wave energy independent of wave height and direction. Drive rods with a hollow acrylic spherical shell were introduced to deliver wave energy, ensuring that the CMLS-TENG can work in all directions from 0° to 360°. Based on the sliding structure, switching the optimized CMLS-TENG is independent of wave heights. The optimized CMLS-TENG can achieve a total power density of 730 mW/m³ at a wave height of only 4.8 cm regardless of wave direction, which can illuminate multiple light-emitting diodes (LEDs) to provide lighting and provide power to a watch and a hygrometer for temperature and humidity monitoring. This work provides new choices and hopes for the effective collection of full-range water wave energy.

Interface functional groups play an essential role in regulating the electrical properties of bulk materials. In this work, we designed a novel strategy to explore a new way to enhance triboelectric performance by regulating the functional groups between nano-fillers and polymer matrix without obvious changes in the dielectric constant. The silica nanoparticles (SNPs) modified perfluoro-silane coupling agents (PFSCAs) with different chain lengths were added to the polyvinylidene difluoride to regulate the transferred charge density (TCD) of triboelectric nanogenerators (TENGs). When the doping concentration of perfluorodecyl modified SNPs is 2.25 wt.%, the nanocomposite film based TENG exhibits the maximum TCD of 166 μC/m² and power density of 3.12 W/m² which are 6 times and 39 times as big as those of pure polyvinylidene difluoride (PVDF) film. The charge accumulation and decay process show that interface functional groups dominate the performance of TENGs. Then, a Fermi level model is proposed and why the TCD could be regulated by the concentration of nanoparticles in bulk materials is explained. This work provides a new concept for understanding the performance of TENG independent dielectric constant and points out a new direction for enhancing TENG’s performance, since wealthy functional groups with selectivity are applicable.

Triboelectric nanogenerator (TENG) can directly convert mechanical energy into electric energy. However, the triboelectric materials are limited to the triboelectric series. Here, for the first time, we choose the isostructural UiO-66-X (X = H, NH₂, NO₂, and Br) family as triboelectric materials to investigate the underlying relationships between different functional groups and the triboelectric performance of TENG. Unlike traditional triboelectric material organic polymers, metal–organic frameworks (MOFs) can be oriented design synthesis and functionalized with various functional groups. The results demonstrate that the largest output voltage and current are from UiO-66-NO₂ TENG, and are about 23.79 V and 0.29 μA, which are 3.19 and 4.14 times over that of the UiO-66 TENG, respectively. The working mechanism of the MOF TENG was discussed in depth through experiments and theoretical calculations. This work proves a novel strategy to obtain high output properties by functionalized MOFs with large electron-withdrawing functional groups and promising guidance for the choice of high-efficiency triboelectric materials.

The mechanism of strain-dependent luminescence is important for the rational design of pressure-sensing devices. The interband momentum-matrix element is the key quantity for understanding luminescent phenomena. We analytically solved an infinite quantum well (IQW) model with strain, in the framework of the 6 × 6 k∙p Hamiltonian for the valence states, to directly assess the interplay between the spin-orbit coupling and the strain-induced deformation potential for the interband momentum-matrix element. We numerically addressed problems of both the infinite and IQWs with piezoelectric fields to elucidate the effects of the piezoelectric potential and the deformation potential on the strain- dependent luminescence. The experimentally measured photoluminescence variation as a function of pressure can be qualitatively explained by the theoretical results.

Detecting/sensing targets underwater has very important applications in environmental study, civil engineering and national security. In this paper, an organic-film based triboelectric nanogenerator (TENG) has been successfully demonstrated for the first time as a self-powered and high sensitivity acoustic sensor to detect underwater targets at low frequencies around 100 Hz. This innovative, cost-effective, simple-design TENG consists of a thin-film-based Cu electrode and a polytetrafluoroethylene (PTFE) film with nanostructures on its surfaces. On the basis of the coupling effect between triboelectrification and electrostatic induction, the sensor generates electrical output signals in response to incident sound waves. Operating at a resonance frequency of 110 Hz, under an acoustic pressure of 144.2 dB_SPL, the maximum open-circuit voltage and short-circuit current of the generator can respectively reach 65 V and 32 μA underwater. The directional dependence pattern has a bi-directional shape with a total response angle of 60°. Its sensitivity is higher than -185 dB in the frequency range from 30 Hz to 200 Hz. The highest sensitivity is -146 dB at resonance frequency. The three-dimensional coordinates of an acoustic source were identified by four TENGs, self-powered active sensors, and the location of the acoustic source was determined with an error about 0.2 m. This study not only expands the application fields of TENGs from the atmosphere to water, but also shows the TENG is a promising acoustic source locator in underwater environments.