Distributed hydrokinetic energy harvesting is essential for enabling sustainable self-powered sensing in aquatic environments. However, natural water flows are typically low-frequency, weak, and highly stochastic, which limits the efficiency of conventional energy harvesters. Here, a gray shark–inspired parallel flapping triboelectric nanogenerator (GS-TENG) is proposed for efficient hydrokinetic energy harvesting and environmental monitoring. A biomimetic flapping hydrofoil inspired by the streamlined morphology of the shark is developed and coupled with an energy storage–release mechanism to enhance energy capture under low-flow conditions. In addition, a deep-learning-assisted framework is employed to optimize key structural parameters of the flapping foil. The optimized biomimetic hydrofoil improves average power by 92.4% compared with the conventional NACA0015 airfoil. The energy storage–release mechanism converts irregular low-frequency flow excitation into stable rotational motion, resulting in a 71.7% enhancement in electrical output. The GS-TENG achieves a peak power of 46.65 mW and a power density of 29.32 W m^-3. Laboratory and open-channel experiments demonstrate that the GS-TENG can continuously power water temperature and water level sensors, highlighting its potential for self-powered water-environment monitoring.

In order to improve the propulsion performance of existing underwater hydrofoil robots, the Taguchi experiments, neural networks and CFD are combined to systematically study the effects of aspect ratio, heaving amplitude, pitching amplitude and flapping frequency on the propulsion performance of a three-dimensional NACA 0012 hydrofoil. First, the parameter combinations for CFD simulation are determined by the Taguchi method. Next, CFD simulations are performed and the results are used as the training set of the neural network. Then, the neural network is trained and used to predict the CFD result. Finally, the mechanism for the optimal propulsion performance at the optimized parameter combinations is analyzed. The results show that the aspect ratio, heaving amplitude, pitching amplitude, and flapping frequency can significantly affect the propulsion performance of the hydrofoil, among which, the flapping frequency (aspect ratio) has the greatest (least) influence on the propulsion performance. The maximum propulsion efficiency of the hydrofoil can reach 55.43% after the optimization of the neural network. Further analysis of the flow field structure around the hydrofoil with different parameters reveals that, under the optimal parameters there forms a stable vortex on the hydrofoil surface, which can stay on the hydrofoil surface for a long time during the flapping process. This is the intrinsic reason for the better propulsion performance at the optimal parameters.

The wind energy in cities cannot be exploited effectively because natural wind is unstable and complex. Therefore, a triboelectric-electromagnetic hybrid generator with swing-blade structures (SBS-TEHG) was designed to effectively harvest intermittent and continuous wind energy in an urban environment. First, the spring structure and base were considered to realize the maximum output performance of triboelectric nanogenerators. Then, the computational fluid dynamics method was applied to optimize the structure of the SBS-TEHG to improve its aerodynamic performance. The starting wind speed of the SBS-TEHG was 2 m/s, and its energy conversion efficiency was 9.04%, 159% higher than that of the SBS-TEHG without guide plates at 4 m/s. The results demonstrated that the SBS-TEHG lit 105 light-emitting diodes (LEDs) under the intermittent-wind harvesting mode at a wind frequency of 1 Hz when the single swing blade operated, while a wireless PM_2.5 & PM₁₀ sensor was powered by the SBS-TEHG after a period of operation under the continuous-wind harvesting mode. The findings of this study provide a novel solution for low-speed wind energy harvesting in cities and demonstrate the potential of SBS-TEHG as a distributed energy source.

The hydrokinetic energy of river current, as one of the essential and widespread renewable energies, is difficult to be harvested in low flow velocity and shallow water areas. In this work, a three-dimensional (3D) fully-enclosed triboelectric nanogenerator (FE-TENG) with bionic fish-like structure for harvesting hydrokinetic energy is reported, which is comprised of the triboelectric power-generation unit, bionic fish-like structure and connection unit. Through the bionic structure, the FE-TENG realizes zero head power generation in shallow water with low flow velocity. What’s more, the effect of external excitations and bionic structures on the electrical performance are systematically studied in this work. The FE-TENG can generate peak power density of 7 and 0.36 W/m³ respectively under the simulated swing state with frequency of 1.25 Hz and simulated river current with flow velocity of 0.81 m/s. In practical applications, due to the 3D fully-enclosed design, the FE-TENG immersed in water for 35 days demonstrates excellent immersion durability with undiminished electrical performance. Therefore, the work proposes an efficient method realizing zero head power generation, and provides a good candidate for long-term service in the river current.