In nature, lakes and water channels offer abundant underwater energy sources. However, effectively harnessing these green and sustainable underwater energy sources is challenging due to their low flow velocities. Here, we propose an underwater energy-harvesting system based on a cylindrical bluff body and a cantilever beam composed of a macro fiber composite (MFC), taking advantage of the MFC’s low-frequency, lightweight, and high piezoelectric properties to achieve energy harvesting in low-frequency and low-speed water flows. When a water flow impacts the cylindrical bluff body, it generates vibration-enhanced and low-frequency vortices behind the bluff body. The optimized diameter of the bluff body and the distance between the bluff body and the MFC were determined using finite element analysis software, specifically COMSOL. According to the simulation results, an energy-harvesting system based on an MFC cantilever beam applied in a low-frequency and low-speed water flow was designed and prepared. When the diameter of the bluff body was 25 mm, and the distance between the bluff body and MFC was 10 mm and the maximum output voltage was 22.73 V; the power density could reach 0.55 mW/cm² after matching the appropriate load. The simulation results and experimental findings of this study provide valuable references for designing and investigating energy-harvesting systems applied in low-frequency and low-speed water flows.

The noticeable difference in the coefficient of thermal expansion (CTE) for polytetrafluoroethylene (PTFE) coatings and copper substrates is a major challenge for thermal debonding of the copper-clad laminate (CCL) in high-frequency communications. Theoretically, ceramic fillers with low CTEs in the coating can effectively reduce the gap, and there remains a trade-off between the dispersibility of fillers and the interfacial interactions with the polymeric matrix. Here, we propose a novel approach to prepare a pentafluorobenzoyl chloride (PFBC)-modified polydopamine (PDA) shell on silica particles by using amidation. Such modified particles perform excellent dispersion and exhibit diminished interfacial gaps in the PTFE matrix, which highly reduces CTE to 77 ppm/°C, accounting for only 48.1% of the neat coating. Moreover, the composite exhibits enhanced mechanical strength and toughness, and consequently suppresses thermal debonding in CCL under high-temperature conditions. Therefore, results present a promising potential for its use in the next-generation CCL of high-frequency communication devices.

Low-frequency vibration of thin-walled materials, which are widely used in aircraft, can lead to fatal damage of aircraft components and even serious accidents. Although active vibration suppression using macro fiber composite (MFC) holds promise, the weak internal interfaces of MFC—specifically, those among the piezoelectric ceramics, the polymer matrix, and the interdigitated electrodes—seriously restrict the actuation strain and effective suppression bandwidth, limiting its engineering application under broadband aerodynamic excitation. In this work, an MFC-based self-feedback device integrating sensor and actuator is proposed. To address this, the performance bottleneck of the MFC actuator is overcome through a combined interface modification strategy combining plasma etching and dopamine-inspired modification. The interfacial modification elevates the maximum actuation strain of the MFC from 915 με to 1105 με (an increase of 20.8%). When applied to an aluminum cantilever beam, a vibration suppression ratio of 98.11% is achieved at the resonant frequency (75 Hz), and the effective suppression bandwidth (suppression ratio > 50%) reaches 77 Hz. Notably, this strategy is effective on aluminum, stainless steel, and carbon fiber substrates, as equally efficient broadband suppression is realized on all three materials. A powerful pathway is thus provided to unlock the full potential of MFC for low-frequency, broadband active vibration control in aerospace applications.

To address the challenge of inefficiently harvesting ubiquitous low-frequency ambient vibration energy, this paper proposes a coupled cantilever array piezoelectric energy harvester. The system aims to satisfy the power-supply demands of diverse application scenarios through the series and parallel topology optimization of the coupled array elements. By coupling multiple piezoelectric secondary beams via a shared elastic primary beam, this study leverages the dynamics coupling effect to enable each secondary beam to maintain effective electrical output at both its intrinsic and adjacent resonant frequencies. A theoretical framework is established using the lumped-parameter method to derive the governing equations, elucidating the output optimization mechanisms of the coupled array under series and parallel topologies. Consequently, a directional design strategy is implemented: the series configuration is employed to elevate voltage, whereas the parallel configuration is utilized to broaden bandwidth. Experimental results demonstrate that through this directional topology optimization, the system successfully achieves the dual objectives of high-voltage output and broadband energy harvesting. Specifically, the series mode enhances the output power by approximately 65.3% compared to a single-beam baseline, while the parallel mode expands the effective operational bandwidth to 5.75 times that of an isolated beam. In practical application verifications, this strategy successfully drove customized loads on-demand, including a wireless temperature sensor requiring a high startup voltage, alongside a low-power internet of things development board and an ultrasonic ranging sensor. This flexible application strategy, based on series/parallel configurations, realizes the goal of tailored energy delivery according to specific application needs, providing an innovative and highly versatile paradigm for self-powered systems operating within diverse low-frequency environments.