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The triboelectric nanogenerator (TENG) represents a burgeoning approach for harvesting ambient mechanical energy. However, practical applications suffer from the issues of insufficient charge density and material abrasion. Here, a rotational TENG that attains exceptional output performance and durability in mechanical energy harvesting and couples an ingenious coplanar charge pump by soft contact with a suspended electrostatic induction mode is presented. Thanks to the continuous and synchronous charge injection from the central charge pumping unit, the charge density can be up to 74.62 µC m−2, resulting in an outstanding peak power density of 20.72 W m−2. Moreover, the utilization of yielding polyester fur in the charge pumping unit as a tribo‐layer for soft contact decreases the material abrasion and then enhances durability and robustness. And the experimental results show that the TENG can maintain 99.2% electrical output after 100 000 operating cycles. With the optimized design, the prototype can continuously drive four commercial lamps rated 12 W in series. Furthermore, a wireless powering system is demonstrated to power the electronics, demonstrating an extensive application of the TENG. Given the compelling characteristics, this work is expected to provide a sound strategy for improving TENGs' output and durability in the field of self‐powered sensor systems. [ABSTRACT FROM AUTHOR]

Electrostatic adsorption is an important complement to the mechanical filtration for high-efficiency air filtering. However, the electrostatic charge decays with time, especially in humid conditions. In this work, a self-charging air filter is presented to capture airborne particles in an efficient and long-lasting manner without the need of external power sources. Leveraging the triboelectric effect between the electrospun poly(vinylidene fluoride) nanofiber film and nylon fabric, the self-charging air filter-based mask excited by breathing can continuously replenish electrostatic charges. As a result, its effective lifespan is up to 60 hours (including 30 hours of wearing), with a minimum filtration efficiency of 95.8% for 0.3-μm particles. The filtration efficiency and lifespan are significantly higher than those of a commercial surgical mask. Furthermore, we uncover the quantitative relation between filtration efficiency and surface electrostatic potential. This work provides an effective strategy to significantly prolong the electrostatic adsorption efficacy for high-performance air-filtering masks. The decay of electrostatic charges largely reduces the protective efficacy of electret masks. Here, the authors report a triboelectrification-based self-charging electrostatic face mask with high airborne particle capture efficiency and prolonged stability. [ABSTRACT FROM AUTHOR]

Energy harvesting devices that prosper in harsh environments are highly demanded in a wide range of applications ranging from wearable and biomedical devices to self-powered and intelligent systems. Particularly, over the past several years, the innovation of triboelectric nanogenerators (TENGs) that efficiently convert ambient kinetic energy of water droplets or wave power to electricity has received growing attention. One of the main bottlenecks for the practical implications of such devices originates from the fast degradation of the physiochemical properties of interfacial materials under harsh environments. To overcome these challenges, here we report the design of a novel slippery lubricant-impregnated porous surface (SLIPS) based TENG, referred to as SLIPS-TENG, which exhibits many distinctive advantages over conventional design including optical transparency, configurability, self-cleaning, flexibility, and power generation stability, in a wide range of working environments. Unexpectedly, the slippery and configurable lubricant layer not only serves as a unique substrate for liquid/droplet transport and optical transmission, but also for efficient charge transfer. Moreover, we show that there exists a critical thickness in the liquid layer, below which the triboelectric effect is almost identical to that without the presence of such a liquid film. Such an intriguing charge transparency behavior is reminiscent of the wetting transparency and van der Waals potential transparency of graphene previously reported, though the fundamental mechanism remains to be elucidated. We envision that the marriage of these two seemingly totally different arenas (SLIPS and TENG) provides a paradigm shift in the design of robust and versatile energy devices that can be used as a clean and longer-lifetime alternative in various working environments. [ABSTRACT FROM AUTHOR]

Highlights • Hybridization of piezoelectric and triboelectric energy generators. • Bifurcation induced superharmonic resonances for low-frequency energy harvesting. • High power outputs with force amplification effect by a truss mechanism and impact. • Capability of harnessing energy from a broad frequency range. • Frequency up conversion approach for higher output power. Abstract In this paper, we report a hybrid generator to harness energy from low-frequency ambient vibrations. The generator is designed with a piezoelectric energy harvester (PEH) patch, a triboelectric nanogenerator (TENG) patch, a spring-mass system and an amplitude limiter. The spring-mass system receives energy from excitations and applies forces to the piezoelectric element and the triboelectric layers. The unique amplitude limiter is deliberately introduced into the system, not only achieving the desired frequency up-conversion effect, but also boosting the voltage responses significantly. The limiter also causes hardening nonlinearity and dynamic bifurcation triggering superharmonic resonance so that the generator resonates at a frequency of about 3 Hz. Furthermore, the proposed PEH adopts the strong compressive operation mode, and employs a truss mechanism to effectively amplify the impact forces. In experiments, open-circuit voltages are 58.4 V from PEH and 60 V from TENG under an excitation of 1.0 g at resonance. The hybridized generator is capable of achieving a maximum power of 19.6 mW from the two sources with matched impedances. The working bandwidths of the PEH and the TENG reach up to 5.39 Hz and 7.25 Hz, respectively, out of our targeted frequency domain [2.5 Hz, 10 Hz] due to the multiple resonances and nonlinearity. In the applications to charge capacitors, the high saturation voltage and relatively short charging time validate the effectiveness of our power management technique. Furthermore, the generator proves to be able to effectively scavenge energy from human body motions and charge a capacitor of 4.7 μF to 7.6 V in around 50 s, which indicates a great potential of practical applications in wearable devices. [ABSTRACT FROM AUTHOR]

This paper originally investigates the influence of frequency-up conversion effect on piezoelectric stack generators for high-performance energy harvesting. A compressive-mode piezoelectric generator is proposed comprised of a piezostack and a spring-mass system for electromechanical transduction and mechanical excitation, respectively. The frequency-up conversion effect is induced by amplitude truncations of the mass under external excitation. A control group, i.e. without truncation, is set for performance comparisons. Experimental results indicate that, with the frequency-up conversion, instantaneous power and average power are enhanced by over 1000 and 177 times, respectively. Each voltage response cycle consists of two stages: high-frequency high-amplitude oscillation and the rest of low-frequency low-amplitude harmonic vibration. The frequency of the former stage determines impedance matching. Due to the frequency converted up by 69 times, and intrinsic high capacitance of the stack, the matched resistance is significantly reduced from over 5 kΩ to 73.10 Ω, resulting much higher power response than that without conversion. Additionally, increase of spring stiffness causes the decrease of voltage responses and less effectiveness of frequency conversion effect. In this work we conclusively report that an instantaneous peak power output of 0.32 W can be generated from a millimeter-size piezoelectric generator, which can foster development of high-viability self-powered applications. [Display omitted] • Original study on frequency-up conversion effect on the piezostack-based generators. • Achieving over two orders of magnitude enhancement of instantaneous power. • Matched impedance is lowered from 5.1 kΩ to 73Ω. • Average power enhanced by over 200 times after frequency conversion. • Study on the restoration spring stiffness affecting frequency converting behaviors. [ABSTRACT FROM AUTHOR]

• The RMS voltage response of the energy harvester is increased by up to 1225%;. • We present a new quasi-zero stiffness mechanism for energy harvesters;. • We derive a stable solution to the adverse effect of the offset distance;. • The nonlinear dynamics of the proposed systems are analyzed comprehensively. The self-powered sensing technology based on gravity-rotation-excited vibration energy harvesting (GRE-VEH) enables information acquisition directly from rotatory machines online. However, the centrifugal effect due to the distance between the mass centroid of the energy harvester and the rotating axis (i.e., offset distance) seriously limits its broad engineering applications. To address this issue, we propose methods of using a tensile force provided by pre-deformed springs to counter the constant centrifugal force around the target rotation speed for improving the performance of the energy harvester affected by offset configurations. The GRE-VEH system with a linear spring is first studied by experiments and simulations, where a distributed-parameter model is developed and experimentally validated. The results well validate the proposed mechanism, where the performance of the harvester prototype significantly increases (by up to 1225%). A parametric study is also performed theoretically. The results indicate that the best performance improvement can be obtained by tuning the parameters related to the tensile length, the stiffness, and the damping of the spring. To enable the proposed mechanism in large centrifugal force cases, a pair of negative springs is introduced to the system for constructing a quasi-zero stiffness (QZS) structure together with the linear spring. The new GRE-VEH system is theoretically studied by an updated model, where the system's main characteristics are revealed. The simulation results well indicate the feasibility of the method using the QZS mechanism. This work paves a new way of solving the offset distance problem for the application of the GRE-VEH and also provides new insight into the application of the QZS mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]