A quantitative standard based on the internal equivalent circuit is proposed to evaluate the effects of different factors on the outputs of the triboelectric nanogenerators (TENGs) in various modes. This paper establishes the relationship between the equivalent circuits and TENGs, and then explores the influence of mechanical structures (e.g. contact area and film thickness) and external excitations (e.g. applied force, displacement distance, and triggering frequency) on output power and matching reactance by the normalization method. Moreover, the prototypes are fabricated to verify the rationality and feasibility of normalization. Experimental results show that the order of influencing factors is contact area > film thickness > applied force > displacement distance. The influence of frequency on the normal-directional moving TENG is greater than that on the tangential-directional moving TENG. This work provides a reference for quantifying the outputs of TENGs with different structures.

In order to solve the problem that when the piezoelectric cantilever generator captures the low-frequency vibration, the structural resonance frequency bandwidth is small and the generating capacity cannot be fully developed. A magnetic excitation cantilever-type piezoelectric energy harvester for rotational motion was presented in this paper. Energy harvesting capability of resonant harvesting structures, such as piezoelectric cantilever beams, can be improved by utilizing coupled oscillations that generate favorable strain mode distribution. The theoretical analysis and simulation analysis of the working state of the piezoelectric energy harvester is performed. The power generation performance of magnetic excitation cantilever-type piezoelectric energy harvester under different environmental excitations was tested by experimental methods. The experimental results show that the magnetic excitation cantilever-type piezoelectric energy harvester has the best power generation performance when the rotational speed is 150 r min ⁻¹ , the installation angle of the piezoelectric cantilever is 60°, the distance between the mass magnet and the excitation magnet is 8 mm, and the number of excitation magnets is 6. The maximum open-circuit voltage of the magnetic excitation cantilever-type piezoelectric energy harvester is 38.49 V. When the load resistance is 40 KΩ, the magnetic excitation cantilever-type piezoelectric energy harvester has a voltage of 24.84 V and an average power of 15.425 mW. Piezoelectric energy harvesting is an attractive technique for the potential powering of wireless sensors and low power devices.

This study presents a high-performance valve-less piezoelectric micropump with crescent-shaped structure. This micropump was designed by finite element analysis (FEA) and fabricated through 3D printing technology. Different configurations of the micropump with different distances from inlet to the crescent-shaped structure ( δ = 0.3, 0.6, 0.9, 1.2, and 1.5 mm) and numbers of crescent-shaped structures (from one up to four stages) were tested. The sound pressure level (SPL) characteristics were experimentally investigated and evaluated at 0.6, 1.5, 2.0, 2.5, and 3.0 mm. The results gave a maximum flow rate of 219.4 ml min ⁻¹ at 0.6 mm under 220 V and 45 Hz. Moreover, the flow rate for the quadruple crescent-shaped structure was 286 ml min ⁻¹ at 220 V and 82 Hz. Besides, the difference of the SPL was 3.2 dB at 0.6 m, making this pump better than others; the difference was kept at about 18 dB when the gap exceeded 2.0 mm. The results suggest that the structure with the best configuration is that with δ = 0.6 mm and four stages, and the SPL fluctuation is smaller as the output performance becomes better. The study offers some valuable insights into improving its performance and practical application.

Valveless piezoelectric pumps are used in the field of drug delivery. However, the output performances are limited by severe reflux. This article is aimed at reducing the reflux and improving the output performances. We use different pressure loss coefficients in the forward and reverse directions and design dome composite structures within the chamber of the valveless pump. The structures and working principles are described. Then, we use the fluid simulation software CFX to simulate the flow state inside the chamber under different parameters such as the dome length, 2 mm, 4 mm, 6 mm, and 8 mm; the trapezoidal one-sided angle, 1°, 3°, 5°, 7°, and 9°; and the rounded corner, from 0 to 6 mm. Finally, we also make the prototypes and test the output performances. The results show that the output flow rate can reach a maximum of 220.6 ml/min; the measured variance is 80.7 in the three experiment tests for the optimal flow rate at the dome length of 8 mm, angle of 5°, and rounded corner of 6 mm under the driving voltage of 190 V at a frequency of 45 Hz; the highest output pressure is 670.0 Pa under the voltage of 190 V at a frequency of 130 Hz. Moreover, the precision is 5.85% of the highest tested pressure compared to the simulated pressure. The output flow rate has a great improvement, and the effectiveness of the structures is proved.