In the past few decades, rotary energy harvesting has received more and more attention and made great progress. The energy harvesting device aims to collect environmental energy around electronic equipment and convert it into usable electrical energy, developing self-powered equipment that does not require replaceable power supplies. This paper provides a holistic review of energy harvesting techniques from rotary motion using piezoelectric materials. It introduces the basic principles of piezoelectric energy harvesting, the vibrational modes of piezoelectric elements, and the materials of piezoelectric elements. There are four types of rotational energy harvesting technologies: inertial excitation, contact execution, magnetic coupling, and hybrid systems. An overview of each technology is made, and then, a detailed analysis is carried out. Different types of rotating energy harvesting technologies are compared, and the advantages and disadvantages of each technology are analyzed. Finally, this paper discusses the future direction and goals of improving energy harvesting technology. This Review will help researchers understand piezoelectric energy harvesting to effectively convert rotational energy into electrical energy.

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.

Piezoelectric pumps are applied in many fields, such as chemical analysis system and fluid pumping systems. Piezoelectric pumps with high output pressure can meet the needs of more fields. This article introduces the design and fabrication of a high output pressure piezoelectric pump with straight arm wheeled check valve. In this paper, the influence of straight arm wheeled check valve on the output pressure of piezoelectric pump is deeply discussed from the aspect of energy loss. This study investigated the effect of valve arm number (N = 2, 3,4, and 5), the valve arm width (W = 0.8, 1.0, and 1.2 mm), and the valve arm length (L = 1.92, 2.02, and 2.12 mm) on the output pressure of piezoelectric pump. The output pressure characteristic of straight arm wheeled check valve piezoelectric pump with different valve parameters is obtained by experiment. Experimental results show that when N = 4, W = 1.0 mm, L = 2.02 mm, the output pressure of the straight arm wheeled check valve piezoelectric pump has the best output pressure of 27.41 kPa at 220 V and 85 Hz. This study provides a reference for the further application of piezoelectric pumps in fluid pumping field.

Piezoelectric pumps are widely applied in medical transportation, bioengineering, and mechanical lubrication. However, the backflow phenomenon of the valveless piezoelectric pump is more prominent. Therefore, this paper designed a lunular piezoelectric pump to reduce the backflow. The three-dimensional flow field of the piezoelectric pump was analyzed using ANSYS Computational Fluid X. Based on the numerical results, the design of the lunular piezoelectric pump was improved, and a new model of the piezoelectric pump with better performance was developed. A prototype was made, and an experimental verification was carried out. The experimental results show that the maximum flow rate per unit area is 404.812 µl/min and maximum back pressure is 22.3 cmH₂O, which achieves the optimal performance of the pump and verifies the rationality of Computational Fluid X simulation. Thus, the performance of a pressure pump with low driving frequency can be predicted by Computational Fluid X simulation, and the structural optimization method is reliable. This research can help to broaden the application of the piezoelectric pump.

Piezoelectric pumps are applied in cooling systems of microelectronic devices because of their small size. However, cooling efficiency is limited by low flow rate. A Straight arm wheeled check valve made of silica gel was proposed, which can improve flow rate of piezoelectric pump, solve the influence of glue aging on the sealing ability of a wheeled check valve and reduce the size of piezoelectric pump. This paper discusses the influence of valve arm number (N=2, 3 and 4), valve arm width (W=1.0, 1.2 and 1.4mm) and valve thickness (T=0.6, 0.8 and 1.0mm) on flow rate characteristics of piezoelectric pumps. When valve opening rises, the flow rate increases. The simulation results show that valves with 2 valve arms, 0.6mm valve thickness and 1.0mm valve arm width have maximum valve opening. Experimental results show that piezoelectric pumps with different valve parameters have different optimal frequencies. In addition, maximum flow rate is 431.6mL/min at 220V and 70Hz. This paper provides a reference for the application of piezoelectric pump in cooling system.