To realize the switching of the multiple locomotion modes, a new insect-scale piezoelectric robot with asymmetric structure is proposed, fabricated, and tested. The robot prototype has a weight of 32.8 g and size of 55 ×50 ×20 mm. Driven by two pieces of piezoelectric ceramics, working at six vibration modes, the piezoelectric robot can realize two kinds of linear motion and four kinds of circular motion by contact friction. Performance assessments show that the robot has a maximum velocity of 155 mm/s and a minimum motion radius of 45 mm. In addition, the robot can move at a speed up to 97 mm/s (100 V _p-p ) with an integrated drive device (45.7 g). The insect-scale piezoelectric robot has simple structure, but has multiple motion modes, large speed range, good output characteristics, and fast response time, which provides a new idea for the design and driving of microrobot.

This article is based on an experimental study on the aerodynamic performance of a flapping wing rotor (FWR) and enhancement by passive pitching angle variation (PPAV) associated with powered flapping motion. The PPAV (in this article, 10 ^o –50 ^o ) is realized by a specially designed sleeve-pin unit as part of a U-shape flapping mechanism. Through experiment and analysis, it is found that the average lift produced by an FWR of PPAV is >100% higher than the baseline model, the same FWR of a constant pitching angle 30 ^o under the same input power. It is also noted that the lift–voltage relationship for the FWR of PPAV is almost linear and the aerodynamic efficiency is also over 100% higher than the baseline FWR when the input voltage is under 6 V. The aerodynamic lift or efficiency of the FWR of PPAV can be also increased significantly by reducing the weight of the wings. An FWR model is fabricated and achieved vertical take-off and free flight powered by 9 V input voltage. The mechanism of PPAV function provides a feasible solution for aerodynamic improvement of a bioinspired FWR and potential application to micro air vehicles.

With the advantages of simple structure, low power consumption, no electromagnetic interference, and fast response, piezoelectric pumps (PPs) have been widely used in the fields of chip cooling, biomedical applications, chemical applications, and fuel supply applications. In recent decades, scholars have proposed various PPs, and this article reviews the recent research results. In this review, according to the “valve” structure, PPs are divided into valve-less piezoelectric pumps (VLPPs), valve-based piezoelectric pumps (VBPPs), and piezoelectric pumps with valve and valve-less state transitions (PPVVSTs). Firstly, the design methods of typical structures were discussed, and comparisons were made in terms of driving frequency, driving voltage, output pressure, flow rate, structure materials, and pump size. The advantages and disadvantages of VLPPs, VBPPs, and PPVVSTs were analyzed. Then, we compared the driving parameters, output performance, structure materials, and pump size of single-chamber piezoelectric pumps (SCPs) and multi-chamber piezoelectric pumps (MCPs) and analyzed the advantages and disadvantages of SCPs and MCPs. Optimization methods proposed in recent years have been summarized to address the issues of the cavitation phenomenon, the liquid back-flow problem, and low output performance in PPs. Subsequently, the application research of PPs and the distribution of academic achievements were discussed. Finally, this review was summarized, and future research hot spots for PPs were proposed. The main contribution of this review is to provide piezoelectric pump (PP) researchers with a certain understanding of the structural design, optimization methods, practical applications, and research distribution of PPs, which can provide theoretical guidance for future research.

In this paper, a resonant cavity piezoelectric cantilever sensor (RCPCS) are designed and optimized for wind velocity and direction measurement. The RCPCS consists of a resonant cavity with a ring groove array and a free-standing piezoelectric cantilever array. The presence of the resonant cavity magnifies the local pressure at the cantilever’s boundary and also increases the cantilever’s vibration amplitude according to a new resonant cavity mathematical model. An structural optimization model is created using MATLAB and the COMSOL optimization module to increase the sensitivity of RCPCS. The analytical results demonstrate that the optimized cantilever’s strain distribution is more uniform than the original results, as well as the physical mechanism of strain and aerodynamic amplification. Several comprehensive experiments are conducted to evaluate the RCPCS prototype’s performance utilizing a new identification method of wind velocity and direction. The experimental results agree well with the mathematical solutions for the RCPCS response voltage and sensitivity, and the optimized cantilever’s sensitivity is noticeably improved over the unoptimized cantilever. Note that the comparison of experimental results demonstrates a significant reduction in the range of direction error (Δθ exp) from 0.34°~ 1.04° to 0.09°~ 0.29°. Similarly, the range of velocity error (Δν exp) is reduced significantly from 1.20%~ 2.27% to 0.14% ~ 0.80%. Additionally, the measured lower limit can reach 0.2 m/s. As a result of these findings, the superiority of the proposed RCPCS’s reaction performance is validated, and a simple, highly sensitive, and high-precision wind sensor is constructed.