Traditional piezoelectric stick–slip actuators often suffer from significant backward motion phenomena, which greatly impact their output performance. To overcome this issue, a novel displacement amplification piezoelectric stick–slip actuator was meticulously designed. It integrates an L-shaped displacement amplification mechanism with a parallelogram-compliant mechanism. By dynamically adjusting the compressive force between the stator and the mover, this actuator effectively increases the single-step displacement, resulting in smooth and stable motion output. The design process involved thorough structural feasibility validation and core dimension optimization, utilizing Castigliano’s second theorem and finite element simulation analysis. These efforts successfully yielded a substantial increase in the single-step output displacement. Experimental results demonstrate the actuator’s capability to achieve smooth and stable motion output, even under challenging conditions, such as symmetric excitation signals and horizontal loading. Under specific operating parameters—preloading force of 3 N, input voltage of 100 VP–P, and driving frequency of 625 Hz sinusoidal excitation signal, the actuator achieves an impressive maximum driving speed of 25.22 mm/s, with a substantial maximum load capacity of 2.1 N. Compared to previous studies, the designed actuator exhibits superior adaptability to various excitation signals, offering significant potential for enhancing the performance and expanding the applications of piezoelectric stick–slip actuators.

As an analog of the role of surface plasmons in optical antenna, spoof surface plasmons enable far-field radiation of antenna in microwave frequency. Here, a plasmonic metamaterial supporting spoof surface plasmons is experimentally demonstrated for horizontally polarized omnidirectional radiation in the microwave region. A simple and intuitive working principle in the spoof surface plasmonic metamaterial design is provided, along with full-wave simulations that agree well with the experimental results. The low profile and compact design with the omnidirectional radiation pattern promise a wide range of applications, such as ceiling antennas, surface-mounted indoor antennas and automobile antennas in microwave and radio frequencies.

To further improve the operational performance of a phononic crystal air-coupled ultrasonic transducer while reducing the number of simulations, an intelligent optimization design strategy is proposed by combining finite element simulation analysis and artificial intelligence (AI) methods. In the proposed strategy, the structural design parameters of 1–3 piezoelectric composites and acoustic impedance gradient matching layer are sampled using the optimal Latin hypercube sampling (OLHS) method. Moreover, the COMSOL software is utilized to calculate the performance parameters of the transducer. Based on the simulation data, a radial basis function neural network (RBFNN) model is trained to establish the relationship between the design parameters and the performance parameters. The accuracy of the approximation model is verified through linear regression plots and statistical methods. Finally, the NSGA-II algorithm is used to determine the design parameters of the transducer. After optimization, the band gap widths of the piezoelectric composites and acoustic impedance gradient matching layer are increased by 16 kHz and 13.5 kHz, respectively. Additionally, the −6 dB bandwidth of the transducer is expanded by 11.5%. The simulation results and experimental results are consistent with the design objectives, which confirms the effectiveness of the design strategy. This work provides a feasible strategy for the design of high-performance air-coupled ultrasonic transducers, which is of great significance for the development of non-destructive testing technology.