This work presents the first demonstration of solidly mounted A3-mode resonators at 18 GHz. The devices were built based on 128° Y-cut lithium niobate (LiNbO3) thin film on top of multiple layers of silicon dioxide (SiO2) and tantalum pentoxide (Ta2 O5), which form a Bragg reflector on a silicon (Si) substrate. By exciting the higher-order antisymmetric Lamb wave mode (A3 mode), the resonator achieves an electromechanical coupling coefficient ($k^{2}$) of 3.09%, a quality factor ($Q$) of 386 and a figure of merit (FoM) of 12. Leveraging the Bragg reflector to support efficient high-frequency odd-order mode reflection, this A3-mode Lamb wave resonator opens up the potential of using solidly mounted acoustic resonators (SMR) for beyond-15-GHz applications in next-generation wireless communication systems.

In this paper, a novel bi-layer Lamb wave resonator (LWR) has been proposed and demonstrated for the first time, with near-zero temperature coefficient of frequency (TCF) and high electromechanical coupling coefficient ($k^{2}$). The suspended resonator features a bi-layer composite structure of silicon oxide $\left(\text{SiO}_{2}\right) / 128^{\circ} \mathrm{Y}$-cut lithium niobate (LN). By carefully designing the thickness of the SiO2 layer on LN and optimizing the electrode dimensions, the TCF and $\boldsymbol{k}^{\mathbf{2}}$ of the A3-mode LWRs are optimized through 2D FEM simulations. The fabricated bilayer A3-mode resonator achieves a high resonant frequency of 18 GHz with a high $\boldsymbol{k}^{\mathbf{2}}$ of 11.0% and a $Q_{{\max}}$ of 285. At the same time, a near-zero $\boldsymbol{T} \boldsymbol{C F}$ of +0.145 ppm/° C has been achieved. More importantly, this work discovers a new path designing suspended thin-film resonator structures to achieve high frequency, low $T C F$, high $\boldsymbol{k}^{\mathbf{2}}$, and good mechanical stability all at the same time, which is illuminating for LWR designs at various frequencies as needed by satellite and 5G/6G wireless communications.

In this work, we present a newly proposed concept of engineering the anchor fins in a suspended Lamb wave resonator and using it as an important design parameter to optimize the resonator performance. The exploration was conducted on antisymmetric Lamb wave resonators based on 128 degrees Y-cut lithium niobate (LN or LiNbO3) and the deformation was adjusted by introducing different anchor fin designs that mount the suspended structure to the supporting substrate. The proposed design methodology was validated by the demonstration of first-order antisymmetric Lamb wave (A1-mode) resonators operating at 12GHz, and also third-order antisymmetric Lamb wave (A3-mode) resonators operating at 36GHz. It has been proved that special anchor fin design serves as an effective means to improve the power handling or linearity of Lamb wave resonators. Therefore, this work opens up a brand new design space for acoustic resonators based on a suspended thin-film structure, which makes it possible to realize further performance enhancement and optimization for Lamb wave resonators especially at centimeter wave (cmWave) and millimeter wave (mmWave) frequencies.

Origami structures have extensive applications in multiple scientific and engineering fields, such as smart structures, sensors, autonomous robotics, and tissue-engineering metamaterials. Origami-inspired mechanical metamaterials’ performance and behavior are intricately linked to their structural design. Square-twist origami, with its unique bistable mechanical properties, has 16 crease patterns (4 independent), but there is a lack of theoretical and quantitative analysis methods for Type 1, resulting in high-cost structural design. In this paper, a mechanical metamaterial structure inspired by square-twist origami is proposed. A Python-ABAQUS framework is used to generate datasets for deep learning training. A deep neural network (DNN) model is built to predict the maximum strain energy of the structure. The results show that the DNN model has a high prediction accuracy (accuracy of 0.95), which can effectively reduce the calculation time compared with traditional methods. The proposed framework can be used to predict structures that meet specific engineering requirements, providing a new way for the design of origami-inspired mechanical metamaterial structures.

As insulators must support conductors and provide insulation, their defects directly threaten the safety of power systems. Traditional manual inspections are inefficient, labor-intensive, and highly susceptible to weather conditions, with difficulty considerably increasing during under severe events such as heavy snow or dense fog. Although inspections using unmanned aerial vehicles offer a safe alternative through high-definition cameras and algorithms, adverse weather conditions degrade the imaging quality and blurs target features. Moreover, overlapping insulators and unclear contours can lead to background false positives or foreground false negatives. To address these problems, we propose the You Only Look Once (YOLO)-GHS network with three key optimizations. (1) YOLO-GHS incorporates the Hierarchical Graph Network (HGNet) V2 to enhance feature extraction, considerably improving object recognition in low-quality images. (2) To address the increased computational burden and parameter count introduced by the HGNetV2, YOLO-GHS employs ghost convolutions to reduce the computational load and optimize resource utilization. (3) YOLO-GHS introduces a novel spatial enhancement and attention module as a detection head, integrating spatial attention mechanisms with detail enhancement to precisely capture target features in overlapping regions, thereby suppressing background false positives and foreground false negatives. Experimental results demonstrate that YOLO-GHS outperforms the baseline YOLOv11 on the Insulator Defect Image Dataset, achieving improvements of 5.5

In this work, a novel design scheme of on-chip frequency shifting is proposed and applied to acoustic resonators for the first time. On the same chip with first-order antisymmetric mode (A1-mode) resonators on 128° Y-cut lithium niobate (LiNbO3 or LN) thin film, LN based capacitors are proposed and realized by rotating the in-plane periodic direction of interdigitated transducer (IDT) electrodes to align the electric field direction at 90° relative to the +X axis. In a ladder-type topology, the series branch achieves an upward shift of the series resonant frequency by connecting an A1-mode resonator in series with an on-chip LN capacitor, while the shunt branch realizes a downward shift of the parallel resonant frequency by connecting an A1-mode resonator in parallel with a capacitor or rotating the IDT electrodes to a specific angle. By aligning these two frequencies through careful design, an acoustic filter is successfully implemented. Compared to traditional A1-mode filters, which rely on differentially localized etching to achieve frequency shifts in the series branch, the proposed novel design scheme reduces at least one photolithography and etching step, thereby greatly lowering process complexity and improving yield. Through this approach, this work demonstrates a high frequency (in the centimeter-wave or cmWave band) filter operating at 14.3 GHz with an insertion loss (IL) of 3.6 dB, a bandwidth of 961 MHz (FBW of 6.7%), and an out-of-band rejection (OoB) of 14 dB. This proves the validity of the pure layout-design based frequency shifting mechanism and enables the Lamb wave resonator technology with better manufacturability for 6G cmWave wireless communications.[2026-0082]

Abstract High-frequency acoustic wave transducers, favored for their compact size, are not only dominating mobile handsets but are also expanding into various interdisciplinary fields. However, as strong vibration can “shake off” substances and produce heat, a long-standing bottleneck has been the ability to harness acoustics under high-power loads, especially for interdigital-transducer-based surface acoustic wave devices. To suppress three fundamental mechanisms: self-heating, thermal instability, and acoustomigration, we propose a layered acoustic wave platform utilizing a quasi-infinite multifunctional top layer that redefines mechanical and thermal boundary conditions. The proposed transducer achieves a 70% reduction in temperature rise, a temperature coefficient of frequency of −13 ppm/°C, and an unprecedented threshold power density of 45.61 dBm/mm2 — over one order of magnitude higher than that of state-of-the-art thin-film surface acoustic wave counterparts. This architecture enables scalable deployment of high-power acoustic wave components in space-constrained hybrid platforms and opens the functional diversification of acoustic wave transducers.

Origami-inspired composite metamaterials exhibit exceptional tunable multistability and programmability, making them highly promising for applications in smart materials, flexible systems and reconfigurable structures. These structures are expected to exhibit low folding energy in energy-constrained scenarios while maintaining strong resistance to external disturbances in the folded state. However, balancing these two characteristics remains a significant challenge. Therefore, this study develops origami-inspired square-twist metamaterials for multistable reconfiguration and optimizes them using a deep reinforcement learning (DRL) framework that considers both minimal folding energy and disturbance resistance. The structural optimization integrates finite element analysis (FEA) and deep reinforcement learning, augmented by a deep neural network (DNN) surrogate model. The optimized structure is fabricated using 3D-printed rigid facets and hyperelastic silicone via composite assembly. A comprehensive comparison is conducted between the proposed DRL method and traditional optimization methods. The proposed method demonstrates superior optimization efficiency and improved mechanical performance compared with conventional optimization approaches. The energy characteristics of the fabricated model are verified through uniaxial compression and tension tests. Finally, the potential application of the structure in reconfigurable antennas is explored.

This article proposes a comprehensive synthesis method for acoustic wave (AW) filters. The complete procedure is composed of characteristic polynomial synthesis and prototype circuit synthesis. The synthesis of the scattering and admittance characteristic polynomials is formulated as a root-finding problem, yielding a unified framework for generalized-Chebyshev, bounded-Chebyshev, reduced-Chebyshev, and even nonequiripple (NE) responses. The characteristic polynomial synthesis is illustrated in the bandpass domain but is also applicable to the lowpass domain. At the stage of prototype circuit synthesis, novel coupling-matrix representations for independent series and shunt AW resonators in the bandpass domain are established without frequency-dependent couplings. Then the synthesis of AW filters is formulated as a coupling-matrix reconfiguration problem. Matrix manipulations for topology reconfiguration are performed with typical ladder configurations. Using the synthesized coupling-matrix model, the corresponding Butterworth-Van Dyke (BVD) model can be obtained via direct mappings. For verification, three examples are presented to demonstrate the effectiveness, unification, and flexibility of the proposed synthesis theory. In one example, the synthesized response is compared with a fabricated filter, showing satisfactory agreement among the synthesized, simulated, and measured responses.

High-frequency acoustic resonators are key elements in radio-frequency (RF) front ends that enable signal selection, filtering, and spectral reconfiguration in modern wireless communication systems. However, achieving both large electromechanical coupling (k2) and high quality factor (Q) in 5G/6G bands (3 to 7 GHz, or sub-7 GHz) remains a critical challenge for acoustic wave devices. Here, we propose and demonstrate a new type of self-aligned nanorod bulk acoustic wave (SN-BAW) resonator fabricated from single-crystal piezoelectric lithium niobate (LiNbO3 or LN) thin film on silicon carbide (SiC) substrate. The resonator features an array of solidly mounted piezoelectric nanorods defined by one step of a self-aligned nanoscale etching process, which eliminates the need for suspended membranes, bottom electrodes, or reflective gratings, as normally required in traditional bulk acoustic wave (BAW) or surface acoustic wave (SAW) devices. This unique nanorod LiNbO3 structure, solidly mounted on SiC substrate, ensures strong acoustic energy confinement within the piezoelectric material and excellent mechanical stability while enabling a good thermal path for heat dissipation, which favors the thermal handling capability of the realized resonators. The fabricated SN-BAW resonators exhibit outstanding performances, with high quality factors (Q) up to 1943 in the 3 to 5 GHz range, scalable electromechanical coupling coefficients (k2) from 23% to 43% depending on design, and a record-high figure of merit (FoM = k2 × Q) of 626 at 3.46 GHz. These results demonstrate a practical route toward wafer-level, low-loss, and frequency-agile acoustic filters with good thermal handling and low cost aimed for next-generation 5G and 6G RF front ends, and highlight LiNbO3 nanostructures as a unifying platform linking photonics, acoustics, and high-frequency electronics.

High-frequency acoustic wave transducers, vibrating at gigahertz (GHz), favored for their compact size, are not only dominating the front-end of mobile handsets but are also expanding into various interdisciplinary fields, including quantum acoustics, acoustic-optics, acoustic-fluids, acoustoelectric, and sustainable power conversion systems. However, like strong vibration can "shake off" substances and produce heat, a long-standing bottleneck has been the ability to harness acoustics under high-power vibration loads, while simultaneously suppressing temperature rise, especially for IDT-based surface acoustic wave (SAW) systems. Here, we proposed a layered acoustic wave (LAW) platform, utilizing a quasi-infinite multifunctional top layer, that redefines mechanical and thermal boundary conditions to overcome three fundamental challenges in high-power acoustic wave vibration: self-heating, thermal instability, and acoustomigration. By simply leveraging a simplified, thick single-material overlayer to achieve electro-thermo-mechanical co-design, this acoustic platform moves beyond prior substrate-focused thermal management in SAW technology. It demonstrates, for the first time from the top boundary, simultaneous redistribution of the von Mises stress field and the creation of an efficient vertical thermal dissipation path. The LAW transducer, vibrating at over 2 GHz, achieves a 70

The three-body problem has captivated generations of scientists for centuries. Inspired by multi-body movements, this study proposes a two-body coupled nonlinear electromagnetic energy harvester (TCN-EMEH) with tunable potential energy, which efficiently scavenges vibration energy from low-frequency and small-amplitude excitation environments. The TCN-EMEH mainly consists of two inclined-spring-based bistable oscillators connected by a linear coupling spring. The governing equations of the system are derived and validated by the experiments. The potential energy distribution of the TCN-EMEH is analyzed. The nonlinear dynamic behavior of the system is characterized by utilizing bifurcation diagrams, maximum Lyapunov exponent, phase portraits, Poincare maps, and basin of attraction maps. It is found that the TCN-EMEH exhibits monostable, asymmetric bistable, bistable, or tristable characteristics depending on the selected system parameters. Besides, the coupling spring can change the motion states of the system, making the TCN-EMEH more prone to large amplitude interwell responses under small excitation amplitudes and low excitation frequency conditions. These dynamic characteristics thus significantly enhance the output power of the device. Furthermore, a global sensitivity analysis is conducted to quantify the influence of key parameters on system performance, offering further insights into the optimization and robust design of nonlinear energy harvesters. The proposed two-body interaction approach paves a new way to improve the performance of nonlinear energy harvesters and provides guidance for future research on multi-body movements.

This paper reports on a S2-mode interdigital-metal-oxide Lamb wave resonator (IMO-LWR), addressing the need for low frequency temperature coefficient (TCF) in lithium niobate (LN) for high-frequency applications. The proposed solution targets 5G/6G and millimeter-wave communication demands. Firstly, we analyze the electromechanical coupling coefficient (k2) of Lamb wave modes versus the SiO2/LN thickness ratio, identifying the S2 mode with maximum k2 at a 1:1 ratio. Then, the impact of substrate materials on LN’s thermal expansion coefficient (CTE) and TCF is simulated. Finally, device fabrication and measurement results are given in detail. The fabricated device excites S2 mode Lamb waves in the SiO2/LN stack, achieving near-zero TCF and a high k2 of 20.4% at 6.5 GHz, surpassing conventional LN resonator performance.

This paper proposes a novel parallel separated multi-input neural network (PSMNN) surrogate model that is used to optimize a comb-like beam piezoelectric energy harvester (CB-PEH) considering multi-parameter. The performance index of optimization is defined as a weighted average of the average output power, maximum output power, and total structural mass of the CB-PEH across 15 optimization parameters. The PSMNN surrogate model conducts parallel separation of inputs, which boosts feature extraction and reduces network complexity, achieving over 98 % accuracy in predicting average output power based on datasets obtained from the finite element model (FEM). The genetic algorithm based on the PSMNN model instead of the rough theoretical derivation and time-consuming FEM process achieved the desired performance improvement. Results show that PSMNN outperforms the traditional fully connected layer (FCL) network in terms of regression prediction accuracy ((increased by 3.03 %) and lower network complexity (reduced by 33.10 %). Compared with the structure before and after optimization, the maximum output power is increased by 152.99 %, the average output power is increased by 32.33 %, and the total structure mass is reduced by 9.69 %. Finally, experimental validation confirms the performance improvement of optimization, with the open-circuit voltage of the optimized CB-PEH increasing by 285.27 %.

Conical shells are widely used in engineering for their ease of manufacture and high load-bearing capacity, their flexibility often induces vibrations that affect the precision of instruments installed inside. This paper proposes a magnet-spring nonlinear energy sink (MS-NES) designed for broadband, low-frequency vibration reduction of the conical shell and stepped beam structure. Combining two pairs of vertically repulsive permanent magnets with two lateral springs creates a double potential well and a smooth negative stiffness segment. The MS-NES leverages internal resonance characteristics to rapidly capture and dissipate vibrational energy of the main structure, thereby achieving vibration reduction. The proposed MS-NES structure reduces the root mean square vibration displacement response at four measurement points of the conical shell and stepped beam structure by 2.36 dB within the 10–100 Hz frequency range, achieving a 71

This paper investigates the stochastic dynamics of a novel bistable vibrational energy harvester with an appended elastic nonlinear boundary (BENB). The BENB system has demonstrated excellent performance for energy harvesting in the case of deterministic excitation but has not been tested under stochastic excitation. The main challenge addressed in the paper is to reveal how BENB performance is affected by a wideband or narrowband stochastic excitation, and what are the key parameters influencing BENB's performance in such an environment. The mathematical model of BENB is experimentally verified under stochastic excitation for the first time. The harvesting performance of BENB under stochastic excitations are carried out to established a theoretical stochastic response framework to guide the design. Subsequently, the comparative study demonstrates that the output power of BENB under a white Gaussian noise excitation and the band-limited white noise excitation is 46.57% and 17.83% higher than that of a linear elastic boundary coupled system under the same excitation levels. This advantage is more evident in comparison to monostable linear system. The results reveal that BENB has a wider operational bandwidth and higher output power due to the nonlinear elastic boundary coupling effect. It provides a new in-depth perspective of the elastic boundary coupled energy harvester and offers a feasible and effective approach to improve energy harvesting performance under different types of stochastic excitation.

This paper proposed an improved metamaterial piezoelectric beam with the acoustic black holes (ABHs) for low-frequency energy harvesting. The ABHs are embedded in the local resonant beams distributed on both sides of the primary beam. Piezoelectric plates are attached to the ABHs, leveraging the energy-focusing effect to enhance the energy harvesting performance. Finite element simulation results indicate that the energy harvesting electrical energy has improved by 6.92 times compared to the traditional metamaterial resonant beam without ABHs. Parameter analysis indicates that increasing the number of local resonators and extending the length of the piezoelectric patches can further enhance energy harvesting performance. However, reducing the truncation thickness of the ABH boosts energy harvesting but compromises structural strength. Extending the ABH length and increasing load resistance within the appropriate range are conducive to energy harvesting. Besides, the optimal load resistance varies with frequency. These findings provide useful guidance for future applications of improved metamaterial beam.

This work reports a significant enhancement in the power handling capacity of interdigital transducer (IDT)-based acoustic wave resonators. We develop a novel layered acoustic wave (LAW) architecture that strategically reshapes the mechanical and thermal boundary conditions on the basis of conventional surface acoustic wave (SAW) designs. This approach effectively suppresses acoustomigration and improves heat dissipation. To quantify the improvement, we presented a detailed power distribution analysis to analyze failure mechanisms at the single resonator level. Guided by this analysis method, we designed and performed comprehensive power handling tests, which confirm a substantial increase in power capacity for the proposed LAW architecture. Our findings underscore the high potential of boundary conditions optimization for enabling acoustic wave devices in next-generation high-power RF applications.

A novel vibration-based tri-stable piezoelectric energy harvester with an elastic boundary (TPEHEB) is conceived in this paper to pursue high-efficiency energy scavenging. The TPEH-EB mainly includes two subsystems, namely a piezoelectric energy harvester (PEH) subsystem and an elastic boundary (EB) subsystem. The PEH subsystem consists of a flexible piezoelectric beam with a tip magnet and a PZT patch boned on the surfaces of the flexible beam. The EB subsystem includes two magnet-mass-spring oscillators, which lowers the potential energy threshold and broadens the inter-well bandwidth of the TPEH-EB. The governing equations of the TPEH-EB are derived, and the potential energy distribution is analyzed. A comprehensive comparative experimental study of the TPEH-EB for different initial positions is conducted with a traditional tri-stable piezoelectric harvester with a rigid boundary (TPEH-RB) to highlight the TPEH-EB's superiority. Furthermore, the insights of the spring stiffness and magnet spacing of the elastic boundary into the energy harvesting performance are revealed. The results show that the introduction of the EB subsystem significantly enhances the output voltage and inter-well bandwidth of TPEH-EB for all three initial positions under a small excitation amplitude (0.6g). The RMS voltage, maximum output voltage, and bandwidth of the TPEH-EB are 452% similar to 630%, 471% similar to 600%, and 1120% similar to 6030% higher than those of the TPEH-RB in the frequency band of inter-well motion for different initial positions, respectively. The introduction of the elastic boundary is beneficial in reducing the sensitivity of different initial positions to nonlinear dynamic responses.

This work investigates the mechanical stability of periodically poled piezoelectric film (P3F) resonators at cryogenic temperatures. Lithium niobate P3F Lamb-mode resonators were experimentally characterized down to 13 K. Comparative measurements show that bilayer devices with identical per-layer thickness degrade below 93 K due to thermal stress, whereas trilayer devices exhibit a monotonic increase in quality factor (Q), reaching 720 at 13 K. The results highlight a unique advantage of the P3F platform: by increasing total film thickness, bending stiffness is enhanced, enabling robust operation across a wider cryogenic range. With further optimization, P3F devices demonstrate strong potential for ultra-low-temperature applications, including deep space exploration and quantum technologies.