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Lamb wave resonators (LWRs) exhibiting high-quality factors and clean spectra demonstrate promising applications in RF communication and sensing. This paper discusses the relationship between the spurious mode, the quality factor, and the effective electromechanical coupling factor of resonators. When the resonant frequency of the spurious mode is slightly below the parallel resonant frequency (fp), the quality factor at fp (Qp) decreases dramatically. To enhance Qp and suppress the spurious mode, the LWRs with busbars including only the top electrode (non-overlap busbars) and the LWRs with busbars incorporating both top and bottom electrodes (overlap busbars) are designed and fabricated. The LWR with 12 μm-wide overlap busbars exhibits a notable enhancement in Qp, elevating it from 553.76 to 1488.17 and suppresses the spurious mode simultaneously. This research introduces a promising approach to suppress the spurious mode and enhance the quality factor of Lamb wave resonators, thereby holding great potential for applications in sensors and mobile communication. [ABSTRACT FROM AUTHOR]

High-performance Lamb wave devices have a vast application prospect in modern wireless communication systems. This paper proposes a method of spurious mode suppression by reducing the overlap length of electrodes according to modal shapes. The AlN/Al0.8Sc0.2N composite film is used to achieve a trade-off between electromechanical coupling coefficient (k t 2) and Q factor. The finite-element analysis (FEA) is employed to study the performance of the lowest-order symmetric mode (S0) Lamb wave resonators (LWRs), and the FEA result shows a spurious mode in the impedance response. According to the results of modal shape analysis, the typical LWR, the LWR with the circle-shaped arrangement of electrodes, the LWR with the circle-shaped apodization, and the LWR with the arc-shaped apodization are fabricated to suppress the spurious mode and investigate the performance of the LWRs. The measurement results show that the spurious mode is effectively suppressed over a wide frequency range (1.9–2.2 GHz) by the three designed electrode configurations. The LWR with the circle-shaped apodization working at 2.023 GHz has a Qp factor of 955, a moderate k t 2 of 2.97%, a figure-of-merit (Q × k t 2) of 28.4, and a large value of f × Q × k t 2 (5.773 × 1010). Utilizing modal shapes to design the electrode configuration of LWRs can suppress spurious modes without significant performance deterioration. [ABSTRACT FROM AUTHOR]

Aims: We aimed to investigate the association between maternal diabetes before or during pregnancy and visual acuity development in offspring at 1 and 4 years old. Methods: This prospective cohort study comprised 301 individuals born in 2015–2017. Those who had maternal diabetes during or before pregnancy (type 1 diabetes, type 2 diabetes and gestational diabetes) were investigated. Two visual examinations were routinely performed on children relatively at the age of 1 at physical examination and at the age of 4 at admission to school to assess the possible effects of gestational exposure to diabetes on the visual system of the offspring. Results: Data were collected on children aged 1 and 4, which consisted of 173 children of mothers exposed to diabetes and 128 children of mothers without diabetes). We found no significant association between maternal diabetes during pregnancy and visual acuity development in 1-year-old offspring. At 4 years old, the incidence of amblyopia and strabismus was similar in both groups. Prenatal exposure to maternal diabetes was associated with a 171% increased risk of high RE: OR 2.71 (95% CI 1.08, 6.81), p < 0.05. Astigmatism (13.3% vs 5.5%) was found to be significantly more prevalent in children born to mothers with GD than in the controls (p = 0.025 in both groups). Moreover, offspring exposed to PGDM had a higher overall risk of high RE than those exposed to GDM during pregnancy (25.0% vs 17.4%). We further found that in the offspring of diabetic mothers, the risk of high RE was significantly increased among children who were female or who spent more time using electronic devices daily. Conclusions: Our findings suggest that maternal diabetes during pregnancy is associated with an increased risk of high RE in offspring. Regular ophthalmological screening should be advised to offspring of mothers with diabetes diagnosed before or during pregnancy. [ABSTRACT FROM AUTHOR]

Background: Merozoite surface protein 1 (MSP1) plays an essential role in erythrocyte invasion by malaria parasites. The C-terminal 19-kDa region of MSP1 has long been considered one of the major candidate antigens for a malaria blood-stage vaccine against Plasmodium falciparum. However, there is limited information on the C-terminal 19-kDa region of Plasmodium ovale MSP1 (PoMSP119). This study aims to analyze the genetic diversity and immunogenicity of PoMSP119. Methods: A total of 37 clinical Plasmodium ovale isolates including Plasmodium ovale curtisi and Plasmodium ovale wallikeri imported from Africa into China and collected during the period 2012–2016 were used. Genomic DNA was used to amplify P. ovale curtisi (poc) msp119 (pocmsp119) and P. ovale wallikeri (pow) msp119 (powmsp119) genes by polymerase chain reaction. The genetic diversity of pomsp119 was analyzed using the GeneDoc version 6 programs. Recombinant PoMSP119 (rPoMSP119)-glutathione S-transferase (GST) proteins were expressed in an Escherichia coli expression system and analyzed by western blot. Immune responses in BALB/c mice immunized with rPoMSP119-GST were determined using enzyme-linked immunosorbent assay. In addition, antigen-specific T cell responses were assessed by lymphocyte proliferation assays. A total of 49 serum samples from healthy individuals and individuals infected with P. ovale were used for the evaluation of natural immune responses by using protein microarrays. Results: Sequences of pomsp119 were found to be thoroughly conserved in all the clinical isolates. rPoMSP119 proteins were efficiently expressed and purified as ~ 37-kDa proteins. High antibody responses in mice immunized with rPoMSP119-GST were observed. rPoMSP119-GST induced high avidity indexes, with an average of 92.57% and 85.32% for rPocMSP119 and rPowMSP119, respectively. Cross-reactivity between rPocMSP119 and rPowMSP119 was observed. Cellular immune responses to rPocMSP119 (69.51%) and rPowMSP119 (52.17%) induced in rPocMSP119- and rPowMSP119-immunized mice were found in the splenocyte proliferation assays. The sensitivity and specificity of rPoMSP119-GST proteins for the detection of natural immune responses in patients infected with P. ovale were 89.96% and 75%, respectively. Conclusions: This study revealed highly conserved gene sequences of pomsp119. In addition, naturally acquired humoral immune responses against rPoMSP1 were observed in P. ovale infections, and high immunogenicity of rPoMSP119 in mice was also identified. These instructive findings should encourage further testing of PoMSP119 for rational vaccine design. [ABSTRACT FROM AUTHOR]

Shear mode‐guided ultrasonic waves are highly regarded for submerged or subterranean structural health monitoring (SHM), owing to their non‐dispersive feature and minimized acoustic energy loss when in contact with liquid or solid. High‐performance shear mode ceramic ultrasonic transducers with robustness and cost‐effectiveness are highly demanded for underwater or underground SHM applications, especially in harsh environments. However, the implementation of discrete shear mode piezoelectric ceramic ultrasonic transducers is hindered by the inconsistency with manual installation, lack of conformability on curved surfaces, and unreliable acoustic coupling between the transducers and the structure. Here, direct‐write conformable shear mode ultrasonic transducers made from piezoelectric lead‐free ceramic coatings, which are in situ produced on steel structures by a scalable thermal spray process, are proposed. The obtained lead‐free lithium‐doped potassium sodium niobate (KNN‐LN) ceramic coatings exhibit a high effective shear piezoelectric strain coefficient (d24, f) above 60 pm V−1 in a broad frequency range from 100 Hz to 200 kHz. The resulting conformable shear mode KNN‐LN ceramic coating transducers successfully showcase the functions of exciting and detecting stable shear mode ultrasonic wave signals with operation temperature exceeding 200 °C and demonstrate reliable capability in defect detection in both air and liquid environments. [ABSTRACT FROM AUTHOR]

The first asymmetric mode (A1 mode) lamb wave resonator (LWR) with a resonant frequency of 6 GHz based on Z-cut lithium niobate (LN) films is presented. An asymmetric electrode structure with different-sized electrode pads in the center and edged regions has been proposed, which can be used to optimize the distribution of the electric field and decrease acoustic impedance mismatch to improve the target mode. Experiment results reveal that LWRs with an asymmetric electrode structure can successfully enhance the A1 mode, achieving a high effective electromechanical coefficient ( k eff 2 ) of 26%, a quality factor (Q) of 1123, and an excellent figure-of-merit (FOM = k eff 2 ∙ Q) of 262. It demonstrates that asymmetric electrode structure provides a new way to suppress the spurious modes for LWRs and shows a great application prospect in wide-bandwidth and low-loss filters used in the sub-6 G frequency range. [ABSTRACT FROM AUTHOR]

The effective electromechanical coupling coefficient (${K}_{eff}^{2}{)}$ of resonators is crucial for application in radio communication such as fabricating bandpass filters. In this letter, we present a $0^{\text {th}}$ symmetry (${S}_{0}{)}$ mode Lamé mode resonator (LMR) operating at 2.563 GHz with a high ${K}_{\vphantom {D_{j}}{eff}}^{2}$ of 7.83%. A 20% Scandium-doped Aluminum Nitride (Sc0.2Al0.8N)/AlN composite piezoelectric film is used as the piezoelectric layer. The ratio of piezoelectric layer thickness (${t}_{\vphantom {D_{j}}{pie}}{)}$ and electrode pitch (${P}_{ele}{)}$ is optimized by finite element analysis (FEA) method and the highest experimental ${K}_{eff}^{2}$ is obtained at ${t}_{pie}/{P}_{ele} =0.65$. The proposed LMR with Sc doping and structural optimization shows fascinating prospects for constructing broadband filters. [2021-0113] [ABSTRACT FROM AUTHOR]

This paper presents a modified Lamé-mode resonator (MLMR) with a high, effective electromechanical coupling coefficient (K e f f 2). With trapezoidal grooves introduced by etching the superficial piezoelectric material between interdigitated electrodes (IDTs), the MLMR can remarkably improve K e f f 2 , eliminate spurious modes, and reduce the internal stress of piezoelectric material. The Lamé mode resonator (LMR) with four different electrode configurations is investigated by using finite element method simulation first; then, the impact of the groove's vertical (h) and horizontal (θ) size on K e f f 2 and spurious modes of MLMRs is theoretically analyzed and optimized. It is noted that all the modified structures can improve K e f f 2 except the IDT-Ground structure. This work demonstrates a simulated K e f f 2 as high as 10.47% in the modified IDT-Floating structure, and 10.73% in the modified IDT-IDT structure, which is the highest ever reported in S0 mode AlN LMR. The MLMR shows great prospect for fabricating broad bandwidth filters. [ABSTRACT FROM AUTHOR]

The thin film bulk acoustic resonator (FBAR) has emerged as a promising choice for liquid sensors because of its high frequency and sensitivity. To investigate the potential of FBAR devices working as the liquid sensors, we study the operating law of FBAR in liquid environments and explore the different loading effects of liquid on the shear mode and longitudinal mode. By analyzing the device and liquid interactions, we modify the Mason model of FBAR in the liquid environment. Subsequently, the influence of the piezoelectric film with different tilt angles and liquids on the characteristics of FBAR is discussed. We also prepared Sc0.2Al0.8N film-based FBAR to confirm the influence of different liquid environments on the resonant performances. The results show that the frequency drift of FBAR in the shear mode is related to density and viscosity of liquid, and the frequency drift of FBAR in the longitudinal mode is related to bulk modulus and density of liquid. The resonant frequency of FBAR in the shear mode is more sensitive with glycerol solution than that of FBAR in the longitudinal mode. This work can provide a research basis for the application of FBAR liquid sensors. [ABSTRACT FROM AUTHOR]

Over the past decade, ultraviolet (UV) detection has been a subject of major interest for both research scientists and engineers because of its important applications in both the civil and military fields. The rapid development of interdisciplinary research has enabled the realization of UV detectors based on a variety of principles. Among these devices, UV detectors based on surface acoustic wave (SAW) technology offer unique advantages of remote wireless operation capability and zero power consumption. This article provides a comprehensive review of the working principles, important parameters, and the acoustic wave and materials types used in SAW-based UV detectors. The research and development status of these detectors are discussed and the most commonly used methods to optimize device performance are also summarized. Novel types of acoustic UV detectors based on thin film bulk acoustic resonators (FBARs) and Lamb wave resonators (LMRs) are briefly introduced. Finally, future development challenges are proposed and suggestions for future directions are provided to aid the development of this important research field. [ABSTRACT FROM AUTHOR]