Search Results (297)

The growing miniaturization of electronic systems and the expansion of sustainable, autonomous IoT technologies emphasize the need for efficient, ultra-low-power energy harvesting devices. This study evaluates fifteen devices from five industry leaders for use in small-scale autonomous seed germination systems. Its novelty lies in applying a competitive profile matrix within a flexible multicriteria evaluation framework based on the simple additive weighting (SAW) method that uses a comprehensive set of competitive technology factors (CTFs). The results demonstrate that a transparent and structured methodology can generate prioritized lists of suitable energy harvesters while accounting for technical, economic, and environmental trade-offs. The study also shows that device rankings depend on the scope and objectives of the project. If these change, then the CTF selection, classification, and weighting adjust accordingly. Therefore, the relevance of this study lies in the adaptability, replicability, and audibility of the proposed framework, which supports the selection of informed technology for autonomous, IoT-based germination systems and other technological projects. Full article

Scandium (Sc)-doped aluminum nitride (AlN) thin films are critical for high-frequency, high-power surface acoustic wave (SAW) devices. A composite Sc doping strategy for AlN thin films is proposed, which combines magnetron sputtering pre-doping with post-doping via ion implantation to achieve gradient doping and tailor microstructural characteristics. The crystal structure, surface composition, and microstructural defects of the films were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Results indicate that the Sc content in pre-doped ScAlN films was optimized from below 10 at.% to above 30 at.%, while the films maintained a stable (002) preferred orientation. XPS analysis confirmed the formation of Sc-N bonds, and EDS mapping revealed a gradient distribution of Sc within the subsurface region, extending to a depth of approximately 200 nm. High-resolution TEM revealed localized lattice distortions and surface amorphization induced by ion implantation. This work demonstrates the feasibility of ion implantation as a supplementary doping technique, offering theoretical insights for developing AlN films with high Sc doping concentrations and structural stability. These findings hold significant potential for optimizing the performance of high-frequency, high-power SAW devices. Full article

This study introduces a new theoretical framework for the ferroelectric phase transition in lithium niobate (LiNbO₃), which explicitly incorporates electrostatic interactions between both first and second nearest-neighbor ions. This extended model is applied to estimate the inverse quality factor (Q⁻¹), the equivalent mechanical resistance (R_m), and the Curie temperature (Tc) of pure and titanium-doped lithium niobate (LiNbO₃:Ti). The proposed analytical expression for Tc is given by: $T_C^{*}={\displaystyle \frac{2\sqrt{\frac{-p^{*}}{3}}\mathrm{c}\mathrm{o}\mathrm{s}\left(\frac{{\theta }^{*}}{3}\right)-\frac{B^{*}}{3}}{2\sqrt{\frac{-p}{3}}\mathrm{c}\mathrm{o}\mathrm{s}\left(\frac{\theta }{3}\right)-\frac{B}{3}}} T_C$. The analysis reveals that variations in Q⁻¹ and Tc are governed by factors such as ionic mass, charge, and defect structure. The theoretical predictions show good agreement with experimental data reported in the literature—particularly for Q⁻¹ in pure LiNbO₃ and for Tc in Ti-doped LiNbO₃—thus validating the reliability of the proposed model. Moreover, at constant temperature, both the inverse quality factor and the equivalent mechanical resistance decrease as the Ti concentration increases. This trend highlights that titanium doping enhances the acoustic performance of LiNbO₃ substrates, making them more suitable for high-performance surface acoustic wave (SAW) device applications. Full article

Acoustofluidic devices use Surface Acoustic Waves (SAWs) to handle small fluid volumes and manipulate nanoparticles and biological cells with high precision. However, SAWs can cause significant heat generation and temperature rises in acoustofluidic systems, posing a critical challenge for biological and other applications. In this work, we studied temperature distribution in a Standing Surface Acoustic Wave (SSAW)-based PDMS microfluidic device both experimentally and numerically. We investigated the relative contribution of Joule and acoustic dissipation heat sources. We investigated the acoustofluidic device in two heat dissipation configurations—with and without the heat sink—and demonstrated that, without the heat sink the temperatures inside the microchannel increased by 43 °C at 15 V. Adding the metallic heat sink significantly reduced the temperature rise to only 3 °C or less at lower voltages. This approach enabled the effective manipulation and alignment of nanoparticles at applied voltages up to 15 V while maintaining low temperatures, which is crucial for temperature-sensitive biological applications. Our findings provide new insights for understanding the heat generation mechanisms and temperature distribution in acoustofluidic devices and offer a straightforward strategy for the thermal management of devices. Full article

Surface-acoustic-wave (SAW) sensors with Langasite (LGS) substrate have broad prospects in the field of wireless passive temperature sensing in harsh environments. However, there are still challenges in terms of accuracy regarding the material temperature coefficient of LGS and the temperature simulation of heavy mass load electrodes. This paper presents a method for fitting the material temperature coefficient of LGS based on a combination of finite element simulation (FEM) and measured data. Eleven different cuts of LGS SAW resonators were fabricated, and the frequency response of each cut device at 30–800 °C was obtained through experiments. Some of the data were used in the training dataset and the material temperature coefficient of LGS was obtained through comsol simulation fitting. The remaining data were used as a test dataset to verify the accuracy of the results. The results show that the material coefficient obtained using this method has good accuracy in the frequency prediction of thick electrode LGS SAW sensors at different temperatures with different cuts. Full article

The process of X-ray diffraction on the X-112° Y-cut of a LiTaO₃ crystal excited by surface acoustic waves (SAW) with a wavelength of $\mathrm{Ʌ}=4$ μm was studied at a synchrotron radiation source in a scheme of a double-crystal X-ray diffractometer. The sinusoidal acoustic modulation of the crystal lattice leads to the appearance of diffraction satellites on the rocking curve; the number and intensity of satellites depend on the amplitude of the SAW. Analysis of X-ray diffraction spectra allowed us to determine the velocity ($V_{SAW}=3300$ m/s) and amplitudes of the SAW. For the first time experimental investigations have demonstrated the presence of the power flow angle in the X-112° Y-cut of a LiTaO₃ crystal, i.e., a situation where the direction of acoustic energy propagation ($PFV$) does not coincide with the direction of the SAW wave vector $K_{SAW}$. The measured power flow angle was $PFA=0.41°$. This $PFA$ value is important for designing acoustoelectronic devices in order to reduce acoustic signal losses. Full article

This paper presents a thermal gas flow sensing system, from surface acoustic wave (SAW) temperature sensor to oscillation circuit and multi-module miniaturization integration. A single-port GaN/Si SAW resonator with single resonant mode and excellent characteristics was fabricated. Combined with an in-house-developed SiGe HBT, a temperature-sensitive high-frequency oscillator was constructed. Under constant temperature control, system-level flow measurement was achieved through dual-oscillation configuration and modular integration. The fabricated SAW device shows a temperature coefficient of frequency (TCF) −28.29 ppm/K and temperature linearity 0.998. The oscillator operates at 1.91 GHz with phase noise of −97.72/−118.62 dBc/Hz at 10/100 kHz offsets. The system demonstrates excellent dynamic response and repeatability, directly measuring 0–50 sccm flows. For higher flows (>50 sccm), a shunt technique extends the test range based on the 0–10 sccm linear region, where response time is <1 s with error <0.9%. Non-contact operation ensures high stability and long lifespan. The sensor shows outstanding performance and broad application prospects in flow measurement. Full article

The study investigates the influence of bias voltage on the structural and morphological properties of aluminum nitride AlN (002) thin films deposited on sapphire substrates via reactive magnetron sputtering for high-frequency surface acoustic wave (SAW) devices. The results indicate that applying a positive bias voltage (>0 V) yields AlN films with compact and uniform surfaces. As bias increases, the deposition rate initially rises before declining, while root–mean–square (RMS) roughness progressively decreases, reaching a minimum at 100 V, significantly enhancing surface quality. X-ray diffraction (XRD) analysis reveals enhanced (002) preferential orientation with increasing bias, indicating improved crystallinity. These findings demonstrate that optimized bias voltage not only refines surface morphology but also strengthens crystal alignment, particularly along the (002) plane, making AlN films highly suitable for high-frequency SAW applications, and provides data for the preparation of higher-quality AlN films. Full article

Vital sign monitoring is fundamental to patient care. Although traditional intermittent systems are flawed, barriers to implementing continuous monitoring systems remain. The SMART MAT is a novel continuous monitoring device that detects vital signs remotely via fibre optic technology. The study aims to validate the SMART MAT and its paired devices against gold/clinical standard measurements for measuring heart rate (HR), respiratory rate (RR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and oxygen saturation (SpO2). Healthy adults aged 21 to 80 were recruited for this cross-sectional study. Participants rested supine on a standardised mattress with the SMART MAT below. Vital signs were recorded over three five-minute intervals. Statistical analysis included descriptive statistics, two-way ANOVA, Mean Absolute Percentage Error (MAPE), and Bland–Altman plots. Among 321 participants recruited, HR and most RR measurements saw non-statistically significant differences (p > 0.05). Statistically significant differences were observed for SBP, SpO2, and most DBP measurements (p < 0.05). Only SBP measurements exceeded the acceptable limits of differences. Effect sizes were small to negligible (n² < 0.04) and MAPE values were <20%. The SMART MAT has demonstrated reasonable accuracy and validity in monitoring vital signs in healthy adults. Alternative paired BP devices are recommended to enhance SBP measurement accuracy. Full article

In recent years, various devices utilizing surface acoustic waves (SAW) have emerged as powerful tools for manipulating particles and fluids in microchannels. Although they demonstrate a wide range of functionalities across diverse applications, existing devices still face limitations in flexibility, manipulation efficiency, and spatial resolution. In this study, we developed a dual-sided standing surface acoustic wave (SSAW) device that simultaneously excites acoustic waves through two piezoelectric substrates positioned at the top and bottom of a microchannel. By fully exploiting the degrees of freedom offered by two pairs of interdigital transducers (IDTs) on each substrate, the system enables highly flexible control of microparticles. To explore its capability on particle aggregation, we developed a two-dimensional numerical model to investigate the influence of the SAW phase modulation on the established acoustic fields within the microchannel. Single-particle motion was first examined under the influence of the phase-modulated acoustic fields to form a reference for identifying effective phase modulation strategies. Key parameters, such as the phase changes and the duration of each phase modulation step, were determined to maximize the lateral motion while minimizing undesired vertical motion of the particle. Our dual-sided SSAW configuration, combined with novel dynamic phase modulation strategy, leads to rapid and precise aggregation of microparticles towards a single focal point. This study sheds new light on the design of acoustofluidic devices for efficient spatiotemporal particle concentration. Full article

Background/Objectives: Decision-analytic Bayesian approaches are ideally suited for designing clinical trials. They have been used increasingly over the last 30 years in developing medical devices and drugs. A prototype trial is a bandit problem in which treating participants is as important as treating patients in clinical practice after the trial. Methods: This article chronicles the use of the Bayesian approach in clinical trials motivated by bandit problems. It provides a comprehensive historical and practical review of Bayesian adaptive trials, with a focus on bandit-inspired designs. Results: The 20th century saw advances in Bayesian methodology involving computer simulation. In the 21st century, methods motivated by bandit problems have been applied in designing scores of actual clinical trials. Fifteen such trials are described. By far the most important Bayesian contributions in clinical trials are the abilities to observe the accumulating results and to modify the future course of the trial on the basis of these observations. In the spirit of artificial intelligence, algorithms are programmed to learn the optimal treatment assignments over the remainder of the trial. Conclusions: Bayesian trials are still nascent and represent a small minority of clinical trials, but their existence is changing the way investigators, regulators, and government and industry sponsors view innovation in clinical trials. Full article

Digital images have been widely applied in fields such as mobile devices, the Internet of Things, and medical imaging. Although significant progress has been made in image encryption technology, it still faces many challenges, such as attackers using powerful computing resources and advanced algorithms to crack encryption systems. To address these challenges, this paper proposes a novel image encryption algorithm based on one-dimensional sawtooth wave chaotic system (1D-SAW) and the three-strand structure of DNA. Firstly, a new 1D-SAW chaotic system was designed. By introducing nonlinear terms and periodic disturbances, this system is capable of generating chaotic sequences with high randomness and initial value sensitivity. Secondly, a new diffusion rule based on the three-strand structure of DNA is proposed. Compared with the traditional DNA encoding and XOR operation, this rule further enhances the complexity and anti-attack ability of the encryption process. Finally, the security and randomness of the 1D-SAW and image encryption algorithms were verified through various tests. Results show that this method exhibits better performance in resisting statistical attacks and differential attacks. Full article

Background: More than merely determining our sleep pattern, our body’s internal clock also improves the quality of our sleep, alleviates the symptoms of depression, and maintains the balance of our gut flora. Methods: We carried out a 12-week randomized controlled trial with 99 adults from Kolkata, New Delhi, and Pune who reported sleep problems and symptoms of depression or anxiety. Participants received either a probiotic formulated to improve sleep quality and reduce depressive symptoms or a placebo. We tracked sleep using overnight studies and wearable devices, assessed depressive symptoms with standardized questionnaires, and analyzed stool samples to profile gut bacteria and their metabolites using gene sequencing and metabolomics. Advanced statistics and machine learning helped us pinpoint the key microbial and metabolic factors tied to sleep and mental health. Results: At the start, participants with disrupted sleep and depressive symptoms had fewer beneficial gut bacteria like Bifidobacterium and Lactobacillus, more inflammation-related microbes, and lower levels of helpful short-chain fatty acids. These imbalances were linked to poorer sleep efficiency, less REM sleep, and higher depression and anxiety scores. After 12 weeks, those taking the circadian-supporting probiotic saw a statistically significant increase in beneficial gut bacteria, improved sleep efficiency (+7.4%, p = 0.02), and greater reductions in depression and anxiety compared to the placebo. Increases in SCFA-producing bacteria most strongly predicted improvements. Conclusions: Our results show that taking a probiotic supplement can help bring your gut back into balance, support better sleep, and lift symptoms of depression and anxiety. This offers a hopeful and practical option for people looking for real relief from these deeply connected challenges. Full article

The signal-processing architecture of passive surface acoustic wave (SAW) sensors presents significant implementation challenges due to its radar-like operational principle and the inherent complexity of discrete component-based hardware design. While System-in-Package (SiP) has demonstrated remarkable success in miniaturizing electronic systems for smartphones, automotive electronics, and IoT applications, its potential for revolutionizing SAW sensor interrogator design remains underexplored. This paper presents a novel architecture that synergistically combines time-domain ADC design with SiP-based miniaturization to achieve unprecedented simplification of SAW sensor readout systems. The proposed time-domain ADC incorporates an innovative delay chain calibration methodology that integrates physical unclonable function (PUF) principles during time-to-digital converter (TDC) characterization, enabling the simultaneous generation of unique system IDs. The experimental results demonstrate that the integrated security mechanism provides variable-length bit entropy for device authentication, and has a reliability of 97.56 and uniqueness of 49.43, with 53.28 uniformity, effectively addressing vulnerability concerns in distributed sensor networks. The proposed SiP is especially suitable for space-constrained IoT applications requiring robust physical-layer security. This work advances the state-of-the-art wireless sensor interfaces by demonstrating how time-domain signal processing and advanced packaging technologies can be co-optimized to address performance and security challenges in next-generation sensor systems. Full article

Advancements in CMOS technology have significantly reduced both transistor dimensions and inter-device spacing, leading to a lower critical charge at sensitive nodes. As a result, SRAM cells used in space applications have become increasingly vulnerable to single-event upset (SEU) caused by the harsh radiation environment. To ensure reliable operation under such conditions, radiation-hardened SRAM designs are essential. In this paper, we propose a low-power read-decoupled radiation-hardened 16T (LDRH16T) SRAM cell to mitigate the effects of SEU. The proposed cell is evaluated against several state-of-the-art soft-error-tolerant SRAM designs, including QUCCE12T, WE-QUATRO, RHBD10T, SIS10T, EDP12T, SEA14T, and SAW16T. Simulations are conducted using a 90 nm CMOS process at a supply voltage of 1 V and a temperature of 27 °C. Simulation results show that LDRH16T successfully recovers its original state after injection at all sensitive nodes. Furthermore, since its storage nodes are decoupled from the bit lines during read operations, the proposed cell achieves the highest read stability among the compared designs. It also exhibits superior write ability, shorter write delay, and significantly lower hold power consumption. In addition, LDRH16T demonstrates excellent overall performance across key evaluation metrics and proves its capability for reliable operation in space environments. Full article