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Highlights An optoelectronic memristor with bioinspired neuromorphic behavior was proposed based on Ag/TiO2 Nanowires: ZnO QDs/FTO. The proposed device establishes superior long/short-term synaptic plasticity in response to electrical and light stimuli, and a neuromorphic computing task is effectively implemented based on its optoelectronic performance. The device emulated complex biological associative learning behaviors, including the four features of acquisition, extinction, restoration, and generalization.

This paper proposes a low-power design method and a low-noise phase offset calibration technique for a gated ring-oscillator time-to-digital converter (GRO-TDC), which normally consumes a large percentage of most all-digital phase-locked loop (ADPLL) power. A single coarse counter logic structure along with time-interleaved even/odd paths significantly reduces the complexity and speed of the TDC logic. The proposed TDC consumes only 0.44 to 24 mW for 0.077 to 24.42 ns of detection range. The multi-path GRO accelerates the oscillation speed and achieves approximately 6.2 ps of time resolution. The GRO-TDC shows –1.43 to 1.35 least-significant bits (LSB) of differential non-linearity (DNL) and –1.32 to 1.96 LSB of integral non-linearity (INL) over a 11-bit dynamic range (DR). The entire ADPLL including the proposed TDC has been fabricated in a 65 nm CMOS process and occupies 0.67 mm2 of active area. The prototype ADPLL consumes 12.22 mW from 1.2 V supply and the TDC consumes only 0.65 mW for a 50-phase offset code. A modified integrating structure in the subsequent digital loop filter (DLF) has been developed to mitigate dithering noise on $V_{ctrl}$ code and the measured reference spur is –69.38 dBc at 3.6 GHz center frequency. The tuning range of the implemented ADPLL is 3.5 to 4.7 GHz by using 2-bit band switching and 5-bit coarse control, while maintaining low- $K_{DCO}$ values to suppress in-band quantization noise. The measured root-mean-square (RMS) jitter is 0.94 ps and 0.99 ps at 3.6 GHz integer-mode and 3.60743 GHz fractional-mode respectively.

Radio frequency (RF) hyperthermia focuses on raising the target area temperature to a value exceeding 45°C. Collagen is stimulated when the temperature rises to 45°C at the dermal layer, resulting in skin tightening. However, most studies on RF hyperthermia have focused on tumor ablation or using electrodes to radiate an electromagnetic field, which is highly inefficient. This study proposed a non-invasive RF hyperthermia skin-tightening system with a compact metamaterial-filled waveguide aperture antenna. The proposed RF system increased the temperature by 11.6°C and 35.3°C with 20 and 80 W of 2.45 GHz RF power, respectively, within 60 s and exhibited a very focused effective area. Furthermore, a metamaterial was proposed to reduce the size of the waveguide aperture antenna and focus the electromagnetic field in the near-field region. The proposed metamaterial-filled waveguide aperture antenna was compact, measuring 10 mm × 17.4 mm, with a peak gain of 2.2 dB at 2.45 GHz. The measured hyperthermia performance indicated that the proposed RF system exhibited better power- and time-efficient hyperthermia performance than other RF hyperthermia systems in the cosmetic skin lifting commercial market. The proposed RF hyperthermia systems will be applied into a new generation of beauty cosmetic devices.

Abstract Developing electronic skins (e‐skins) that are comparable to or even beyond human tactile perception holds significant importance in advancing the process of intellectualization. In this context, a machine‐learning‐motivated micropyramid array bimodal (MAB) e‐skin based on capacitive sensing is reported, which enables spatial mapping applications based on bimodal sensing (proximity and pressure) implemented via fringing and iontronic effects, such as contactless measurement of 3D objects and contact recognition of Braille letters. Benefiting from the iontronic effect and single‐micropyramid structure, the MAB e‐skin in pressure mode yields impressive features: a maximum sensitivity of 655.3 kPa−1 (below 0.5 kPa), a linear sensitivity of 327.9 kPa−1 (0.5–15 kPa), and an ultralow limit of detection of 0.2 Pa. With the assistance of multilayer perceptron and convolutional neural network, the MAB e‐skin can accurately perceive 6 materials and 10 surface shapes based on the training and learning using the collected datasets from proximity and pressure modes, thus allowing it to achieve the precise perception of different objects within one proximity‐pressure cycle. The development of this MAB e‐skin opens a new avenue for robotic skin and the expansion of advanced applications.

This work proposes a microwave resonator built from gallium arsenide using integrated passive device (IPD) technology. It consists of a three-layered interlaced spiral structure with airbridges and inner interdigital structures. For integrated systems, IPD technology demonstrated outstanding performance, robustness, and a tiny size at a low cost. The airbridges were made more compact, with overall dimensions of 1590 × 800 µm2 (0.038 × 0.019 λg2). The designed microwave resonator operated at 1.99 GHz with a return loss of 39 dB, an insertion loss of 0.07 dB, and a quality factor of 1.15. Additionally, an experiment was conducted on the properties of the airbridge and how they affected resistance, inductance, and S-parameters in the construction of the resonator. To investigate the impact of airbridges on the structure, E- and H-field distributions of the resonator were simulated. Furthermore, its use in sensing applications was explored. Various concentrations of glucose solutions were used in the experiment. The proposed device featured a minimum detectable concentration of 0.2 mg/mL; high sensitivity, namely, 14.58 MHz/mg·mL−1, with a linear response; and a short response time. Thus, this work proposes a structure that exhibits potential in integrated systems and real-time sensing systems with high sensitivity.

This paper presents a highly integrated radio frequency (RF) CMOS receiver module for monitoring the core body temperature thermometer, which operates in the dual band 1.35 and 2.75 GHz ranges. The RF receiver IC, such as a Dicke radiometer, includes the full receiver circuits, RF switch and modulator, and duty calibrating circuit using a 65 nm CMOS process. With the proposed duty cycle modulation, accurate temperature sensing is achievable even with a receiver gain mismatch and fluctuation. The measured temperature ranges from 22 to 47.3°C, and the measured voltage slope is 2.97 mV/ms • °C, and the temperature error is less than 0.9°C in 1.35 GHz band. The radiometric RF CMOS IC has a size of $1.6\times2.3$ mm2 and the current consumption of 52 mW. Unlike the general skin temperature measurement of existing infrared (IR) sensors, the RF microwave core body thermometer equipped with an RF receiver IC that measures core body temperature inside a human body will be used in various fields as a digital healthcare and medical device.

Human deep core temperature is a vital health condition parameter. Human body temperature change begins from the deep core followed by change in skin temperature. Measuring deep core temperature is the first action for rapid detection of health condition. Infrared thermometer can measure temperature; however, the only measures the skin temperature. The use of microwave radiometer for measuring deep core temperature has garnered attention. The antenna, an important component of the microwave radiometer, has rarely been focused upon in studies on measurement of deep core temperature. This study proposed compact dual-band on-body near field antenna with a reflector for measuring deep core temperature using a microwave radiometer. The proposed antenna size is 13 mm $\boldsymbol {\times }\,\,13$ mm with a 20 mm $\boldsymbol {\times }\,\,20$ mm reflector 3 mm above the radiator. The proposed antenna was simulated and designed on a full 3D body model and simplified flat phantom and measured on real human wrist. It achieved sufficient bandwidth and volume loss density can be used in microwave radiometers for measuring deep core temperature.

Abstract Recently, polymer materials have been at the forefront of other materials in building high‐performance flexible electronic skin (e‐skin) devices due to conspicuous advantages including excellent mechanical flexibility, good compatibility, and high plasticity. However, most research works just paid considerable attention and effort to the design, construction, and possible application of e‐skins that reproduce the tactile perception of the human skin sensory system. Compared with tactile sensing devices, e‐skins that aim to imitate the non‐contact sensing features in the sensory system of human skin tend to avoid undesired issues such as bacteria spreading and mechanical wear. To further promote the development of e‐skins to the human skin sensory system where tactile perception and non‐contact sensing complement each other, significant progress and advances have been achieved in the field of polymer materials enabled e‐skins for both tactile perception and non‐contact sensing applications. In this review, the latest progress in polymer material‐based e‐skins with regard to tactile, non‐contact sensing capabilities and their practical applications are introduced. The fabrication strategies of polymer materials and their role in building high‐performance e‐skins for tactile and non‐contact sensing are highlighted. Furthermore, we also review the research works that integrated the polymer‐based tactile and non‐contact e‐skins into robots and prostheses, smart gloves, and VR/AR devices and addressed some representative problems to demonstrate their suitability in practical applications in human–machine interactions. Finally, the current challenges in the construction of high‐performance tactile and non‐contact e‐skins are highlighted and promising properties in this direction, by taking advantage of the polymer materials, are outlined.

Abstract Intelligent perception means that with the assistance of artificial intelligence (AI)‐motivated brain, flexible sensors achieve the ability of memory, learning, judgment, and reasoning about external information like the human brain. Due to the superiority of machine learning (ML) algorithms in data processing and intelligent recognition, intelligent perception systems possess the ability to match or even surpass human perception systems. However, the built‐in flexible sensors in these systems need to work on dynamic and irregular surfaces, inevitably affecting the precision and fidelity of the acquired data. In recent years, the strategy of introducing the developed functional materials and innovative structures into flexible sensors has made some progress toward the above challenges, and with the blessing of ML algorithms, accurate perception and reasoning in various scenarios have been achieved. Here, the most representative functional materials and innovative structures for constructing flexible sensors are comprehensively reviewed, the research progress of intelligent perception systems based on flexible sensors and ML algorithms is further summarized, and the intersection of the two is expected to unlock new opportunities for next‐stage AI development.

Abstract In this study, the chemical decomposition of a polyimide-film (i.e., a PI-film)-surface into a soft-film-surface containing negatively charged pyromellitic dianhydride (PMDA) and neutral 4,4′-oxydianiline (ODA) was successfully performed. The chemical decomposition was conducted by designing the slurry containing 350 nm colloidal silica abrasive and small molecules with amine functional groups (i.e., ethylenediamine: EDA) for chemical–mechanical planarization (CMP). This chemical decomposition was performed through two types of hydrolysis reactions, that is, a hydrolysis reaction between OH− ions or R-NH3 + (i.e., EDA with a positively charged amine groups) and oxygen atoms covalently bonded with pyromellitimide on the PI-film-surface. In particular, the degree of slurry adsorption of the PI-film-surface was determined by the EDA concentration in the slurry because of the presence of R-NH3 +, that is, a higher EDA concentration resulted in a higher degree of slurry adsorption. In addition, during CMP, the chemical decomposition degree of the PI-film-surface was principally determined by the EDA concentration; that is, the degree of chemical composition was increased noticeably and linearly with the EDA concentration. Thus, the polishing-rate of the PI-film-surface increased notably with the EDA concentration in the CMP slurry.

Deep core temperature is the most basic and important information about health conditions. Non-contact infrared thermometers are widely used for human body temperature measurement. However, infrared thermometers are not suitable for deep core temperature measurement. To overcome this limitation, measuring deep core temperature with a microwave radiometer is gaining attention. In this study, we propose a dual-band on-body near-field antenna for measuring deep core temperature with a microwave radiometer application. The proposed antenna has a compact size of 20 mm $\times30$ mm $\times1.52$ mm. The negative (−) radiator is located at the top of the substrate and the positive (+) radiator is located at the bottom of the substrate. The dual-band is proposed for high temperature resolution and is achieved by a meander slot on the radiator. The antenna is fabricated on a high dielectric substrate and the stubs are proposed to reduce the size of the proposed antenna so that it can be used on various human body parts.

Due to the current limitations of three-dimensional (3D) simulation graphics technology, mind wandering commonly occurs in virtual reality tasks, which has impeded it being applied more extensively. The right ventrolateral prefrontal cortex (rVLPFC) plays a vital role in executing continuous two-dimensional (2D) mental paradigms, and transcranial direct current stimulation (tDCS) over this cortical region has been shown to successfully modulate sustained 2D attention. Accordingly, we further explored the effects of electrical activation of the rVLPFC on 3D attentional tasks using anodal high-definition (HD)-tDCS. A 3D Go/No-go (GNG) task was developed to compare the after effects of real and sham brain stimulation. Specifically, GNG tasks were periodically interrupted to assess the subjective perception of attentional level, behavioral reactions were tracked and decomposed into an underlying decision cognition process, and electroencephalography data were recorded to calculate event-related potentials (ERPs) in rVLPFC. The p-values statistically indicated that HD-tDCS improved the subjective mentality, led to more cautious decisions, and enhanced neuronal discharging in rVLPFC. Additionally, the neurophysiological P300 ERP component and stimulation being active or sham could effectively predict several objective outcomes. These findings indicate that the comprehensive approach including brain stimulation, 3D mental paradigm, and cross-examined performance could significantly lengthen and robustly compare sustained 3D attention.

Humidity-sensing devices are widely utilized in various fields, including the environment, industries, food processing, agriculture, and medical processes. In the past few years, the development of noncontact sensors based on moisture detection has increased rapidly due to the COVID-19 pandemic. Moisture-detection, noncontact and breath-monitoring sensors have promising applications in various fields. In this study, we proposed a rapid-response graphene oxide (GO)-doped P(VDF-TrFE)/LiCl nanocomposite-based moisture sensor fabricated on an interdigitated electrode. The synthesis of GO/P(VDF-TrFE)/LiCl resulted in a porous structure with nano-sized holes due to the effect of LiCl. Moreover, doped GO improved the conductivity of the sensing film. The created nanoporous structure improved the recovery time better than the response time, with the times being 4.8 s and 7.8 s, respectively. Not only did our sensor exhibit rapid response and recovery times, it also exhibited a high sensitivity of 1708.8 pF/%RH at 25% to 93%RH. We also presented a real-time breath-monitoring system for noncontact sensing applications based on GO-doped P(VDF-TrFE)/LiCl composites. The results revealed that GO-doped P(VDF-TrFE)/LiCl is a good candidate for fabricating real-time moisture-detection noncontact sensing devices.

In this study, a hybrid bipolar arc plasma stimulation (BAPS) and dual pulse electroporation (DPEP) technique was used to form microchannels, and the effect of highly efficient transformation drug delivery (TDD) on the skin was analyzed. The BAPS technique was applied to pig skin to form a microchannel as a biological sample to measure and observe the plasma as a micropore. During the BAPS, an output voltage of 1 kVpp at 40 kHz was applied at duty rates of 20%, 40%, and 60%. The BAPS technique was applied to the keratin skin layer, and microchannels with an average size of 30 μm × 30 μm and up to 77 μm × 55 μm were formed only in the keratin layer without any damage to the dermal layer. Next, DPEP was stimulated to increase the permeability of the endothelial membrane in the structure with the microchannels. The proposed hybrid technique effectively introduces TDD deeper into the employed 20 female subjects skin test with average age of 44 years, and the results in the absorption rate increase about 418%.

Virtual reality (VR), a rapidly evolving technology that simulates three-dimensional virtual environments for users, has been proven to activate brain functions. However, the continuous alteration pattern of the functional small-world network in response to comprehensive three-dimensional stimulation rather than realistic two-dimensional media stimuli requires further exploration. Here, we aimed to validate the effect of VR on the pathways and network parameters of a small-world organization and interpret its mechanism of action. Fourteen healthy volunteers were selected to complete missions in an immersive VR game. The changes in the functional network in six different frequency categories were analyzed using graph theory with electroencephalography data measured during the pre-, VR, and post-VR stages. The mutual information matrix revealed that interactions between the frontal and posterior areas and those within the frontal and occipital lobes were strengthened. Subsequently, the betweenness centrality (BC) analysis indicated more robust and extensive pathways among hubs. Furthermore, a specific lateralized channel (O1 or O2) increment in the BC was observed. Moreover, the network parameters improved simultaneously in local segregation, global segregation, and global integration. The overall topological improvements of small-world organizations were in high-frequency bands and exhibited some degree of sustainability.

Enzyme production by microorganisms on an industrial scale has demonstrated technical bottlenecks, such as low efficiency in enzyme expression and extracellular secretion. In this study, as a potential tool for overcoming these technical limits, radio-frequency electromagnetic field (RF-EMF) exposure was examined for its possibility to enhance production of an enzyme, α-amylase, in a filamentous fungus, Aspergillus oryzae. The RF-EMF perfectly resonated at 2 GHz with directivity radiation pattern and peak gain of 0.5 dB (0.01 Watt). Total protein concentration and activity of α-amylase measured in media were about 1.5–3-fold higher in the RF-EMF exposed (10 min) sample than control (no RF-EMF) during incubation (the highest increase after 16 h). The level of α-amylase mRNA in cells was approximately 2–8-fold increased 16 and 24 h after RF-EMF exposure for 10 min. An increase in vesicle accumulation within fungal hyphae and the transcription of some genes involved in protein cellular trafficking was observed in RF-EMF-exposed samples. Membrane potential was not changed, but the intracellular Ca2+ level was elevated after RF-EMF exposure. Our results suggest that RF-EMF can increase the extracellular level of fungal total proteins and α-amylase activity and the intracellular level of Ca2+.

Recently, as an alternative solution for overcoming the scaling-down limitations of logic devices with design length of less than 3 nm and enhancing DRAM operation performance, 3D heterogeneous packaging technology has been intensively researched, essentially requiring Si wafer polishing at a very high Si polishing rate (500 nm/min) by accelerating the degree of the hydrolysis reaction (i.e., Si-O-H) on the polished Si wafer surface during CMP. Unlike conventional hydrolysis reaction accelerators (i.e., sodium hydroxide and potassium hydroxide), a novel hydrolysis reaction accelerator with amine functional groups (i.e., 552.8 nm/min for ethylenediamine) surprisingly presented an Si wafer polishing rate >3 times higher than that of conventional hydrolysis reaction accelerators (177.1 nm/min for sodium hydroxide). This remarkable enhancement of the Si wafer polishing rate for ethylenediamine was principally the result of (i) the increased hydrolysis reaction, (ii) the enhanced degree of adsorption of the CMP slurry on the polished Si wafer surface during CMP, and (iii) the decreased electrostatic repulsive force between colloidal silica abrasives and the Si wafer surface. A higher ethylenediamine concentration in the Si wafer CMP slurry led to a higher extent of hydrolysis reaction and degree of adsorption for the slurry and a lower electrostatic repulsive force; thus, a higher ethylenediamine concentration resulted in a higher Si wafer polishing rate. With the aim of achieving further improvements to the Si wafer polishing rates using Si wafer CMP slurry including ethylenediamine, the Si wafer polishing rate increased remarkably and root-squarely with the increasing ethylenediamine concentration.

This paper describes the implementation of a miniaturized quad flat no-lead (QFN)-packaged bandpass filter (BPF) with a combination of an intertwined circular spiral inductor and two types of integrated center-located capacitors using gallium-arsenide-based integrated passive device (IPD) fabrication technology. Air-bridge structures were introduced into the outer circular spiral inductor to save space and to provide the filter with a compact chip area of 1192.5 × 1012.7 μm2. An equivalent circuit was modeled, the current density and variable dimensional parameters were simulated, and the fabrication process was introduced to achieve a better understanding of the IPD BPF. The proposed device was packaged using the QFN-packaging technology and was measured to possess a single passband with a central frequency of 1.91 GHz (return loss: 28.8 dB) and a fractional bandwidth of 72.69% (insertion loss: 0.62 dB). One transmission zero was obtained on the right side of the passband at 4.78 GHz with an amplitude of 35.95 dB. The fabricated BPF can be used in various L-band applications, such as mobile service, satellite navigation, telecommunications, and aircraft surveillance, due to its miniaturized chip size and high-performance characteristics.

In this study, we propose a miniaturized bandpass filter (BPF) developed by combining an approximate circular (36-gon) winding inductor, a circinate capacitor, and five air-bridge structures fabricated on a gallium arsenide (GaAs) substrate using an integrated passive device (IPD) technology. We introduced air-bridge structures into the outer metal wire to improve the capacitance per unit volume while utilizing a miniaturized chip with dimensions 1538 μm × 800 μm (0.029 λ0 × 0.015 λ0) for the BPF. The pattern was designed and optimized by simulating different dimensional parameters, and the group delay and current density are presented. The equivalent circuit was modeled to analysis various parasitic effect. Additionally, we described the GaAs-based micro-nano scale fabrication process to elucidate the proposed IPD technology and the physical structure of the BPF. Measurements were conducted with a center frequency of 1.53 GHz (insertion loss of 0.53 dB) and a 3-dB fractional bandwidth (FBW) of 70.59%. The transmission zero was located at 4.16 GHz with restraint of 35.86 dB. Owing to the benefits from its miniaturized chip size and high performance, the proposed GaAs-based IPD BPF was verified as an excellent device for various S-band applications, such as satellite communication, keyless vehicle locks, wireless headphones, and radar.

In this study, we propose a high-performance resonator-based biosensor for mediator-free glucose identification. The biosensor is characterized by an air-bridge capacitor and fabricated via integrated passive device technology on gallium arsenide (GaAs) substrate. The exterior design of the structure is a spiral inductor with the air-bridge providing a sensitive surface, whereas the internal capacitor improves indicator performance. The sensing relies on repolarization and rearrangement of surface molecules, which are excited by the dropped sample at the microcosmic level, and the resonance performance variation corresponds to the difference in glucose concentration at the macroscopic level. The air-bridge capacitor in the modeled RLC circuit serves as a bio-recognition element to glucose concentration (εglucoseC0), generating resonant frequency shifts at 0.874 GHz and 1.244 GHz for concentrations of 25 mg/dL and 300 mg/dL compared to DI water, respectively. The proposed biosensor exhibits excellent sensitivity at 1.38 MHz per mg/dL with a wide detection range for glucose concentrations of 25–300 mg/dL and a low detection limit of 24.59 mg/dL. Additionally, the frequency shift and concentration are highly linear with a coefficient of determination of 0.98823. The response time is less than 3 s. We performed multiple experiments to verify that the surface morphology reveals no deterioration and chemical binding, thus validating the reusability and reliability of the proposed biosensor.

This article presents a high-sensitivity, quantified, linear, and mediator-free resonator-based microwave biosensor for glucose sensing application. The proposed biosensor comprises an air-bridge-type asymmetrical differential inductor (L) and a center-loaded circular finger-based inter-digital capacitor (C) fabricated on Gallium Arsenide (GaAs) substrate using advanced micro-fabrication technology. The intertwined asymmetrical differential inductor is used to achieve a high inductance value with a suitable Q-factor, and the centralized inter-digital capacitor is introduced to generate an intensified electric field. The designed microwave sensor is optimized to operate at a low resonating frequency that increases the electric field penetration depth and interaction area in the glucose sample. The microwave biosensor is tested with different glucose concentrations (0.3–5 mg/ml), under different ambient temperatures (10–50 °C). The involvement of advanced micro-fabrication technology effectively miniaturized the microwave biosensor (0.006λ0 × 0.005λ0) and enhanced its filling factor. The proposed microwave biosensor demonstrates a high sensitivity of 117.5 MHz/mgmL-1 with a linear response (r2 = 0.9987), good amplitude variation of 0.49 dB/mgmL-1 with a linear response (r2 = 0.9954), and maximum reproducibility of 0.78% at 2 mg/mL. Additionally, mathematical modelling was performed to estimate the dielectric value of the frequency-dependent glucose sample. The measured and analyzed results indicate that the proposed biosensor is suitable for real-time blood glucose detection measurements.

This article presents a compact quad flat no-lead (QFN)-packaged second-order bandpass filter (BPF) with intertwined inductors, a dendritic capacitor, and four air-bridge structures, which was fabricated on a gallium arsenide (GaAs) substrate by integrated passive device (IPD) technology. Air-bridge structures were introduced into an approximate octagonal outer metal track to provide a miniaturized chip size of 0.021 × 0.021 λ0 (0.8 × 0.8 mm2) for the BPF. The QFN-packaged GaAs-based bandpass filter was used to protect the device from moisture and achieve good thermal and electrical performances. An equivalent circuit was modeled to analyze the BPF. A description of the manufacturing process is presented to elucidate the physical structure of the IPD-based BPF. Measurements were performed on the proposed single band BPF using a center frequency of 2.21 GHz (return loss of 26.45 dB) and a 3-dB fractional bandwidth (FBW) of 71.94% (insertion loss of 0.38 dB). The transmission zero is located at the 6.38 GHz with a restraint of 30.55 dB. The manufactured IPD-based BPF can play an excellent role in various S-band applications, such as a repeater, satellite communication, and radar, owing to its miniaturized chip size and high performance.

In this work, a miniaturized bandpass filter (BPF) constructed of two spiral intertwined inductors and a central capacitor, with several interdigital structures, was designed and fabricated using integrated passive device (IPD) technology on a GaAs wafer. Five air-bridge structures were introduced to enhance the mutual inductive effect and form the differential geometry of the outer inductors. In addition, the design of the differential inductor combined with the centrally embedded capacitor results in a compact construction with the overall size of 0.037λ0 × 0.019λ0 (1537.7 × 800 μm2) where λ0 is the wavelength of the central frequency. For the accuracy evolution of the equivalent circuit, the frequency-dependent lumped elements of the proposed BPF was analyzed and modeled through the segment method, mutual inductance approach, and simulated scattering parameters (S-parameters). Afterward, the BPF was fabricated using GaAs-based IPD technology and a 16-step manufacture flow was accounted for in detail. Finally, the fabricated BPF was wire-bonded with Au wires and packaged onto a printed circuit board for radio-frequency performance measurements. The measured results indicate that the implemented BPF possesses a center frequency operating at 2 GHz with the insertion losses of 0.38 dB and the return losses of 40 dB, respectively, and an ultrawide passband was achieved with a 3-dB fraction bandwidth of 72.53%, as well. In addition, a transmission zero is located at 5.32 GHz. Moreover, the variation of the resonant frequency with different inductor turns and metal thicknesses was analyzed through the simulation results, demonstrating good controllability of the proposed BPF.

This paper reports on the use of gallium arsenide-based integrated passive device technology for the implementation of a miniaturized bandpass filter that incorporates an intertwined circle-shaped spiral inductor and an integrated center-located capacitor. Air-bridge structures were introduced to the outer inductor and inner capacitor for the purpose of space-saving, thereby yielding a filter with an overall chip area of 1178 μm × 970 μm. Thus, not only is the chip area minimized, but the magnitude of return loss is also improved as a result of selective variation of bridge capacitance. The proposed device possesses a single passband with a central frequency of 1.71 GHz (return loss: 32.1 dB), and a wide fractional bandwidth (FBW) of 66.63% (insertion loss: 0.50 dB). One transmission zero with an amplitude of 43.42 dB was obtained on the right side of the passband at 4.48 GHz. Owing to its miniaturized chip size, wide FBW, good out-band suppression, and ability to yield high-quality signals, the fabricated bandpass filter can be implemented in various L-band applications such as mobile services, satellite navigation, telecommunications, and aircraft surveillance.

We present a microfabricated spiral-coupled passive resonator sensor realized through integrated passive device (IPD) technology for the sensitive detection and characterization of water-ethanol solutions. In order to validate the performance of the proposed device, we explicitly measured and analyzed the radio frequency (RF) characteristics of various water-ethanol solution compositions. The measured results showed a drift in the resonance frequency from 1.16 GHz for deionized (DI) water to 1.68 GHz for the solution containing 50% ethanol, whereas the rejection level given by the reflection coefficient decreased from −29.74 dB to −14.81 dB. The obtained limit of detection was 3.82% volume composition of ethanol in solution. The derived loaded capacitance was 21.76 pF for DI water, which gradually decreased to 8.70 pF for the 50% ethanol solution, and the corresponding relative permittivity of the solution decreased from 80.14 to 47.79. The dissipation factor increased with the concentration of ethanol in the solution. We demonstrated the reproducibility of the proposed sensor through iterative measures of the samples and the study of surface morphology. Successive measurement of different samples had no overlapping and had very minimum bias between RF characteristics for each measured sample. The surface profile for bare sensors was retained after the sample test, resulting a root mean square (RMS) value of 11.416 nm as compared to 10.902 nm for the bare test. The proposed sensor was shown to be a viable alternative to existing sensors for highly sensitive water-ethanol concentration detection.

Sports injuries among young athletes are associated with increased mental health risks. This case study explored the effects of a 10-week yoga program combined with psychological skills training (PST) on mental health coping in injured young athletes. Ten male soccer players (Mage = 16.2 ± 0.92) who had sustained sports injuries in the past year participated in the yoga-PST program. Pre- and post-intervention questionnaires assessed coping skills tailored to athletes' mental health (e.g., learned resourcefulness, psychological skills in sports, and post-sport injury stress). The intervention led to significant improvements in mental health coping skills, including problem-focused coping (+14%), goal setting (+19%), hyperarousal reduction (-40%), and re-experience reduction (-35%). Cohen's d results indicated positive impacts on the sub-domains of coping skills. The study suggests that yoga-PST intervention can enhance mental health coping in injured young athletes, fostering positive coping responses and potentially preventing long-term mental health issues [ABSTRACT FROM AUTHOR]