Search Results (283)

Microwave energy is ideal for wearable devices due to its stable wireless power transfer capabilities. However, rigid receiving antennas in conventional RF energy harvesters compromise wearability. This study presents a wearable system using a flexible dual-band antenna (915 MHz/2.45 GHz) fabricated via conformal 3D printing on arm-mimicking curvatures, minimizing bending-induced performance loss. A hybrid microstrip–lumped element rectifier circuit enhances energy conversion efficiency. Tested with commercial 915 MHz transmitters and Wi-Fi routers, the system consistently delivers 3.27–3.31 V within an operational range, enabling continuous power supply for real-time physiological monitoring (e.g., pulse detection) and data transmission. This work demonstrates a practical solution for sustainable energy harvesting in flexible wearables. Full article

Background/Objectives: Salvage liver transplantation (SLT) is a well-established option for hepatocellular carcinoma (HCC) recurrence after liver resection. Laparoscopic microwave ablation (L-MWA) represents another curative strategy for early-stage HCC. However, its role within this therapeutic framework remains unexplored. Methods: Between 2014 and 2023, we treated 1341 patients with HCC using L-MWA. From this cohort, patients with Child-Pugh class A liver function, HCC within the Milan criteria, no contraindications to transplantation, and ≥12 months of follow-up were selected. SLT failure was defined as non-transplantable recurrence or death, resulting in the loss of a potentially curative therapeutic opportunity. The primary endpoint was overall survival (OS); secondary endpoints included predictors of survival and SLT failure. Results: A total of 341 patients met the inclusion criteria. Five-year OS was 62%. Independent predictors of poorer survival included the presence of cardiac disease or oesophageal varices, a Child-Pugh score of 6, tumour size, and elevated alpha-fetoprotein (AFP) levels. Treatment was successful in 255 patients (74.8%): 102 (29.9%) underwent SLT, 67 (19.6%) received alternative therapies, and 93 (27.3%) remained recurrence-free. Treatment failure occurred in 86 patients (25.2%) due to non-transplantable recurrence or death. Independent predictors of failure included older age, non-HBV aetiology, and elevated AFP levels. Five-year OS rates were 79% in the success group and 22% in the failure group (p < 0.001). Conclusions: A combined L-MWA and SLT strategy is safe and effective, yielding a 62% 5-year OS rate. This approach supports more efficient graft use with a consequent increase in the population transplant benefit. Improved selection may further reduce failure rates. Full article

In this article, we propose a novel near-field holographic microwave imaging technique designed to accelerate the data acquisition process. The system employs a novel electronic switching mechanism utilizing two switching networks that virtually rotate the transmitting and receiving antennas along the azimuthal direction for efficient data collection. This minimizes the need for mechanical scanning of the antennas which, in turn, leads to faster data acquisition. To enhance the quality of the imaging outcome, the number of samples can be increased by combining only a few mechanical scanning steps with the electronic scanning. This data acquisition scheme leverages the system’s space-invariant property to enable convolution-based near-field holographic microwave image reconstruction. By capturing and processing scattered fields over a cylindrical aperture, the system achieves high-resolution imaging of concealed objects across multiple range positions. Both simulation and experimental results validate the effectiveness of the proposed approach in delivering high-quality imaging results. Its ability to provide faster and enhanced imaging outcomes highlights its potential for a wide range of applications, including biomedical imaging, security screening, and non-destructive testing of the materials. Full article

Drying is a key method for food preservation; however, conventional techniques often lead to the degradation of bioactive compounds, compromising nutritional quality. This systematic review, following the PRISMA protocol, examines emerging food drying technologies designed to enhance process efficiency while preserving nutritional and functional properties. A bibliometric analysis was conducted to identify research trends from 2014 to 2024. Searches were performed in the Scopus and Web of Science databases accessed on 17 January 2025, including only original research articles published in English focusing on food drying applications. Reviews, editorials, and studies unrelated to the food sector were excluded. Due to the technological nature of the outcomes, a formal risk of bias assessment was not applicable. This review highlights several emerging drying technologies, such as microwave, radiofrequency, infrared, ultrasound, freeze-drying, and cold plasma. The qualitative synthesis indicates these technologies improve the retention of phenolics, flavonoids, and vitamins, thus enhancing nutritional stability. Nevertheless, challenges remain in industrial-scale implementation, particularly regarding the economic feasibility and optimization of operational parameters. This review received no funding and was not registered in any public database. The findings underscore the need for continued research to develop sustainable and functional dried food products that meet current market demands and consumer expectations. Full article

In general, the acceptance of edible insects by consumers is low. Therefore, the aim of this research was to develop protein supplements from desiccated crickets. The objectives of this research were to study the effects of four different drying methods on the chemical properties of crickets and the effects of cricket powder fortification in vegetable chips on the chemical and physical qualities and consumer acceptance. Through an analysis of the chemical composition of cricket powder dried using hot air, vacuum, microwave, and freeze-drying methods, it was found that freeze-drying resulted in the highest protein content in the cricket powder, followed by vacuum drying, hot air drying, and microwave drying. However, the antioxidant activity, which was analyzed using DPPH, showed no significant differences across the four drying methods (p > 0.05). The sensory testing of chips by 30 consumers revealed that the chips with a 10:10 ratio of vegetable powder to cricket powder received the highest satisfaction results in all of the test attributes, ranging from “like” to “like very much”. When studying the chemical composition, hardness, and color of the chips, it was found that increasing the amount of cricket powder resulted in a decrease in lightness and yellowness, while redness and hardness increased. The antioxidant activity and phenolic content of the chips increased with the addition of cricket powder, while the flavonoid and potassium contents decreased as vegetable powder was replaced with cricket powder. In the formula most preferred by consumers, the antioxidant activity, phenolic content, flavonoid content, and potassium content were 60.90%, 6.25 ± 0.46 mg GAE/mg sample, 11.16 ± 0.1 mg QE/mg sample, and 0.66 ± 0.01%, respectively. Full article

A non-uniform antenna array is proposed to enhance the accuracy of medical microwave imaging systems by increasing the amount of useful information captured about the imaged domain without increasing the number of antennas. These systems have so far been using uniform antenna arrays, which lead to highly correlated signals, limiting the amount of imaging information and adversely affecting diagnostic accuracy. In the proposed non-uniform antenna array method, the optimal number and positions of antennas are calculated with the aim of enhancing spatial diversity and reducing information redundancy. The mutual information coefficient is used as a metric to evaluate and minimize redundancy between received signals. A microwave head imaging system is used to verify the proposed approach. The results of the investigated scenarios show that using a non-uniform antenna configuration outperforms a uniform setup in imaging accuracy and clarity, when using the same number of antennas. Moreover, the reconstructed images demonstrate that using an optimized non-uniform antenna array with fewer elements can outperform a uniform array with more elements in terms of localization accuracy and image quality. The proposed approach improves imaging performance and reduces system complexity, cost, and power consumption, making it a practical solution for real-world biomedical imaging applications. Full article

A microwave photonic approach for measuring the angle of arrival (AOA) and frequency is proposed and experimentally demonstrated. The AOA-dependent phase difference and frequency of two received signals were mapped to intensity information through subtractive and differential operations, which were achieved by a delayed superposition structure with phase inversion. By measuring the output signal powers, both the phase difference and frequency of the two signals could be determined. The theoretical analysis results are given in detail. In this proof-of-concept experiment, the system had a phase difference measurement range of 340 degrees, with a maximum error of 2.9 degrees. The frequency measurement covered 1–10 GHz, with a maximum error of 2.2%. The proposed approach offers a straightforward method for measuring the AOA and frequency under the same configuration, which provides new insight into AOA- and frequency-measurement techniques. Full article

This paper presents two cryogenic low-noise amplifiers (LNAs) based on the WIN’s 0.18 $\mathrm{\mu }$m gate length gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) process designed for radio telescope receivers. Discrete transistors with gate peripheries spanning 50–600 $\mathrm{\mu }$m were DC-characterized at 290 K and 15 K, respectively. The LNAs underwent on-chip noise characterization under 15 K using a Y-factor measurement setup, which integrated a calibrated noise source and a noise figure analyzer. This approach directly quantified the noise temperature—critical metrics for radio telescope receiver front-ends. The top-performing LNA variant identified through on-chip characterization was packaged and evaluated in a cryogenic test-bed. This LNA, spanning a bandwidth of 0.3–15 GHz, demonstrated a gain of 26 dB and a minimum noise temperature of 6 K when operated at an ambient temperature of 15 K. In contrast, a second LNA architecture, tested solely on-chip, demonstrated a gain of 30 dB and a minimum noise temperature of 15 K across the 0.3–7 GHz range. Full article

The impact of breast cancer on public health is serious, and due to risk/benefit assessment, screening programs are usually restricted to women older than 49 years. Microwave imaging devices offer advantages such as non-ionizing radiation, low cost, and the ability to distinguish between cancerous and healthy tissues due to their electrical properties. Ensuring the safety of this technology is vital for its potential clinical application. To estimate the temperature increase in breast tissues from a microwave imaging scanner, cases of healthy, benign, and malignant breast tissues were analyzed using three digital models and adding two healthy breast models with varying densities. Virtual experiments were conducted using the Sim4Life software (version 7.2) with a system consisting of a horn antenna in transmission and a Vivaldi antenna in reception. Temperature increases were estimated based on the Specific Absorption Rate distributions computed for different configurations and frequencies. The highest temperature increase obtained in this analysis is lower than 60 μK in fibroglandular tissue or skin, depending on the frequency and breast density. The presence of a receiving antenna acting as a scatterer modifies the temperature increase, which is almost negligible. Microwave examination can be performed without harmful thermal effects due to electromagnetic field exposure. Full article

Background/Objectives: The development of effective therapies for brain disorders is highly correlated with the ability of drugs or nanosystems to cross the blood–brain barrier (BBB), which has been limited. Recently, carbon dots (CDs) have been receiving attention to be used as BBB-crossing theranostic agents due to their inherent advantages, such as low size, excellent biocompatibility, high quantum yield (QY), tunable fluorescence, high drug loading, and relatively easy synthesis at low cost. The aim of this study was to design CDs with precisely controlled fluorescence properties for advanced bioimaging and an in-depth assessment of BBB permeability. Methods: CDs were synthesized using a microwave-assisted approach, optimized through microwaves’ irradiation time, and employing citric acid, urea, and sodium fluoride as precursors. The optimized sample was labeled as NF-CD. Results: A comprehensive physicochemical, photoluminescence, and biological characterization revealed the ability of NF-CD to diffuse across a neuromimetic-BBB model, mainly due to their small size (average diameter of 4.0 ± 1.1 nm), exhibiting excitation-dependent fluorescence in the blue and green wavelengths, high biocompatibility and QY, and exceptional photostability. Conclusions: Owing to the exceptional fluorescence characteristics and biological compatibility, NF-CD presents promising opportunities in theranostic applications, particularly in brain-targeted bioimaging, nanocarrier-based drug and immunotherapy delivery, early-stage diagnostics, and personalized medicine. NF-CD’s ability to cross the BBB further underscores the relevance of pioneering nanomaterial-based strategies for neurological disorder diagnostics and precision-targeted therapeutic interventions. Overall, this research contributes to the broader field of nanotechnology-driven biomedical advancements, fostering innovations in neurological diagnostics and therapeutic delivery systems. Full article

The widespread use of electronic devices in daily life, industry and military has led to a large amount of electromagnetic pollution, which has become an increasingly serious security issue. To eliminate or mitigate such risks and hazards, various advanced microwave absorption technologies and materials have been reported. As a new type of microwave absorber, biomass-derived carbon-based materials have received extensive attention. They have the characteristics of low cost, easy preparation, high porosity and environmental friendliness while retaining the advantageous adjustable dielectric properties, high conductivity and good stability of traditional carbon materials. The development of biomass microwave-absorbing materials not only provides a new idea for solving electromagnetic radiation but also helps to create an environmentally friendly and harmonious environment. Herein, various biomass-derived carbon-based microwave-absorbing materials (MAMs) including plant shells, plant fibers and other potential biomass materials are generalized and discussed including their preparation technology, microstructure design and so on. The two critical factors affecting microwave absorption properties, impedance matching and attenuation characteristics, are analyzed in detail. Finally, the confronting challenges and future development prospects of biomass-based microwave-absorbing materials are pointed out. Full article

With the advancement of power electronics, control systems, and related technologies, devices such as unmanned aerial vehicles (UAVs), airships, and electric vehicles (EVs) have become integral to modern life and industry. However, limited battery capacity, short battery life, attenuated battery performance, environmental sensitivity, and long charging time result in range anxiety in electrically driven devices, which has become an important factor restricting their development. This paper reviews the current status of power supply technologies for moving targets, categorizing them into contact charging, autonomous power supply, and wireless power transfer (WPT) methods. The principles, advantages, disadvantages, and applications of each approach are thoroughly analyzed. Comparative analysis highlights that WPT technology, which eliminates the need for electrical connections between the transmitter and receiver, offers notable advantages, including high flexibility, extended charging distances, and simultaneous power delivery to multiple targets. These features make it particularly well suited for the energy requirements of moving devices. Accordingly, this paper emphasizes the key technologies and future development directions of microwave WPT (MWPT) and laser WPT (LWPT) to facilitate the broader adoption of dynamic wireless power supply systems for moving targets. Full article

Background/Objectives: The development of bioproducts that can accelerate wound healing is a key focus in biomedicine, especially when these products are derived from sustainable by-products. This study investigates the wound-healing potential of an extract obtained from Agave angustifolia Haw bagasse (BagEE) using microwave extraction.Methods: HPLC-MS analysis was performed to identify the main compounds present in BagEE, revealing quercetin, isorhamnetin, diosgenin, hecogenin, manogenin, β-sitosterol glucoside, and β-sitosterol as tentative constituents. A murine excision wound model was employed to assess the efficacy of BagEE. The experimental group received a topical application of 8 mg of BagEE, while the control group was treated with water only. Wound closure, re-epithelialization, and collagen deposition were evaluated to determine the effects of BagEE on skin healing. Results: The BagEE-treated group exhibited significantly accelerated wound healing, achieving a 99.4% closure rate by day 13 compared to the control group’s 92.8% closure rate on day 22. Additionally, wounds treated with BagEE displayed complete re-epithelialization and a well-organized skin structure. Conclusions: These findings suggest that BagEE promotes effective wound healing and shows promise as a topical agent for skin regeneration. Further studies are necessary to investigate its anti-inflammatory and wound-healing activities in both in vivo and in vitro settings. Full article

The microwave sintering of various materials is a promising technology, which has received much attention for its demonstrated potential. Both the conventional (furnace) and microwave sintering rely on thermal activation for particle bonding, for which a high temperature environment is essential. In comparison, microwave treatment achieves the same degree of densification as furnace sintering in a time shorter by a factor of two or higher and at a temperature lower by 5% to 15%. However, this is a phenomenon not yet fully understood and is commonly referred to as a non-thermal effect. Its understanding is a subject of both physics and practical interest. The non-thermal effect has been studied under years of research in order to broaden the applicability of microwave sintering. Here, we first present an overview of experimentally demonstrated advantages of microwave sintering. To facilitate further studies, we then review the literature and put together four commonly recognized interpretations of the non-thermal effects: the ponderomotive force-driven mass transport, magnetism-created cohesive forces, polarization charge-enhanced wave electric field, and polarization charge-induced attractive force among the sintered particles, with an emphasis on recent development. Full article

Eugenol is the key bioactive compound in clove oil, which has a variety of biological functions and is extensively employed in the medicinal and food industries. Nowadays, deep eutectic solvents (DESs) have received considerable attention as green solvents that enhance extraction efficiency. The present study investigated the effects of DESs on the eugenol composition in clove essential oils (CEOs) extracted from clove buds using ultrasonic- and microwave-assisted hydrodistillation techniques. The study revealed that both DES-based microwave-assisted hydrodistillation (DES-MHD) and ultrasonic-assisted DES pretreatment followed by microwave-assisted hydrodistillation (U-DES-MHD) significantly enhanced the eugenol purity in CEOs compared to the MHD method without the use of DESs. The great CEOs with a high amount of eugenol obtained via choline chloride–oxalic acid (ChCl-OA) at a 1:2 molar ratio were used as DESs. Their oils had a eugenol content of 82.90% and 83.34%, respectively, corresponding to the extraction by DES-MHD and U-DES-MHD methods, which were raised from the oil’s extraction without DES by MHD 7.42% and 8.36%, respectively. Corresponding to a strong antioxidant agent of eugenol, the oils extracted by ChCl-OA-based MHD and ultrasonic-assisted ChCl-OA-based MHD methods had significantly stronger DPPH radical scavenging activity with an IC₅₀ level of 2.16 ± 0.11 and 2.19 ± 0.05 μg/mL, respectively, than the oils extracted without DESs. Hence, these innovative processes offer a promising approach to improving the bioactivity of clove oils, while providing straightforward operation and environmentally friendly extraction methods. Additionally, these novel processes may find application in other edible essential oil extractions for the food and pharmaceutical industries. Full article