Search Results (31)

Optically triggering the core coalescence of double-emulsion droplets remains challenging. Herein, we utilize a photovoltaic field generated by laser illumination on LiNbO₃ crystals to trigger the core coalescence in a high-throughput manner. The synergy between the interfacial pressure of the shell droplet and the internal flow induced by the photovoltaic field facilitates the core coalescence. With an increase in the core number, the illumination intensity required for the core coalescence is found to increase initially, whereas it tends to saturate at 5 × 10⁷ W/m², an intensity that does not cause a large temperature increase (<4 °C). The effective mixing of the substances contained in two core droplets after their coalescence is also verified. The proposed technique provides a precise, non-thermal and electrodeless strategy for high-throughput biochemical microreactions. Full article

Currently, there is a need for dynamic space missions based on small satellites. These missions can be supported by propulsion systems with thrust-vectoring capabilities. This capability can be realized based on electrodeless plasma thrusters (EPTs). EPTs stand out for their versatility, offering adjustable thrust characteristics and fewer components, making them ideal for small satellites. However, their efficiency remains below optimal levels, largely due to complexities in plasma acceleration. This research aims to better understand dominant acceleration mechanisms in EPTs by studying ion energy distribution function changes based on exhaust orifice diameter and power variations. The total power supplied to the thruster varies in the range of 24 to 40 W, and the exhaust diameter varies in the range from 6.5 to 10.5 mm. It was found that the ion velocity does not change as a function of the diameter of the exit aperture. This indicates the insignificance of the mechanism of the gas-dynamic acceleration of plasma in EPTs with a small form factor and supports recent views that the main contribution to the acceleration of particles in EPT is made by electromagnetic effects. The findings could help refine EPT designs, enhancing their overall effectiveness and reliability for future space missions. Full article

The current study, as part of a PhD project on the design of a helicon thruster, aims to provide a rational methodology for the design of the helicon thruster’s main component, i.e., the helicon antenna. A helicon thruster is an innovative electrodeless plasma thruster that works by exciting helicon waves in a magnetized plasma, and its antenna is capable of producing a uniform, low-temperature, high-density plasma. A magnetic nozzle is used to accelerate the exhaust plasma in order to generate a propulsive thrust. In this paper, we consider a simple helicon antenna, specifically the Nagoya type-III antenna. We consider a common experimental setup consisting of a quartz tube with finite length containing a uniform magnetized plasma and a Nagoya type-III antenna placed at the tube centre. Considering previous studies on helicon waves theory, we compare three different design methods, each based on simplifying different modelling assumptions, and evaluate the predictions of these models with results from full-wave 3D simulations. In particular, we concentrate on deriving a rational design method for the helicon antenna length, given the dimension of the quartz tube and the desired target plasma parameters. This work aims to provide a practical and fast method for dimensioning the antenna length, useful for initializing more accurate but computationally heavier full-wave simulations in 3D geometry or simply for a rapid prototyping of the helicon antenna. These results can be useful for the development of a helicon thruster but also for the design of a high-density radiofrequency plasma source. Full article

Microwave electrodeless ultraviolet (MWUV) technology, as an emerging food processing technique, has garnered growing attention in the realm of food science in recent years. Based on different application requirements, MWUV equipment types are categorized as microwave oven reactor, continuous-flow UV-microwave reactor, coaxially driven MWUV reactor, and complete ultraviolet reactor. The luminescence properties of MWUV equipment depend on their filler gas; mercury is commonly used as a filler gas to produce a wavelength at 253.7 nm for food non-thermal sterilization. The microbial sterilization effect of MWUV is primarily attributed to the synergistic action of microwave and ultraviolet (UV): MWUV enhances reactive oxygen species (ROS) production, disrupts the cell membrane structures of bacteria, leads to bacterial endosome leakage, and induces nucleic acid damage. MWUV extends food shelf-life by eliminating microorganisms without significantly altering food quality compared with traditional thermal sterilization methods. Additionally, MWUV, combined with digestion reagents such as HNO₃ and H₂O₂, can effectively enhance the digestion of food samples to detect essential and toxic elements. Studies on MWUV technology hold broad potential in the food industry, with promising implications for food safety and consumer demand for high-quality food. Future research may focus on optimizing the equipment parameters and integrating with other food processing technologies to facilitate further development and application of MWUV. Full article

MXenes attract considerable attention due to their unique properties, in particular, their high electrical conductivity. The physical processes occurring during the electrodeless study of the specific electrical conductivity σ of MXenes in distillation water and in a polar non-aqueous solvent of N-Methyl-2Pyrrolidone (NMP) at fixed resonant frequencies for five solenoids (f₁ = 160 kHz, f₂ = 270 kHz, f₃ = 1.6 MHz, f₄ = 4.8 MHz, and f₅ = 23 MHz) are considered. The oscillating circuit was tuned to resonance by changing the capacitance of the BM-560 Q-factor meter. The Q factor of the oscillating circuit was measured in the range of 100–300 with a maximum relative error of ±5% and in the range of 30–100 with a maximum relative error of ±3%. The cylinder with the liquid was placed in the middle of the measuring solenoid, in the area of a homogeneous magnetic field. The measurements were performed for four control volumes of the liquids under study (1 mL, 2 mL, 3 mL, and 4 mL). The best measurement sensitivity was observed for the maximum volume of the liquid (4 mL). A difference between the experimental dependences of the introduced attenuation d of the oscillating circuit with a cylinder with MXenes in aqueous and non-aqueous polar solvent NMP was observed. The nonlinear dependence of the attenuation of the oscillatory circuit d on the volume of the studied liquids was analyzed. The maximum value of the attenuation of the oscillating circuit for the solenoid at the resonant frequency of 160 kHz was observed for the NMP-MXenes measurement, in contrast to the study of MXenes in distillation water having the highest attenuation at a frequency of 1.6 MHz. Full article

Solid-state batteries offer significant advantages but present several challenges. Given the complexity of these systems, it is good practice to begin the study with simpler models and progressively advance to more complex configurations, all while maintaining an understanding of the physical principles governing solid-state battery operation. The results presented in this work pertain to cells without traditional electrodes, thus providing a foundation for guiding the development of fully functional solid-state cells. The open circuit voltage (OCV) of the Cu/Na_2.99Ba_0.005ClO composite in a cellulose/Zn pouch cell achieves 1.10 V, reflecting the difference in the chemical potentials of the current collectors (CCs), Zn and Cu, serving as electrodes. After 120 days, while set to discharge, conversely to what was expected, a higher potential difference of 1.13 V was attained (capacity of 5.9 mAh·g⁻¹_electrolyte). By incorporating a layer of carbon felt, the OCV became 0.85 V; however, after 95 days, the potential difference increased to 1.20 V. Ab initio simulations were additionally performed on a Cu/Na₃ClO/Zn heterojunction showing the formation of dipoles and the Na deposition on Zn which is demonstrated experimentally. The sodium plating on the negative CC (Zn) takes place as the cell is set to discharge at room temperature but is not observed at 40 °C. Full article

Electrodeless Low-Frequency (LF)/Radio-Frequency (RF) plasma sources often suffer from low power coupling efficiencies due to the lack of overlapping field with the dynamic plasma load. However, the power supplies for these plasma sources typically have very high power efficiencies (>90%) and are more cost-effective compared to microwave sources. If the coupling efficiency to the plasma can be increased, these plasma sources offer a competitive technology for the sustainable electrification of the chemical industry. This work experimentally investigates five power coupling methods, applied to toroidal CO₂ plasmas in a quartz vessel. The research was based on similar ferrite coupling as used in energy-efficient plasma lamps. The higher resistance of the CO₂ plasma decreased the power coupling from 90% (for mercury-vapor plasma) to 66% at 1 mbar. High coupling efficiencies in LF/RF powered discharges can be achieved in two manners: either the inductance of the transformer cores can be increased, or the electromagnetic wave frequency can be increased. Furthermore, additional ferrite cores in parallel with the primary coils can be used to increase the impedance transformation. An experiment with six ferrite cores with a single primary winding in parallel, at a frequency of about 10 MHz and a power of 1 kW, showed that this frequency has a detrimental effect on the magnetic permeability and the losses in the ferrite result in a decrease of coupling to 33% at 1.5 mbar. At a frequency of 66 kHz with a nanocrystalline soft magnetic material core, a coupling of 89% was achieved in 1.5 mbar plasma for a power of 3.1 kW. This configuration exhibits decreasing coupling efficiencies at higher pressures since the plasma impedance increases, which again limits the coupling of the transformer due to a lack of inductance. The investigation of alternative coreless coil plasma configurations resulted in coupling efficiencies up to 89% decreasing to 50% at 102 mbar for a toroidal plasma enclosed by toroidally spiraling coils. Full article

Multidirectional plasma thrusters are of particular interest for dynamic space missions due to the adjustability of their integral characteristics. One type of multidirectional plasma thrusters is -directional, consisting of a symmetric electromagnetic system surrounding the gas discharge chamber, capable of generating a propulsion minimum in two directions. The experimental results of this study of the starting modes of a multidirectional plasma thruster utilizing krypton as propellant are reported. The thruster is placed in a vacuum chamber. The magnetic field strength is adjusted in the range of 35 to 400 G in peaks. The current of 13.56 MHz frequency applied to the antenna is regulated in the range of 0 to 25 A. The diameter of the orifices is varied in the range of 3 to 10 mm. In contrast to the unidirectional electrodeless plasma thruster, the radiofrequency breakdown threshold of the multidirectional plasma thruster decreases with increasing static magnetic field due to the symmetry of the magnetic system and the gas discharge chamber. The influence of the magnetic field on the radiofrequency breakdown threshold in the multidirectional plasma thruster is shown theoretically by the classical diffusion theory and ponderomotive effects, and discussed in the electron circulation hypothesis. Full article

Polyaniline (PANI) was synthesized from liquid aniline, a nitrogen-containing aromatic compound, through the atmospheric pressure (AP) plasma process using a newly designed plasma jet array with wide spacing between plasma jets. To expand the area of the polymerized film, the newly proposed plasma jet array comprises three AP plasma jet devices spaced 7 mm apart in a triangular configuration and an electrodeless quartz tube capable of applying auxiliary gas in the center of the triangular plasma jets. The vaporized aniline monomer was synthesized into a PANI film using the proposed plasma array device. The effects of nitrogen gas addition on the morphological, chemical, and electrical properties of PANI films in AP argon plasma polymerization were examined. The iodine-doped PANI film was isolated from the atmosphere through encapsulation. The constant electrical resistance of the PANI film indicates that the conductive PANI film can achieve the desired resistance by controlling the atmospheric exposure time through encapsulation. Full article

This study investigated the influence of alkali content on the early-age hydration process of slag-based geopolymer and the feasibility of non-destructive resistivity. Results showed that there existed a threshold of alkali content in adjusting the early-age hydration. Initially, increasing the alkali content tended to accelerate the dissolution period (detected by resistivity and heat release rate) and resulted in a denser microstructure (detected by TEM). When the alkali content surpassed 6 wt%, the increasing alkali content mitigated the structural development of a slag-based geopolymer, as it lowered the liquid water content and caused local precipitation, which trapped the early-age ions transmission and, therefore, the later-age mechanical development was inhibited. It was proven that the resistivity acted as a linkage among the reaction degree, workability, and strength development. Full article

In recent years, the emergence of COVID-19 and other epidemics caused by RNA(ribonucleic acid)-type genetic viruses has aroused the close attention of governments around the world on emergency response to public safety and health emergencies. In this paper, an electrodeless biosensing detection chip for RNA virus medical detection is designed using quartz crystal microbalance technology and local surface plasmon resonance technology. The plasmonic resonance characteristic in the nanostructures of gold nanorods-quartz substrates with different parameters and the surface potential distribution of the quartz crystal microbalance sensing chip were studied by COMSOL finite element simulation software. The results show that the arrangement structure and spacing of gold nanorod dimers greatly affect the local surface plasmon resonance of nanorods, which in turn affects the detection results of biomolecules. Moreover, high concentrations of “hot spots” are distributed between both ends and the gap of the gold nanorod dimer, which reflects the strong hybridization of the multiple resonance modes of the nanoparticles. In addition, by simulating and calculating the surface potential distribution of the electrode area and non-electrode area of the biosensor chip, it was found that the biosensor chip with these two areas can enhance the piezoelectric effect of the quartz chip. Under the same simulation conditions, the biochip with a completely electrodeless structure showed a better sensing performance. The sensor chip combining QCM and LSPR can reduce the influence of the metal electrode on the quartz wafer to improve the sensitivity and accuracy of detection. Considering the significant influence of the gold nanorod dimer plasma resonance mode and the significant advantages of the electrodeless biosensor chip, an electrodeless biosensor combining these two technologies is proposed for RNA virus detection and screening, which has potential applications in biomolecular measurement and other related fields. Full article

Heart rate (HR) and respiratory rate (RR) are two vital parameters of the body medically used for diagnosing short/long-term illness. Out-of-the-body, non-skin-contact HR/RR measurement remains a challenge due to imprecise readings. “Invisible” wearables integrated into day-to-day garments have the potential to produce precise readings with a comfortable user experience. Sleep studies and patient monitoring benefit from “Invisibles” due to longer wearability without significant discomfort. This paper suggests a novel method to reduce the footprint of sleep monitoring devices. We use a single silver-coated nylon fabric band integrated into a substrate of a standard cotton/nylon garment as a resistive elastomer sensor to measure air and blood volume change across the chest. We introduce a novel event-based architecture to process data at the edge device and describe two algorithms to calculate real-time HR/RR on ARM Cortex-M3 and Cortex-M4F microcontrollers. RR estimations show a sensitivity of 99.03% and a precision of 99.03% for identifying individual respiratory peaks. The two algorithms used for HR calculation show a mean absolute error of 0.81 ± 0.97 and $0.86\pm 0.61$ beats/min compared with a gold standard ECG-based HR. The event-based algorithm converts the respiratory/pulse waveform into instantaneous events, therefore reducing the data size by 40–140 times and requiring 33% less power to process and transfer data. Furthermore, we show that events hold enough information to reconstruct the original waveform, retaining pulse and respiratory activity. We suggest fabric sensors and event-based algorithms would drastically reduce the device footprint and increase the performance for HR/RR estimations during sleep studies, providing a better user experience. Full article

Owing to their biocompatibility, optical, and catalytic properties, Au nanoparticles (NPs) have been the subject of much research. Since smaller NPs have enhanced catalytic properties and NP morphology greatly impacts their effectiveness, controlled and reproducible methods of generating Au NPs are still being sought. Herein, Au NPs were electrochemically generated at a water|ionic liquid (w|IL) immiscible micro-interface, 25 µm in diameter, using a redox active IL and compared to results at a water|oil (w|o) one. The liquid|liquid interface is advantageous as it is pristine and highly reproducible, as well as an excellent means of species and charge separation. In this system, KAuCl₄ dissolved in the aqueous phase reacts under external potential control at the water|P₈₈₈₈TB (tetraoctylphosphonium tetrakis(pentafluorophenyl)borate) with trioctyl(ferrocenylhexanoyl)phosphonium tetrakis(pentafluorophenyl)borate (FcIL), an electron donor and redox active IL. FcIL was prepared with a common anion to P₈₈₈₈TB, which greatly enhances its solubility in the bulk IL. Simple ion transfer of AuCl₄⁻ and AuCl_(4−γ)(OH)_γ⁻ at the w|P₈₈₈₈TB micro-interface were characterized voltammetrically as well as their heterogeneous electron transfer reaction with FcIL. This interfacial reaction generates Au NPs whose size can be thermodynamically controlled by modifying the pH of the aqueous phase. Critically, at low pH, nanoclusters, <1.7 nm in diameter, were generated owing to inhibited thermodynamics in combination with the supramolecular fluidic nature of the IL microenvironment that was observed surrounding the as-prepared NPs. Full article

This study was conducted to evaluate the effects of different artificial light sources on the growth characteristics and various biological activities of the Atractylodes macrocephala x Atractylodes japonica hybrid cv. ‘Dachul’, which is highly useful for medicinal purposes. The plant had the largest biomass with a plant height of 38.20 ± 1.95 cm when treated with microwave electrodeless light (MEL). The chlorophyll content of the plants treated with fluorescent light (FL) was 53.93 ± 1.05 SPAD and was the highest. The antioxidant effect, determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH), was the highest with 92.7 ± 0.2% in plants treated with light-emitting diode (LED)-green light. Total phenol and flavonoid contents were significantly higher with 19.7 ± 0.5 mg GAE/g and 40.2 ± 2.2 mg QE/g in the sample treated with LED-green light, respectively. For antimicrobial activity using the minimum inhibitory concentration (MIC) technique, the inhibitory ability against Escherichia coli was at 0.25 mg/mL under LED-green light treatment. The whitening activity using tyrosinase enzyme showed the highest tyrosinase inhibitory ability at 62.1 ± 1.2% of the above extract treated with MEL light. To confirm the immune activity in lipopolysaccharide (LPS)-induced RAW 264.7 cells, NO production of inflammation-related substances was measured. In addition, the inflammation-related genes iNOS (inducible nitric oxide synthase), COX-2 (cyclooxygenase-2), and TNF-α (tumor necrosis factor-α) in the same sample were confirmed using reverse transcriptase (RT)-PCR, and the result showed that gene expression was suppressed compared with that in the control group. It is expected that Dachul plants treated with LED-blue light will play an important role in enhancing intracellular anti-inflammatory activity. From these results, the effect for various biological activities appeared in a significantly diverse spectrum in response to different wavelengths of artificial light sources in Dachul. Full article

An atmospheric pressure microwave plasma source operating on water vapor has many potential applications. To avoid the corrosion of metal electrodes in a traditional water vapor microwave plasma system, we propose a simple water vapor electrodeless microwave plasma device. By introducing a ceramic tube, the device can work directly with liquid water without complex evaporation equipment. This study examined the relationship between microwave power and water vapor torch plasma duration. When the microwave power is greater than 800 W, the plasma torch can be excited permanently and stably without the loss of ceramic. The excitation of the oxygen atom, hydroxyl radical, and hydrogen atom was found using optical spectroscopy, confirming the water vapor’s decomposition. In addition, it was also found that the crystallinity of the ceramic was improved after microwave discharge. This work enriches the microwave plasma techniques for water vapor for various applications, such as electric propulsion, hydrogen production, and surface treatment. Full article