Needle Surface Research Articles

Complex assessment of ambient particulate matter in a small settlement with coal-handling port

Relevance. Russian coal exports have been steadily increasing in recent years, and Far Eastern ports, originally not adapted to dusty cargoes, have switched to coal operations. Unoptimized coal handling leads to increased content of coal-containing particles in the air and to various environmental problems. Aim. To analyze the concentration of particulate matter in the air and the chemical composition of particles on the surface of conifer needles in the Posyet settlement (Primorsky Krai, Russia), where a large coal terminal operates. Materials and methods. The chemical composition was studied on the surface of conifer needles by X-ray fluorescence and in washout of conifer needle samples using Raman spectroscopy and energy dispersive analysis. Concentrations of particles with the diameter of 2.5 and 10 μm (PM2.5 and PM10, respectively) were measured using automatic monitoring stations. Results and conclusions. Chemical composition was dominated by mineral particles (calcite, silicates, etc.). However, the presence of coal particles (up to 8.3%) and metal particles was also observed. Mean concentrations of PM2.5 and PM10 were within the Russian and international health standards, but close to their upper limits. Concentrations of both measured particle fractions were highest during the winter months (as well as in March, which is traditionally a cold month in the Far East), followed by a gradual decrease. The study obtained new data on the annual variations of concentrations of PM2.5 and PM10, as well as on the basic composition of particles from the surface of woody vegetation (needles) as an indicator of the state of air pollution in this settlement.

Иглоподобные листовые органы хвойных. Часть II. Моделирование площади поверхности иглы

In ecological and physiological studies of plant cover, the predominant participation of leaves in the processes of photosynthesis, transpiration and respiration determines the key role of such a morphometric parameter as leaf surface area. The estimation of the area of needle-like leaf organs of conifers often requires an individual approach. The diversity of needle shapes is determined by species affiliation, morphological structure, ecological conditions and age, and, in turn, determines the diversity of methods for estimating the needle surface area. Therefore, the search for simple standard methods for determining the surface area of leaf organs of conifers is an urgent task for plant physiologists. The aim of this work has been to create a universal model for estimating the needle surface area, independent of species. To achieve it, the needle cross-section model proposed by the authors has been used, based on the transformation of the perimeter of the cross-section into an equivalent circle, the perimeter of which is associated with the parameters of the needle cross-section before the transformation. To estimate the surface area of the needle, it is possible to approximate the needle with a geometric body, which is a combination of an ellipsoid of revolution, a cone and a cylinder, with the radius of the cylinder being estimated using the needle cross-section model. The model allows to estimate the surface area of the needle by its 4 morphometric parameters: thickness, width, length of the middle part and total length. Full verification of the model proposed in the article has turned out to be impossible due to the lack of methods for accurate estimation of the needle surface area. The developed method has been compared to other methods for estimating the surface area of needle-like samples by the examples of the needles of Siberian fir (Abies sibirica L.) and common juniper (Juniperus communis L.), as well as banana fruits (Musa paradisiaca L.), and the good predictive ability of the model has been demonstrated. It can be characterized as universal with a theoretical relative error of no more than 5 %.

Solution Synthesis and Diffusion-Mediated Formation Pathway of NbTe4 Particles.

NbTe4 is an important material because of its fundamental low-temperature electronic behavior and its potential interest for thermoelectric, catalytic, and phase-change applications, especially as nano- and microscale particles. As a tellurium-rich group V transition metal telluride, bulk NbTe4 is typically synthesized through high-temperature solid-state or metal flux reactions and NbTe4 films can be made by sputtering and annealing, but NbTe4 is generally not amenable to the lower-temperature solution-based syntheses that yield small particles. Here, we demonstrate a solvothermal route to NbTe4 particles that is based on mainstream colloidal nanoparticle synthesis. We find that the reaction proceeds in situ through a multistep pathway that begins by first forming elemental tellurium needles. NbTe4 then deposits on the surface of the tellurium needles through a diffusion-based process. Time-point studies throughout the reaction reveal that crystallographic relationships between Te and NbTe4 define how the diffusion-based reaction proceeds and help to rationalize the morphology of the resulting NbTe4 particles. As synthesized, NbTe4 particles exhibit a surface consisting of predominantly Nb-Te and reduced NbOx species, but after storage, surface oxidation transforms these species to primarily Nb2O5 and TeO2, while the NbTe4 remains unchanged. These synthetic capabilities and reaction pathway insights for NbTe4, made using a solvothermal method, will help to advance future studies on the properties and applications of this and related tellurides.

Machine learning-assisted label-free colorectal cancer diagnosis using plasmonic needle-endoscopy system

Early and accurate detection of colorectal cancer (CRC) is critical for improving patient outcomes. Existing diagnostic techniques are often invasive and carry risks of complications. Herein, we introduce a plasmonic gold nanopolyhedron (AuNH)-coated needle-based surface-enhanced Raman scattering (SERS) sensor, integrated with endoscopy, for direct mucus sampling and label-free detection of CRC. The thin and flexible stainless-steel needle is coated with polymerized dopamine, which serves as an adhesive layer and simultaneously initiates the nucleation of gold nanoparticle (AuNP) seeds on the needle surface. The AuNP seeds are further grown through a surface-directed reduction using Au ions-hydroxylamine hydrochloride solution, resulting in the formation of dense AuNHs. The formation mechanism of AuNHs and the layered structure of the plasmonic needle-based SERS (PNS) sensor are thoroughly analyzed. Furthermore, a strong field enhancement of the PNS sensor is observed, amplified around the edges of the polyhedral shapes and at nanogap sites between AuNHs. The feasibility of the PNS sensor combined with endoscopy system is further investigated using mouse models for direct colonic mucus sampling and verifying noninvasive label-free classification of CRC from normal controls. A logistic regression-based machine learning method is employed and successfully differentiates CRC and normal mice, achieving 100% sensitivity, 93.33% specificity, and 96.67% accuracy. Moreover, Raman profiling of metabolites and their correlations with Raman signals of mucus samples are analyzed using the Pearson correlation coefficient, offering insights for identifying potential cancer biomarkers. The developed PNS-assisted endoscopy technology is expected to advance the early screening and diagnosis approach of CRC in the future.

Designing Microneedle Patch for Prophylaxis of Postoperative Atrial Fibrillation.

Postoperative atrial fibrillation (POAF) is a common complication following cardiac surgery, which often occurs within 30 postoperative days, especially peaking at 2-3 days. Antiarrhythmic medications such as amiodarone are recommended in clinical practice for the prophylaxis and treatment of POAF. However, conventional oral administration is hindered due to delayed drug action and high risks of systemic toxicity, and emerging localized delivery strategies suffer from a limited release duration (less than 30 days). Herein, we develop a microneedle (MN) patch for localized delivery of amiodarone to the atria in a "First Rapid and Then Sustained" dual-release mode. Specifically, this patch is composed of a needle array integrated with an amiodarone-loaded reservoir for a sustained and steady release for over 30 days; and an amiodarone-containing coating film deposited on the needle surface via the Langmuir-Blodgett technique for a rapid release at the first day. Upon this design, only one MN patch enables a higher drug accumulation in the atrial tissue at the first day than oral administration and simultaneously remains therapeutical levels for over 30 days, despite at a significantly reduced drug dosage (5.08 mg in total versus ∼10 mg per day), thereby achieving ideal preventive effects and safety in a rat model. Our findings indicate that this MN device provides a robust and efficient delivery platform for long-term prophylaxis of POAF.

Hierarchical NiCo2O4 needle-like heterostructure arrays anchored on WO3 as high- performance asymmetric supercapacitors for energy storage applications

The current work employs a novel approach to construct a composite nanostructure to improve the capacitive performance of a supercapacitor device. The work involved preparing cube-shaped WO3 particles and depositing them onto the surface of NiCo2O4 needles using a microwave technique. The structure of the composites enables efficient paths for ion transport and electron diffusion in supercapacitors. The hybrid composite electrode demonstrates a specific capacitance of 716 F g−1 at a current density of 5 Ag−1. The asymmetric capacitor device, which utilizes NiCo2O4@WO3 as the positive electrode and AC as the negative electrode, exhibits an energy density of 48.57 Wh kg−1 at a power density of 1120 W kg−1. In addition, the NiCo2O4@WO3//AC device has a favourable cycle life, maintaining 85.7 % of its capacitance retention after 10,000 cycles. The findings demonstrate the potential of NiCo2O4@WO3//AC to be used in the development of advanced hybrid electrodes for improved supercapacitors.

Unraveling cEMG-wet sEMG Correlation Dynamics: Investigating Influential Factors

The electromyography (EMG) signal provides insight into neuromuscular activity which is used in medical and technological fields. Traditional needle electrodes and surface electrodes have several drawbacks making them less suitable for portable and long-term use. In contrast, emerging capacitive electrodes offer promising features over the existing electrodes. Yet, the full potential of capacitive electrodes remains untapped due to the lack of comprehensive design optimization for consistently reliable signal quality. This study highlights the complex interplay of factors influencing correlation in capacitive EMG (cEMG) and wet surface EMG (wet sEMG) signals. The study emphasizes the importance of the surface area of capacitive electrodes, muscle force, preprocessing, and sampling frequency in understanding and improving the correlation between cEMG and wet sEMG signals, providing valuable insights for future research and applications in the field. The study reveals that the electrode area has no significant effect on the correlation. However, the correlation significantly depends on the muscle force. In addition, removing artifacts from the cEMG signal increases the correlation, especially for lower force where artifacts are significant. Again, oversampling the EMG signal above 800 Hz does not have any impact on increasing the correlation but the correlation decreases with higher inter-electrode distance (IED). In this research, the highest correlation of 82.89% (normalized-91.62%) between cEMG and sEMG has been achieved for high muscle force with a plate area of 4 cm2. Therefore, the capacitive electrode can be an alternative for EMG signal acquisition.

Иглоподобные листовые органы хвойных. Часть I. Моделирование периметра поперечного сечения иглы

Despite the availability of measuring systems for estimating the surface area of leaf organs of higher plants, the need for simple standard methods for determining this indicator area remains relevant for plant physiologists. The methods for estimating the surface area of needle-like leaf organs of conifers, based on the geometry of an individual needle rest on the general principle of calculating the needle surface area as the product of its length by the perimeter of its cross-section. This makes the cross-section perimeter one of the most important parameters needed to characterize the needle surface area. The strong variability of this parameter depending on the species necessitates the development of individual models of the cross-section of individual needles. The aim of this study has been to create a universal model for estimating the needle cross-section perimeter, irrespective of the tree species. For the practical implementation of the aim, a method was proposed for estimating the perimeter of the needle cross-section, based on the well-known fact that any closed line is transformable into an equivalent circle, while the length of the closed line does not change. The perimeter of the equivalent circle can be related to the parameters of the geometric figure before the transformation. This approach allows us to relate the width and thickness of the needle cross-section to its perimeter. The developed universal model of the needle cross-section has been verified on cross-sections of Siberian fir (Abies sibirica L.) and common juniper (Juniperus communis L.) needles. The samples of needles of these woody plants have been collected from a bilberry-sphagnum spruce forest in the boreal zone of the north-east of the European part of Russia (Knyazhpogostkiy district, the Komi Republic). Statistical analysis has shown the significance and adequacy of the model. It can be used to assess the perimeter of coniferous needles, irrespective of their species. In this case, the accuracy of perimeter estimation is comparable to the accuracy of direct perimeter measurement by the piecewise linear approximation method.

Evaluation of Forces on the Needle for Regulation of Pelton Turbine Injector

Abstract In hydropower plants, the Pelton turbine is a commonly used hydraulic turbine where flow is regulated with a dual mechanism of needle and deflector. The needle is controlled by a servomotor and governor system, where the flow rate varies by adjusting the needle strokes. The needle is operated under the hydraulic force caused by the high-water pressure inside the injector acting on the needle surface. The objective of computing the force balance in a Pelton injector is to determine the force to be supplied by the servomotor. The closing trend is crucial to design the injector for safe operation during an emergency. In this study, the function of the needle and nozzle curve generalizes the variable needle surface area, allowing the geometric properties of the nozzle and needle to be suitable for the needle force evaluation. The single-axis force transducer, which is mounted on the needle rod, has been used in the experimental method for determining the needle forces. The experimental findings are compared to analytical calculations and serve as validation for the accuracy and reliability of the computed results obtained through the analytical approach.

The Effects of Passage Through Vaccine Vial Septa on Needle Sharpness

Veterinarians anecdotally report changing needles before injection after drawing up a vaccine due to concerns for needle dulling. However, there is little information on the impact on needles during passage through vial septa, and the CDC does not recommend this practice. Sharps are considered medical waste and their disposal incurs regulatory burden while recapping a needle to remove it represents a hazard to veterinary personnel. Due to the large volume of vaccines administered in shelters, the cost to dispose and repurchase needles can be high. The aim of this study was to determine whether needles commonly used by veterinarians dull after passage through vial septa. A survey to determine the most common brands and gauges of needles, as well as needle-changing practices, was promoted to veterinarians and staff via social media from 5/5-5/12/23 (IRBAZ-5222). A Wagner FDIX ForceOne force gauge was used to measure peak force required to penetrate 0.020” thick Abrasion-Resistance Polyurethane Rubber (ISO 7864) for new needles, needles passed through 1 vial septum, and needles passed through 2 via septa (0, 1, 2) across 3 different brands (a, b, c) and 4 sizes (20, 22, 25 G) of single-use veterinary hypodermic needles. Needle tip and surfaces were visualized via 3D infinite focus microscopy (Bruker Alicona InfiniteFocusSL) with a 5XAX objective and subsequent deviation maps were created in Zeiss Inspect Professional (formerly GOM) to facilitate defect identification. Multivariable linear regression was used to determine the association between peak force and number of passages through a vaccine vial septum while controlling for needle brand, gauge, and vaccine vial penetration force (VVPF) and logistic regression to determine associations between gross defects and brand, gauge, and VVPF. Of the 482 survey respondents, 76% reported changing needles used to draw up a vaccine, primarily due to concerns about needle dulling. The peak force through a standard material was measured for 330 needles. The mean VVPF through the first septum was 2.1±0.7 N (range 0.4-5.0). New 20 G needles of brand a (referent) required 1.05 N to penetrate the standard material. One pass through a septum at the lowest recorded VVPF required an additional 0.09 N, an increase of 9% from baseline P < 0.0001, while 2 passes, both at the lowest recorded VVPF, required additional 0.21 (19%) N of force (P <0.0001). Compared to brand a, brand b and c required an additional 0.12 (11%) and 0.10 (10%) N, respectively, both P <0.0001. Smaller needles required less force, with 22, 25, and 29 G needles requiring -0.06 (-6%), -0.23 (-22%), and -0.47 (-45%) N, respectively (all P <0.003). VVPF increased the peak force by 0.03 N for each additional 0.5 N (P=0.003) during the first septum penetration, but was not significant for a second penetration (P=0.337). Fifty-two needles were scanned with the InfiniteFocus SL microscope after one and two passages through a vial septum. Twenty-one of 52 needles had visual defects after 1 passage and 27 had visual defects after 2 passages, which was not different (P = 0.241). Only VVPF was significant for predicting visual defects (OR 4.6; P = 0.001). Passage once or twice through vial septa resulted in less than a 20% change in force required to penetrate standard material. The impact of other factors, including brand, needle size, and force used to penetrate the vial, all had a greater impact on force than passage through a single vial septum. The clinical significance of these peak force differences is unknown.

Distribution of 35 Polycyclic Aromatic Hydrocarbons in Pine Needle Samples from Selected Locations in the Republic of Korea.

Polycyclic aromatic hydrocarbons (PAHs), dust, and wax were measured in pine needles, and PAHs were also measured in surface soil. Pearson correlation analysis was performed between the analytical values. The main compounds responsible for the increase in total PAHs were non-carcinogenic phenanthrene and fluoranthene. Therefore, the % content of carcinogenic PAHs decreased with a slope = -0.037 (r = 0.47, p < 0.01), as the total PAH concentration in pine needles increased. Correlations between individual PAHs in pine needles and surface soil were very high when only low-number ring PAHs (2R- and 3R-PAHs) were statistically analyzed and significant when only high-number ring PAHs were statistically analyzed. Low-number ring PAH mainly moves in the gas phase and diffuses into the wax layer, so it was found to be statistically significant with the wax content of pine needles. High-number ring PAHs showed a high correlation with the amount of dust in pine needles because they mainly attached to dust particles and accumulated on the surface of pine needles. The ratios of fluoranthene/pyrene and methylphenanthrene/phenanthrene for predicting the origin of atmospheric PAHs have also been proven valid for pine needles.

Analysis of Sediment Erosion in Pelton Nozzles and Needles Affected by Particle Size

The sediment erosion of Pelton turbine components is a major challenge in the operation and development of high-head water resources, especially in mountainous areas with high sediment yield. In this paper, a study using numerical simulation was conducted with different sediment particle sizes in the fine sand range. And the erosion mechanism of the Pelton turbine injector was analyzed. The Eulerian Lagrange method was adopted to simulate the gas–liquid–solid flow. The Mansouri’s model was applied to estimate the injector erosion. The predicted erosion results were in accord with field erosion photographs. In particular, the asymmetrical erosion distribution on the needle surface was physically reproduced. With the sediment particle size increasing from 0.05 mm, the needle erosion rate decreased, while the nozzle casing erosion rate increased dramatically. In order to clarify this tendency, the characteristics of the three-phase flow were analyzed. Interestingly, the results show that with the rise in particle size, the separation of particles and water streamlines became more serious in the contraction section of the nozzle mouth. Consequently, it caused the enhancement of erosion of the nozzle surfaces and weakened the erosion of the needle surfaces. Significant engineering insights may be provided for weakening Pelton injector erosion with needle guides in the current study.

Research on the influence of needle roughness of Pelton turbine on flow characteristics

The needle in the jetting mechanism of Pelton turbine may be uneven on the surface of the needle due to the knife marks in the cutting process or the erosion of the sediment in the water flow, resulting in the surface roughness of the needle, which affects the flow at the wall. In order to study the influence of the surface roughness of the needle on the jet flow characteristics, the jet flow characteristics and sediment characteristics of the jetting mechanism under different roughnesses were analyzed in this paper. The results show that the flow characteristics of the smooth wall and the rough wall are obviously contrasted. With the increase of the needle roughness, the jet velocity of the jetting mechanism gradually decreases, the turbulent kinetic energy of the needle surface gradually increases, the shear stress on the needle surface gradually increases, the wear amount gradually increases, the wear area increases, and the efficiency of the jet mechanism with a 1mm roughness wall decreases by about 22.3% compared with the smooth wall.

Needle bacterial community structure across the species range of limber pine.

Bacteria on and inside leaves can influence forest tree health and resilience. The distribution and limits of a tree species' range can be influenced by various factors, with biological interactions among the most significant. We investigated the processes shaping the bacterial needle community across the species distribution of limber pine, a widespread Western conifer inhabiting a range of extreme habitats. We tested four hypotheses: (i) Needle community structure varies across sites, with site-specific factors more important to microbial assembly than host species selection; (ii) dispersal limitation structures foliar communities across the range of limber pine; (iii) the relative significance of dispersal and selection differs across sites in the tree species range; and (iv) needle age structures bacterial communities. We characterized needle communities from the needle surface and tissue of limber pine and co-occurring conifers across 16 sites in the limber pine distribution. Our findings confirmed that site characteristics shape the assembly of bacterial communities across the host species range and showed that these patterns are not driven by dispersal limitation. Furthermore, the strength of selection by the host varied by site, possibly due to differences in available microbes. Our study, by focusing on trees in their natural setting, reveals real needle bacterial dynamics in forests, which is key to understanding the balance between stochastic and deterministic processes in shaping forest tree-microbe interactions. Such understanding will be necessary to predict or manipulate these interactions to support forest ecosystem productivity or assist plant migration and adaptation in the face of global change.

An ultrasensitive electrochemical sensor for detecting Cd(II) in aquatic products based on CS/COFs/PEDOT: PSS modified acupuncture needle electrode

The use of low-cost working electrodes is of great importance for the development of sensor industrialization. Acupuncture needles electrode (ANE) was selected as working microelectrode, a sensor was designed based on poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT: PSS) and chitosan (CS) modified covalent organic frameworks (COFs) (CS/COFs) for detection of cadmium (Cd(II)). First, a mixture of PEDOT and PSS was electrodeposited on the surface of the acupuncture needles to synthesize a PEDOT: PSS as conductive polymeric film to support the electron transfer capability and enhance the conductive efficiency of the sensor. Then, CS/COFs was self-assembled and attached to the PEDOT: PSS/ANE surface by π-π stacking intermolecular interaction forces and the viscosity of CS, thus increasing the specific surface area of the electrode. Differential pulse anodic stripping voltammetry (DPASV) was used as the electrochemical method for detection of Cd(II). And the results indicated that the CS/COFs/PEDOT: PSS/ANE was linearly responsive in the range of 400 μg/L to 2400 μg/L, and the LOD was 13.8 ng/L for Cd(II). The constructed sensor also showed great selectivity, reproducibility, and stability. Additionally, the sensor demonstrated outstanding recovery in the detection of Cd(II) in real sample scallops. This sensing construction method based on acupuncture needles as working electrodes is of great significance to the development of sensor industrialization and aquatic product safety detection.

Study of Tissue Damage Induced by Insertion of Composite-Coated Needle

Medical interventions have significantly progressed in developing minimally invasive techniques like percutaneous procedures. These procedures include biopsy and internal radiation therapy, where a needle or needle-like medical device is inserted through the skin to access a target inside the body. Ensuring accurate needle insertion and minimizing tissue-damage or cracks are critical in these procedures. This research aims to examine the coated needle effect on the force required to insert the needle (i.e., insertion force) and on tissue-damage during needle insertion into the bovine kidney. Reducing the needle insertion force, which is influenced by needle surface friction, generally results in a reduction in tissue-damage. Surgical needles were coated with a composite material, combining Polytetrafluoroethylene, Polydopamine, and Activated Carbon. Force measurement during needle insertion and a histological study to determine tissue-damage were conducted to evaluate the effectiveness of the coating. The insertion force was reduced by 49 % in the case of the coated needles. Furthermore, a histological analysis comparing tissue-damage resulting from coated and uncoated needles revealed an average 39 % reduction in tissue-damage with the use of coated needles. The results of this study demonstrate the potential of coated needles to enhance needle insertion and safety during percutaneous procedures.

Synthesis and performance of tetragonal BaTiO3 fine powders via a facile tartaric acid assisted method

A facile tartaric acid assisted method using metatitanic acid, barium hydroxide and tartaric acid as starting materials is proposed to prepare tetragonal BaTiO3 fine powders. Owing to the ultrafine character of the as-formed BaCO3 with high chemical activity, and its arrangement coating the surface of intermediate TiO2 nanoscale needles, pure cubic phase BaTiO3 homogeneous powders with size of about 50 nm was obtained via calcining treatment at 650℃, which subsequently transformed as tetragonal BaTiO3 uniform powders with size of about 240 nm and high tetragonality (c/a=1.0095) after calcining treatment at 1050℃. The BaTiO3 ceramic prepared from the BaTiO3 uniform powders displayed much improvement performances with high permittivity of about 5980 and low dielectric loss of about 0.014 at room temperature in comparison to the BaTiO3 ceramic prepared respectively from the BaTiO3 synthesized via a traditional solid-state method, and commercial BaTiO3, suggesting it’s compatible in application of MLCCs with high performance.

Performance Improvement of an STS304-Based Dispensing Needle via Electrochemical Etching.

In this study, we explored the formation of micro-/nanosized porous structures on the surface of a needle composed of STS304 and examined the effect of conventional needles and needles capable of liquid ejection. Aqua regia, composed of HCl and HNO3, was electrochemically etched to form appropriately sized micro-/nanoporous structures. We observed that when dispensing liquids with low surface tension, they do not immediately fall downward but instead spread over the exterior surface of the needle before falling. We found that the extent of spreading on the surface is influenced by an etched porous structure. Furthermore, to analyze the effect of surface tension differences, we dispensed liquids with varying surface tensions using etched needles. Through the analysis, it was confirmed that, despite the low surface tension, the ejected droplet volume and speed could be stably maintained on the etched needle. This indicates that the spreading phenomenon of the liquid on the needle surface just before ejection can be controlled by the micro/nanoporous structure. We anticipate that these characteristics of etched needles could be utilized in industries where precision dispensing of low-surface-tension liquids is essential.

Numerical investigation of highly viscous droplet generation based on level set method

Piezo-driven needle valves are widely used in electronic packaging due to their fast response, high resolution and good dispensing consistency. However, the stable generation of high-viscosity droplets is one of the key issues to its packaging quality. To investigate the formation mechanism of the high-viscosity droplet. In this paper, a 2D finite element model of the drop-on-demand injection process of the high-viscosity droplet is established based on the level set method, the droplet formation and separation processes are numerically simulated, and the reliability of the simulation results is checked by comparing the outcomes with published data. Specifically, the detailed evolution of the high-viscosity droplet formation and separation process is gained by coupling the two-phase flow-level set method and the dynamic grid technique, and the pressure distribution in the injection chamber is further discussed and the effects of operating parameters on the droplet formation volume are examined. The results of the study show that the needle motion is the main factor of pressure fluctuations in the injection chamber. Moreover, we also found that among the parameters of needle stroke, nozzle diameter, supply pressure, fluid viscosity, and surface tension, the nozzle diameter has the most significant effect on droplet volume, while surface tension has the least effect on droplet formation.

Practical Electrochemical Method to Enhance Needle Visibility during Ultrasound Imaging.

Ultrasound-guided needle interventions play a pivotal role in the diagnosis and treatment processes in clinical practice. However, existing echogenic needles face challenges in achieving a balance between effectiveness, ease of manufacturing, and inexpensiveness. In this study, we developed an echogenic needle that encompassed the aforementioned advantages through the use of the electrolysis technology. The overall contour of the needle after electrolysis was observed using bright-field microscopy, while scanning electron microscopy (SEM) was employed to examine the micro-variations on the needle's surface. Subsequently, we validated the enhanced visualization effects in vitro (pork) and in vivo (anesthetized rabbit's thigh) puncture phantoms. To ensure the safety of the needles after the puncture procedure, we conducted Vickers hardness tests, SEM detection, bright-field microscopy, and DAPI staining. The results demonstrated that the surface roughness of the needle increased with the duration of electrolysis. Taking into account the comprehensive safety tests, the needle, subjected to 40 s of electrolysis, demonstrated a safe and effective enhancement of ultrasound visualization.