Water Drop Research Articles

First report of Colletotrichum siamense causing anthracnose in Oenocarpus bacaba in Brazil.

Bacaba (Oenocarpus bacaba Mart.) is a native palm tree from Brazilian Amazon and Cerrado biomes. This tree produces a small, rounded fruit with dark skin and approximately 1.5 mm thick pulp, extensively utilized for palm heart extraction, juices, and jellies (De Cól et al. 2021). However, several diseases can adversely impact fruit yield and quality. During the 2021 growing season, anthracnose symptoms were observed in Bacaba fruits, with a disease incidence of 58% in fruits collected from the Abreulândia (9°37'15″ S, 49°9'3″ W) and Gurupi (12°25'46" S; 49°16'42" W) municipalities in Tocantins state, Brazil. A total of 198 fruits exhibiting anthracnose symptoms, characterized by deep necrotic spots, were collected. In the laboratory, symptomatic fruits had their external surfaces sterilized for 30 seconds in 70% ethanol, 1 min in 1.5% NaOCl, and then rinsed with sterile distilled water. Sterilized pieces of the fruit tissue were transferred to PDA medium and incubated for 7 days at 28 ºC with a 12 h photoperiod. After this period, two isolates were obtained from the colonies and were identified both macroscopically and microscopically as Colletotrichum sp. The colonies grown at PDA showed a white to grey cottony mycelia, with straight and fusiform conidia, ranging from 14.0 to 21.0 (mean value of 15.8 ± 1.8) µm in length and 4.0 to 7.0 (mean value of 5.5 ± 0.7) µm in width, (n = 50). For species identification, the intergenic spacer between DNA lyase, mating-type locus MAT1-2-1 (APN2/MAT-IGS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), glutamine synthetase (GS), and β-tubulin (TUB) loci were amplified and sequenced. Resulting sequences were deposited in GenBank (OR333843, OR333844, OR333845 and OR333846). BLAST analysis of the partial APN2/MAT-IGS (99%), GAPDH (99,48%), GS (99,32%) and TUB (99,48%) sequences showed highly similarity to C. siamense isolates (IIFT223 and CBS130147). Maximum likelihood multilocus analysis placed the isolate UFTC16 within the C. siamense clade with 98% bootstrap support, clearly assigning the isolate to this species. Morphological features were consistent with the description of C. siamense (Prihastuti et al., 2009). Inoculation of Bacaba fruits and seedlings was conducted to confirm pathogenicity. The surface of uninjured Bacaba fruits was inoculated with two drops (20 μL) of conidial suspension (106 conidia mL-1). The same methodology was adopted to placed healthy leaves of 35-day-old seedlings grown in plastic tubes. Two drops of sterile distilled water were inoculated on nonwounded healthy fruits and seedlings as a negative control. The fruits and seedlings were incubated for five days in a controlled chamber at 28 °C, 70-80% humidity and a "12-h photoperiod". The experiment was conducted with five replicates (five fruits and five seedlings inoculated per isolate) and repeated once. Typical symptoms of anthracnose were observed in the fruits and leaves of Bacaba seedlings five days after inoculation. No symptoms were observed in the negative control. The pathogen was reisolated from symptomatic fruits and leaves, showing similar morphological characteristics as the original isolate, fulfilling Koch's postulates. The identification of C. siamense as the causal agent of Bacaba anthracnose helps in the diagnosis and disease control strategies of the disease. Colletotrichum siamense is a cosmopolitan species and easily found in cultivated and non-cultivated species (Batista et al. 2023). However, to the best of our knowledge, this is the first report of C. siamense causing anthracnose on Bacaba.

Wettability patterning of titanium surfaces through pulsed laser melting for enhanced condensation heat transfer

Wettability engineering of different surfaces has been in the spotlight for the last few decades for enhanced condensation heat transfer in various applications. In this study, we experimentally investigated the water vapor condensation on a wettability-tailored Titanium-based (Ti-6Al-4V) grade 5 alloy. We utilize the microsecond laser to texture the surface by melting at various scanning speeds to realize a wide range of scalable surface structures. We further render these surfaces hydrophobic through chemical vapor deposition of silane at atmospheric pressure. Further water vapor condensation experiments are performed on these surfaces. The results show that the increased surface roughness due to laser-based melting altered the surface wettability of the Ti-surface and made it hydrophilic, exhibiting water drop contact angles ranging between 18° and 56° for the scan speeds between 25mm/s and 50 mm/s, respectively. The vapor deposition of silane on laser-melted Ti-surfaces lowered its surface energy and made them hydrophobic, showing contact angles of water drop up to ~106° specifically at lower scan speeds (~ 25 mm/s). Finally, the vapor condensation experiments showed an enhanced amount of condensed water collection with dropwise mode compared to the bare Ti surface due to a change in the wetting nature altered by laser melting.

Numerical contact line behavior prediction for drop-wall impact using Basilisk

Drop-wall impact and spray cooling have a wide technical application. There are still fundamental problems associated with wettability and its effect on the drop spreading. Experiments and direct numerical simulations are performed in a wide range of initial drop velocities (0.2–3.6 m/s). The 3D simulation is implemented by solving the incompressible Navier-Stokes equations along with the volume-of-fluid method in the Basilisk software. An adaptive mesh refinement near the interfacial surface provides a cell size of 5 µ m. The effect of the contact angle calculated using the Hoffman function on the minimum drop height and its maximum spreading is explored. The contact angle affects the dynamics of the contact line. Moreover, the mesh cell size and the initial velocity of a water drop before impact define the development of the drop rim instability when compared with experimental results. Experimental and numerical findings are compared to estimate quantitatively numerical model capabilities.

Sporulation and Dispersal of the Biological Control Agent Aspergillus flavus AF36 Under Field Conditions.

Aflatoxins are carcinogens produced by the fungi Aspergillus flavus and A. parasiticus that contaminate pistachio crops. International markets reject pistachio when aflatoxins exceed permitted maximum levels. Releasing the atoxigenic strain AF36 of A. flavus is the leading aflatoxin pre-harvest control method. The product AF36 Prevail, sorghum grains coated with AF36 propagules, has been used in California since 2017. However, a high percentage of grains of the Prevail fail to sporulate in orchards. Here, the effect of soil moisture on the percentage of AF36 product grains sporulating (SG) and the quantity of spores per grain using a sporulation index (SI) was determined. Under controlled conditions, SG was higher than 85% when soil moisture was 13% or more, and SI increased with increasing soil moisture from 8.4 to 21%. The highest AF36 sporulation occurred near the micro-sprinklers when the grains were not impacted by the irrigation water drops. Arthropod predation was responsible for lost product grains, which was more pronounced in non-tilled soil than in tilled soil. Dispersal of the AF36 spores decreased markedly with the height and distance from the inoculum source, following a pattern of diffusion equations. However, AF36 spores easily reached canopies of pistachios located 10 m from the inoculum source. Our results indicate that AF36 Prevail should be applied close to the irrigation line in the moist soil area but avoiding the areas where excess irrigation causes water accumulation. The biocontrol of aflatoxins in California's pistachio production areas was optimized by improving the field realization of the biological control agent.

Plastocapillarity: Partial and full Newtonian drop embedding into immiscible yield stress substrates

HypothesisRecent advances have been made in elastocapillarity; reversible 3D deformations of solid substrates with low elastic moduli from the surface tension of deposited drops. This study explores permanent deformations caused by liquid drops on immiscible yield stress substrates. We hypothesize that the substrate's rheological properties play a major role in determining the shape and stability of the drop-substrate interface, and govern partial or full embedding into the substrate. ExperimentsSubstrate yield stress magnitudes are modified through altering the mixture ratios of petroleum jelly to paraffin oil. Water drops are deposited on substrates and deformation profiles of the deformed interface are quantified. FindingsAbove a critical Bingham-Capillary number, which characterizes the ratio of yield stress magnitude to surface tension, deposited water drops deform the substrate surface permanently, but minimally. Below this value, drops become increasingly embedded as the substrate yield stress magnitude decreases, with larger indentation depths and increased circumferential ridge heights. With sufficiently low yield stress magnitudes, where surface tension forces dominate over yield stress forces, the plastically deformed ridges fully encapsulate the liquid drop surface, resulting in full drop embedding within the substrate. These results advance knowledge of interfacial wetting on soft yield stress substrates and has implications for binary fluids, functional materials, and new drug delivery systems.

Periodate oxidation of nanofibrillated cellulose films for active packaging applications

An alternative packaging material based on cellulose that possesses excellent barrier properties and is potentially useful for active packaging has been developed. Cellulose nanofibril was efficiently and selectively oxidized with sodium periodate generating reactive aldehyde groups. These groups formed hemiacetal and hemialdal bonds during film formation and, consequently, highly transparent, elastic and strong films were created even under moisture saturation conditions. The periodate oxidation treatment additionally decreased the polarity of the films and considerably enhanced their water barrier properties. Thus, the water contact angle of films treated for 3 and 6 h was 97° and 102°, their water drop test value was higher than in untreated film (viz., 138 and 141 min with 3 and 6 h of treatment) and their water vapour transmission rate was substantially better (3.31 and 0.78 g m−2 day−1 with 3 and 6 h, respectively). The presence of aldehyde groups facilitated immobilization of the enzyme laccase, which efficiently captures oxygen and prevents food decay as a result. Laccase-containing films oxidized 80 % of Methylene Blue colorant and retained their enzymatic activity after storage for 1 month and 12 reuse cycles, opening the door to the possible creation of a reusable packaging to replace the single-use packaging.

Different Methods to Modify the Hydrophilicity of Titanium Implants with Biomimetic Surface Topography to Induce Variable Responses in Bone Marrow Stromal Cells.

The osteoblastic differentiation of bone marrow stromal cells (bMSCs), critical to the osseointegration of titanium implants, is enhanced on titanium surfaces with biomimetic topography, and this is further enhanced when the surfaces are hydrophilic. This is a result of changing the surface free energy to change protein adsorption, improving cell attachment and differentiation, and improving bone-to-implant contact in patients. In this study, we examined different methods of plasma treatment, a well-accepted method of increasing hydrophilicity, and evaluated changes in surface properties as well as the response of bMSCs in vitro. Commercially pure Ti and titanium-aluminum-vanadium (Ti6Al4V) disks were sand-blasted and acid-etched to impart microscale and nanoscale roughness, followed by treatment with various post-processing surface modification methods, including ultraviolet light (UV), dielectric barrier discharge (DBD)-generated plasma, and plasma treatment under an argon or oxygen atmosphere. Surface wettability was based on a sessile water drop measurement of contact angle; the elemental composition was analyzed using XPS, and changes in topography were characterized using scanning electron microscopy (SEM) and confocal imaging. The cell response was evaluated using bMSCs; outcome measures included the production of osteogenic markers, paracrine signaling factors, and immunomodulatory cytokines. All plasma treatments were effective in inducing superhydrophilic surfaces. Small but significant increases in surface roughness were observed following UV, DBD and argon plasma treatment. No other modifications to surface topography were noted. However, the relative composition of Ti, O, and C varied with the treatment method. The cell response to these hydrophilic surfaces depended on the plasma treatment method used. DBD plasma treatment significantly enhanced the osteogenic response of the bMSCs. In contrast, the bMSC response to argon plasma-treated surfaces was varied, with an increase in OPG production but a decrease in OCN production. These results indicate that post-packaging methods that increased hydrophilicity as measured by contact angle did not change the surface free energy in the same way, and accordingly, cells responded differently. Wettability and surface chemistry alone are not enough to declare whether an implant has an improved osteogenic effect and do not fully explain how surface free energy affects cell response.

Cavitation and jetting from shock wave refocusing near convex liquid surfaces

We study the physical mechanisms behind the ejection of a liquid jet from a curved free surface, specifically a free-falling water drop. The jet is produced after a spherical shock wave emitted from a micro-explosion created by a focused laser pulse is refocused on the opposite side of its source. The analysis of high-speed videos of the liquid jet formation revealed that it originates from a larger, prolate cavitation bubble created by the strong tension produced after the reflection of the original wave on the air–liquid interface. The shock wave propagation and jet formation are modeled separately with finite volume simulations in OpenFOAM. Initially we study the pressure evolution inside the drop by comparing the numerical simulations with the distribution of bubbles nucleated after the passage of the negative pressure wave. The jet formation dynamics is explained by comparing the experiments with numerical results. The jet velocity is higher if the laser focus is closer to the drop surface.

Temperature Etching and Metallic Agent Concentration Effect on Structure, Morphology and Wettability of Silicon Nanowires

Abstract. Structural, Morphologycal and Wettability of SiliconNanowires (SiNWs) elaborated using Ag assisted electroless chemical etching are investigated. Prior the etching, Ag nanoparticles (AgNPs) were deposited at room temperature in a HF/AgNO3 solution with different concentration of AgNO3. The XRD spectra of the Ag NPs deposit show a good crystallinity. The effects of temperature etching bath and concentrations of AgNO3 on the etching process were examined. The morphological study, performed using a Scanning Electron Microscopy (SEM), shows porous silicon layer of 2µm for the lower temperature etching. For 25°C, perpendicular silicon nanowires about 15µm were formed. For the higher etching temperature (50°C), the silicon nanowire about 50 nm in diameter and 50µm in length were formed. The impact of Ag concentration on the SiNWs formation is examined in the second part of the present work. It is shown that the etching depth decreases as the Ag concentration decreases with values of 2.8 μm and 2 μm for concentrations of 0.025M and 0.0125M, respectively. The hydrophobicity of the samples was monitored by measuring the contact angle between a drop of water and the sample surface. It was established that the morphology is strongly influenced by etching conditions and their wettability changes from superhydrophilic to hydrophobic. FTIR analysis confirms the oxide-free silicon nanowires.

High Pressure 3 × 30 Minute Compression Methods for Advanced Lower Limb Lymphedema Patients.

Introduction: In advanced lymphedema of lower limbs, stage III bandaging under the routinely applied pressure of 40-60 mmHg remains largely ineffective. This is caused by skin and subcutaneous tissue stiffness due to fibrosis. Edema fluid accumulates deep in the subcutaneous tissue. Evacuating this fluid requires a high external compression force to overcome the resistance of fibrous tissue. We aimed to investigate the effectiveness of the compression method, with high pressure lasting for 3 days. Methods and Results: Twenty-one patients with lower limb lymphedema, stage III, of the postinflammatory type were included. Patients with acute inflammatory symptoms, venous thrombosis, profuse varicose veins, diabetes, and cardiac insufficiency with edema were excluded. A 10-cm-wide rubber bandage was applied to the foot and calf. The interface pressure measured using PicoPress ranged from 58 to 120 mmHg. Skin and deep tissue tonometry, skin water concentration, leg circumference, and drop of interface pressure were measured. Ultrasound examination was done before and after each compression session. The calf circumference decreased by 15.9 ± 5.4%, deep tissue stiffness by 58.9 ± 18.9%, skin stiffness by 69.6 ± 13.5%, and skin water concentration by 43.8 ± 11.5%. Interface pressure dropped to 66.3 mmHg (28-110 mmHg); ultrasonography images showed less fluid in the tissue. Conclusions: High-pressure 30-minute leg compression can remove excess edema fluid within 3 days and enable adjustment of nonstretch compression stockings. This method is more effective in advanced lymphedema at the beginning of therapy than the standard 30-50-mmHg bandaging as it provides an immediate effect.

Soil structure and solute transport pathways in biogas digestate-amended soils

Here, we investigated the effects of biogas digestate application on flow pathways and soil properties in a sandy soil aiming at unraveling phosphorus accumulation and depletion processes in fertilized soils. Dye tracer experiments were conducted to visualize and distinguish between various flow pathways, while X-ray tomography was utilized to characterize the soil structure. The dye tracer experiments revealed differences between the control and the digestate-treated group of soil profiles in the top-soils although no statistical verification was possible amid a single plot per treatment. The stained soil profiles in both treatments indicate extensive areas of homogeneous and heterogeneous matrix flow. However, the digestate-treated group showed a decrease in homogeneous matrix flow and a notable presence of preferential flow with low interaction. The application of biogas digestate impacted various soil properties, including organic carbon content, water drop penetration time, and pH levels. Accordingly, the topsoil experienced an increase in soil organic carbon, water repellency, and a decrease in pH levels. The fraction of macropores also increased in the topsoil of the digestate-treated group, accompanied by an increase in tortuosity.Double lactate-extractable phosphorus (DL-P) distribution varied across the different flow pathways, with higher concentrations detected in matrix flow and a depletion observed in preferential flow regions in both treatments. These findings confirm the close relationship between the type of flow pathway and phosphorus distribution in soils. Additionally, a significant correlation was observed between pH levels and DL-P in the digestate-treated group, indicating potential implications for phosphorus availability. Overall, the results of this study suggest that the long-term application of biogas digestate is likely to improve soil properties as related to soil organic matter content, particularly in the topsoil of sandy soils. The study highlights the significance of the prevailing flow and transport pattern on nutrient distribution, with potential implications for nutrient management in agricultural systems. While the study design presented prevents the unequivocal assignment of differences to treatment effects, our data likely illustrate the impacts of biogas digestate amendment on the investigated sandy soil.Further research should focus on assessing the long-term effects of digestate application in loamy and clayey soils.

Self‐assembly aryl cyclopalladated imine film supported on the silicon surface—Fabrication, formation of active PdPd/PdO sites, and catalytic properties for Sonogashira cross‐coupling reaction

Tailoring the structure and arrangement of the organometallic catalyst are essential for the fundamental investigating and applications, and the impacting challenges, such as the size, active species distribution, and composition, as well as the orientation of catalyst, are critical for determining their activities and efficiencies. Herein, a series of aryl cyclopalladated catalysts containing different alkane chains were synthesized, and their self‐assembly films covalent binding to the silicon surface were fabricated and characterized with water drop contact angle, Raman, atomic force microscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The catalytic performances of these catalytic films were explored using Sonogashira cross‐coupling reaction as a template. One of these catalytic films exhibited a higher catalytic activity with a TON value of up to 68,333 h−1, which was 20 times higher than that of homogeneous catalyst due to the ordered arrangement of this catalyst on the silicon surface, and could be reused at least seven times. The catalytic mechanism was heterogeneous catalysis occurred at interface confirmed by hot filtration tests, poisoning tests, and ReactIR. The real active site was PdPd/PdO, and the synergistic effect between Pd and PdO in the active sites (PdPd/PdO) made the key initial oxidation step easily proceed, improving its catalytic activity. The loss of active sites and residues absorbed on the surface of catalytic film were the main reason for deactivation.

Emergent Properties in Chemistry - Relating Molecular Properties to Bulk Behavior.

Certain properties of an object only emerge when a sufficient number of those objects are present in a definite arrangement. For example, one or two water molecules cannot said to be in a liquid state, but a drop of water can be. This concept of emergence has been studied extensively, but only occasionally discussed explicitly in the context of chemistry. In this paper, we aim to show the fruitfulness of the concept of emergence for chemical inquiry by considering four case studies of emergent chemical properties, i. e., the liquidity and freezing of water, structural properties of crystals, thermodynamical phase transitions and quantum mechanical phenomena. We show that some of these properties emerge gradually, some at discrete points, and some should be taken to emerge only when the number of constituents tends to infinity. We argue that studying the way in which chemical properties emerge presents a useful avenue for research that promises greater insight into the nature of those properties.

Bubble ring entrapment during a water drop impact on viscous oil films

Air entrapment during the drop impact on a liquid surface is crucial to the ocean–atmosphere mass transfer process. Herein, we report a new mechanism of air entrapment. When a water drop impacts a highly viscous oil film, a bubble ring with a volume of approximately 2% of that of the initial drop is entrapped and disintegrated into multiple bubbles underneath the spreading lamella, which eventually float and burst to emit singular jets near the free surface. The reconstructed profile of the deformed oil film by the laser-induced fluorescence technique reveals the formation of the ridge and valley, which leads to the bubble ring entrapment between the two layers. The effect of the impact velocity on the annular ridge structure and bubble volume is discussed. The onset of the bubble ring disintegration is theoretically predicted, which agrees well with experimental data. Finally, the parameter space of bubble ring entrapment is presented in the regime maps, where three parameters including the impact Weber number, the dimensionless oil viscosity, and film thickness are considered.

First Report of Phytophthora ramorum Causing Leaf Spots on Cornus capitata (Evergreen Dogwood) in United States.

Cornus capitata Wall. ex Roxb. (evergreen dogwood) is a bushy evergreen tree or shrub native to East Asia grown for its showy creamy bracts in late spring followed by attractive red fruit. In Feb 2023, a sample of foliage with leaf spots and tip dieback from C. capitata 'Mountain Moon' was submitted from a Humboldt Co. nursery as part of a CDFA inspection program for Phytophthora ramorum. The leaf spots were medium to dark brown, irregularly shaped, and ranged from 5 to 8 mm in diameter. They were located primarily along the leaf midrib and covered up to 1/4 of the leaf surface. Six 6-mm-diameter leaf discs taken from the margins of brown lesions and tip dieback were plated on Phytophthora selective CMA-PARP (PARP) media (Jeffers and Martin 1986). After 6 to 10 days, colonies resembling P. ramorum, with coralloid coenocytic hyphae, chlamydospores, ellipsoidal semi-papillate and caducous sporangia, and a relatively slow growth rate were recovered. Abundant sporangia formed on agar singly or in clusters on sympodially branched sporangiophores (n = 50), varying in size from 35 to 60 μm × 20 to 30 μm (mean 45.6 × 24.8 μm) with a length/breadth ratio ranging from 1.3 to 2.3 (mean 1.8). Chlamydospores (n = 50) ranged from 35 to 62 μm in diameter (mean 51.9 μm) on 14-day-old PARP cultures. The internal transcribed spacer region (ITS) using primers ITS5/ITS4 (White et al. 1990; accession no. OR636225) and cytochrome oxidase subunit 1 region (cox1) using primers OomCox1Levup/Fm85mod (Robideau et al. 2011; OR635665) of one isolate (0254-32A) were amplified and sequenced. BLAST analysis showed 100% identity of both regions to P. ramorum ex-type strain (MG865581 and MH136973). Microsatellite loci placed the P. ramorum isolate in the NA2 clonal lineage (Goss et al, 2011). Pathogenicity of P. ramorum isolate 0254-32A was tested using five C. capitata plants (2.5-year-old, 28-cm-tall, 3.78-liter pot). Zoospore inoculum was produced as described in Blomquist et al. (2021). Above ground parts of each plant were sprayed with inoculum (15 ml, 1.3 × 105 zoospores/ml). Inoculated plants were incubated in a dew chamber in the dark at 23°C for 72 h and then placed in a 23±1°C growth chamber with a 12-h photoperiod. Five control plants were treated as above but with sterile water instead of the zoospore suspension. Two days after inoculation, brown spots were visible on leaves on all inoculated plants, initiating from where the drops of inoculum had persisted. After 3 days, brown lesions, from water drop- to majority of entire leaf-sized, were observed on approximately 75% of inoculated leaves. After 6 days, lesions expanded to the edges of leaves, causing leaf curling and defoliation. Lesions stopped expanding after 3 weeks, and by 4 weeks, most infected leaves had abscised, with no new infections observed. Phytophthora ramorum was consistently isolated from foliar lesions of inoculated plants on PARP. It was not isolated from leaf or stem tissues of control plants, which remained asymptomatic during the 4-week experiment period. Phytophthora ramorum was detected on C. capitata in the UK in 2015 (DEFRA 2015). To our knowledge, this is the first report of P. ramorum infecting C. capitata in the United States and the completion of Koch's postulates on any Cornus spp. Incidence on C. capitata in the California nursery was low. However, their proximity to other infected foliar hosts suggests Cornus spp. may present a potential risk for the spread of P. ramorum.

The effect of walnut shell (juglans regia) on colour fastness of leather

After a long way of development, leather production is considered as one of the leading industries in many countries of the world, using advanced achievements of science, technology and new technologies. Leather is considered a raw material after the use of animal products as meat products. However, many chemicals are additionally used to treat the skin. This creates a barrier to the environmental friendliness of the skin and the environment. But recently, due to environmental pollution, the question of replacing chemical production substances with natural substitutes has arisen. The purpose of the work is to replace chemical dyes with natural extracts in the leather industry in order to protect the environment, to determine the resistance of colored leather to water drops. This work was carried out in order to study the colour fastness of leather, what colored with natural extract. Colour fastness to water spotting was determined and analyzed. Walnut shells were used as extracts of natural dye. Three different samples were taken as control samples: a sample prepared using a standard chemical pigment, a sample prepared using water instead of a chemical pigment, and a leather sample that had not been finished. According to the results of the analysis, it was found that the leather dyed with natural extracts has a good coloring quality. Extract of walnut shell can be used as a dye instead of chemical pigments in the leather industry.

Shaping a Surface Microdroplet by Marangoni Forces along a Moving Contact Line of Four Immiscible Phases

AbstractThe ability to transfer microdroplets between fluid phases offers numerous advantages in various fields. This study focuses on the stability and morphology of a sessile oil microdropletduring the transfer from underwater to air. A distinct transition in microdroplet dynamics is observed, characterized by a shift from a scenario dominated by Marangoni forces to one dominated by capillary forces. In the former regime, the oil microdroplets spread in response to the contact between the water‐air interface and the water‐oil interface. The spreading distance follows a power law relationship of t3/4, reflecting the balance between Marangoni forces and viscous forces. On the other hand, in the capillarity‐dominated regime, the oil microdroplets remain stable at the contact line and after being transferred into the air. The crossover between these two regimes is identified in the parameter space defined by three factors: the approaching velocity of the solid‐water‐air contact line (vcl), the radius of the oil microdroplet (ro), and the radius of the water drop (rw). Furthermore, how to use the four‐phase contact line for shaping oil microdroplets is demonstrated using a full liquid process by the contact line lithography.

Evaluation of Botanicals against Rice Case Worm Parapoynx stagnalis Zeller. (Lepidoptera: Pyralidae)

Rice, Oryza sativa L. is the staple food of two thirds of world population. Several insect pests are reported to cause damage to rice crop. Rice case worm, unlike other lepidopteran rice pests, have an aquatic larval period and hence depends on dissolved oxygen in the water drop it carries in its case, made from rice leaf. Application of insecticide spray, does not give much control of this pest. No botanicals are yet reported as effective against this pest. In the present study, six botanicals were tested on rice case worm under laboratory and field conditions. Of the six plants, Anamirta cocculus gave promising results at five percent concentration followed by Glyricida sepium under both field and laboratory conditions.

Effect of Conformal Coating on Electrochemical Migration Behavior of Multi-Layer Ceramic Capacitor for Automotives Based on Water Drop Test

A large amount of multi-layer ceramic capacitor (MLCC) is mounted inside a printed circuit board (PCB) constituting electronic components. The use of MLCC in electric vehicles and the latest mobile phones is rapidly increasing with the latest technology. Environments in which electronic components are used are becoming more diverse and conformal coatings are being applied to protect mounted components from these environments. In particular, MLCCs in electronic components mainly have voltage applied. They might be used in environments where humidity exists for various reasons. In a humid environment, electrochemical migration (ECM) will occur, with the cathode and anode on the surface of the MLCC encountering each other. This can result in product damage due to a short circuit. In this study, the effects of voltage, NaCl concentration, and distance between electrodes on a non-mount MLCC, surface mount MLCC, and solder pad pattern were evaluated using a water drop test (WDT). Based on the analysis of the effects of the presence of conformal coating, applied voltage, concentration of NaCl, and the distance between electrodes, a mechanism model for ECM behavior in MLCCs was proposed.

Exploring the impact of pillar edge effects on water drop evaporation

A water drop placed on a small pillar unveils an edge effect, which amplifies volume accumulation within the same contact area. This effect stems from an increased apparent contact angle, resembling hydrophobic surfaces. This emphasizes the influence of surface geometry beyond chemical properties.This study explores the characteristics of the drop by dissecting the interplay between surface forces, geometric attributes, and the evaporation process, enabling a comprehensive understanding of their combined impact on drop behavior.Two distinct evaporation stages were identified: the first stage, characterized by a constant contact line along the pillar edge, and the second stage, involving the detachment of edges and shape alterations influenced by surface roughness.The evaporation rate from the pillar is determined by applying the D2 law and empirical observations. Moreover, the interplay among the key parameters in the process—namely, the evaporation rate, contact angle, volume, and pillar diameter—has been elucidated.