Contact Angle Of Droplet Research Articles

Experimental study on dynamic wetting behavior of liquid droplets on the aluminum surfaces excited by ultrasonic waves

In this paper, an anti-frosting strategy utilizing ultrasonic excitation to drive droplets away from cold surfaces was proposed. Based on this strategy, experimental studies were conducted to investigate the dynamic wetting behavior of droplets on aluminum surfaces under ultrasonic excitation. Specifically, the vibration characteristics of the plate and the properties of the droplets were revealed under the influence of ultrasonic waves. The results indicate that the droplet will undergo three stages of spreading-movement-contraction under ultrasonic excitation and the maximum contact angle hysteresis and maximum diameter spreading rate exhibit a positive correlation with droplet volume and ultrasonic power. It is also found that ultrasonic excitation can significantly reduce the droplet contact angle, which can be reduced by up to 70°. The contact angle hysteresis, diameter spreading rate and movement velocity show almost the same trend with time under ultrasonic action, that is, increasing first and then decreasing. Notably, the contact angle hysteresis and the diameter spreading rate reached a peak later than the movement velocity, which is attributed to the droplet's deformation relies on the full propagation of the ultrasonic vibration inside the droplet, resulting in hysteresis. Finally, it is found that the droplet-wetting state is permanently changed under ultrasonic action and the final contact angle is greatly reduced compared to the initial value even after stopping ultrasonic excitation.

Preparation of SiO2/chitosan composite coating on stainless steel mesh for efficient and stable oil/water separation

In recent years, the application of underwater superoleophobic coatings in the field of oil/water separation has received increasing attention, and chitosan (CS) coatings have become a research hotspot due to their advantages of hydrophilicity, non-toxicity, biodegradability, and antibacterial properties. In this work, a SiO2/CS underwater superoleophobic composite coating was prepared on 304 stainless steel mesh by a simple dip-coating method. The underwater oil droplet contact angle (OCA) of the SiO2/CS coating was 151.2°, and the oil droplet showed a stable underwater Cassie state on the coating. The stainless steel mesh with SiO2/CS coating could effectively separate different kinds of oil/water mixtures, and the separation efficiency for the kerosene/water mixture was 99.2 %. After 20 cycles of separation, the separation efficiency was more than 98 %, indicating that the SiO2/CS coating had excellent recycling performance. In addition, the prepared underwater superoleophobic coating exhibited excellent long-term stability, acid and alkali resistant stability and UV resistant stability. This SiO2/CS coating has promising practical application, which could expand the use of underwater superoleophobic coatings.

Hollow NiMo-based nitride heterojunction with super-hydrophilic/aerophobic surface for efficient urea-assisted hydrogen production

Hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) are key reactions of the water-cycling associated catalytic process/device. The design of catalysts with a super-hydrophilic/aerophobic structure and optimized electron distribution holds great promise. Here, we have designed a three-dimensional (3D) hollow Ni/NiMoN hierarchical structure with arrayed-sheet surface based on a one-pot hydrothermal route for efficient urea-assisted HER based on a simple hydrothermal process. The Ni/NiMoN catalyst exhibits super-hydrophilic/aerophobic properties with a small droplet contact angle of 6.07° and an underwater bubble contact angle of 155.7°, thus facilitating an escape of bubbles from the electrodes. Density functional theory calculations and X-ray photoelectron spectroscopy results indicate the optimized electronic structure at the interface of Ni and NiMoN, which can promote the adsorption/desorption of reactants and intermediates. The virtues combining with a large specific surface area endow Ni/NiMoN with efficient catalytic activity of low potentials of 25 mV for HER and 1.33 V for UOR at 10 mA cm−2. The coupled HER and UOR system demonstrates a low cell voltage of 1.42 V at 10 mA cm−2, which is approximately 209 mV lower than water electrolysis.

The impact of salinity on the cohesion process of quartz substracts: A molecular dynamics study.

The moisture with salt ions adsorbed on the mineral soil surface is crucial to the cohesion process when the media is exposed to marine or coastal environments. However, the impact of salinity on the cohesion of soils is not well studied at the nanoscale. In this study, the salinity effect was investigated by studying the wettability and capillary force of NaCl solutions on quartz substrates via a molecular dynamics-based approach. Besides, a new visualization method was proposed to measure the contact angle of liquid droplets from the aspect of nanoscale. The results indicated that salt ions can weaken the wettability of the liquid on the quartz surface and inhibit the capillary force. Compared with water, the liquid with a 10% NaCl solution can achieve a capillary force reduction of around 70%, resulting in a detrimental effect on the cohesion of soils. Overall, this study enhanced the understanding of the nanoscale salinity effect on the cohesion process and provided insights into the modification of the mechanical properties of soils from the aspect of nanoscale.

Multifunctional carbon nanotubes coated stainless steel mesh for electrowetting, hydrophobic, and dye absorption behavior

Electrowetting behaviour for carbon nanotubes (CNT) grown on stainless steel mesh was investigated. The effect of temperature, time, and applied bias voltage on the contact angle of water droplets was studied. The impact of temperature variation on contact angle was also performed for the temperature ranging from 25 to 70 °C. A decrement of contact angle by 68% was observed for the mentioned range indicating a transition from a hydrophobic to hydrophilic nature. A similar trend was observed on the application of electric potential to the CNT-modified stainless-steel mesh ranging from 0 to 8 V with a transition of contact angle from 146 to 30 deg respectively. A comparative analysis for the contact angle variation with time for CNT-coated mesh and uncoated mesh was performed for 180 min. It is observed that uncoated mesh shows a reduction in contact angle to 0 deg with time while the CNT coated mesh shows surplus hydrophobicity with a 2 deg decrement in the extent of time. CNT-modified mesh successfully absorbs 95% of rhodamine B (RB) dye and detergent from water in 10 cycles.

Cellulose Nanofiber as Mask/Personal Protective Equipment Surface Agent for Enhanced Anti-Bacterial Performance

The utilization of face-covering masks as an extended form of personal protective equipment has led to exponential waste measures during the COVID-19 pandemic, with estimations of up to 7200 tons of medical-type waste daily. A primary cause of this waste is surgical layered disposable masks that are constructed by melt-blown nonwovens usually made of non-biodegradable thermoplastic polymers like polypropylene. To increase widespread sustainable options to the public, commercialized or do-it-yourself-based fabric masks serve as a solution, but their resistance to harmful molecules is less than that of the medical-grade masks due to the fabric structure that leaves space for penetration. This project examines a water-soluble dispersion composed of cellulose nanofiber and polyvinyl alcohol, as a spray agent capable of treating the mask fabric surface to promote protection and sustainability against harmful aerosol particles. Cellulose nanofiber spray is also low-cost and biocompatible and could allow multi-use through home laundering. Polyvinyl alcohol was chosen as the water-soluble bonding system and polymer matrix to effectively adhere cellulose nanofiber onto the mask surface. This project follows the biomimic concept of dragonfly wings having uneven nanopillar surfaces to trap and rip bacterial membranes, as the spray decreases the water droplet contact angle on fabric surface, resulting in an increase in adhesion for incident bacteria and/or viruses.

Preparation of super-hydrophobic BN nanotube mesh and theoretical research of wetting state

In this study, we have fabricated stainless steel mesh with columnar super-hydrophobic boron nitride nanotubes (BNNTs) through the ‘gas-liquid-solid’ mechanism annealing method. We employed iron (Fe) powder as the catalyst and utilized boron (B) and boron oxide (B2O3) as the raw materials. The synthesis took place within a tubular furnace, operating under an NH3 atmosphere at a temperature of 1250C∘. The contact angle of water droplets on the experimental surface measures approximately 150∘, while the sliding angle is approximately 3∘. In the next place, the laboratory carried out a series of experiments on the tensile properties, corrosion resistance, and erosion resistance of the prepared samples. The experimental results showed that the sample material had good mechanical properties and corrosion resistance. In addition, the erosion resistance test results showed that the sample material even at high speed (2800 rpm/min). After washing the sample for 5 min, the surface of the material still has good wettability (contact angle is 136.49∘). Finally, droplet bouncing experiments have demonstrated that the adhesion force on the surface of the boron nitride nanotube stainless steel mesh is notably minimal, indicating its substantial hydrophobic properties. Additionally, we conducted an investigation into the wetting interaction between droplets and the surface of the boron nitride nanotube stainless steel mesh. By applying the Wenzel and Cassie formulas and considering the pertinent geometric parameters of the material surface, we theoretically elucidated that, upon contact, the droplets assume a ‘Cassie’ state on the surface of the super-hydrophobic boron nitride nanotube stainless steel mesh. The research results show that the superhydrophobic boron nitride nanotube stainless steel mesh has broad application prospects in the fields of hydrogen storage, sewage treatment and oil-water separation.

Green Nanopesticide: pH Response and Molybdenum Selenide Carrier with Photothermal Effect to Transport Prochloraz to Inhibit Sclerotinia Disease.

Accurate pesticide delivery is a key factor in improving pesticide utilization, which can effectively reduce the use of pesticides and environmental risks. In this study, we developed a nanocarrier preparation method which can be controlled by pH/near-infrared response. Mesoporous molybdenum selenide (MoSe2) with a high loading rate was used as the core, poly(acrylic acid) (PAA) with acid response was used as the shell, and prochloraz (Pro) was loaded to form a pH-/near-infrared-responsive core-shell nanosystem (Pro@MoSe2@PAA NPs, abbreviated as PMP). Sclerotinia sclerotiorum infection secretes oxalic acid, forming an acidic microenvironment. In an acidic environment, PMP could quickly release Pro, and the cumulative release amount of Pro at pH = 5.0 was 3.1 times higher than that at pH = 7.4, and the efficiency of releasing Pro in the acidic environment was significantly enhanced. In addition, the release rate of PMP under near-infrared light irradiation was also significantly improved, and the cumulative release of Pro under simulated sunlight was 2.35 times higher than that under no light. The contact angles of PMP droplets on rapeseeds were reduced by 31.2 and 13.9% compared to Pro and MoSe2, respectively, which proved that the nanosystems had good wettability. In addition, PMP shows excellent adhesion and resistance to simulated rain washout. In the plate antibacterial experiment, the inhibitory effect of 0.5 μg/mL PMP on S. sclerotiorum was as high as 75.2% after 6 days, which showed a higher bactericidal activity than Pro. More importantly, PMP shows excellent biocompatibility and safety to plants, microorganisms, and cells. In a word, PMP is a green nanopesticide with a dual response of pH/near-infrared light, which provides a new strategy for the sustainable development of agriculture.

Cotton fabrics modified with tannic acid/1-eicosanamine grafting layer for oil/water separation

The wettability of the surface of hydrophilic cotton fabrics was modified using a one-step protocol with tannic acid (TA) to provide its excess catechol groups to be grafted with 1-eicosanamine at pH 8.5 and room temperature with catalysts CuSO4/H2O2. The modification over the synthesis conditions revised the contact angles of water and diiodomethane droplets from 132.68 ± 0.49° to 143.95 ± 0.80° and from 100.08°±1.42° to 82.96 ± 1.38°, respectively. The corresponding dispersive of the so-yielded cotton surface ranged from 8.6 to 16.0 mJ/m2, and the polar components ranged from 0.08 to 2.7 mJ/m2, much lower than polytetrafluoroethylene. The modified cotton fabrics are omniphobic and can repel water and commercial oil products. The absorption tests revealed that the modified cotton fabrics absorbed 1.10 g hexane/g cotton by contacting hexane (top)-water (bottom) layers and absorbed 1.26 g hexane/g cotton by contacting water first for 30 s, then hexane for another 30 s. The modified fabrics reveal good absorption reusability as hexane absorbent is even pre-saturated with water. This conclusion is also valid for commercial unleaded gasoline #95 and diesel. A parametric study revealed that the added catalysts and prolonged reaction time would enhance the hydrophobicity of the surface. These modified cotton fabrics can absorb oil from water and oil spills. Mechanisms corresponding to this observation are discussed.

Laser peening without coating fabricated superhydrophobic aluminum alloy with favorable mechanical properties

This study prepared 2024-T351 aluminum alloy surfaces with excellent hydrophobic properties by laser peening without coating(LPwC) and post-treatment process (silane solution immersion modification treatment). The surface morphology, microhardness, roughness and residual stress of the specimens before and after LPwC were characterized. Besides, the surface composition and droplet contact angle of the specimens before and after LPwC were measured to investigate the mechanism of enhancing the hydrophobic properties by LPwC. The results showed that after LPwC treatment, the surface of the specimen was uniformly distributed with a large number of micro-nano porous structures and the surface roughness was significantly increased. After the modification treatment with fluorosilane solution, the F element on the surface of the specimen significantly increased, the surface energy decreased, the droplet contact angle rose to above 150°, and the sliding angle dropped to below 10°, which imparted the superhydrophobicity on the surface. After LPwC treatment, the grain size of the specimen near-surface layer was reduced, and high magnitude residual compressive stress was generated inside the matrix, which increased the microhardness of material. The as-prepared superhydrophobic surface exhibits excellent water flow repellency and favorable mechanical properties, which promoted the application of superhydrophobic preparation process in the aerospace field.

Extraction and characterization of cellulose microfibers from cornhusk for application as reinforcing agent in biocomposite

This study aims to extract and characterize cellulose microfibers from cornhusk, an agricultural by-product. The extracted fibers will then be used as a reinforcing agent in a biocomposite made of thermoplastic corn starch. The process of extracting cellulose microfibers involved two treatments: sequential alkali treatment (using sodium hydroxide at 120 °C for 120 min) and peroxide bleach treatment (using hydrogen peroxide at 90 °C for 60 min). Various techniques such as Fourier transform infrared (FTIR), X-Ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to characterize the extracted fibers. The properties of the composite were examined through tensile strength tests, contact angle measurements, and UV–Vis spectrophotometry. The study found that cellulose microfibers were successfully extracted from cornhusks, with a diameter of 7 to 30 μm and a crystallinity of 65 %. The treated fibers showed gradual degradation between 150 °C and 350 °C, indicating a lower amount of non-cellulosic substances compared to untreated cornhusks. Adding 10 % of the microfibers to the thermoplastic starch composite increased the tensile stress at breaking and the Young's modulus, but decreased the contact angle of water droplets and the film's transparency.

Investigation into the optoelectrowetting droplet transport mechanism.

To explore the optoelectronic wetting droplet transport mechanism, a transient numerical model of optoelectrowetting (OEW) under the coupling of flow and electric fields is established. The study investigates the impact of externally applied voltage, dielectric constant of the dielectric layer, and interfacial tension between the two phases on the dynamic behavior of droplets during transport. The proposed model employs an improved Young's equation to calculate the instantaneous voltage and contact angle of the droplet on the dielectric layer. Results indicate that, under the influence of OEW, significant variations in the interface contact angle of droplets occur in bright and dark regions, inducing droplet movement. Moreover, the dynamic behavior of droplet transport is closely associated with various parameters, including externally applied voltage, dielectric layer material, and interfacial tension between the two phases, all of which impact the contact angle and, consequently, the transport process. By summarizing the influence patterns of the three key parameters studied, the optimization of droplet transport performance is achieved. The study employs two-dimensional simulation models to emulate the droplet motion under the influence of the electric field, investigating the OEW droplet transport mechanism. The continuous movement of droplets involves three stages: initial wetting, continuous transport, and reaching a steady position. The findings contribute theoretical support for the efficient design of digital microfluidic devices for OEW droplet movement and the selection of key parameters for droplet manipulation.

Experiment of contact angle hysteresis of a droplet on hydrophobic fibrous membrane

Fibrous membranes are widely used in liquid-gas filtration and separation, porous structures formed by randomly cross-layered fibers have a significant influence on interfacial free energies, showing complex changes in contact angle. The present paper aims to measure the pore structures of a hydrophobic ((C2F4)n, PTFE) fibrous membrane by Confocal Laser Scanning Microscope (CLSM), and analyze the droplet contact angle hysteresis along its circumference. The capillary force of the solid-liquid interface is calculated by the surface integral of Laplace pressure on half droplet surface, and the solid-liquid and liquid-vapor interface area ratios are obtained according to the Cassie-Baxter model. The liquid penetration depth in pore structures is calculated by the quasi-equilibrium of the interface free energy. The experimental result shows that for the PTFE fibrous membrane, the liquid-vapor interface area ratio (f2The experimental result shows that for the PTFE fibrous membrane, the liquid-vapor interface area ratio (f2

Electrowetting-on-dielectric behavior of aqueous droplets and gold nanofluid on an electrospun poly(vinyl chloride) microfiber layer

Morphology and wettability of dielectric layers are crucial properties that affect the electrowetting-on-dielectric (EWOD) performance of a working liquid. In this work, the use of a poly(vinyl chloride) (PVC) microfiber-modified PVC dielectric layer as an electrowetting-on-dielectric (EWOD) substrate is explored. Imaging with scanning electron and atomic force microscopy revealed intertwined microfibers on the original PVC film after PVC deposition via electrospinning. Hydrophobicity of the PVC layer was enhanced by the presence of microfibers, with the contact angle (CA) for a water droplet increasing from 84.9° to 123.9°. EWOD behavior of various liquids on the microfiber-modified PVC layer was investigated within a DC voltage range of 0 to 200 V DC. Gold nanofluid exhibited the largest change in CA of 57°, while smaller changes were observed for KOH (19.6°), KCl (21.2°), and water (21°). A mechanism explaining the observed reduction in contact angle for a gold nanofluid droplet is presented. Our results suggest the promising potential of PVC film-PVC microfiber as a hydrophobic dielectric material for EWOD applications involving diverse liquids, including gold nanofluids.

Fabrication of biodegradable superhydrophobic Zn-Fe coating on ultra-light Mg-Li alloy

As a typical biodegradable and biocompatible light metal, magnesium (Mg) and its alloys exhibit significant prospects for various applications, especially in biomedical materials. Unfortunately, their actual application fields have been restricted by too fast degradation/corrosion rate. Both zinc (Zn) and iron (Fe) are biodegradable and biocompatible but stabler thermodynamically. It's one of the considerable refreshing strategies for controlling the degradation rate of Mg substrate by constructing a ZnFe coating with superhydrophobicity on it. However, it's challenging and rarely reported due to the high chemical reactivity of Mg. This study reports the successful in-situ synthesis of ZnFe coatings with hierarchical micro-/nano-scale structures and superhydrophobicity on ultra-light MgLi alloy by employing an innovative weak alkaline aqueous bath followed by simple chemical modification. Their micromorphology, chemical and phase compositions as well as surface wettability were comprehensively analyzed by FE-SEM, EDS, XRD, XPS, FT-IR, and a contact angle measuring instrument. Furthermore, the degradation behavior of the typical samples was evaluated by modern electrochemical measurement technology. The results revealed that the coating comprised dense micro-papillary structures and nanosheets, exhibiting a static contact angle of droplets up to 161.5° and a sliding angle of 3.0°. In addition, the obtained sample demonstrated a significantly reduced degradation rate compared to the bare magnesium alloy.

Three‐dimensional simulation of dripping and jetting phenomenon in a flow‐focusing geometry

Abstract3D simulations have been achieved on a flow‐focusing geometry employing the VOF method to study the consequence of viscosity, surface tension, wettability, and geometry on drop generation for the dripping regime. Here the dispersed phase is the PDMS oil (polydimethylsiloxane), and the continuous phase is the water. Simulations were performed at different oil‐to‐water viscosity ratios of 3, 12, 27, and 50. The interfacial tension between PDMS oil and water is 0.0118 N/m. It has been abridged to 0.008 N/m, 0.005 N/m, and 0.002 N/m, and simulations were performed. The walls of the microchannel are considered to be PMMA surfaces. The contact angle of an oil droplet on the PMMA surface in the presence of water is 140°. The effect of wettability was shown at various contact angles (angle created by water droplet on the PMMA surface in the presence of oil) of 0°, 40°, 90°, 135° and 180°. The frequency of droplet generation (1/s), non‐dimensional droplet length (L/Wc), droplet volume (nl), and droplet velocity (m/s) have been calculated for each of the cases. A flow pattern map has been industrialized classifying the dripping and jetting regimes. A comparison between normal geometry and two constricted geometries (having different orifice lengths) based on the frequency of droplet, non‐dimensional drop length, drop volume, and drop velocity has been made for both dripping and jetting regimes. Prediction of simulated non‐dimensional droplet length has also been made using dimensional analysis.

The effect of Aceria litchii (Keifer) infestation on the surface properties of litchi leaf hosts.

The wettability of target crop surfaces affects pesticide wetting and deposition. The structure and properties of the leaf surface of litchi leaves undergo severe changes after infestation by Aceria litchii (Keifer). The objective of this study was to systematically investigate the surface texture and wettability of litchi leaves infested. Firstly, the investigation focused on the surface structure and physicochemical properties of litchi leaves infested with Aceria litchii. Subsequently, different levels of Contact Angle (CA) were measured individually on the infested litchi leaves. Lastly, Surface Free Energy (SFE) and its polar and dispersive components were calculated using the Owens-Wendt-Rabel-Kaelble (OWRK) method. The outcomes revealed distinctive 3D surface structures of the erineum at various stages of mycorrhizal growth. At stage NO. 1, the height of the fungus displayed a peaked appearance, with the skewness value indicating a surface characterized by more crests. In contrast, at stages NO. 2 and NO. 3, the surface appeared relatively flat. Furthermore, post-infestation of litchi leaves, the CA of droplets on the abaxial surface of diseased leaves exhibited an increase, while the SFE value on the abaxial surface of leaves decreased significantly, in contrast to the abaxial surface of healthy leaves. The infestation behavior of Aceria litchii changed the surface structure and chemistry of litchi leaves, which directly affected the CA value of foliar liquids and the SFE value of leaves, changing the surface wettability of litchi leaves from hydrophobic to superhydrophobic. This study provides useful information for improving the wetting and deposition behavior of liquid droplets on the surface of infested leaves. © 2024 Society of Chemical Industry.

Effects of ultrasound combined with hydrothermal treatment on the quality of brown rice

In order to improve the rough mouthfeel of brown rice, the effects of ultrasound (U) combined with hydrothermal (H) treatment on texture, sensory score and cooking quality of brown rice were studied, and the improvement mechanism was revealed from the aspects of room temperature water absorption, water droplet contact angle, microstructure and starch ordered structures. The results showed that ultrasound hydrothermal treatment cycle (UH-UH) can significantly improve the eating quality of brown rice. After UH-UH, the hardness, chewiness, optimal cooking time and volume expansion rate all reached to the level of white rice, and the stickiness significantly increased from 0.126 N of the control to 1.114 N. The sensory score of cooked brown rice rose from 57.37 to 76.70. On the other hand, room temperature water absorption rate far exceeded that of white rice, and the water droplet contact angle and relative crystallinity decreased significantly. In addition, scanning electron microscopy found that the cracks and micropores on the surface of treated brown rice grains increased greatly, which may be the underlying reasons for the improvement in the eating quality of brown rice. This study helps to provide a new way for producing high-quality brown rice.

Analogous Charging Effect of Surfactant-Pesticide Spray Jet on Droplet Characteristics and Deposition on Hydrophobic Leaf Surfaces

An induction charging principle had been applied to enhance spray droplet characteristics and quantity deposition on hydrophobic abaxial-adaxial leaf surfaces from pesticide EC Glyphosate [C3H8NO5P] and surfactant Silwet L-77 [C13H34O4Si3] formulations. A nozzle cap containing two electrodes (spacing at 9 mm apart) was used to superpose charges to spray droplets under applied voltages of 2–12 kV in an electric field (E) of 8.9 × 105 V/m. From a tee-jet flat fan (TP11004VS) nozzle tip fitted into the electrode cap and positioned at 60 cm high above targeted Brassica campestris leave surfaces, the spray droplets were directed onto the leaves at a liquid flow pressure of 4 bar and travelling speed of 2 m/s. The measurements were done using Keithsley picoammeter to quantify spray chargeability (CMR), droplet sizes by lesser particle size analyzer (LPSA) and deposition on leaf surfaces by high-speed camera. In effect, droplet sizes of EC, L-77 and EC + L-77 decreased with an increasing applied voltage. The CMR of L-77 was lower than EC and highest for EC + L-77 composite solution. Based on Image analysis of droplets density per leaf area, maximum exposure of adaxial leaf surfaces intercepted many charged spray droplets than abaxial surfaces. As regressed, the quantity of charged spray deposition from EC + L-77 formulation was highest at both adaxial (approx. 27.44 Qd/cm2) and abaxial (approx. 5.57 Qd/cm2) hydrophobic leaf surfaces than EC of 26.12: 3.19 Qd/cm2 and L-77 of 24.80: 2.53 Qd/cm2, respectively. Also, contact angle, Theta E, of charged spray droplets was smaller than Theta C on adaxial than abaxial leave surfaces, a phenomenon attributed to high chemo-electrical properties of formulations that aided the direct flight, coiling and deposition of droplets in order of EC > EC + L-77 > L-77. Generally, there was no observable droplet rebound; hence, surfactant-pesticide composite spraying is considered suitable for electrostatic application in plant protection technology. Therefore, for effective application, charged droplets from glyphosate EC in silwet L-77 solution should be recommended, as it provides optimum droplet sizes, chargeability, contact angle and deposition on hydrophobic leave surfaces.

The design and performance research of PTFE/PVDF/PDMS superhydrophobic radiative cooling composite coating with high infrared emissivity

High infrared emissivity in the atmospheric transparent spectral band, high reflectivity in the solar radiation band, self-cleaning and no heat treatment process are crucial for the application of the radiative cooling materials. In this work, a superhydrophobic radiative cooling composite coating was facilely prepared by using two sizes of polytetrafluoroethylene (PTFE) particles as main fillers and silica (SiO2) nanoparticles as auxiliary fillers, and polydimethylsiloxane (PDMS) and polyvinylidene fluoride (PVDF) as binders. The coating can be scraped onto the substrate through a scraper without any heat treatment procedure. The water droplet contact angle (WCA) and rolling angle (SA) of the coating can reach a maximum of 158 ± 0.5° and a minimum of 3 ± 0.3°, respectively. The average reflectance of the coating in the visible spectral band was around 90.6%. The average infrared emissivity of the coating in 8 ∼ 13 µm spectral band was about 0.989. The test results show that the coating has excellent self-cleaning and cooling properties. Furthermore, the coating also exhibits good abrasion resistance, preferable adhesion performance, ultraviolet radiation resistance, high temperature stability, self-cleaning and anti-icing performance.