Sessile Drop Method Research Articles

Effect of boron on surface tension of liquid Fe-3.0%Si alloys

Based on Butler and Toop models, the surface tensions of liquid Fe-3.0%Si (wt.%, same as below) alloys with different Boron (B) additions were calculated. Meanwhile, the surface tensions of Fe-3.0%Si and Fe-3.0%Si-0.5%B alloys at 1550–1650 °C were also measured with the sessile drop method. The calculated results indicated that the surface tension of liquid Fe-3.0%Si alloys decreased with the increase of B content from 0.5% to 2%, which is in good agreement with the measured results. Si and B with lower surface tension tend to aggregate on the surface of the liquid alloy, while Fe with higher surface tension tends to aggregate inside the liquid alloy. With temperature increased from 1550 to 1650 °C, the surface concentration of each element is approaching the ideal concentration. Finally, a linear fit is used to correct β values. When β values are between 0.762–0.867, the calculated results of Fe-3.0%Si and Fe-3.0%Si-0.5%B alloys are close to the experimental results.

Wettability of mg-ha/Chitosan-based membrane surfaces: blood vs. autologous platelet liquid (APL).

The physical and physical chemistry is able to influence the interaction of the scaffolds and bone substitutes with the body fluid and blood. The aim of the present investigation was to evaluate the wettability properties of an Mg-HA Chitosan-based Gel with blood vs. autologous platelet gel. A total of 6 study groups were evaluated according to the Mg-HA Chitosan-based Gel thickness (1, 2 and 3 mm) and the fluids (blood vs. autologous platelet gel). The biomaterial wettability was conducted through the sessile drop technique. The study findings showed a significant difference in contact angle between the APL and blood groups (p<0.05). The MG-Ha Chitosan-based membrane thicknesses seem to produce no significant effects on contact angles measurement for all groups (p>0.05). In the present investigation, a similar MG/Ha gel membranes wettability was reported between APL and blood groups. In addition, a high hydrophilicity of MG/Ha gel membranes was reported with a potential advantage in terms of a more effective osteogenic capability in the clinical practice.

Prediction and evaluation the moisture damage resistance of rejuvenated asphalt mixtures based on neural network

The aim of this paper is to establish a model for predicting the moisture damage resistance of the rejuvenated asphalt mixture. Based on the surface free energy theory, the contact angels between asphalt and aggregate were measured with known reagents using the sessile drop method. The adhesion work, spalling work and moisture damage resistance index of the asphalt-aggregate interface system were then calculated. Secondly, the tensile strength ratio of the rejuvenated asphalt mixture was determined, and the influence of six indices, including RAP content, rejuvenator content, adhesion work, spalling work, per cent air voids in bituminous mixtures (VV) and freeze–thaw cycle on the performance of the moisture damage resistance of rejuvenated asphalt mixture was analyzed using the gray correlation entropy method. Finally, a three-layer neural network was used to predict the moisture damage resistance of the rejuvenated asphalt mixture. The results show that as the content of aged asphalt increases, the adhesion work of the asphalt- aggregate interface system decreases. Furthermore, for the system of the same rejuvenated asphalt and different aggregates, the rank of adhesion and water resistance from strong to weak is asphalt-limestone＞asphalt- granite, and the rank of the gray entropy correlation between six indices and moisture damage resistance from strong to weak is adhesion work＞spalling work＞VV＞rejuvenator content＞RAP content＞freeze-thaw cycles. Finally, the accuracy of the neural network predicting the moisture damage resistance of rejuvenated asphalt mix reaches 96.188%, which provides a new method to predict the moisture damage resistance of rejuvenated asphalt mixture.

Combining experiments and modelling to predict the competition between liquid spreading and impregnation in porous media for Metal Binder Jetting applications

A predictive model accounting for binder spreading and impregnation in powders during Metal Binder Jetting was set. Presintered cylindrical samples were 3D printed considering main printing orientations and two types of wetting tests were carried out on samples : imbibition or wicking tests using a tensiometric method and spreading-impregnation tests using a sessile drop method with a goniometer. Tensiometric tests showed results on impregnation rate in powders and goniometric tests gave the impregnated volume of the binder drop into the powder. Both those experiments allowed to identify physical parameters depending on the binder and powder bed interaction. All parameters injected in the model have been identified in the present study. The proposed model accurately described experiments and showed the dependence of impregnated volume on wetting parameters but also on printing orientation.

Bacterial Adhesion on Dental Polymers as a Function of Manufacturing Techniques.

The microbiological behavior of dental polymer materials is crucial to secure the clinical success of dental restorations. Here, the manufacturing process and the machining can play a decisive role. This study investigated the bacterial adhesion on dental polymers as a function of manufacturing techniques (additive/subtractive) and different polishing protocols. Specimens were made from polyaryletherketone (PEEK, PEKK, and AKP), resin-based CAD/CAM materials (composite and PMMA), and printed methacrylate (MA)-based materials. Surface roughness (Rz; Ra) was determined using a laser scanning microscope, and SFE/contact angles were measured using the sessile drop method. After salivary pellicle formation, in vitro biofilm formation was initiated by exposing the specimens to suspensions of Streptococcus mutans (S. mutans) and Streptococcus sanguinis (S. sanguinis). Adherent bacteria were quantified using a fluorometric assay. One-way ANOVA analysis found significant influences (p < 0.001) for the individual parameters (treatment and material) and their combinations for both types of bacteria. Stronger polishing led to significantly (p < 0.001) less adhesion of S. sanguinis (Pearson correlation PC = -0.240) and S. mutans (PC = -0.206). A highly significant (p = 0.010, PC = 0.135) correlation between S. sanguinis adhesion and Rz was identified. Post hoc analysis revealed significant higher bacterial adhesion for vertically printed MA specimens compared to horizontally printed specimens. Furthermore, significant higher adhesion of S. sanguinis on pressed PEEK was revealed comparing to the other manufacturing methods (milling, injection molding, and 3D printing). The milled PAEK samples showed similar bacterial adhesion. In general, the resin-based materials, composites, and PAEKs showed different bacterial adhesion. Fabrication methods were shown to play a critical role; the pressed PEEK showed the highest initial accumulations. Horizontal DLP fabrication reduced bacterial adhesion. Roughness < 10 µm or polishing appear to be essential for reducing bacterial adhesion.

Laminated Cyclic Olefin Copolymer Foil by Pulsed Laser Deposition

A cyclic olefin copolymer (COC) is a thermoplastic polymer endowed with glass-like optical transparency, unique biocompatibility, low autofluorescence, good chemical stability, and excellent water vapor barriers. COC is a promising new material for optics, medical devices, nanotechnology, and microelectronics. The applicability of the COC depends on its modification through different techniques from plasma treatment to lithography. Presently, pulsed laser deposition (PLD) is employed to deposit an aluminum thin film on selected areas of the COC surface. The study of the wettability, morphology, composition, and optical characteristics of both pristine and modified COC has been evaluated by scanning electron and atomic force microscopies, the sessile drop method, and UV/ViS optical spectroscopy. The prospective recycling of the COC deposited by PLD is proposed.

The Interfacial Phenomena Between Graphene on Cu Substrate Covered by Ni, Cu, or W Layer, with Liquid Ga-Sn-Zn Alloy

To obtain better parameters of wetting and interfacial properties, the Cu substrate was covered by graphene. The first experiment showed that the liquid metal mechanically destroys the graphene layer. Therefore, the Ni, Cu, or W layer was sputtered to secure the graphene. The obtained graphene was examined by micro-Raman spectrometry. The thickness of the Cu, Ni, or W layer was ~ 25 nm, compared to previous work, where the thickness of the Ni-W electrochemically deposited layer varied from 8-10 μm. To observe changes at the interface, the experiments were performed with Ga-Sn-Zn eutectic alloy using the sessile drop method at temperatures of 100, 150, and 250 °C long-time contact of 1, 10, or 30 days. Atomic force microscopy was used to show the topology of obtained samples. The microstructure observation of the cross-sectioned samples was made by scanning electron microscopy combined with energy dispersive x-ray spectroscopy. The x-ray diffraction was conducted to identify occurring phases at the interface from the Cu-Ga system. The investigation showed that such a very thin Ni, Cu, or W layer is not sufficient to protect the Cu substrate from a reaction with liquid metals such as eutectic Ga-Sn-Zn, which can be used in cooling systems. The performed XRD analysis and microstructure observations show the occurring CuGa2 phase at the interface and dissolution of the Cu substrate in molten alloy with increasing temperature and time. The interfacial CuGa2 phase grows very slowly at annealing temperatures below 150 °C for the graphene/Ni and graphene/W coatings. Therefore, these coatings can be used to protect a copper substrate in cooling electronic devices.

Effect of Al Content in Steel on Interfacial Interaction between Molten Steel and MgO Substrate

The apparent contact angles between the molten steel with different [Al] contents (w[Al]) from 0.002% to 0.831% (mass fraction) and the microporous MgO (MM) substrates are measured at 1823 K using the sessile drop method. In particular, the contact angles of No. 1 (w[Al] = 0.002%) and No. 5 (w[Al] = 0.831%) molten steels gradually increase with time at the initial stage. As w[Al] increases from 0.002% to 0.831%, the transformation route of interfacial products between molten steel and the MM substrate is MgO–FeO → MgO·Al2O3 → CaO·2Al2O3 + MgO·Al2O3. The w[Al] of No. 1 molten steel is small, and the dissolution of CaO·ZrO2(s) in the substrate is mainly affected by FeO. As w[Al] increases gradually, [Al] consumes the (MgO) contained in CaO·MgO·SiO2 (CMS), and turns the CMS into (CaO·SiO2) slag layer, which promotes the CaO·ZrO2(s) dissolving and thus increasing the interaction area percentage. When w[Al] is 0.831%, [Al] can react with (CaO·SiO2) slag layer or CaO·ZrO2(s) to form CaO·2Al2O3(s).

Biologically produced elemental sulfur clogging induced by thiols in gas biodesulfurization systems

The gas bio-desulfurization process involves the biotic oxidation of hydrogen sulfide (H2S) into hydrophilic and usable sulfur, which possesses favorable settleability, facilitating its separation and recovery from the bioreactor. Nonetheless, in thiol-containing gas bio-desulfurization systems, elemental sulfur is prone to aggregating and adhering to packings, pipes, pumps, and valves, leading to sulfur clogging and impeding the operation of the BDS process. This study systematically investigates the underlying mechanisms of sulfur agglomeration and clogging. A suite of analytical techniques, including laser diffraction, scanning electron microscopy (SEM), electrophoretic light scattering (ELS), X-ray diffraction (XRD), and sessile drop method, were employed to analyze the sulfur clogging phenomenon. The results reveal that the presence of thiols is a primary contributor to sulfur agglomeration and clogging. Thiols are commonly found in natural gas, biogas, and landfill gas and have a lowering effect on the surface hydrophilicity of sulfur particles, making them more hydrophobic and exacerbating sulfur aggregation. The accumulation of more agglomerated and less hydrophilic sulfur particles on packings and pipes leads to sulfur clogging. It occurs due to the nucleophilic S8 dissolution that promotes polysulfide formation and removes the hydrophilic biomacromolecules on the particle surface, making the sulfur particles more prone to aggregation. This study represents a pioneering effort to illuminate the mechanism behind sulfur clogging and attribute it to thiols, offering valuable insights for addressing the industrial challenge of sulfur clogging and expanding the application scope of gas bio-desulfurization.

Wettability and Reactivity of Liquid Magnesium with a Pure Silver Substrate

For the first time, experimental data on the high-temperature interaction of liquid Mg with pure Ag are presented. The study was performed by the sessile drop method and capillary purification procedure. The test was carried out under isothermal conditions at 720 °C in a protective atmosphere of Ar + 5 wt.% H2. The solidified couple was subjected to detailed microstructural observations by scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDS). Under the used conditions, immediately after contact with the Ag substrate, liquid Mg drop showed a good wetting (θ0 ~ 65°) followed by fast spreading over the substrate in subsecond time to form the final contact angle of θf ~ 31°.SEM/EDS analysis showed that θf is apparent because of a deep crater (200 μm) formed in the substrate under the drop by the dissolution of Ag in liquid Mg. SEM/EDS observations of complex structural transformations in the Mg/Ag couple due to high-temperature contact and subsequent cooling are in good agreement with the Ag-Mg phase diagram. Besides substrate dissolution, the interaction between liquid Mg and solid Ag at 720 °C is accompanied with the alloying of the Mg drop with Ag and the formation of a continuous layer of the β-AgMg phase at the Mg/Ag interface. During cooling, the chemical composition of the Mg(Ag) drop continuously changes, and this process is followed by the formation of the β-AgMg phase by secondary precipitation from Ag-saturated liquid, a partial transformation of the β-AgMg to ε′-Ag17Mg54 phase by peritectic reaction, followed by the solid-state transformation of the ε′-phase to the ε-AgMg3 phase, and finally, the solidification of residual liquid in the form of the two-phase eutectic mixture of AgMg4 + (Mg). The results obtained suggest that a very good wetting and fast spreading observed experimentally for the Mg/Ag couple is caused by high reactivity between liquid Mg and Ag substrate leading to the combined effect of two reactive wetting mechanisms, i.e. through dissolutive wetting and wetting through the formation of the interfacial reaction product (β-phase).

Determination of Sessile Drop Wetting Angle Based on μCT without the Direct Angle Measurement.

Wettability is an important factor that controls the position and transport of fluids in the porous structure of a hydrocarbon reservoir. Direct quantitative wettability measurement methods include determination of the contact angle. One of the popular laboratory methods for its measurement is the sessile drop method, where the droplet of liquid is set onto the solid sample surface and the angle between liquid and solid phases in a 2D profile image is measured using a high-resolution optical subsystem. However, this method has disadvantages connected with three complex factors: two-dimensionality of data, image resolution, and the presence of wetting domains on the solid surface. In this work, we propose a method based on 3D μCT scanning of a sessile drop on the surface of a material and determination of the value of the wetting angle using drop height and volume measurements. Since the contact angle is not measured directly, this makes it possible to obtain averaged contact angle values for the entire droplet and leads to more stable values for individual measurements in comparison with the standard optical method. The results demonstrate that contact angles obtained using the μCT method differ from the values obtained by various fitting techniques of the 2D optical method: μCT-values are higher for hydrophilic interaction by 4-6° and lower for hydrophobic interaction by 12-17°. Such differences are associated with the lower susceptibility of the proposed method to the influence of the gravitational effect, which leads to a flattening of the droplet shape and distortion of angle measurements on the 2D projections. However, the described method showed close contact angles for water drops on a polytetrafluoroethylene surface with values obtained in microgravity and can be helpful for its prediction. It also has relatively low sensitivity to the absolute values of the drop volume and drop segmentation errors.

Effect of rare earth oxide microparticles on mechanical, corrosion, antibacterial, and hemolytic behavior of Mg-Hydroxyapatite composite for orthopedic applications - A preliminary in-vitro study.

The current study focused on developing a multifunctional Mg-based biodegradable composite that mitigates the trade-off between strength, antibacterial, and cytotoxicity behavior for orthopedic bone implants. The composite has been reinforced with natural mineral-based Hydroxyapatite and rare earth oxide (REO): Neodymium oxide. The effect of different concentrations of REO on the mechanical, antibacterial, and corrosion properties was analyzed. The antibacterial properties were assessed against gram-positive B. Subtilis and gram-negative E. Coli bacterial pathogens. Moreover, the cytotoxicity of the composites was assessed via Hemolysis percentage calculations. In addition, the microstructure characterization was performed via FESEM, XRD, and EDS techniques, and different intermetallic phase formations were recorded. Contact angle measurements were done via the sessile drop method to analyze the impact of rare earth oxide on the surface properties of the synthesized composites and their relationship with bacterial adhesion. The corrosion studies and swelling rates were performed under PBS and DMEM solutions. The composite with the addition of 1.5% REO outperformed the experiments with a compressive strength of 126.4MPa, and a corrosion rate less than 0.2 mm/yr. The corrosion rates and degree of swelling were seen to be more stable in DMEM solution as compared to PBS. Improved antibacterial rates were observed against both pathogens after the addition of REO along with a hemolysis percentage less than 5% for Mg-HA-1.5Nd2 O3 . The composites showed increased hydrophobicity (>75%) by the addition of 1.5% REO. Hence, it was concluded that REO (Nd2 O3 ) addition to the Mg-Hydroxyapatite composite is a feasible choice as a biomaterial for bone implant applications.

Does Spontaneous Secondary Succession Contribute to the Drying of the Topsoil?

The aim of the study was to analyse the moisture content (θ) and the persistence and strength of water repellency (SWR) on sandy soil excluded from cultivation and then undergoing spontaneous afforestation or weed infestation during an abnormally warm period. Three site plots in close proximity were selected, i.e., Scots pine forest—S1 (Dicrano-Pinion), birch forest—S3 (Molinio-Frangulion) 25 years old, and an abandoned field—S2 (Scleranthion annui) 1 year old, in Central Poland. The study covers the growing period in 2020 for the two upper soil layers. For the top layer, the average θ values for S1, S2, and S3 were 0.069, 0.101, and 0.123 cm3cm−3, respectively. In S1, the θ values were close to the permanent wilting point, and the actual SWR classes (water drop penetration time WDPT test) indicated the top layer as belonging to the extremely repellent class continuously for almost the whole study period. For other sites and soil layers, the wettable SWR classes were assessed. Whereas the severity of the potential SWR, based on measured values of the wetting contact angle (sessile drop method), also showed hydrophobicity for the top layer under the birch forest. The study provides new information regarding the risk of drying out the soil due to the SWR in sandy soils, depending on land use and climate warming.

Wetting, infiltration, and interaction behavior of calcium-magnesium-alumino-silicate towards Gd/Yb-modified SrZrO3 coatings deposited by solution precursor plasma spray

Wetting of thermal barrier coatings (TBCs) with calcium-magnesium- alumino-silicate (CMAS) leads to sintering and phase transition, which are major issues in the aerospace industry. We prepared Sr(Zr1−2xYbxGdx)O3−x (x = 0, 0.05, 0.1, and 0.15) coatings using solution precursor plasma spraying with inter-pass boundaries (IPBs) and vertical cracks, and analyzed the CMAS wettability at 1350 °C using the sessile-drop method. The wetting and diffusion dynamics of the CMAS melt on the surface of the coating were studied using a CCD camera, revealing that the Sr(Zr0.7Yb0.15Gd0.15)O2.85 coating had the lowest spreading speed (2.60 × 10−4 mm/s, spreading balance process). Furthermore, a greater extent of crack bending and smaller crack diameter can prevent the coatings from penetration of the CMAS melt.

Effect of cationic and anionic surfactants on the wettability and interfacial tension of oil-brine systems in analogous rocks from the Chicontepec Paleochannel, Mexico

The chemical enhanced oil recovery (cEOR) uses substances to improve the mobility of petroleum in reservoirs. Among these substances are the surfactants, whose purpose is to change the wettability and interfacial tension (IFT). We focus on experiments of surfactants in rocks from Chicontepec Paleochannel. CTAB, DTAB and SDS surfactants in brines of NaCl and KCl and mineral oil were investigated for reduction of IFT and contact angle alteration. The sessile and pendant drop methods were used to determine the IFT. The electrical affinity of the rock surface, dissolved ions, and the surfactant molecules, play key roles in the alteration of wettability and IFT. Thus, one scheme of interactions between the electrical charges is proposed on the basis of the rocky characterization and the following results: the lowest contact angle was 106° with CTAB at 0.01 wt% in brines at 9.25 g/L NaCl, and 108° with SDS at 0.01 wt% in brines at 20 g/L NaCl. The smallest IFT was 0.813 dyn/cm with CTAB at 0.5 wt% in brines at 5 g/L KCl. This work serves as first assessments of these surfactants to enhance the production in Chicontepec, employing cheap tensoactives to increase the applicability. Besides, these results will guide future displacement tests as cEOR lab simulation.

Evaluation of Surface Tension of CaO–SiO2–Al2O3‐Based Mold Flux Containing Ce2O3

The calculation model based on the surface tension of CaO–SiO2–Al2O3‐based mold flux containing Ce2O3 is studied using the modified Butler equation, and the surface tension of mold flux is measured by the sessile drop method. The experimental results show that the calculated surface tension based on the model agrees well with the experimental values, and the absolute value of the error is less than 3.23%. With the content of Ce2O3 in the mold flux increasing from 0% to 20%, the surface tension of the mold flux increases from 0.380 to 0.405 N m−1. The O2− dissociated from Ce2O3 makes the radius of the silicon–oxygen tetrahedral anion decrease, and the ion‐to‐ion interaction force in the melt increase. Therefore, the surface tension of the melt increases with the increase of Ce2O3 content in the mold flux. However, the amount of dissociated O2− is limited, so the effect of Ce2O3 on the surface tension of the mold flux is limited.

Methodology for characterizing the printability of hydrogels.

280Currently, the characterization techniques for hydrogels used in bioprinting are extensive, and they could provide data on the physical, chemical, and mechanical properties of hydrogels. While characterizing the hydrogels, the analysis of their printing properties is of great importance in the determination of their potential for bioprinting. The study of printing properties provides data on their capacity to reproduce biomimetic structures and maintain their integrity after the process, as it also relates them to the possible cell viability after the generation of the structures. Current hydrogel characterization techniques require expensive measuring instrument that is not readily available in many research groups. Therefore, it would be interesting to propose a methodology to characterize and compare the printability of different hydrogels in a fast, simple, reliable, and inexpensive way. The aim of this work is to propose a methodology for extrusion-based bioprinters that allows determining the printability of hydrogels that are going to be loaded with cells, by analyzing cell viability with the sessile drop method, molecular cohesion with the filament collapse test, adequate gelation with the quantitative evaluation of the gelation state, and printing precision with the printing grid test. The data obtained after performing this work allow the comparison of different hydrogels or different concentrations of the same hydrogel to determine which one has the most favorable properties to carry out bioprinting studies.

Electrochemical, Biological, and Technological Properties of Anodized Titanium for Color Coded Implants.

Anodization coloring of titanium tools or implants is one of the common methods for the differentiation of each application by its size or type. Commercial purity titanium grade 4 plates (50 × 20 × 0.1 mm) were tested to obtain their electrochemical and other technological properties. The coloring process was done using the potential of 15, 30, 45, 60, and 75 Volts for 5 s in 1 wt. % citric acid in demineralized water solution. Organic acids solutions generally produce better surface quality compared to inorganic acids. The contact angle of colored surfaces was measured by the sessile drop method. Electrochemical impedance spectroscopy and potentiodynamic polarization were used for the determination of selected electrochemical and corrosion parameters of the tested surfaces. It was found that the anodization process decreases corrosion potential significantly. It was also confirmed that a higher potential used for anodization results in higher polarization resistance but also a decrease in corrosion potential. The anodization process at 75 V produces surfaces with the lowest corrosion rate under 1 nm/year and the noblest corrosion potential. It was confirmed that the anodization process in citric acid does not affect titanium cytotoxicity.

SURFACE TENSION AND DENSITY OF INDIUM–TIN MELTS AND THEIR DEPENDENCE ON COMPOSITION AND TEMPERATURE

The paper presents the results of measuring the surface tension (σ) and density (ρ) of indium-tin melts. The measurements of σ and ρ were carried out by different methods. The surface tension was measured by the sessile drop method and the maximum pressure in the droplet, while the density was measured by the areometer and sessile drop methods. High-purity metals In-00, tin – VHF were used for research. The maximum measurement error σ is 0.8%, and ρ is 0.2%. The dependence of σ of In–Sn melts on the composition is characterized by an extremum (flat minimum) in the region of equimolar composition. As the temperature increases, the depth of the minimum decreases, and its position shifts towards pure indium. Molar volumes have small positive deviations from additive values. As the temperature increases, the molar volumes approach additive values. The sessile drop method was used to measure the temperature dependences of σ and ρ of In–Sn solutions diluted with indium. It has been shown that indium additives lower the surface tension of tin. Given that the value of the surface tension of indium is higher than that of tin, this result indicates that the surface tension isotherms of the indium-tin system must pass through a minimum.

Leaf Wettability Difference Among Tea Leaf Ages and Analysis Based on Microscopic Surface Features

The wettability of leaf surface, commonly represented by contact angle (CA), affects various physiological and physical processes. The present study aims to better understand the wettability of tea leaves and elucidate its influence on the energy barrier of the droplet condensation process. The CA values of different leaf ages (young, mature and old) of five famous tea cultivars (Maolu, longjing 43, Huangjinya, Zhongcha 108 and Anji Baicha) were measured via the sessile drop method, and the micro-morphology of two cultivars leaves (Maolu, Zhongcha 108) was investigated by a 3D super depth-of-field digital microscope. Specifically, two radically distinctive types of CA trends were observed, one was the decreased firstly and then increased slightly with the increase of leaf age, while the other stayed constant. The valley depth or maximum height (RZ) of Maolu leaf surface increased with the leaf age while the RZ of Zhongcha 108 leaf remained unchanged by comparing the microscopic features. The Maolu mature leaf CA decline attributed to the young leaf was hydrophilic (θ < 90°), and it was considered that surface structures like folds and pits on old leaf played a crucial role in making CA increased. Small deviation in CA can lead to significant error in calculation of the contact angle function of energy barrier in phase change. It will have great significant for simulating and better understanding the formation of frost on tea leaves.