Critical Contact Angle Research Articles

Theoretical analysis of the initial nucleation characteristics of trace water vapor frosting on a cryogenic surface

In certain extreme conditions characterized by ultra-low water vapor content and ultra-low temperatures (e.g. cryogenic wind tunnel), trace water vapor frosting can also pose significant hazards. Considering the crucial role of initial nucleation on subsequent frosting processes, this study firstly investigated and compared the nucleation characteristics of frosting at different water vapor contents (0.1−1000 ppmv) from humid air to trace water vapor based on classical nucleation theory. The preferred nucleation phase diagrams and critical nucleation conditions were analyzed. Sensitivity of the nucleation mass transfer rate, as well as the frosting pathways were further identified. Results show that the nucleation characteristics of trace water vapor frosting (<100 ppmv) is significantly different from that of humid air frosting (>1000 ppmv). Trace water vapor frosting is more inclined towards desublimation nucleation due to its lower nucleation temperature and larger critical contact angle. The critical contact angles for 1000 ppmv, 100 ppmv and 0.1 ppmv are 49°, 75° and 120°, respectively. Furthermore, trace water vapor nucleation requires a greater subcooling degree, has a smaller critical nucleation radius, and is highly sensitive to surface contact angle and further-subcooling degree. At a surface contact angle of 120°, the nucleation subcooling degree of 0.1 ppmv is 2.9 K greater than that of 1000 ppmv. This study helps understanding the nucleation characteristics under different water vapor content conditions, which indicates that reducing subcooling degree and increasing contact angle are more effective anti-frosting methods than reducing water vapor content for trace water vapor frosting.

Model-guided navigation of magnetic soft guidewire for safe endovascular surgery

The emergent magnetic soft guidewires (MSGs) that can be remotely navigated by magnetic fields hold great promise in minimally invasive endovascular surgery. However, existing models of MSGs have been limited in practical applications, largely due to insufficient consideration of contacts within actual endovascular settings. In this work, we present a theoretical model incorporating the magneto-mechanical behavior of MSGs with these critical contacts, allowing for a detailed evaluation of their navigation capability in various vascular configurations. Specifically, we categorize blood vessels into two main types: curved vessels and bifurcated vessels and identify a critical contact angle between the MSG tip and the vessel wall, beyond which the vascular damage may occur. By applying the principles of hard-magnetic elastica to account for the large deflection of MSGs, we develop a numerical framework that employs polynomial approximations and an energy minimization strategy. Through parametric analysis of different vessel types, we propose a method for adjusting magnetic fields for the safe navigation of MSGs through them. Our theoretical predictions have been substantiated by finite element modeling and experimental validation. The results of this paper offer a solid foundation for establishing practical guidelines for remote MSG navigation with minimal risk of vascular damage.

The influence of geometric boundary features on droplet wetting and directional motion

Structured surfaces with micro and nanostructures have shown great potential for a wide range of applications, such as self-cleaning, deicing, and drag reduction. Previous research has extensively explored the interactions between droplets and microstructures, particularly in terms of Cassie-Baxter and Wenzel states. However, there is still a notable gap in systematically studying the interactions between droplets and various types of geometrical boundary features. In this study, we employed molecular dynamics simulations to investigate how different geometric boundary features affect the wetting behavior and motion of water droplets. Our detailed analysis led to the derivation of a formula to calculate the critical contact angle for a droplet interacting with any geometric boundary feature from a mechanical perspective. Based on these findings, we successfully controlled motion direction of water droplets along a separation membrane. We observed that due to the influence of geometric boundary features at the holes, droplets exhibited unidirectional motion on the separation membrane. By considering the influence of geometric boundary features, our research provides valuable insights for preventing wetting transition, enhancing the storage of lubricating oil in grooves, facilitating efficient oil–water separation, and regulating fluid flow in microchannels.

Simulation of the surface and volume stress in the contact archwire/bracket for classical friction and critical contact angle

AbstractAimThe occlusion of the teeth is affected due to the appearance of micro-cracks resulting from maximum stresses in the contact zones between the wire and the bracket under normal and tangential loading. The objective of this study is to evaluate the surface and volume constraints in the presence of bonding and partial sliding zones on the contact surface between wires and supports. Knowledge of these stress fields will make it possible to better limit the surfaces where most of the micro-cracks occur. Indeed, the evaluation of the stress will facilitate the modelling or application of established micro crack models on this subject, because the initiation of micro-cracks often appears on the contact surface or just below it.Materials and methodsIn this study, the two most common situations of contact between the wire and the bracket were studied; the first corresponds to the situation where the wire is positioned in the center of the support (classic friction), and the second corresponds to the situation where the inclined wire touches the ends of the supports (critical contact angle).The MATHCAD software was used to simulate the damage zones for normal loading in the two cases studied (classic friction, critical contact angle). We proposed a Hertzian loading for the first case and a linear loading for the second case. Also, the effect of the additional load during wire tightening applied by the orthodontist was studied.ResultsThe charge concentration is located above the contact zone, of the order of 0.3P0 (pressure per unit of arbitrary normal length), according to Mathcad simulation results. The adhesion zone/micro-slip zone contact generates the largest tangential load, which is directed towards the side experiencing the most stress. We also observed that the stick area shifts towards the recessed side when the additional load is applied. Additionally, comparing the configurations, the critical contact angle resulted in a higher maximum shear stress.

Investigation on spontaneous liquid–liquid imbibition in capillaries with varying axial geometries using lattice Boltzmann method

Spontaneous liquid–liquid imbibition in capillaries with irregular axial geometries is common in the petroleum industry. Monitoring the real-time dynamic contact angle (DCA) of the meniscus is crucial during such processes. In this work, we extend the Bell–Cameron–Lucas–Washburn (BCLW) equation by considering the axial shape of the capillaries, inertial force, and non-wetting fluid viscosity. We also develop a cascaded multi-component Shan–Chen lattice Boltzmann method (CLBM) with a modified mass-conservative curved boundary scheme to accurately simulate imbibition processes in sinusoidal capillaries. The results indicate that the DCA is highly sensitive to variations in the axial geometry of the capillary during imbibition, displaying a periodic time evolution pattern. When the axial geometry diverges, the DCA increases, and when it converges, the DCA decreases. The viscosity ratio affects the imbibition velocity, controlling the evolution period and extreme values of the DCA. A critical contact angle exists for a fixed capillary axial geometry and viscosity ratio. Continuous spontaneous imbibition occurs if the static contact angle is smaller than this critical value. However, if it exceeds this threshold, imbibition ceases within regions where axial geometry divergence. Moreover, we noticed a discrepancy in imbibition lengths predicted by the extended BCLW equation that ignores the DCA compared to those computed through the CLBM. To address this issue, we employed CLBM to monitor the DCA in real time and used the gathered data to refine the extended BCLW equation. As a result, the prediction of imbibition lengths by the extended BCLW equation for coupling the DCA became more accurate.

Adaptation of application of drop area method to characterize hydrophobicity of materials

The drop area can characterize hydrophobicity of materials. To improve accuracy of the drop area method, a large number of drop profiles with different contact angles, drop volumes and liquid parameters (Δρ/γ) are numerically generated. Based on the generated profiles, the influences of contact angle, drop volume and liquid parameter on the drop area and its sensitivity dS/dθ are systematically investigated. The results reveal that the sensitivity of the drop area method reduces with increasing contact angle, and increases with increasing drop volume and liquid parameter. The drop area method is particularly suitable for application in the case with small contact angle and at the same time, the drop volume and liquid parameter should be not so low. The relationship between water drop area and contact angle at some common drop volumes is obtained by numerical calculation. The concept of critical contact angle for the drop area method is proposed and the values of critical contact angle corresponding to different water drop volumes are presented. And it can be used to determine whether the drop area method or the static contact angle method should be selected. Finally, the contact angle method and the drop area method are used to measure hydrophobicity of glass and silicone rubber with different water drop volumes. The results validate the above analysis and at the same time it is consistent with the corresponding numerical calculation. This work is helpful to improve the accuracy in the drop area method and to generalize the use of it.

Insight into the influence of surface wettability on flotation properties of solid particles – Critical contact angle in flotation

Bubble-particle attachment is a fundamental element of the flotation process, and its occurrence depends on the stability of the thin liquid film separating these objects. In this study, the effect of surface wettability on the stability of liquid film and subsequent attachment was investigated by flotation of glass microspheres (70–110 μm) with controlled contact angles (9–89°) in a Hallimond tube. Additionally, pH was varied to determine the electrostatic interactions between the bubble and particles. The results showed that for the flotation process to take place, the minimum (critical) value of the contact angle must be exceeded. This value was found to be ca. 25° when the electrostatic interactions were either attractive or weakly repulsive and as high as 62° for strong repulsive electrostatic interactions. These findings highlight the role of attractive hydrophobic interactions, whose importance increases with increasing surface contact angle in the context of stability of thin liquid films.

Transients of Marangoni and Stefan advection dynamics during generic sessile droplet evaporation

We probe the transient evolution of Marangoni thermo-hydrodynamics in the liquid domain and the Stefan advection in the gaseous domain during evaporation of sessile droplets with generic contact line dynamics [both constant contact radius (CCR) and constant contact angle (CCA) modes]. A transient arbitrary Lagrangian–Eulerian framework was considered to computationally model the evaporation phenomenon over the droplet lifetime. The governing equations corresponding to the transport processes in both liquid and gaseous domains are simulated in a fully coupled manner, while precisely tracing the liquid–vapor interface and three phase contact line. The effects of the wetting state and contact line dynamics during CCR and CCA modes were explored, and good agreement with experimental observations is noted. The results show that the non-uniformity in an internal temperature field due to evaporation leads to formation of multi-vortex Marangoni patterns in the flow field at initial periods. At the quasi-stable state, the temperature variation becomes monotonic, thereby resulting in a single recirculation vortex in both liquid and gaseous domains. For the CCR mode, the strength of these advection fields is solely governed by a critical contact angle of ∼32°, which is determined to correspond to the critical Marangoni number. Beyond this critical point, viscous action becomes significant, and the fluid motion mitigates progressively with the formation of twin vortices at final stages due to localized heat advection near the contact line. For the CCA mode, the strength of initial vortices augments with progressing time due to amplified evaporative fluxes at smaller contact radius. The internal thermofluidic patterns and evaporative modes in turn modulate the external Stefan flow fields and neighborhood temperature fields. These findings may hold strong implications for efficient functioning of practical droplet based processes involving transport, mixing, and deposition of dissolved particles.

Three-phase contact formation between an air bubble and solid surfaces with different hydrophobicity degrees in liquid

Interactions between gas bubbles and solid particles are crucial in numerous industrial processes, including froth flotation, in which particle-bubble attachment plays a vital role. The process efficiency depends on differences in the surface wettability (i.e., hydrophobicity, expressed by the contact angle) of separated particles. This study aimed to investigate the influence of surface hydrophobicity and zeta potential on the formation of a three-phase contact (TPC) between a single air bubble and planar glass surfaces. Different degrees of hydrophobicity were achieved by esterification with a range of alcohols and time. The interaction between the bubble and surface was monitored using a high-speed camera with a time resolution of 1 ms, allowing for measurements of the time of thin liquid film drainage, time and diameter of TPC formation, TPC line expansion velocity, and dynamic contact angles. The observations suggest that TPC formation occurs when the solid surface has a sufficient degree of hydrophobicity (critical contact angle) and is dependent on the differences in zeta potential values between the air bubble and the solid surface in water. When both surfaces are negatively charged, the limiting value of the water contact angle is ca. 35°, whereas for oppositely charged surfaces, the value slightly decreases to ca. 31°. The results show that increasing surface hydrophobicity enhances the bubble adhesion effectiveness by increasing both the propagation velocity of the TPC perimeter and its size (measured by the diameter of the formed TPC). The article also discusses the mechanism of bubble-solid adhesion in relation to the hydrophobicity and zeta potential of the solid surface based on the obtained results.

Nanobubble-Induced Aggregation of Ultrafine Particles: A Molecular Dynamics Study.

Nanobubble-induced aggregation (NBIA) of fine and ultrafine particles in liquid is a promising method for enhancing floatation rates in mineral processing, cleaning contaminants from water, and reviving marine ecosystems. Although the current experimental techniques can measure the nanobubble capillary force between two surfaces with controlled approach speed, they are not capable of imaging NBIA dynamics of fine/ultrafine particles by real-time observation with nanoscale spatial resolution. In this work, we use molecular dynamics (MD) simulations to study dynamics of NBIA of Ag particles in a Lennard-Jones fluid system. The molecular-level modeling allows us to study microscopic details of NBIA dynamics that are inaccessible by current experimental means. Using MD simulations, we investigated the effects of NB size, surface wettability, surface roughness, and contact line pinning on NBIA dynamics. Our modeling results show that both concave NB bridges between two hydrophobic surfaces and convex NB bridges between two hydrophilic surfaces can result in an attractive nanobubble capillary force (NBCF) that causes the aggregation of Ag particles in liquids. The equilibrium separation between two fully aggregated particles can be well predicted by the improved capillary force model. We also observe that the change of contact angle after the contact line pinning occurs at the sharp edge of a particle, which slows the aggregation process. Our thermodynamics analysis shows that there is a critical contact angle below which the merged surface NBs will detach from the surface instead of causing aggregation. The prediction of the critical contact angle is corroborated by our MD simulation results.

Critical contact angle of a bouncing droplet

Bouncing droplets on solid surfaces is of great significance in diversified applications such as anti-icing and self-cleaning. It is important to establish a unified model to predict whether an impacting droplet can rebound from a surface or not. This work focuses on the rebound dynamic of a droplet impacting a hydrophobic surface via theoretical methods. Based on energy conservation, a new theoretical model to predict the rebound behavior of an impacting droplet is established. For an ideal surface, the contact angle hysteresis Δθ can be ignored and the rebound condition is θ ≥ θc,i, where θ is the equilibrium contact angle and θc,i is the critical rebounding contact angle (CRCA) of an ideal surface. For a real surface, Δθ is considered and the rebound condition is θr ≥ θc,r, where θr is the receding contact angle and θc,r is CRCA of a real surface. Especially, when Δθ is not large enough, the rebound condition for a real surface can be expressed as θr ≥ θc,i. This work is the first to establish the theoretical model considering both the energy dissipation throughout the impact process and the contact angle hysteresis, which shows a higher consistency with the previous works.

Critical contact angle for triggering dynamic Leidenfrost phenomenon at different surface wettability: A molecular dynamics study

The microscopic mechanism of the dynamic Leidenfrost phenomenon involving the impact of droplets on high-temperature surfaces remains unclear, although many efforts have been devoted to the static Leidenfrost phenomenon of evaporative sessile droplets. In this work, we study the dynamic Leidenfrost phenomenon of droplets impacting high-temperature surfaces with different wettability by using water and copper. The simulations by the molecular dynamics method show that determined by the atomic potential energy, a hydrophilic surface favors a lower dynamic Leidenfrost temperature compared to a hydrophobic surface. It is found that there is a critical contact angle that can trigger the Leidenfrost phenomenon at different surface temperatures. The critical contact angles are about 44.06°, 87.93°, and 92.63° when the surface temperatures are 998 K, 1,098 K, and 1,198 K, respectively. That the critical contact angle becomes larger with elevated surface temperature is helpful for industrial designs, in which novel insulating materials with higher Leidenfrost temperatures are required.

Rough capillary rise

Capillary rise within rough structures is a wetting phenomenon that is fundamental to survival in biological organisms, deterioration of our built environment, and performance of numerous innovations, from 3D microfluidics to carbon capture. Here, to accurately predict rough capillary rise, we must couple two wetting phenomena: capillary rise and hemiwicking. Experiments, simulations, and theory demonstrate how this coupling challenges our conventional understanding and intuitions of wetting and roughness. Firstly, the critical contact angle for hemiwicking becomes separation-dependent so that hemiwicking can vanish for even highly wetting liquids. Secondly, the rise heights for perfectly wetting liquids can differ between smooth and rough systems, even with the same 0∘ contact angle. Finally, the raised liquid volumes are substantially increased in rough compared to smooth systems. To explain and predict all rise heights and volumes with quantitative accuracy, we present the Dual-Rise model that is valid for general roughness, liquids, and surface wettabilities.

Study on droplet wettability of low surface tension working medium based on special-shaped microstructure surface

The wetting properties of droplets on microstructure surfaces directly determine the hydrophobic properties of the surface, and the size effect is an important part of the study of droplet wettability on microstructure surfaces. Taking reentrant special-shaped microstructure and doubly-reentrant special-shaped microstructure as the research objects, the influences of many geometric parameters of microstructure on the wetting characteristics of droplet with low surface tension were obtained by numerical simulation and theoretical analysis, and the concept of critical intrinsic contact angle was proposed. It is found that the two kinds of special-shaped microstructures can suspend the droplet with low surface tension, and the droplet finally presents a large apparent contact angle. However, there are three kinds of wetting transition (Cassie state →Wenzel state transition) on the surface of the doubly-reentrant special-shaped microstructure, so the wetting regulation mechanism of the surface with the same geometric parameters is different from that of the reentrant special-shaped microstructure. In addition, by analyzing the energy barrier at the pinning point, it is further proved that the doubly-reentrant special-shaped microstructure has better performance of inhibiting the wetting transition of droplet.

Effect of environmental factors on the kinetics of evaporation of droplets containing bacteria or viruses on different surfaces

The efficacy of antimicrobial surfaces at solid-air interfaces can be assessed using standardised testing methods, typically by placing a droplet inoculated with microorganisms onto the surface and monitoring changes in microbial counts over time (hours). However, the mode of action of the putative antimicrobial may rely on the presence of moisture on the surface, thus it is important to know the time taken for the inoculum to dry, since this will affect resultant counts and thereby deduction as to the efficacy of the antimicrobial. Droplet (+/− microorganisms) evaporation time was measured on four different surfaces (copper, PVC, polypropylene and nitrile rubber) where temperature, relative humidity and airflow in the test chamber were controlled. The data were compared with simple models based on external mass transfer for predicting the evaporation time: (i) one assuming constant wetted area (CWA), where the diameter of the drop is unchanged but the volume/height decreases; (ii) constant contact angle (CCA), where the diameter of the droplet decreases but the droplet profile/contact angle remains unchanged; and (iii) a mixed mode model. The mixed mode model gave the best fit to the data, in which evaporation initially followed CWA kinetics, then shifted to CCA when a critical contact angle was reached. The presence of microorganisms consistently and often significantly reduced the evaporation time. Deposited bacteria were visible over the whole wetted area, with a noticeable ring at the original edge of the droplet (the location of the initial solid-liquid-air contact line), consistent with the mixed mode model. Accumulation of microorganisms and the decrease in evaporation time may affect the effectiveness of antimicrobial materials. The speed of droplet evaporation is affected by a wide range of factors: temperature, humidity, airflow, the nature of the surface and the presence (and nature) of microorganisms. If these factors are not adequately recognised or controlled, then results from testing methods carried out under different (unspecified) environmental conditions in different laboratories, are liable to vary and give rise to confusion and misinterpretation. • The way antimicrobial efficacy is tested does not address the reality of end-use. • This work describes the first assessment of evaporation time on non-porous materials of droplets containing bacteria and viruses, using lab data, and modelling to understand the behaviour of droplet evaporation and its potential impact on different surfaces. • This data will have impact on efficacy assessment of antimicrobial surfaces, and of interest to those who design and manufacture as well as the end-users of such materials.

Marangoni convection instabilities in an evaporating droplet on a non-isothermal substrate

• The maximum number of LRs is smaller than that on the isothermal substrate • The instability patterns preferentially occur at the lower temperature side • LRs continuously propagate along azimuthal direction towards cold side • Propagation speed increases with increase of the temperature gradient • Critical contact angles for the onset of LRs decrease with increasing Ma The Marangoni convection instabilities are investigated in a sessile ethanol droplet as it evaporates on a non-isothermal substrate. The instability structures consistently, preferentially occur at the lower temperature side of substrate. Drifted by the azimuthal thermocapillary flow under externally imposed temperature gradient, the longitudinal rolls are found to propagate from the hot side to the cold side for the droplet, while a radial propagation of the BM cells directly from the cold side to the hot side along the droplet diameter occurs at the last period of evaporation process. The azimuthal propagation speed of longitudinal rolls increases with the increase of temperature gradient, but is independent of the mean temperature of the substrate. Effects of the mean temperature of substrate and the temperature gradient on the Marangoni instabilities are investigated, and the critical conditions for the onset of longitudinal rolls are determined.

A condition for spontaneous capillary flow in open microgrooves

In this work, we investigate the behaviour of liquids in symmetric open microgrooves and give a criterion for spontaneous capillary flow. To that end, we use a two-dimensional model and analyse the liquid morphologies minimizing the Gibbs energy of the system. We find that the condition of a flat liquid surface, which was hitherto assumed, is indeed the solution minimizing the Gibbs energy, so that it can safely be accepted to investigate whether open capillaries fill spontaneously. Furthermore, we find a condition for spontaneous capillary flow that depends on the cross-section of the channel alone. We use the findings to derive the critical contact angle, below which spontaneous capillary flow happens, for three examples including V-grooves, Gaussian grooves, and lenticular grooves.

Droplet and bubble wetting behaviors: The roles of surface wettability and roughness

Droplet and bubble wettability are important parameters for characterizing the wetting propensity of solid surface. Recent studies have shown significant differences between the wetting behaviors of droplet and bubble, specifically apparent contact angle (ACA) and contact angle hysteresis (CAH). However, very few studies have systematically investigated and examined the differences. Additionally, there is a lack of comprehensive knowledge and experimental observations about the effects of surface roughness on the droplet and bubble wetting behaviors under different wetting states. These knowledge gaps restrict our understanding of the wetting dynamic process. In this study, by varying surface roughness and modifying wettability with silane coupling agent KH-550, we evaluated droplet and bubble CAHs from strong hydrophilicity to hydrophobicity using a novel gas-driven method and the moving needle method, and analyzed the measurements using the friction force model. Young contact angle (YCA) was calculated to characterize the intrinsic wettability of three-phase system and experimental observations were interpreted in detail. The results show that the impact of roughness on droplet CAH varies in different wetting states caused by coupled effect between solid-liquid affinity and rough microstructure. A critical YCA for effective spreading is observed in bubble wetting behaviors for the first time, above which bubble ACA and CAH abruptly change. The increase of roughness reduces bubble ACA and CAH. With a critical Young contact angle as the turning point, the difference between droplet and bubble wetting behaviors as well as the effect of roughness vary. Additionally, after bubble fully spreads, its advancing angles are equal to droplet ACAs, and its ACAs are equal to droplet receding angles on relatively smooth surface. These intriguing findings are supplementary to current knowledge about droplet and bubble wetting behaviors.

Coalescence-Induced Bubble Departure: Effects of Dynamic Contact Angles.

Coalescence-induced bubble departure is a common phenomenon in boiling and gas evolution reactions, which has significant impacts on the heat/mass transport. In this work, we systematically investigate the effects of dynamic contact angles on the coalescence and departure processes of two equal-sized bubbles. A critical contact angle (θcr) of 76° is determined for an ideal surface on the basis of a surface energy analysis, beyond which the coalesced bubble does not depart from the wall. Using 3D multi-relaxation-time (MRT) lattice Boltzmann simulations, we demonstrate that the advancing contact angle mainly governs the movement of the outer side of the contact lines, and the increase of the advancing contact angle may delay or even prevent the departure of the coalesced bubble. On the other hand, the receding contact angle dominates the motion of the inner side of the contact lines, and the decrease of the receding contact angle facilitates the departure of the coalesced bubble. We identify a regime map for the coalescence-induced bubble departure with respect to the contact angles, which includes four regions: the all-departure region, the advancing contact angle dominated region, the receding contact angle dominated region, and the nondeparture region. Numerically simulated critical contact angles that separate the above-mentioned regions agree well with theoretical analyses. The results of this study will contribute to the manipulation of bubble behaviors and the optimal design of working surfaces in a variety of energy systems involving boiling and gas-evolving reaction processes.

Dynamic behavior of impinging drops on water repellent surfaces: Machine learning-assisted approach to predict maximum spreading

The study of drop dynamic undergoing collision with solid surfaces seems quite necessary due to its practical applications ranging from coating industries to anti-icing and self-cleaning surfaces. Therefore, we experimentally studied the dynamic of impinging drop on water-repellent surfaces for a wide range of drop properties and initial velocities in terms of weber number (We). We considered the maximum spreading diameter to quantify the spreading dynamic. We modified one of the existing energy-balance models to analytically predict the observed maximum spreading diameters. We showed that above a critical We number (roughly 60–80), the maximum spreading diameter of superhydrophobic surfaces starts to deviate from those of hydrophobic surfaces. Therefore, we incorporated an adjusting factor into the energy-balance model to consider the transition from hydrophobicity to superhydrophobicity. Moreover, we developed a machine learning approach to predict the maximum spreading diameter as a function of drop properties and surface characteristics. Using the machine learning approach, it was found that beyond a critical contact angle (CAadv ∼ 150°–160°) the maximum spreading diameter does not depend on the contact angle anymore. Moreover, for low We numbers, the maximum spreading diameter decrease with increasing the contact angle, while for high We numbers they are directly proportional.