Three-phase Contact Line Research Articles

Experiment of droplet anisotropic wetting behavior on micro-grooved PDMS membranes.

Wetting behavior of droplets on a substrate with micro-grooves plays a key role in super-hydrophobicity. This paper aims to study the influence of groove width, droplet size, and surface tension on the anisotropic wetting behavior of droplets on micro-grooved PDMS membranes. Three types of PDMS membranes are made by mold replication. Profiles of droplets along the circumferential direction are observed by HD camera, and the 3D model of the droplet is reconstructed. Capillary forces at the three-phase contact line are obtained using the surface tension integration method. Additionally, liquid's wetting depth within the micro-grooves is calculated using an interfacial free energy equilibrium approach. The experiment shows that the micro-grooved PDMS membrane has anisotropic constrain to droplets due to wetting depth change in micro-grooves. Meta-equilibrium states at the three-phase contact line are influenced not only by substrate free energy, but also by wetting depth, interface pressure, and substrate structure.

Tunable Topological Wetting State of Water Droplets on Planar Surfaces: Closed-Loop Chemical Heterogeneity by Design.

Understanding droplet wetting on surfaces has broad implications for surface science and engineering. Here, we report a joint theoretical/experimental study of the topological wetting states of water droplets on chemically heterogeneous closed-loop and planar surfaces. Interestingly, we provide both simulation and experimental evidence of biloop or even multiloop transition wetting states of water droplets. Specifically, in our molecular dynamics simulations, we designed surfaces patterned with alternating closed-loop superhydrophilic and hydrophobic nanobands. On these surfaces, we find that the contact shape and contact angle of water nanodroplets can be tailored by changing the shape of the nanobands. Overall, the contact angle of the droplets is dependent on the initial location of the water droplet, the interaction between the water molecules and hydrophobic particles, and the width of the superhydrophilic and hydrophobic nanobands. The wetting-state transition dynamics is also dependent on the nanoband shape. In the biloop or multiloop transition wetting states, the three-phase contact line is not limited to only one loop nanoband but can be located at two or more distinct loops. Guided by the simulation results, the corresponding experiments confirmed the presence of topological wetting states and multiloop wetting states on planar chemically heterogeneous surfaces with closed-loop microbands. Importantly, we provide an explanation of the mechanism of the topological wetting state formation and transition. Our study facilitates a deeper understanding of the droplet-surface interactions and offers an alternative way to tune the droplet shape and contact angle on planar surfaces by engineering chemically heterogeneous surface textures.

Photo-Induced liquid-based slippery materials for highly efficient particle aggregation

The drying of droplets containing non-volatile solutes presents significant potential for sensing applications, including disease diagnosis, and the detection of harmful substances. Colloidal droplets form various patterns on surfaces after evaporation, and controlling the deposited patterns to achieve the desired characteristics is crucial in sensing applications. In this study, we propose a novel approach that employs a slippery organogel (SOG) surface that can be rapidly fabricated based on a photo-induced process to enhance the sensitivity and reproducibility during detection. The SOG forms a thin lubricating layer on the surface, which reduces the pinning of the three-phase contact line, causing the aggregation of particles within a confined area. To analyze the aggregation characteristics of colloidal droplets on the SOG, we compared the deposited particles after evaporating four types of colloidal droplets on the following different surfaces: hydrophilic, hydrophobic, organogel (OG), and SOG. The SOG surface demonstrated a superior particle aggregation capability across various colloidal droplets, which is crucial for the future development of high-sensitivity detection technologies.

Effect of the advancing contact angle on coal particle–bubble detachment at the mesoscopic scale

Improving particle–bubble adhesion stability and reducing particle–bubble detachment are crucial in froth flotation processes. In this study, a nonequilibrium molecular dynamics approach is applied to investigate the dynamic detachment process of low-rank coal particles adhering with/without a collector from bubbles under different pull forces at the mesoscopic scale. Results indicate that a collector oil film on the surface of a low-rank coal particle can considerably increase the advancing contact angle and counteract the contraction of the three-phase contact line, enabling the particle to withstand a greater detachment force. Conversely, the residual water clusters on the particle surface tend to cause contraction of the contact line. Force analysis of the liquid surrounding the particle and the contact line indicates that the maximum static capillary force between the particle and the bubble is equivalent to the capillary force when the bending angle of the liquid surface reaches the advancing contact angle. When the bending angle of the liquid surface exceeds the forward contact angle, the force on the liquid around the contact line becomes unbalanced, causing the contact line to move to decrease the bending angle of the liquid surface and restore balance to the surrounding liquid. Hence, on mesoscopic scales of ten to tens of nanometers, the advancing contact angle still determines particle–bubble detachment. The study of particle–bubble detachment mechanisms at the mesoscopic scale is expected to establish a relation between microscopic mechanisms at the molecular scale and macroscopic experimental studies at the micrometer to millimeter scale

Coating flow of a liquid film with colloidal particles on a vertical fiber

A thin liquid film of colloidal suspension is considered which is spreading down on a vertical cylinder under the effect of gravity. A precursor film model is employed at the three-phase contact line to relieve the stress singularity. The curvature pressure leads to the formation of a capillary ridge at the contact-line. Bulk and surface colloids are assumed to be present in the liquid film. The interfacial pattern is governed by the film evolution equation, obtained by simplifying mass and momentum balance equations within the lubrication assumption, while rapid vertical diffusion is assumed for the advection–diffusion equation of the bulk concentration. Fluid viscosity and diffusivity are considered to be functions of the particle volume fraction. The effects of the bulk and surface colloids on the spreading film dynamics are systematically studied. The presence of bulk colloids leads to the thinning of the capillary ridge for smaller inlet bulk colloid concentrations. On the other hand, a larger inlet bulk concentration leads to the formation of a secondary advancing front behind the capillary ridge in the film profile. A reduced contact point velocity is observed with an increase in the upstream bulk concentration. Surface concentration is found to result in a hump-like structure behind the capillary ridge in the upstream direction due to solutal Marangoni stress. The Marangoni stress also hinders the surface-tension-driven spreading, resulting in a smaller contact line velocity. Reducing the Bond number results in unstable film profiles, which lead to a wave-like structure in the region with no bulk concentration gradients.

Precursor-film-driven ultra-early depinning of the three-phase contact line

Hypothesis: Despite its importance in colloid and interface science, contact line pinning remains poorly understood, especially in the presence of a precursor film. We hypothesized that this is due to a lack of an experimental method capable of directly observing their physics at the nanoscale. MethodsUsing coherence scanning interferometry, we visualized the three-dimensional behavior of contact lines with a precursor film near a nanogroove structure composed of flat terrace surfaces and steps with an inclination angle of 30° while achieving nanoscale vertical resolution. FindingsWe found that even when the contact line is pinned at the edge of the step, the precursor film is not and advances beyond the edge. Furthermore, we discovered that the precursor film has two distinct effects on contact line motion. Specifically, the precursor film facilitates depinning when the contact line descends the step — a contact angle change was 0.9°, only 3.0% of the value predicted by a classical theory of contact angle at a solid edge. This ultra-early depinning is attributed to the formation of a new liquid film past the edge, driven by the progression of the precursor film that overcomes the pinning effect. In contrast, when the contact line ascends the step, the precursor film acts as a resistance to movement due to steric interaction.

Exceptional anisotropic superhydrophobicity of sword-lily striated leaf surface and soft lithographic biomimicking using polystyrene replica

Herein, we report unusually high anisotropic superhydrophobicity, unidirectional self-cleaning, and biomimicking of adaxial sword-lily (Gladiolus hortulanus) leaf comprising three distinct levels of surface textures. Observably, the static anisotropic wetting and rolling of water droplets are more favourable in the parallel (or, striation) direction than in the perpendicular direction. Inspired from such water repellency of the sword lily leaf surface, here bio-mimicked polystyrene (PS) leaf construct is developed through a soft lithographic technique. Considering different water droplet sizes (4–10 μl) on natural lily leaf and bio-mimicked PS construct surfaces, the respective parallel (θ ||) and perpendicular (θ ⊥) water contact angles (WCAs) stand at, θ || ∼143°–147°, θ ⊥ ∼156°–169°; and θ || ∼130°–139°, θ ⊥ ∼142°–145°. Moreover, the specimens under study exhibit roll-off angles ranging, α || ∼8°–23° (α ⊥ ∼16°–41°) and α || ∼21°–49° (α ⊥ ∼40°–55°) along parallel (and perpendicular) directions; respectively. A noticeable difference in α ⊥ and α || values can be ascribed to the profound three-phase contact line (TCL) pinning along the perpendicular direction taking advantage of striation as means of barrier. The roll-off angles can also alter due to a variation in the droplet volume. The unusual anisotropic superhydrophobicity and unidirectional droplet roll-off can be attributed to the entrapped air within the micro-nano texture beneath the water droplet along with the pinning effect in the perpendicular direction caused by the striated heights.

Pore-Scale Simulation of the Effect of Wettability Alteration on Flow Transport Kinetics in 3D Natural Porous Media

Summary Wettability alteration commonly occurs in subsurface two-phase displacements, such as enhanced hydrocarbon recovery, hydrogen storage, and carbon dioxide sequestration. A comprehensive understanding of two-phase flow transport kinetics during wettability alteration in natural rocks is essential for optimizing these processes. To address this, a wettability alteration model induced by low-salinity waterflooding (LSWF) was implemented based on the volume of fluid (VOF) method and the compressive continuous species transfer (C-CST) method in the OpenFOAM platform, which integrates the pore-scale two-phase fluid flow and the advection-diffusion of species. Following validation against experimental data from existing literature, extensive direct numerical simulations (DNSs) were conducted in an actual 3D sandstone sample obtained by microcomputed tomography (micro-CT) images. The effects of the wettability alteration degree, wettability alteration model, and capillary number on dynamic salt dispersion and fluid redistribution are considered in simulation works. The findings indicate that a higher wettability alteration degree facilitates the release of more oil trapped in smaller pores toward the outlet, while the mobilized oil might become trapped again due to snap-off in larger downstream pores. Moreover, due to the presence of alternative flow pathways in the system, the backflowed oil induced by heterogeneous salinity distribution might not be effectively recovered. A faster wettability alteration rate enhances the performance of LSWF because of the rapid reduction of entry capillary pressure and the delayed negative effect of salt dispersion. In terms of the capillary number, a higher capillary number accelerates the diffusion of species to the three-phase contact line and reduces the occurrence of snap-off retrapping, thereby increasing ultimate oil recovery. This study contributes to a deeper understanding of the microscopic displacement mechanism during the wettability alteration processes, especially for LSWF, in 3D heterogeneous porous media.

Three-dimensional mesoscopic investigation of directional coalescence of two droplets impacting on a wall with wettability difference

In this work, a three-dimensional (3D) nonorthogonal pseudopotential lattice Boltzmann method (LBM) was proposed to investigate the coalescence dynamics of two droplets impacting on a wall with wettability difference. The influences of the wettability difference, Weber number, offset distance on the low-wettability side on the coalescence dynamics and the contact-line evolution processes were systematically examined. Both symmetric and asymmetric distributions of the droplet-coalescence behaviors were considered. Our findings reveal that the wettability difference has a significant influence on the asymmetric-retracting and wetting-equilibrium stages, identifying three modes: pin-slip, slip and no-rebound, and slip and rebound. The rebound time is dominated by the high-wettability wall. At a larger Weber number, droplets exhibit a large retracting velocity, which results in increased pumping velocity and earlier rebound time. In addition, a dramatic retraction of the three-phase contact line (TPCL) on the low-wettability wall is observed, leading to the detachment of the liquid bridge from the low-wettability wall, and the formation of a cavity. With increasing offset distance on the low-wettability wall, three different evolution modes are found: coalescence-rebound, coalescence-separation, and non-coalescence. A power function relationship is reported between the Weber number We and the offset distance L* both on the high-wettability wall and low-wettability wall for three modes of coalescence behavior with We∼L*α. The value of the exponent α ranges from 4.6 to 7.4. This study showcases the effectiveness of the 3D nonorthogonal pseudopotential LBM in predicting the complex interface phenomena and characteristics of the multiphase flow structures under investigation.

Physical modeling of conjugate heat transfer for multiregion and multiphase systems with the Volume-of-Fluid method

AbstractThe Volume-of-Fluid (VOF) method is commonly used for numerical simulations of phase change phenomena, such as nucleate boiling or droplet evaporation. A key issue with the standard VOF method is the averaging of the liquid and vapor properties in interface cells, which causes non-physical conjugate heat transfer with a solid wall. Therefore, we aim at a physical model for conjugate heat transfer between a solid and a multiphase fluid. The first measure for higher quality simulations is the splitting of the single temperature field in the fluid region into separate liquid and vapor temperature fields. The second measure is the development of a new, more physical temperature boundary condition for conjugate heat transfer between a solid region and a multiphase fluid, based on experimental results, theoretical models and theoretical considerations. In interface cells, the vapor phase is excluded from the conjugate heat transfer because only heat transfer to the liquid phase occurs resp. dominates. Additionally, the conjugate heat transfer between solid and liquid in the interface cells is performed with virtual subcells, depending on the respective volume fraction of the liquid phase. This new approach (we name it distinctive approach) is successfully validated for energy conservation, and stability issues are discussed for the first time. Significant differences to simulations with averaged properties are observed due to the (now) physically correct modeling of conjugate heat transfer. In our boiling cases, the more accurate numerical simulations lead to considerably larger bubble growth rates. Higher quality simulations are also expected for nearly all applications, where there is a three-phase contact line, be it vapor bubbles in nucleate boiling or droplets impacting on a heated surface.

Theoretical model of dynamics and stability of nanobubbles on heterogeneous surfaces

Surface nanobubbles have revealed a new mechanism of gas–liquid–solid interaction at the nanoscale; however, the nanobubble evolution on real substrates is still veiled, because the experimental observation of contact line motions at the nanoscale is too difficult. HypothesisThis study proposes a theoretical model to describe the dynamics and stability of nanobubbles on heterogeneous substrates. It simultaneously considers the diffusive equilibrium of the liquid–gas interface and the mechanical equilibrium at the contact line, and introduces a surface energy function to express the substrate’s heterogeneity. ValidationThe present model unifies the nanoscale stability and the microscale instability of surface bubbles. The theoretical predictions are highly consistent to the nanobubble morphology on heterogeneous surfaces observed in experiments. As the nanobubbles grow, a lower Laplace pressure leads to weaker gas adsorption, and the mechanical equilibrium can eventually revert to the classical Young-Laplace equation above microscale. FindingsThe analysis results indicate that both the decrease in substrate surface energy and the increase in gas oversaturation are more conducive to the nucleation and growth of surface nanobubbles, leading to larger stable sizes. The larger surface energy barriers result in the stronger pinning, which is beneficial for achieving stability of the pinned bubbles. The present model is able to reproduce the continual behaviors of the three-phase contact line during the nanobubble evolution, e.g., “pinning, depinning, slipping and jumping” induced by the nanoscale defects.

Effect of turbulence on the detachment between an air bubble and a glass bead with different hydrophobicity: Experiments and simulations

The effect of turbulence on the detachment between an air bubble and a glass bead (soda-lime) with different hydrophobicity was comprehensively researched. An experimental apparatus was designed to simulate the turbulent environment during the actual flotation process, which was used to research the detachment of different hydrophobic glass beads from bubble surfaces. It is indicated that three different hydrophobic glass beads detached from the bubble surfaces in the same way but at different speeds. The three-phase contact line (TPCL) shrank rapidly when the centrifugal detachment force of glass beads reached a critical value. The deformation of bubbles increased, and the three-phase contact (TPC) area continuously decreased. When the critical value was exceeded, the sliding and contraction speed around the TPCL further increased until a clear necking phenomena appeared near the TPC. Furthermore, the centrifugal detachment force, capillary force and total pressure force increased with increasing hydrophobicity in the detachment process.

Marine biofouling mitigation of PDMS-based network coating with cross-linked contact- and release-active organoalkoxysilane

Poly (dimethylsiloxane) (PDMS) elastomer is one of key polymer resins for fouling release (FR) coatings, but it shows extremely poor antifouling (AF) activity in seawater since bacteria and diatoms could readily attach to surface. Modifying PDMS-based coatings via incorporating antifouling additives is effective for enhancing overall FR and AF activity. In this work, we prepared a well-defined organoalkoxysilane coating additive with quaternary ammonium and benzoisothiazolinone pendent groups, and the synthesized copolymers were covalently conjugated onto PDMS network in a one-pot reaction. AF and FR activities of the modified PDMS coatings were studied against soft fouling microorganisms. When microorganisms come into contact the coating surface, contact-active action mode works, quaternary ammonium groups could cause bacteria cell membrane disruption and microalgae photosynthesize inhibition via positive charge. Unexpectedly, a surprisingly lasting antimicrobial efficiency could be still observed in the neighboring coating, even the top-surface was completely covered with bacteria biofilm. Chemically conjugated benzoisothiazolinone could be sustainably released via side-group hydrolysis, thus, repelling and preventing the planktonic foulings from approaching the coating surface via release-active action mode. The modified PDMS coating with dual antifouling action modes could inhibit the biofilm formation at solid-liquid-air three-phase contact line, and could find valuable applications in marine transportation, water treatment and other antifouling fields.

Enhancing extinguishing efficiency for lithium-ion battery fire: Investigating the extinguishing mechanism and surface/interfacial activity of F-500 microcapsule extinguishing agent

Due to the high flammability and combustion enthalpy, electrolyte solvents such as dimethyl carbonate (DMC) are regarded as the main fuel in combustion reactions for lithium-ion batteries (LIBs). Herein, to understand the combustion reaction kinetics of LIB fires and explore the efficient extinguishing agent, the chemical oxidation kinetics of DMC at 740–1160 K are studied through a jet-stirred reactor system coupled to the synchrotron vacuum ultraviolet photoionization mass spectrometry and GC. The major consumption path of DMC is the H-abstraction reaction of OH∙ and H∙ radicals. CH3∙ radicals produce to CH4, C2H4 and other common alkane gases in LIB fires through H-abstraction reactions and compound reaction. On this basis, the extinguishing mechanism of F-500 extinguishing agent for LIB fires is studied. The hydrophilic (-[CH2-CH2-O]5) and oleophilic ([C16H33]-) groups give F-500 molecules the amphiphilic characteristics of adsorbing on the solution surface and associating inside the solution to form micelles. Based on the results of dynamic light scattering and cryo-electron microscopy, the size and number of micelles continue to increase and the structure of micelles gradually changes from spherical to rod-shaped, which enhance the solubilization effect. F-500 can strengthen the extinguishing effectiveness of water mist by capturing and encapsulating the DMC inside the water to form “DMC-F-500-Water” microcapsule. DMC is dispersed in the water, which leads to the heat loss and the reduction of concentration and flammability. Moreover, the adsorption of F-500 molecules along the solid-liquid-gas three-phase contact line can reduce the interfacial tension of water and promote wetting process, which leads to the larger spreading area and speed of evaporation. During the application of the extinguishing agent, F-500 agent can improve the cooling efficiency of water. This work provides a reference for the design and development of novel extinguishing agent for LIB fires.

Scaling laws of droplets on vibrating liquid-infused surfaces

Droplets oscillating on vibrating substrates are very interesting scientifically, with applications such as anti-icing, droplet transportation, and measuring dynamic surface tension. Reported here are the dynamics of droplets with different volumes on a vibrating smooth surface infused with liquid of different viscosities. The movement of the three-phase droplet contact line is used to quantify the droplet dynamics, and it is found that this movement is linearly proportional to the amplitude of the substrate and inversely proportional to the viscosity of the liquid infused therein. When the substrate viscosity is relatively low, the droplet volume also affects the contact-line movement. Scaling laws for the contact-line movement are derived involving the Ohnesorge number and the reciprocal of the capillary number. Also elucidated is the relationship between the resonance frequency and the substrate viscosity, and the characteristic droplet morphology under different substrate viscosities is extracted to describe the contact-line movement. Interestingly, the substrate viscosity is controlled in an innovative way to achieve almost the same contact-line movement on the present surface as on superhydrophobic and hydrophilic surfaces.

Driving waveform optimization of electrowetting displays based on pixel's 2-D model for reducing oil reflux.

Electrowetting displays (EWD) are believed to represent a new generation of electronic paper technology with fast responses, high reflectivity, and low power consumption. Despite their bright market prospects, the luminance stability of displays is still hindered by oil film reflux. So, we presented a combination of simulation and experimentation to enhance the performance of EWD. Firstly, an EWD simulation model was established using the phase field method (PFM). To ensure the accuracy of the model, it was proposed that the use of velocity field parameters could suppress mass non-conservation. During a 10-second simulation process, the total mass decreased by only 7.94x10-6%. Furthermore, the charge accumulation field was introduced to simulate oil film reflux. For the 5-second simulation, the maximum charge accumulation in the DC driving waveform was 2.61x10-5C/m2. Meanwhile, it was demonstrated that the AC driving waveform reduced charge accumulation in the three-phase contact line (TPCL) by 7.62% compared to the DC driving waveform. Based on this simulation model, a driving waveform was proposed, which included a driving waveform with a gradient changing waveform to achieve fast opening, and an alternating current (AC) driving waveform stage to inhibit the charge accumulation. The experimental results indicated that the maximum luminance fluctuation was 8.82, and the luminance data variance was 3.34 by using the proposed driving waveform. Compared to the traditional waveform, the response time was improved by 75.9%, the luminance was improved by 4.70%, and the luminance fluctuation stability improved by 79.34%.

Enhanced CHF of pool boiling and its predictive correlation for heterogeneous distributed composite microstructured surfaces with microcavities on micro-pin-fins

In the present study, several heterogeneous distributed composite microstructured surfaces (HDCMs) with different geometry parameters were prepared. The effect of the widths of the composite microstructured region, the widths of the smooth channels, the pitch of the micro-pin-fins, and the porosity of the surfaces on the pool boiling performance in HFE-7100 was examined under different liquid subcoolings. During the experiments, the three-phase contact lines of bubbles can be restricted by composite microstructured regions. Thus, reasonable geometry parameters can further enhance the liquid supply, promoting pool boiling heat transfer performance. The maximum critical heat flux of the HDCM is 14.1 % higher than that of the uniformly distributed composite microstructured surface (UDCM). Considering the effects of subcooled Jakob number (Jasub), composite microstructured region density number (SD), capillary resistance number (CR), and porosity (φ) on the critical heat flux (CHF) of HDCMs, an empirical correlation predicted the CHF for DCMs with different geometry parameters was proposed. The prediction results meet well with the experimental data, with an error within ±15 %.

Instability and breakup of rayleigh-plateau jets with capillary wave induced by electrowetting-on-dielectric

This paper discusses the lateral disturbances of vertical liquid flow enhancement using electrowetting-on-dielectric (EWOD) technique, which effectively reducing the breakup length of the liquid flow and minimizing the formation of satellite droplets. The EWOD technology is characterized by its minimal space occupation and low energy consumption. The successful implementation of the EWOD phenomenon relies on the formation of a three-phase contact line (TPCL) between the electrodes and the liquid, and the novel EWOD tube structure design provides an extended TPCL, enhancing the amplitude of capillary waves. Through experimental and theoretical analysis, this paper identifies key parameters affecting the liquid breakup process, such as the gap depth, angle of the EWOD tube, EWOD voltage amplitude, and frequency of the AC electrical signal. The research results indicate that the proposed EWOD tube responds rapidly and can consistently and stably manage liquid breakup and reduce the number of satellite droplets.

On-Demand Transport Bubbles Adhering to Noncontiguous Patterned Superhydrophobic Surfaces Using a Superhydrophobic Tweezer.

Bubble transportation and related flotation are ubiquitous phenomena in nature and industry. Various surfaces with distinct morphologies and specific wettability properties have been engineered by organisms in nature and by humans to facilitate the targeted movement of bubbles. However, existing methods predominantly rely on continuous surfaces, limiting the ability of bubbles to deviate from their path before reaching their intended destination. Therefore, directional transportation of bubbles using noncontiguous surfaces still remains a significant challenge. Inspired by water spiders' ability to capture bubbles underwater using their hydrophobic surface for survival, we propose a novel transport strategy that utilizes patterned superhydrophobic surfaces (PSHSs) and a superhydrophobic tweezer. This strategy is implemented by switching between the hood mode and puncture mode of the moving three-phase contact lines to load and unload the bubble. To quantitatively evaluate the loss ratio of the bubble during transportation, a simple and exquisite bubble-weighing apparatus is devised. Our findings indicate that circular PSHSs demonstrate superior bubble adhesion and achieve the highest bubble transport ratio of 95.1%. In order to validate the promising application of this novel method, we employ the computer numerical control (CNC) technology to facilitate the autonomous loading and precise transportation of underwater bubbles, as well as the blending and ionization of combustible gas bubbles with air bubbles at different volume ratios.

Suppressing the Leidenfrost effect by air discharge assisted electrowetting-on-dielectrics

The Leidenfrost effect for a droplet on an over-heated substrate always results in a superhydrophobic state, significantly hindering the water evaporation for heat dissipation. Here, we demonstrate a strategy of air discharge assisted electrowetting-on-dielectrics (ADA-EWOD), overcoming this challenge. This strategy increases the solid surface free energy by generating air discharge near the three-phase contact line of the droplet and combines it with the electromechanical force to decrease the contact angle, which makes ADA-EWOD have stronger wetting capabilities than traditional electrically control methods that only rely on electromechanical force. The water contact angle on an over-heated surface (above 350 °C) is decreased from nearly 180° down to less than 10°. This superhydrophilicity at high temperature reduces the droplet lifetime by at least 10 times, well inhabiting the Leidenfrost effect. Furthermore, we use ADA-EWOD in droplet evaporation for heat dissipation, where a heated silicon wafer at 600 °C is cooled down to less than 200 °C within 20 s. We believe that the present work provides a perspective on suppressing the Leidenfrost effect, which may have important potential applications in the field of heat dissipation.