Many-body Dissipative Particle Dynamics Simulations Research Articles

Channel width-dependent viscosity and slip length in nanoslits and effect of surface wettability

The channel width-dependent behaviors of viscosity (μ) and slip length (ls) in nanoslits are investigated using many-body dissipative particle dynamics simulation in both Poiseuille and Couette flow systems. In both systems, the viscosity and slip length increase as the channel width (w) grows in smaller channels, while they reach bulk values in larger channels. Moreover, as the surface wettability decreases, the slip length is found to increase, while the viscosity remains the same. The channel width-dependent behavior in nanoslits can be explained by the unique structure of the confined fluid. As the channel width narrows, the uniform density profile in the central region diminishes, and an oscillation pattern appears throughout the system. The change in the microstructure with the channel width alters friction between layers of fluid in laminar flow and fluid-solid friction, leading to a w-dependent μ and ls. Nonetheless, the alteration of surface wettability influences only fluid–solid interactions but not the friction between layers of fluid.

Characterization of partial wetting by CMAS droplets using multiphase many-body dissipative particle dynamics and data-driven discovery based on PINNs

The molten sand that is a mixture of calcia, magnesia, alumina and silicate, known as CMAS, is characterized by its high viscosity, density and surface tension. The unique properties of CMAS make it a challenging material to deal with in high-temperature applications, requiring innovative solutions and materials to prevent its buildup and damage to critical equipment. Here, we use multiphase many-body dissipative particle dynamics simulations to study the wetting dynamics of highly viscous molten CMAS droplets. The simulations are performed in three dimensions, with varying initial droplet sizes and equilibrium contact angles. We propose a parametric ordinary differential equation (ODE) that captures the spreading radius behaviour of the CMAS droplets. The ODE parameters are then identified based on the physics-informed neural network (PINN) framework. Subsequently, the closed-form dependency of parameter values found by the PINN on the initial radii and contact angles are given using symbolic regression. Finally, we employ Bayesian PINNs (B-PINNs) to assess and quantify the uncertainty associated with the discovered parameters. In brief, this study provides insight into spreading dynamics of CMAS droplets by fusing simple parametric ODE modelling and state-of-the-art machine-learning techniques.

Many-body dissipative particle dynamics simulations of micellization of sodium alkyl sulfates.

We present a study of micelle formation in alkyl sulfate surfactants using the simulation method of many-body dissipative particle dynamics (MDPD). We parametrise our model by tuning the intermolecular interactions in order to reproduce experimental values for the chemical potential and density at room temperature. Using this approach, we find that our model shows good agreement with experimental values for the critical micelle concentration (CMC). Furthermore, we show that our model can accurately predict CMC trends, which result from varying properties such as surfactant tail length and the salt concentration. We apply our model to investigate the effect of aggregation number on various micellar properties, such as the shape of individual micelles and the fraction of bound counterions. We show that micelles become aspherical at large aggregation numbers, in line with experimental predictions, and that longer tail surfactants are generally more spherical at all aggregation numbers compared to those which are shorter. We find excellent agreement between our simulations and experimental values for the degree of counterion binding, a factor that is crucial to accurately studying micellar shape, but one that is typically overlooked in the existing literature.

Sliding motion of highly deformed droplets on smooth and rough surfaces: Shape oscillation, chaotic breakage, corner shape, and pearling

The sliding behavior of droplets on smooth and rough surfaces with various surface wettabilities is investigated by many-body dissipative particle dynamics simulations. On a smooth surface, as the driving force (Bo) increases, the droplet shape and velocity (Cac) before breakage can be classified into four distinct regimes: (I) nearly spherical cap with Cac∝Bo; (II) oval shape with negative deviation from the linear relation; (III) elongated shape without a neck, where Cac decreases with increasing Bo; and (IV) oscillation of an elongated shape with fluctuating sliding velocity. On rough surfaces, corner-shaped droplets, which are absent on a smooth surface, can be observed. A further increase in Bo leads to the formation of cusp and pearling. Different from pinching-off on rough surfaces, which produces a cascade of smaller droplets through groove-induced shedding, chaotic breakage of a droplet on a smooth surface is caused by an unsteady flow field. Finally, a universal linear relationship between the sliding velocity based on the surface velocity (Cas) and the modified driving force (Bo**) is derived to take into account the effects of surface wettability and roughness.

Two local slip modes at the liquid–liquid interface over liquid-infused surfaces

A liquid–liquid interface (LLI) at liquid-infused surfaces (LISs) plays a significant role in promoting slip flow and reducing frictional drag. By employing the transverse many-body dissipative particle dynamics simulations, the behavior of local and effective slip at a flat LLI for shear flows over periodically grooved LISs has been studied. With increasing viscosity ratio between the working fluid and lubricant fluid, two local slip modes are identified. For a small viscosity ratio, the local slip length remains finite along the LLI, while a hybrid local slip boundary condition holds along the LLI for large viscosity ratios, i.e., the local slip length is finite near the groove edge and unbounded in the central region of the LLI. The vortical flow inside the groove can be enhanced by increasing viscosity ratio due to the change in the local slip mode from the finite state to the hybrid one. Moreover, the results suggest two scenarios for the variation of the effective slippage. For LISs with a large LLI fraction, the effective slip length increases significantly with increasing viscosity ratio, while for a small LLI fraction, the effective slippage is rather insensitive to the viscosity ratio. The underlying mechanism for the relationship between the effective slip length and the viscosity ratio for different LLI fractions is revealed based on the two slip modes. These results elucidate the effect of LLI on slip boundary conditions and might serve as a guide for the optimal design of LISs with enhanced slip properties.

In Situ Liquid Phase TEM of Nanoparticle Formation and Diffusion in a Phase-Separated Medium.

Colloidal nanoparticles are synthesized in a complex reaction mixture that has an inhomogeneous chemical environment induced by local phase separation of the medium. Nanoparticle syntheses based on micelles, emulsions, flow of different fluids, injection of ionic precursors in organic solvents, and mixing the metal organic phase of precursors with an aqueous phase of reducing agents are well established. However, the formation mechanism of nanoparticles in the phase-separated medium is not well understood because of the complexity originating from the presence of phase boundaries as well as nonuniform chemical species, concentrations, and viscosity in different phases. Herein, we investigate the formation mechanism and diffusion of silver nanoparticles in a phase-separated medium by using liquid phase transmission electron microscopy and many-body dissipative particle dynamics simulations. A quantitative analysis of the individual growth trajectories reveals that a large portion of silver nanoparticles nucleate and grow rapidly at the phase boundaries, where metal ion precursors and reducing agents from the two separated phases react to form monomers. The results suggest that the motion of the silver nanoparticles at the interfaces is highly affected by the interaction with polymers and exhibits superdiffusive dynamics because of the polymer relaxation.

Transverse effect on liquid viscosity: A many-body dissipative particle dynamics simulation study

Fluid viscosity plays an important role in multiphase flows, and the many-body dissipative particle dynamics (MDPD) method is an efficient means of simulating such flows at the mesoscopic scale. As the viscosity of the standard MDPD (S-MDPD) fluid cannot be efficiently adjusted, a transverse MDPD (T-MDPD) scheme is newly proposed to tune the viscosity of an MDPD fluid over a large range. With a lateral friction coefficient added to the S-MDPD form, the viscosity of the T-MDPD fluid is higher than that of an S-MDPD fluid, and the viscosity is about five times larger than that of an S-MDPD fluid with a friction coefficient of 40.5. In a T-MDPD fluid, the viscosity is much more sensitive to the new transverse friction coefficient, as it increases about five times higher when this coefficient increases from 4.5 to 40.5, while the viscosity only increases two times higher with the same variation of the original coefficient. By increasing the repulsive coefficient, the liquid particle number density, or the cutoff radius, the viscosity of the T-MDPD fluid is enhanced as well. Based on this extension of the MDPD scheme, a quantitative expression for the variation of the viscosity in the current T-MDPD fluid is derived. In future simulations of multiphase flows using an MDPD scheme, the transverse effect can be extended to effectively tune the viscosity, and this empirical expression will be useful to predict the viscosity of the T-MDPD fluid.

Influence of hydrophobicity and roughness on the wetting and flow resistance of water droplets on solid surface: A many-body dissipative particle dynamics study

Hydrophobicity and roughness are crucial properties for determining rock wetting and flow resistance. The wetting and flow behavior of water droplets on smooth and rough solid surfaces are investigated by performing a many-body dissipative particle dynamics simulation. The results show that, in terms of the roughness, a solid surface can be divided into three regions. In Region I, as inherent hydrophobicity increases, roughness can enhance the apparent hydrophilicity of a hydrophilic surface. In Region II, the increased hydrophobicity improves the apparent hydrophobicity of a more hydrophobic surface. In Region III, when the hydrophobicity is beyond the superhydrophobic boundary, the enhancement effect of the rough surface on the apparent hydrophobicity is weakened or even disappears. With an increase in the roughness, the boundaries among these three regions and their ranges show nonmonotonic changes, making the contact mode (Wenzel state/Cassie and Baxter state), contact angle hysteresis and drag reduction effect change nonmonotonically.

Flow reduction of hydrocarbon liquid in silica nanochannel: Insight from many-body dissipative particle dynamics simulations

A modified many-body dissipative particle dynamics (mDPD) model recently developed for realistic mesoscale multiphase flow simulations is rigorously parameterized, calibrated, and applied for elucidating the flow mechanisms of hydrocarbon liquids (i.e., heptane in this work) in amorphous silica cylindrical nanochannels with inner diameters ranging from 4.5 to 22.5 nm. The simulation results suggest the presence of a strong threshold of pressure gradient under which heptane cannot be driven to flow. The threshold for the 4.5 nm diameter pore is 10 to 100 times as high as for the 9–22.5 nm diameter pore, highlighting a remarkable nanoconfinement effect. Fluid viscosity is found to exhibit a shear-thinning phenomenon with intensity to weaken with increasing channel diameter — a phenomenon not observed in nanochannel flow of liquid water and gas in literature. Most remarkably, the radial profiles of average longitudinal flow velocity fitted by the modified Hagen-Poiseuille equation showed a negative slip length (−2.5% to −0.5% relative to the diameter) and a reduction of apparent permeability by 16% to 23%. This finding suggests silica nanochannels tend to deter hydrocarbon flow, a phenomenon that is opposed to the flow enhancement reported in most of the prior nanochannel flow studies in literature.

Interfacial behavior of phospholipid monolayers revealed by mesoscopic simulation

A mesoscopic model with molecular resolution is presented for dipalmitoyl phosphatidylcholine (DPPC) and palmitoyl oleoyl phosphatidylcholine (POPC) monolayer simulations at the air-water interface using many-body dissipative particle dynamics (MDPD). The parameterization scheme is rigorously based on reproducing the physical properties of water and alkane and the interfacial property of the phospholipid monolayer by comparison with experimental results. Using much less computing cost, these MDPD simulations yield a similar surface pressure-area isotherm as well as similar pressure-related morphologies as all-atom simulations and experiments. Moreover, the compressibility modulus, order parameter of lipid tails, and thickness of the phospholipid monolayer are quantitatively in line with the all-atom simulations and experiments. This model also captures the sensitive changes in the pressure-area isotherms of mixed DPPC/POPC monolayers with altered mixing ratios, indicating that the model is promising for applications with complex natural phospholipid monolayers. These results demonstrate a significant improvement of quantitative phospholipid monolayer simulations over previous coarse-grained models.

Many-body dissipative particle dynamics study of the local slippage over superhydrophobic surfaces

The gas–liquid interface (GLI) over superhydrophobic surfaces (SHSs), where the flow slips, is the key to reduce frictional drag in underwater applications. Many-body dissipative particle dynamics simulations are used to explore the slip behavior of a shear flow over a rectangular grooved SHS, and a flat GLI is obtained by tuning the contact angle of the GLI. Due to the slip, the normal profiles of the local velocity, which are perpendicular to the GLI, are curved and shifted away from the linear form near the GLI. Then, a polynomial function is proposed to fit the velocity profile to extract the local shear rate and calculate the slip length. Based on this fitting method, a hybrid slip boundary condition is derived for both longitudinal and transverse flows. That is, the shear stress and slip length are finite near the groove edge, and the stress is nearly zero and the slip length is infinite in the center region of the GLI. This new hybrid slip boundary condition not only explains the inconsistent slip conditions reported in the literature under different groove length scales, but also unifies the existing exclusive slip assumptions.

Molecular View of the Distortion and Pinning Force of a Receding Contact Line: Impact of the Nanocavity Geometry.

We present a molecular view using many-body dissipative particle dynamics simulations to unravel the pinning phenomenon of a liquid film receding over a solid substrate with a nanocavity. We find that the pinning force and distortion of the pinned contact line vary across different nanocavity shapes. We show that the mechanism of a caterpillar motion, which has previously been proposed for advancing precursor films, persists in a partially pinned receding contact line. Our results also demonstrate a localized clamping effect, which is originated from the variation of the dynamic contact angle along the pinned contact line. The simulation results suggest that the clamping effect can be controlled by the geometry of the nanocavity and hydrophilicity of the underlying substrate.

Mechanisms of Nucleation and Solid-Solid-Phase Transitions in Triblock Janus Assemblies.

A model, including the chemical details of core nanoparticles as well as explicit surface charges and hydrophobic patches, of triblock Janus particles is employed to simulate nucleation and solid-solid phase transitions in two-dimensional layers. An explicit solvent and a substrate are included in the model, and hydrodynamic and many-body interactions were taken into account within many-body dissipative particle dynamics simulation. In order not to impose a mechanism a priori, we performed free (unbiased) simulations, leaving the system the freedom to choose its own pathways. In agreement with the experiment and previous biased simulations, a two-step mechanism for the nucleation of a kagome lattice from solution was detected. However, a distinct feature of the present unbiased versus biased simulations is that multiple nuclei emerge from the solution; upon their growth, the aligned and misaligned facets at the grain boundaries are introduced into the system. The liquid-like particles trapped between the neighboring nuclei connect them together. A mismatch in the symmetry planes of neighboring nuclei hinders the growth of less stable (smaller) nuclei. Unification of such nuclei at the grain boundaries of misaligned facets obeys a two-step mechanism: melting of the smaller nuclei, followed by subsequent nucleation of liquid-like particles at the interface of bigger neighboring nuclei. Besides, multiple postcritical nuclei are formed in the simulation box; the growth of some of which stops due to introduction of a strain in the system. Such an incomplete nucleation/growth mechanism is in complete agreement with the recent experiments. The solid-solid (hexagonal-to-kagome) phase transition, at weak superheatings, obeys a two-step mechanism: a slower step (formation of a liquid droplet), followed by a faster step (nucleation of kagome from the liquid droplet).

Stability of pinned surface nanobubbles against expansion: Insights from theory and simulation

While growth and dissolution of surface nanobubbles have been widely studied in recent years, their stability under pressure changes or a temperature increase has not received the same level of scrutiny. Here, we present theoretical predictions based on classical theory for pressure and temperature thresholds (pc and Tc) at which unstable growth occurs for the case of air nanobubbles on a solid surface in water. We show that bubbles subjected to pinning have much lower pc and higher Tc compared to both unpinned and bulk bubbles of similar size, indicating that pinned bubbles can withstand a larger tensile stress (negative pressure) and higher temperatures. The values of pc and Tc obtained from many-body dissipative particle dynamics simulations of quasi-two-dimensional (quasi-2D) surface nanobubbles are consistent with the theoretical predictions, provided that the lateral expansion during growth is taken into account. This suggests that the modified classical thermodynamic description is valid for pinned bubbles as small as several nanometers. While some discrepancies still exist between our theoretical results and previous experiments, further experimental data are needed before a comprehensive understanding of the stability of surface nanobubbles can be achieved.

Size-dependent behavior and failure of young’s equation for wetting of two-component nanodroplets

HypothesisFor macroscopic systems, the interfacial properties are size-independent and Young’s equation is generally valid for smooth substrates. For nanoscale systems, however, size-dependence and failure of Young’s equation may emerge. ExperimentsThe wetting behavior of a nanodroplet containing two miscible liquids on a smooth substrate is explored by many-body dissipative particle dynamics simulations. The size-dependent surface tension of nanofilms is investigated as well. FindingsIt is found that Young’s equation is valid for nanodroplets of pure fluids but fails for two-component nanodroplets. The actual contact angle is always larger than the Young’s contact angle, and their difference is getting smaller as the composition approaches pure fluids or the compatibility of the mixture is increased. The failure of Young’s equation is closely associated with the size-dependent behavior in two-component nanodroplets and nanofilms. As the nanodroplet size is increased, the actual contact angle is found to decline but approaches a constant expected in macroscopic systems. Similarly, as the nanofilm thickness is increased, surface tension decreases and reaches its macroscopic value. The change of surface tension is attributed to the size-dependent surface composition, which is responsible for the failure of Young’s equation.

Many-body dissipative particle dynamics simulation of Newtonian and non-Newtonian nanodroplets spreading upon flat and textured substrates

To deposit droplets on substrates efficiently is critical for many technological and industrial applications, which requires a systematic understanding of the droplet spreading process. In the paper, mesoscopic modeling of viscous nanodroplets spreading on different solid surfaces has been conducted by many-body dissipative particle dynamics. The influence of fluid viscosity has been particularly analyzed by changing the interaction parameters and the maximum droplet spreading diameter has been obtained. The dimensionless maximum spreading diameter is correlated to the Reynolds numbers (Re) and Weber numbers (We) as βmax = 0.7Re0.1445We0.066. With the droplets partially attached by polymer chains to exhibit a shear-thinning non-Newtonian property, we demonstrate that the maximum spreading diameters are extremely different under a small initial kinetic energy, and gradually become consistent at a larger Weber number. Investigation of the spreading process on the intricate surfaces decorated by regular pillared structures shows a special expansion effect to improve the intrinsic wetting characteristic of the substrates, which is strongly controlled by the surface fraction of the pillared structures. Moreover, it is found that the fluid viscosity can profoundly affect the rebounding behavior of the droplet.

Many-body dissipative particle dynamics simulation of the anisotropic effect of droplet wetting on stripe-patterned heterogeneous surfaces

The droplet anisotropic wetting on chemically heterogeneous stripe-patterned substrates after impact is studied by using many-body dissipative particle dynamics in this work. After a low-velocity impact on substrates with different length ratio (ratio of stripe width to the initial droplet size) and Cassie area fraction, the droplet can show various shapes and contact angles in parallel and orthogonal directions to the stripes. The elongation of the droplet can be increasingly evident when increasing the length ratio. Also, the contact angles at both directions follow the Cassie-Baxter predicted values well at low length ratio while deviate from them at high length ratio. Both the capillary and kinetic effects have a significant influence on the anisotropic wetting. When impact with higher velocity, the droplet leaves some residues on the hydrophilic stripes of the substrates. Surprisingly, the residues for substrates with certain length ratio (≤0.316) are distributed in circular regions with almost identical radii, indicating the spreading stages of them are independent on the surface properties and dominated by the kinetic effect. When the droplet reaches a stable state, the main body shows anisotropic wetting behavior, indicating the capillary effect dominates the wetting instead of the kinetic effect at the retraction stage.

Strong competition between adsorption and aggregation of surfactant in nanoscale systems

HypothesisThe size-dependent behavior including surface tension, surface density (Γ), and critical micelle concentration (CMC) of a nanoscale liquid film containing surfactant has not been investigated until now. ExperimentsStrong competition between surface adsorption and bulk aggregation of surfactant in nanoscale systems was explored by Many-body Dissipative Particle Dynamics simulations. FindingsIn nanoscale systems, as the surfactant concentration increases, Γ continues rising even after CMC is exceeded. The saturation level of Γ is achieved only when the surfactant bulk concentration is over ten times of CMC. Moreover, both surface micelles formed by adsorbed surfactant and the sublayer below the adsorbed layer are clearly identified. The former can reduce the contacts of adsorbed surfactant with water, while the latter has the surfactant concentration significantly higher than that in bulk. The strong coupling between adsorption and micellization is attributed to large surface-to-volume ratio compared to macroscopic systems, and can be simply realized by the fact that the ratio of the numbers of surfactant distributed in bulk (nbulk) and at interface (nads) is always less than unity (nbulk/nads < 1) in nanoscale systems.

Slipping moving contact lines: critical roles of de Gennes’s ‘foot’ in dynamic wetting

In the context of dynamic wetting, wall slip is often treated as a microscopic effect for removing viscous stress singularity at a moving contact line. In most drop spreading experiments, however, a considerable amount of slip may occur due to the use of polymer liquids such as silicone oils, which may cause significant deviations from the classical Tanner–de Gennes theory. Here we show that many classical results for complete wetting fluids may no longer hold due to wall slip, depending crucially on the extent of de Gennes’s slipping ‘foot’ to the relevant length scales at both the macroscopic and microscopic levels. At the macroscopic level, we find that for given liquid height $h$ and slip length $\unicode[STIX]{x1D706}$, the apparent dynamic contact angle $\unicode[STIX]{x1D703}_{d}$ can change from Tanner’s law $\unicode[STIX]{x1D703}_{d}\sim Ca^{1/3}$ for $h\gg \unicode[STIX]{x1D706}$ to the strong-slip law $\unicode[STIX]{x1D703}_{d}\sim Ca^{1/2}\,(L/\unicode[STIX]{x1D706})^{1/2}$ for $h\ll \unicode[STIX]{x1D706}$, where $Ca$ is the capillary number and $L$ is the macroscopic length scale. Such a no-slip-to-slip transition occurs at the critical capillary number $Ca^{\ast }\sim (\unicode[STIX]{x1D706}/L)^{3}$, accompanied by the switch of the ‘foot’ of size $\ell _{F}\sim \unicode[STIX]{x1D706}Ca^{-1/3}$ from the inner scale to the outer scale with respect to $L$. A more generalized dynamic contact angle relationship is also derived, capable of unifying Tanner’s law and the strong-slip law under $\unicode[STIX]{x1D706}\ll L/\unicode[STIX]{x1D703}_{d}$. We not only confirm the two distinct wetting laws using many-body dissipative particle dynamics simulations, but also provide a rational account for anomalous departures from Tanner’s law seen in experiments (Chen, J. Colloid Interface Sci., vol. 122, 1988, pp. 60–72; Albrecht et al., Phys. Rev. Lett., vol. 68, 1992, pp. 3192–3195). We also show that even for a common spreading drop with small macroscopic slip, slip effects can still be microscopically strong enough to change the microstructure of the contact line. The structure is identified to consist of a strongly slipping precursor film of length $\ell \sim (a\unicode[STIX]{x1D706})^{1/2}Ca^{-1/2}$ followed by a mesoscopic ‘foot’ of width $\ell _{F}\sim \unicode[STIX]{x1D706}Ca^{-1/3}$ ahead of the macroscopic wedge, where $a$ is the molecular length. It thus turns out that it is the ‘foot’, rather than the film, contributing to the microscopic length in Tanner’s law, in accordance with the experimental data reported by Kavehpour et al. (Phys. Rev. Lett., vol. 91, 2003, 196104) and Ueno et al. (Trans. ASME J. Heat Transfer, vol. 134, 2012, 051008). The advancement of the microscopic contact line is still led by the film whose length can grow as the $1/3$ power of time due to $\ell$, as supported by the experiments of Ueno et al. and Mate (Langmuir, vol. 28, 2012, pp. 16821–16827). The present work demonstrates that the behaviour of a moving contact line can be strongly influenced by wall slip. Such slip-mediated dynamic wetting might also provide an alternative means for probing slippery surfaces.

Self-Cleaning of Hydrophobic Rough Surfaces by Coalescence-Induced Wetting Transition.

The superhydrophobic leaves of a lotus plant and other natural surfaces with self-cleaning function have been studied intensively for the development of artificial biomimetic surfaces. The surface roughness generated by hierarchical structures is a crucial property required for superhydrophobicity and self-cleaning. Here, we demonstrate a novel self-cleaning mechanism of textured surfaces attributed to a spontaneous coalescence-induced wetting transition. We focus on the wetting transition as it represents a new mechanism, which can explain why droplets on rough surfaces are able to change from the highly adhesive Wenzel state to the low adhesion Cassie-Baxter state and achieve self-cleaning. In particular, we perform many-body dissipative particle dynamics simulations of liquid droplets (with a diameter of 89 μm) sitting on mechanically textured substrates. We quantitatively investigate the wetting behavior of an isolated droplet as well as coalescence of droplets for both Cassie-Baxter and Wenzel states. Our simulation results reveal that droplets in the Cassie-Baxter state have much lower contact angle hysteresis and smaller hydrodynamic resistance than droplets in the Wenzel state. When small neighboring droplets coalesce into bigger ones on textured hydrophobic substrates, we observe a spontaneous wetting transition from the Wenzel state to the Cassie-Baxter state, which is powered by the surface energy released upon coalescence of the droplets. For superhydrophobic surfaces, the released surface energy may be sufficient to cause a jumping motion of droplets off the surface, in which case adding one more droplet to the coalescence may increase the jumping velocity by one order of magnitude. When multiple droplets are involved, we found that the spatial distribution of liquid components in the coalesced droplet can be controlled by properly designing the overall arrangement of droplets and the distance between them. These findings offer new insights for designing effective biomimetic self-cleaning surfaces by enhancing spontaneous Wenzel-to-Cassie wetting transitions, and additionally, for developing new noncontact methods to manipulate liquids inside the small droplets via multiple-droplet coalescence.