Material drag phenomena in nanotubes

Bioinspired Separator with Ion-Selective Nanochannels for Lithium Metal Batteries

The free transport of anions through commercial polyolefin separators used in lithium metal batteries (LMBs) gives rise to concentration polarization and rapid growth of lithium dendrites, leading to poor performance and short circuits. Here, a new poly(ethylene-co-acrylic acid) (EAA) separator with functional active sites (i.e., carboxyl groups) distributing along the pore surface was fabricated, forming bioinspired ion-conducting nanochannels within the separator. As the carboxyl groups effectively desolvated Li⁺ and immobilized anion, the as-prepared EAA separator selectively accelerated the transport of Li⁺ with transference number of Li⁺ (t_Li⁺) up to 0.67, which was further confirmed by molecular dynamics simulations. The battery with the EAA separator can be stably cycled over 500 h at 5 mA cm^-2. The LMBs with the EAA separator have exceptional electrochemical performance of 107 mAh g^-1 at 5 C and a capacity retention of 69% after 200 cycles. This work provides new commercializable separators toward dendrite-free LMBs.

Water flow in graphene nanochannels driven by imposed thermal gradients: the role of flexural phonons

Accurate control of fluid transport in nanoscale structures is key to enable the design of foreseeable nanofluidic devices with applications in many fields such as chip cooling, energy conversion, drug delivery and medical diagnosis. Here, inspired by the experimental observation of intrinsic thermal ripples in graphene and by recent advances in the manipulation of 2D nanomaterials, we introduce a graphene-based thermal nanopump which produces controlled and continuous liquid flow in nanoslit channels. We investigate the performance of this thermal nanopump employing large scale molecular dynamics simulations. Upon systematically imposing thermal gradients, a net water flow towards the low-temperature zone is observed, achieving flow velocities up to 4 m s^-1. We observe that water flow rates increase monotonically due to larger ripple fluctuations on the graphene layers as higher thermal gradients are applied. Moreover, we find that the out-of-plane flexural phonons in graphene are responsible for flow generation wherein lower frequency phonon branches are activated with higher imposed thermal gradients. Furthermore, by modifying the wettability of the channel walls, an increase of 50% in the water flow rates is observed, showing that the efficiency of the proposed thermal pump can be enhanced by tuning the channel wall hydrophobicity. Our results indicate that thermal gradients can be employed to drive continuous water flow in graphene nanoslit channels with potential applications in nanofluidic devices.

Electropumping Phenomenon in Modified Carbon Nanotubes

Controlling the water transport in a given direction is essential to the design of novel nanofluidic devices, which is still a challenge because of thermal fluctuations on the nanoscale. In this work, we find an interesting electropumping phenomenon for charge-modified carbon nanotubes (CNTs) through a series of molecular dynamics simulations. In electric fields, the flowing counterions on the CNT inner surface provide a direct driving force for water conduction. Specifically, the dynamics of cations and anions exhibit distinct behaviors that lead to thoroughly different water dynamics in positively and negatively charged CNTs. Because of the competition between the increased ion number and ion-CNT interaction, the cation flux displays an interesting maximum behavior with the increase in surface charge density; however, the anion flux rises further at higher charge density because it is less attractive to the surface. Thus, the anion flux is always several times larger than cation flux that induces a higher water flux in positive CNTs with nearly 100% pumping efficiency, which highly exceeds the efficiency of pristine CNTs. With the change in charge density, the translocation time, occupancy number, and radial density profiles for water and ions also demonstrate a nontrivial difference for positive and negative CNTs. Furthermore, the ion flux exhibits an excellent linear relationship with the field strength, leading to the same water flux behavior. For the change in salt concentration, the pumping efficiency for positive CNTs is also nearly 100%. Our results provide significant new insight into the ionic transport through modified CNTs and should be helpful for the design of nanometer water pumps.

Nanoscale Venturi-Bernoulli Pumping of Liquids

We use molecular dynamics simulations to show that the Venturi-Bernoulli effect can pump liquids at the nanoscale. In particular, we found that water flowing in an open reservoir close to a static substrate experiences a friction which converts its kinetic energy into breaking of hydrogen bonds. This water flowing under friction acquires a lower density, which can be used in pumping fluids positioned under a nanoporous substrate.

Effect of temperature on the coupling transport of water and ions through a carbon nanotube in an electric field

Temperature governs the motion of molecules at the nanoscale and thus should play an essential role in determining the transport of water and ions through a nanochannel, which is still poorly understood. This work devotes to revealing the temperature effect on the coupling transport of water and ions through a carbon nanotube by molecular dynamics simulations. A fascinating finding is that the ion flux order changes from cation > anion to anion > cation with the increase in field strength, leading to the same direction change of water flux. The competition between ion hydration strength and mobility should be a partial reason for this ion flux order transition. High temperatures significantly promote the transport of water and ions, stabilize the water flux direction, and enhance the critical field strength. The ion translocation time exhibits an excellent Arrhenius relation with the temperature and a power law relation with the field strength, yielding to the Langevin dynamics. However, because of self-diffusion, the water translocation time displays different behaviors without following the ions. The high temperature also leads to an abnormal maximum behavior of the ion flux, deciphered by the massive increase in water flow that inversely hinders the ion flux, suggesting the coexistence of water-ion coupling transport and competition. Our results shed deep light on the temperature dependence of coupling transport of water and ions, answering a fundamental question on the water flux direction during the ionic transport, and thus should have great implications in the design of high flux nanofluidic devices.

The speed-locking effect of particles on a graphene layer with travelling surface wave

Fast diffusion induced by thermal fluctuation and vibration has been detected at nanoscales. In this paper, the movement of particle on a graphene layer with travelling surface wave is studied by molecular dynamics simulation and theoretical model. It is proved that the particle will keep moving at the wave speed with certain prerequisite conditions, namely speed-locking effect. By expressing van der Waals (vdW) potential between particle and wavy surface as a function of curvatures, the mechanism is clarified based on the puddle of potential in a relative wave-frame coordinate. Two prerequisite conditions are proposed: the initial position of particle should locate in the potential puddle, and the initial kinetic energy cannot drive particle to jump out of the potential puddle. The parametric analysis indicates that the speed-locking region will be affected by wavelength, amplitude and pair potential between particle and wave. With smaller wavelength, larger amplitude and stronger vdW potential, the speed-locking region is larger. This work reveals a new kind of coherent movement for particles on layered material based on the puddle potential theory, which can be an explanation for fast diffusion phenomena at nano scales.

Phonon-Induced Ratchet Motion of a Water Nanodroplet on a Supported Black Phosphorene

Phonons are not supposed to carry any physical momentum as lattice vibrational modes; thus, it is believed no mass transport could be induced by phonons. In this Letter, we show that a ratchet motion of a water nanodroplet could be induced on a two-dimensional puckered lattice like black phosphorene (BP) by exciting its flexural phonons through a moving substrate. The water nanodroplet exhibits a forward motion along the armchair or a backward motion along the zigzag directions on a BP lattice that is supported on a substrate possessing a relative armchair or zigzag forward motion with BP. Through the analysis of the structure and vibrational density states of BP, it is found that in-plane lattice displacement asymmetry and the in-plane vibration asymmetry are induced by the excited flexural phonons, which determine the water nanodroplet motion as an anisotropic Brownian motor. Simulations of the nanodroplet motion as functions of the substrate relative motion speed and direction and also the substrate coupling strength with BP are performed. Results of the nanodroplet ratchet motion exhibit good agreement with the theoretical predications from calculating the Brownian motor asymmetry. Our findings reveal a promising mass transport strategy and a further understanding of phonon-related interactions in crystalline solids.

An Electrically Actuated, Carbon-Nanotube-Based Biomimetic Ion Pump

Single-walled carbon nanotubes (SWCNTs) are well-established transporters of electronic current, electrolyte, and ions. In this work, we demonstrate an electrically actuated biomimetic ion pump by combining these electronic and nanofluidic transport capabilities within an individual SWCNT device. Ion pumping is driven by a solid-state electronic input, as Coulomb drag coupling transduces electrical energy from solid-state charge along the SWCNT shell to electrolyte inside the SWCNT core. Short-circuit ionic currents, measured without an electrolyte potential difference, exceed 1 nA and scale larger with increasing ion concentrations through 1 M, demonstrating applicability under physiological (∼140 mM) and saltwater (∼600 mM) conditions. The interlayer coupling allows ionic currents to be tuned with the source-drain potential difference and electronic currents to be tuned with the electrolyte potential difference. This combined electronic-nanofluidic SWCNT device presents intriguing applications as a biomimetic ion pump or component of an artificial membrane.

Tuning nanotubular structures by templateless electropolymerization with thieno[3,4-b]thiophene-based monomers with different substituents and water content

Here, templateless electropolymerization is employed to produce nanotubular structures from various thieno[3,4-b]thiophene-based monomers that differ in substituent structure and size, as well as the linker connecting the thieno[3,4-b]thiophene core and substituent. The formation of densely packed vertically aligned are obtained from monomers with a pyrene substituent and when a significant amount of water (CH₂Cl₂ + H₂O) is included in the solvent. The geometrical parameters of the nanotubes are highly dependent on the electopolymerization method. A significant amount of air is trapped within the structure of the densely packed open nanotubes obtained with Qs = 100 mC cm^-2 causing an increase in water contact angle (θ_w) up to 82.6° (intermediate state between the Wenzel and the Cassie-Baxter state), and θ_w can become even more hydrophobic by further modifying the deposition method or the electrolyte.

The Role of Interface Ions in the Control of Water Transport through a Carbon Nanotube

Controlling the water transport toward a given direction is still challenging, particularly due to thermal fluctuations of water motion at the nanoscale. While most of the previous works focus on the symmetric hydrophobic membrane systems, the role of the membrane in affecting the water transport remains largely unexplored. In this work, by using extensive molecular dynamics simulations, we find an interesting electropumping phenomenon, that is, the flowing counterions on an asymmetric hydrophobic-hydrophilic membrane can significantly drive the single-file water transport through a carbon nanotube, suggesting a nanometer water pump in a highly controllable fashion. The ion-water coupling motion in electric fields on the charged surface provides an indirect driving force for this pumping phenomenon. The water dynamics and thermal dynamics demonstrate a unique behavior with the change in electric fields, surface charge density, and even charge species. Particularly, due to the ion flux bifurcation for the positive and negative surfaces, the water dynamics such as the water flow, flux, and translocation time also exhibit similar asymmetry. Surprisingly, the positive surface charge induces an abnormal three-peak dipole distribution for the confined water and subsequent high flipping frequency. This can be attributed to the competition between the surface charge and interface water orientation on it. Our results indicate a new strategy to pump water through a nanochannel, making use of the counterion flowing on an asymmetric charged membrane, which are promising for future studies.

How ions block the single-file water transport through a carbon nanotube

Understanding the blockage of ions for water transport through nanochannels is crucial for the design of desalination nanofluidic devices. In this work, we systematically clarify how ions block the single-file water transport through a (6,6) carbon nanotube (CNT) by using molecular dynamics simulations. We consider various pressure differences and salt concentrations. With the increase of pressure difference, the water flux shows a linear growth that coincides with the Hagen-Poiseuille equation. Interestingly, the dependence of the CNT-ion interaction on the salt concentration results in a distinct ion blockage effect that ultimately leads to water flux bifurcation. The water translocation time shows a power law decay with pressure, depending on the salt concentration. Furthermore, with the increase of salt concentration, the water flux shows a linear decay with a larger slope for higher pressure, while the water translocation time shows an opposite behavior. Therefore, the ions can not only block the water entering but also slow down the water motion inside the CNT. Notably, the probability of cations and anions appearing at the CNT entrance is quite similar, suggesting a similar blockage effect; however, anions show deeper interactions with the CNT because of their larger size. We finally find a unique linear relation between the water flux and occupancy divided by the translocation time. Our results provide insightful information on the ion blockage effect for the single-file water transport, and are thus helpful for the design of novel filtration membranes.

Ultralarge Modulation of Fluorescence by Neuromodulators in Carbon Nanotubes Functionalized with Self-Assembled Oligonucleotide Rings

Noncovalent interactions between single-stranded DNA (ssDNA) oligonucleotides and single wall carbon nanotubes (SWNTs) have provided a unique class of tunable chemistries for a variety of applications. However, mechanistic insight into both the photophysical and intermolecular phenomena underlying their utility is lacking, which results in obligate heuristic approaches for producing ssDNA-SWNT based technologies. In this work, we present an ultrasensitive "turn-on" nanosensor for neuromodulators dopamine and norepinephrine with strong relative change in fluorescence intensity (Δ F/ F₀) of up to 3500%, a signal appropriate for in vivo neuroimaging, and uncover the photophysical principles and intermolecular interactions that govern the molecular recognition and fluorescence modulation of this nanosensor synthesized from the spontaneous self-assembly of (GT)₆ ssDNA rings on SWNTs. The fluorescence modulation of the ssDNA-SWNT conjugate is shown to exhibit remarkable sensitivity to the ssDNA sequence chemistry, length, and surface density, providing a set of parameters with which to tune nanosensor dynamic range, analyte selectivity and strength of fluorescence turn-on. We employ classical and quantum mechanical molecular dynamics simulations to rationalize our experimental findings. Calculations show that (GT)₆ ssDNA form ordered rings around (9,4) SWNTs, inducing periodic surface potentials that modulate exciton recombination lifetimes. Further evidence is presented to elucidate how dopamine analyte binding modulates SWNT fluorescence. We discuss the implications of our findings for SWNT-based molecular imaging applications.

Atomistic insights into the nanofluid transport through an ultra-confined capillary

Nanofluid or nanoparticle (NP) transport in confined channels is of great importance for many biological and industrial processes. In this study, molecular dynamics simulation has been employed to investigate the spontaneous two-phase displacement process in an ultra-confined capillary controlled by the surface wettability of NPs. The results clearly show that the presence of NPs modulates the fluid-fluid meniscus and hinders the displacement process compared with the NP-free case. From the perspective of motion behavior, hydrophilic NPs disperse in the water phase or adsorb on the capillary, while hydrophobic and mixed-wet NPs are mainly distributed in the fluid phase. The NPs dispersed into fluids tend to increase the viscosity of the fluids, while the adsorbed NPs contribute to the wettability alteration of the solid capillary. Via capillary number calculations, it is uncovered that the viscosity increase of fluids is responsible for the hindered spontaneous displacement process by hydrophobic and mixed NPs. The wettability alteration of the capillary induced by adsorbed NPs dominates the enhanced displacement in the case of hydrophilic NPs. Our findings provide guidance for modifying the rate of capillary filling and reveal the microscopic mechanism transporting NPs into porous media, which is significant to the design of NPs for target applications.

Enantioselective Molecular Transport in Multilayer Graphene Nanopores

Multilayer superstructures based on stacked layered nanomaterials offer the possibility to design three-dimensional (3D) nanopores with highly specific properties analogous to protein channels. In a layer-by-layer design and stacking, analogous to molecular printing, superstructures with lock-and-key molecular nesting and transport characteristics could be prepared. To examine this possibility, we use molecular dynamics simulations to study electric field-driven transport of ions through stacked porous graphene flakes. First, highly selective, tunable, and correlated passage rates of monovalent atomic ions through these superstructures are observed in dependence on the ion type, nanopore type, and relative position and dynamics of neighboring porous flakes. Next, enantioselective molecular transport of ionized l- and d-leucine is observed in graphene stacks with helical nanopores. The outlined approach provides a general scheme for synthesis of functional 3D superstructures.

Carbon Nanotubes as Thermally Induced Water Pumps

Thermal Brownian motors (TBMs) are nanoscale machines that exploit thermal fluctuations to provide useful work. We introduce a TBM-based nanopump which enables continuous water flow through a carbon nanotube (CNT) by imposing an axial thermal gradient along its surface. We impose spatial asymmetry along the CNT by immobilizing certain points on its surface. We study the performance of this molecular motor using molecular dynamics (MD) simulations. From the MD trajectories, we compute the net water flow and the induced velocity profiles for various imposed thermal gradients. We find that spatial asymmetry modifies the vibrational modes of the CNT induced by the thermal gradient, resulting in a net water flow against the thermal gradient. Moreover, the kinetic energy associated with the thermal oscillations rectifies the Brownian motion of the water molecules, driving the flow in a preferred direction. For imposed thermal gradients of 0.5-3.3 K/nm, we observe continuous net flow with average velocities up to 5 m/s inside CNTs with diameters of 0.94, 1.4, and 2.0 nm. The results indicate that the CNT-based asymmetric thermal motor can provide a controllable and robust system for delivery of continuous water flow with potential applications in integrated nanofluidic devices.

Asymmetric osmotic water permeation through a vesicle membrane

Understanding the water permeation through a cell membrane is of primary importance for biological activities and a key step to capture its shape transformation in salt solution. In this work, we reveal the dynamical behaviors of osmotically driven transport of water molecules across a vesicle membrane by molecular dynamics simulations. Of particular interest is that the water transport in and out of vesicles is highly distinguishable given the osmotic force are the same, suggesting an asymmetric osmotic transportation. This asymmetric phenomenon exists in a broad range of parameter space such as the salt concentration, temperature, and vesicle size and can be ascribed to the similar asymmetric potential energy of lipid-ion, lipid-water, lipid-solution, lipid-lipid, and the lipid-lipid energy fluctuation. Specifically, the water flux has a linear increase with the salt concentration, similar to the prediction by Nernst-Planck equation or Fick's first law. Furthermore, due to the Arrhenius relation between the membrane permeability and temperature, the water flux also exhibits excellent Arrhenius dependence on the temperature. Meanwhile, the water flux shows a linear increase with the vesicle surface area since the flux amount across a unit membrane area should be a constant. Finally, we also present the anonymous diffusion behaviors for the vesicle itself, where transitions from normal diffusion at short times to subdiffusion at long times are identified. Our results provide significant new physical insights for the osmotic water permeation through a vesicle membrane and are helpful for future experimental studies.

One-Dimensional Self-Organization and Nonequilibrium Phase Transition in a Hamiltonian System

Self-organization and nonequilibrium phase transitions are well known to occur in two- and three-dimensional dissipative systems. Here, instead, we provide numerical evidence that these phenomena also occur in a one-dimensional Hamiltonian system. To this end, we calculate the heat conductivity by coupling the two ends of our system to two heat baths at different temperatures. It is found that when the temperature difference is smaller than a critical value, the heat conductivity increases with the system size in power law with an exponent considerably smaller than 1. However, as the temperature difference exceeds the critical value, the system's behavior undergoes a transition and the heat conductivity tends to diverge linearly with the system size. Correspondingly, an ordered structure emerges. These findings suggest a new direction for exploring the transport problems in one dimension.

Correlated Rectification Transport in Ultranarrow Charged Nanocones

Using molecular dynamics simulations, we reveal ion rectification in charged nanocones with exit diameters of 1-2 nm. The simulations exhibit an opposite rectification current direction than experiments performed in conical channels with exit diameters larger than 5 nm. This can be understood by the fact that in ultranarrow charged cones screening ions are trapped close to the cone tip at both field directions, which necessitates them to be released from the cone in a correlated multi-ion fashion. Electroosmosis induced by a unidirectional ion flow is also observed.

Desalination by dragging water using a low-energy nano-mechanical device of porous graphene

We propose a dragging nano-structured suction system based on graphene sheets for water desalination processes.

Slip divergence of water flow in graphene nanochannels: the role of chirality

Graphene has attracted considerable attention due to its characteristics as a 2D material and its fascinating properties, providing a potential building block for fabrication of nanofluidic conduits.

Interface nanoparticle control of a nanometer water pump

A nanoparticle is forced to move on a membrane surface, inducing considerable water flux through a carbon nanotube, suggesting a controllable nanometer water pump.

A current-driven nanometer water pump

The design of a water pump, which has huge potential for applications in nanotechnology and daily life, is the dream of many scientists. In this paper, we successfully design a nanometer water pump by using molecular dynamics simulations. Ions of either sodium or chlorine in a narrow channel will generate electric current under electric fields, which then drives the water through a wider channel, similar to recent experimental setups. Considerable water flux is achieved within small field strengths that are accessible by experimentation. Of particular interest, is that for sodium the water flux increases almost linearly with field strengths; while for chlorine there exists a critical field strength, the water flux exhibits a plateau before the critical value and increases linearly after it. This result follows the behavior of ion velocity, which is related to friction behavior. We also estimate the power and energy consumption for such a pump, and compare it to the macroscopic mechanical pumps. A further comparison suggests that different ions will have different pumping abilities. This study not only provides new, significant results with possible connection to existing research, but has tremendous potential application in the design of nanofluidic devices.

Towards nanoprinting with metals on graphene

Graphene and carbon nanotubes are envisaged as suitable materials for the fabrication of the new generation of nanoelectronics. The controlled patterning of such nanostructures with metal nanoparticles is conditioned by the transfer between a recipient and the surface to pattern. Electromigration under the impact of an applied voltage stands at the base of printing discrete digits at the nanoscale. Here we report the use of carbon nanotubes as nanoreservoirs for iron nanoparticles transfer on few-layer graphene. An initial Joule-induced annealing is required to ensure the control of the mass transfer with the nanotube acting as a ‘pen' for the writing process. By applying a voltage, the tube filled with metal nanoparticles can deposit metal on the surface of the graphene sheet at precise locations. The reverse transfer of nanoparticles from the graphene surface to the nanotube when changing the voltage polarity opens the way for error corrections.

The precise delivery of materials onto graphene is important for nano-processing but little is known about the mechanisms of such processes. Here, the authors use a range of microscopic techniques for the real-time observation of nanoparticle transfer from the inner channel of a carbon nanotube onto graphene.

Pumping of water by rotating chiral carbon nanotube

Water transportation inside carbon nanotubes is of great importance for designing novel nanodevices. In this article, by using molecular dynamics simulations, we systematically investigate the pumping of water by rotating carbon nanotube (CNT). It is found that the chirality and rotation of the CNT are two preconditions for stable water flux inside it. Besides, we find that the water flux shows an approximately logarithmic dependence on the angular velocity of the rotation, a linear dependence on the radius of the CNT, and interestingly, independence of its length within a certain range of CNT size and angular velocity. Further, we also use a dragging theory which successfully describes the water flux behaviors inside the CNT and can fit well with the results obtained from simulations. The present study provides insight into the designing of nanodevices based on the CNT for real applications.

Molecular-scale hydrophilicity induced by solute: molecular-thick charged pancakes of aqueous salt solution on hydrophobic carbon-based surfaces

We directly observed molecular-thick aqueous salt-solution pancakes on a hydrophobic graphite surface under ambient conditions employing atomic force microscopy. This observation indicates the unexpected molecular-scale hydrophilicity of the salt solution on graphite surfaces, which is different from the macroscopic wetting property of a droplet standing on the graphite surface. Interestingly, the pancakes spontaneously displayed strong positively charged behavior. Theoretical studies showed that the formation of such positively charged pancakes is attributed to cation–π interactions between Na⁺ ions in the aqueous solution and aromatic rings on the graphite surface, promoting the adsorption of water molecules together with cations onto the graphite surface; i.e., Na⁺ ions as a medium adsorbed to the graphite surface through cation–π interactions on one side while at the same time bonding to water molecules through hydration interaction on the other side at a molecular scale. These findings suggest that actual interactions regarding carbon-based graphitic surfaces including those of graphene, carbon nanotubes, and biochar may be significantly different from existing theory and they provide new insight into the control of surface wettability, interactions and related physical, chemical and biological processes.

Molecular Friction-Induced Electroosmotic Phenomena in Thin Neutral Nanotubes

We reveal by classical molecular dynamics simulations electroosmotic flows in thin neutral carbon (CNT) and boron nitride (BNT) nanotubes filled with ionic solutions of hydrated monovalent atomic ions. We observe that in (12,12) BNTs filled with single ions in an electric field, the net water velocity increases in the order of Na(+) < K(+) < Cl(-), showing that different ions have different power to drag water in thin nanotubes. However, the effect gradually disappears in wider nanotubes. In (12,12) BNTs containing neutral ionic solutions in electric fields, we observe net water velocities going in the direction of Na(+) for (Na(+), Cl(-)) and in the direction of Cl(-) for (K(+), Cl(-)). We hypothesize that the electroosmotic flows are caused by different strengths of friction between ions with different hydration shells and the nanotube walls.

Wetting on flexible hydrophilic pillar-arrays

Dynamic wetting on the flexible hydrophilic pillar-arrays is studied using large scale molecular dynamics simulations. For the first time, the combined effect of the surface topology, the intrinsic wettability and the elasticity of a solid on the wetting process is taken into consideration. The direction-dependent dynamics of both liquid and pillars, especially at the moving contact line (MCL), is revealed at atomic level. The flexible pillars accelerate the liquid when the liquid approaches, and pin the liquid when the liquid passes. The liquid deforms the pillars, resulting energy dissipation at the MCL. Scaling analysis is performed based on molecular kinetic theory and validated by our simulations. Our results may expand our knowledge of wetting on pillars and assisting the future design of active control of wetting in practical applications.