Top Of Pillars Research Articles

Spatiotemporal analysis of F-actin polymerization with micropillar arrays reveals synchronization between adhesion sites.

We repurposed micropillar-arrays to quantify spatiotemporal inter-adhesion communication. Following the observation that integrin adhesions formed around pillar tops we relied on the precise repetitive spatial control of the pillars to reliably monitor F-actin dynamics in mouse embryonic fibroblasts as a model for spatiotemporal adhesion-related intracellular signaling. Using correlation-based analyses we revealed localized information-flows propagating between adjacent pillars that were integrated over space and time to synchronize the adhesion dynamics within the entire cell. Probing the mechanical regulation, we discovered that stiffer pillars or partial actomyosin contractility inhibition enhances inter-adhesion F-actin synchronization, and that inhibition of Arp2/3, but not formin, reduces synchronization. Our results suggest that adhesions can communicate and highlight the potential of using micropillar arrays as a tool to measure spatiotemporal intracellular signaling. [Media: see text].

Fog Harvesting Via Multistage Edge‐Effect Condensation

AbstractThe escalating global population and rapid industrialization have precipitated a severe freshwater scarcity crisis. To address this challenge, innovative strategies are essential to exploit unconventional water sources such as atmospheric vapor. This study proposes a novel approach integrating 3D printing technology with surface chemistry principles for atmospheric fog harvesting. The approach entails leveraging 3D printing technology, chosen for its cost‐effectiveness, unparalleled design flexibility to design intricate geometries, and time efficiency to fabricate cylindrical millimeter‐scale size vertical pillars. Harnessing the intricate interplay of surface phenomena, condensation preferentially occurs on the pillar tops due to surface phenomena. The pillars are imbued with nonadecane, a hydrocarbon renowned for its low surface energy characteristics ensures the uninterrupted progression of water droplet formation, coalescence, and seamless transportation, unveiling a symphony of molecular interactions at the microscale. The design demonstrates promising results, yielding an impressive yield of ≈3.956 g of water per hour from 1 cm2 area. Geometric discontinuities associated with parahydrophobic pillars amplify water harvesting via an edge effect. This study represents a significant step toward a more sustainable and technologically advanced solution for the global water crisis.

Experimental study of pool boiling heat transfer on mini-pillar surfaces with different hydrophobic dot arrays

In this study, we conducted experimental research on the pool boiling performance of mini-pillar surfaces with different hydrophobic dot arrays. The experimental results show that the distribution and total area of hydrophobic dot arrays on pillar tops significantly influence the boiling performance of mini-pillar surfaces. In comparison with the mini-pillar surface without wettability modification, introducing hydrophobic dot arrays on the pillar tops can improve the bubble nucleation density and diminish the wall superheat at boiling onset. Therefore, the boiling performance of mini-pillar surfaces can be gradually improved by increasing the total area of hydrophobic dot arrays at low heat fluxes. However, a further increase in the total area of hydrophobic dot arrays may lead to the reduction of the bubble departure frequency at high heat fluxes, which is not conducive to the segregation of the liquid and vapor pathways. The experimental results indicated that when the total area of hydrophobic pillar tops accounts for 10.24 % of the projected area of the mini-pillar surfaces, an optimal enhancement is achieved, and the optimal enhancement of boiling performance on the mini-pillar surfaces with hydrophobic dot arrays results from a suitable balance between promoting the bubble nucleation and maintaining higher bubble departure frequency.

Spray cooling of micropillared steel plates: Two-stage quenching phenomenon

Spray cooling is a crucial process of steel manufacturing, nuclear power plants and electronics thermal management. However, its precise control is challenging due to the various boiling regimes involved at different temperature levels. Transition from film boiling to nucleate boiling, namely, the onset of quench is our particular interest as it remarks the thermal history of the hot object. Based on our previous findings that quench occurs at a specific temperature defined at the droplet-surface interface we demonstrate that micropillars on steel plates can increase the quench temperature Tq . We performed water spray cooling tests with stainless-steel samples, on which various configurations of micropillars were fabricated using laser texturing. Interestingly, we observed two stages of quench for a specific sample: a drastic increase in the cooling rate at ca. 450 °C, followed by another increase at ca. 250 °C. The first cooling rate increase is attributed to the initiation of stable liquid-solid contact at the pillar tops. Eventually, water wets the entire pillars and the bottom surface, further increasing the cooling rate. Samples with higher pillars showed no film boiling regime in the experiment, implying higher quenching temperature (Tq > 600 °C). We attribute the increased apparent Tq to the narrow heat conduction path within the micropillar, resulting in a significant temperature drop at the tip which enhances liquid-solid contact.

Enhanced dropwise condensation on downward-facing cross-shaped pillar-structured surfaces with mixed wettability

In this paper, a novel downward-facing cross-shaped pillar-structured surface with mixed wettability is conceived for enhancing dropwise condensation. A three-dimensional thermal lattice Boltzmann model is employed to investigate the condensation performance on the downward-facing cross-shaped pillar-structured surface with mixed wettability and the associated enhancement mechanism of dropwise condensation. The numerical investigation shows that the cross-shaped pillar-structured surface with mixed wettability exhibits much better condensation performance than the square pillar-structured surface with mixed wettability and the flat surface with mixed wettability due to the synergistic effects of structural effects and mixed wettability, which can promote the droplet nucleation and accelerate the condensate removal. Moreover, for different contact angles of the pillar top (θtop), there exists a competition between the droplet nucleation and the condensate removal on the downward-facing cross-shaped pillar-structured surface. It is found that, when θtop=60°, an optimal droplet dripping rate can be achieved due to a suitable balance between a relatively large mass of detached droplets and a short condensation cycle time. Furthermore, the aspect ratio (γ) has an important influence on the droplet dripping rate, i.e., as γ increases, the droplet dripping rate first exhibits small fluctuations, then increases rapidly before γ=1.0, and after that experiences a slight variation. The large droplet dripping rate achieved at γ=1.0 is mainly attributed to the fact that an optimum structure of the concave corner can promote the droplet nucleation, increase the length of the triple-phase contact line, advance the appearance of droplet coalescence, and finally accelerate the condensate removal.

GPR survey on underwater archaeological site: A case study at Jenipapo stilt village in the eastern Amazon region, Brazil

In this work we present and discuss the results of a pioneering Ground Penetrating Radar (GPR) survey performed at the underwater archaeological stilt village called Jenipapo in the eastern Amazon region. Jenipapo stilt village is located on the Turiaçu River, Maranhão State, Northeast of Brazil. The region is known as the Maranhense wetland where settlements were built by indigenous populations that inhabited this region during the pre-colonial period (∼AD 1 – 1100). These settlements were built on the margin of rivers and lakes, being supported by wooden pillars, corresponding to prehistoric stilt houses. The objectives of this research are to refine the wooden pillars location at the Turiaçu River bottom and guide the search for underwater archaeological artifacts. A total of twelve GPR profiles were acquired with 270 MHz antennas using a rubber boat. The GPR results indicated clear signal reflection from the river bottom and several diffraction hyperbolas suspended over the river bottom related to the top of the wooden pillars. To support the interpretation of the results, a GPR numerical modeling was performed to simulate the diffraction hyperbolas suspended in the water related to the wooden pillars. The synthetic result presented a good agreement with real data. Finally, the location of several diffraction hyperbolas can guide the divers to find and collect archaeological artifacts around the underwater wooden pillars that are the best evidence of the stilt houses of indigenous settlements found in the eastern Amazon region. Several archaeological artifacts were found during previous work, including ceramic materials. The results of this research show the capability of the GPR method to map an underwater wooden pillar and increase the probability of finding archaeological artifacts on the river bottom, which contributes to improve the knowledge of the Amazonian archaeology in Brazil.

Electric field enhancement of pool boiling of dielectric fluids on pillar-structured surfaces: A lattice Boltzmann study

In this paper, by using a phase-change lattice Boltzmann (LB) model coupled with an electric field model, we numerically investigate the performance and enhancement mechanism of pool boiling of dielectric fluids on pillar-structured surfaces under an electric field. The numerical investigation reveals that applying an electric field causes both positive and negative influences on the pool boiling of dielectric fluids on pillar-structured surfaces. It is found that under the action of an electric field, the electric force prevents the bubbles nucleated in the channels from crossing the edges of the pillar tops. On the one hand, such an effect results in the bubble coalescence in the channels and blocks the paths of liquid supply for the channels, which leads to the deterioration of pool boiling in the medium-superheat regime. On the other hand, it prevents the coalescence between the bubbles in the channels and those on the pillar tops, which suppresses the formation of a continuous vapor film and, therefore, delays the occurrence of a boiling crisis. Meanwhile, the electric force can promote the departure of the bubbles on the pillar tops. Accordingly, the critical heat flux (CHF) can be improved. Based on the revealed mechanism, wettability-modified regions are applied to the pillar tops for further enhancing the boiling heat transfer. It is shown that the boiling performance on pillar-structured surfaces can be enhanced synergistically with the CHF being increased by imposing an electric field and the maximum heat transfer coefficient being improved by applying mixed wettability to the pillar-structured surfaces.

Experimental investigation of pool boiling heat transfer on pillar-structured surfaces with different wettability patterns

• Pool boiling on pillar-structured surfaces with different wettability patterns is investigated. • The combined effects of surface structure and mixed wettability are experimentally explored. • MPoPi mixed pattern always leads to a leftward shift of the boiling curve but gives a lower CHF. • The performance of MPiPo mixed pattern is strongly dependent on the channel-to-pillar width ratio. In this paper, we experimentally investigate the pool boiling heat transfer on pillar-structured surfaces with different wettability patterns and different values of the channel-to-pillar width ratio. Five types of wettability patterns are compared, i.e., homogeneous hydrophilicity (HPi), homogeneous hydrophobicity (HPo), homogeneous near-superhydrophilicity (SHPi), a mixed pattern with hydrophilic bottom and hydrophobic pillar top (MPiPo), and another mixed pattern with hydrophobic bottom and hydrophilic pillar top (MPoPi). The effects of homogenous wettability patterns on the boiling performance of pillar-structured surfaces are basically consistent with those on plain surfaces, but the differences between the HPi and HPo patterns are found to be gradually enlarged with the decrease of the channel-to-pillar width ratio. Moreover, compared with the base HPi pattern, the MPoPi mixed pattern leads to a leftward shift of the boiling curve and an upward shift of the heat transfer coefficient (HTC) curve but gives a lower value of the critical heat flux. Such a tendency of the MPoPi mixed pattern is not affected when the channel-to-pillar width ratio is decreased from 2.0 to 0.5. In contrast, the boiling performance of the MPiPo mixed pattern is found to be significantly affected by the channel-to-pillar width ratio as it performs best among the five types of wettability patterns when the channel-to-pillar width ratio γ ⩾ 1 , but it deteriorates the boiling heat transfer at high heat fluxes when the ratio γ is reduced to 0.5.

Programmable Stepwise Collective Magnetic Self-Assembly of Micropillar Arrays.

Chain-like magnetic self-organizations have been documented for micron/submicron-scale magnetic particles. However, the positions of the particles are not stationary in a sustaining fluid owing to Brownian translational motion, resulting in irregular magnetic self-assembly. Toward the development of a programmable and reversible magnetic self-assembly, we report a stepwise collective magnetic self-assembly with periodic polymeric micropillar arrays containing magnetic particles. Under an external magnetic field, the individual micropillar acts as a micromagnet; magnetic polarities of embedded ferromagnetic particles are arranged in the same direction. The nearest pillar tops undergo a pairwise assembly owing to the anisotropic quadrupolar interaction, whereas the pillar bases remain stationary because of the presence of a magnetically inert substrate. By increasing the magnetic flux density, a collective quad-body assembly of vicinal paired micropillars is accomplished, finally leading to long-range connectivity of the pillar tops. Simple evaporation of the polymeric solution yields shape-fixation of the connected micropillar architectures even after magnetic fields are removed. We investigate geometric effects on this stepwise collective magnetic self-assembly using rectangular, square, and circular micropillars. Also, we demonstrate spatially selective magnetic self-assembly (e.g., arbitrary letters) using a masking technique. Finally, we demonstrate on-demand programming of bidirectional liquid spreading through long-range ordered magnetic self-assembly.

Enhanced pool boiling on microstructured surfaces with spatially-controlled mixed wettability

Surface wettability is a very important factor that affects the pool boiling heat transfer performance and the surfaces with mixed wettability have attracted much attention in recent years for enhancing pool boiling. However, the existing experimental studies were mainly focused on plain surfaces with mixed wettability or microstructured surfaces whose tops of microstructures were entirely subjected to wettability modification. In this work, we fabricated microstructured surfaces with spatially-controlled mixed wettability by controlling the size of the hydrophobic spots on the tops of microstructures. Saturated pool boiling of water on the surfaces was experimentally investigated to explore the synergistic enhancement of pool boiling by optimally utilizing the combined effects of mixed wettability and microstructures. The experimental results indicate that the size of the hydrophobic spots on the tops of microstructures has a significant influence on the boiling performance of microstructured surfaces with mixed wettability. By controlling the size of the hydrophobic spots on the tops of microstructures to optimize the combined effects of mixed wettability and microstructures, the novel microstructured surface performs much better than a base microstructured surface without wettability modification and the one whose tops of pillars are entirely subjected to wettability modification. The heat transfer coefficient (HTC) was found to be significantly enhanced together with a higher critical heat flux (CHF). Specifically, the achieved largest HTC and highest CHF are 257.6 kW/(m2 K) and 2190.8 kW/m2, respectively, which are 4.55 times and 1.87 times, respectively, over those of the plain copper surface.

Enhancing dropwise condensation on downward-facing surfaces through the synergistic effects of surface structure and mixed wettability

In this paper, the condensation performance and the dynamic behavior of condensed droplets on a downward-facing structured surface with mixed wettability are numerically investigated using a thermal multiphase lattice Boltzmann model, with a focus being placed on exploring the enhancement mechanism of dropwise condensation on downward-facing structured surfaces. The numerical investigation shows that the downward-facing structured surface with mixed wettability exhibits much better condensation performance than those with homogeneous wettability owing to the synergistic effects of surface structure and mixed wettability, which increase the droplet departure frequency and prevent the flooding phenomenon. Furthermore, it is found that the dynamic behavior of condensed droplets on the downward-facing structured surface with mixed wettability can be divided into three stages, i.e., the nucleation-growth stage, the coalescence-slip stage, and the stick-departure stage. Particularly, there exists a competition between the time of the first stage and that of the third stage in terms of the contact angle of the pillar top (θtop). The former reduces but the latter increases with decreasing θtop, because the contact lines are always pinned at the edges of the pillar top during the third stage when θtop is small. An optimal θtop is therefore found, which provides the best droplet dripping rate by achieving a suitable balance between a large droplet departure volume and a relatively short condensation cycle time.

Nucleate boiling enhancement by structured surfaces with distributed wettability-modified regions: A lattice Boltzmann study

In this paper, we conceive a novel pillar-structured surface for enhancing nucleate boiling heat transfer, namely a pillar-structured surface with distributed wettability-modified regions on the top of each pillar. A three-dimensional thermal multiphase lattice Boltzmann model with liquid–vapor phase change is employed to investigate the boiling performance on the pillar-structured surface with distributed wettability-modified regions and the associated mechanism of nucleate boiling heat transfer enhancement. According to the distribution of the wettability-modified regions, the bubble dynamics on the newly conceived pillar-structured surface can be classified into three regimes, i.e., regimes I, II, and III, among which the regime II shows relatively better boiling performance than the other two regimes due to the synergistic effects of surface structure and mixed wettability. It is found that in the regime II the bubbles nucleated at the wettability-modified regions do not coalesce with each other, which therefore elongates the length of the triple-phase contact lines on the pillar top in comparison with the pillar-structured surface with a unified wettability-modified region. Meanwhile, in the regime II the bubbles on the pillar top receive a strong bubble-wake effect supplied by the bubbles generated at the bottom substrate, which shortens the bubble growth cycle and promotes the departure of the bubbles on the pillar top, and also reduces the area of dry spots on the pillar top. The influences of the pillar width and the width of the wettability-modified regions are also studied. It is shown that the best boiling performance is always achieved in the cases that fall into the regime II.

Selective-area growth study of GaN micropillars for quasi-vertical Schottky diodes

In this work, metal organic vapor phase epitaxy (MOVPE) is employed for selective-area growth (SAG) of undoped and lightly n-doped GaN micropillars on masked GaN-on-sapphire templates. In micropillar geometry, the limits of GaN drift layer thickness in hetereoepitaxial Schottky diodes are expected to be significantly pushed upwards. This is an important step towards the realization of GaN-based quasi-vertical power devices with high breakdown voltage (V br) on low-cost foreign substrates. Micropillar growth evolution and the impact of growth rate and V/III ratio on micropillar morphology and parasitic GaN deposition on AlOx hard masks are investigated. By using a combination of low growth rate and high V/III ratio, 12–22 µm high micropillars with planar pillar tops are grown in circular mask openings with radii of 35–100 µm. The threading dislocation density of the highest pillars is (1.4 ± 0.3) × 107 cm−2. Schottky diodes on micropillars with lowest net doping concentration (N D − N A) of 1.3 × 1016 cm−3 exhibit excellent forward characteristics with ideality factors , on/off-ratios up to 1010, and on-resistances R on 1 m cm−2.

Tunable self-jumping of melting frost on macro-patterned anisotropic superhydrophobic surfaces

Controllable fast self-removal of frost pieces from surfaces can effectively reduce energy consumption and residual droplets during defrosting. In this work, a tuning strategy of melting frost directional self-jumping on regular macro-patterned anisotropic superhydrophobic surface (MASS) was proposed. Under high-rate cooling condition, patterned frost on MASS with significantly different thickness distribution was observed, due to the water vapor gradient in and out of the deep grooves. During defrosting process, L-shaped melting frost on MASS shrank independently with two arms retracting inward, which further caused the melting frost's centroid/mass center to shift out of the pillar top. Partial contact with pillar tops and circular fillet introduced directional lifting force and enabled the directional self-jumping of the melting frost. Influencing factors on directional self-jumping of melting frost on MASS were also discussed. Utilizing macro-patterned anisotropic structure, the frost splitting process and its jumping direction were both tuned, which could promote the self-jumping of melting frost and thus improve the efficiency of defrosting.

Durable poly(N-isopropylacrylamide) grafted PDMS micropillared surfaces for temperature-modulated wetting

Surface grafting of polymer brushes has become an area of significant research to deliver desired material properties such as smart wetting. In this research the grafting of Poly(N-isopropylacrylamide)(PNIPAAm) by benzophenone-initiated UV polymerization on micro-pillared surfaces was performed. By increasing polymerization time PNIPAAm first coats the top of the mushroom pillars then bridges the gap between pillars rather than penetrating the inter-pillar spaces due to the intrinsic features of Poly(dimethylsiloxane) (PDMS) pillars. This enables controlled grafting via control of polymerization time. Above the lower critical solution temperature (LCST), the grafted PNIPAAm brushes are immiscible with water and the surfaces displayed a strongly hydrophobic state with a large contact angle of 120°. Below the LCST, the grafted PDMS micropillars surface swells and absorbs water significantly faster than flat grafted surfaces, displaying a hydrophilic state with a small contact angle 33°. Interestingly, grafting on micropillars as opposed to flat surfaces enhanced the magnitude of the contact angle change across PNIPAAm’s hydrophobicity-hydrophilicity switch and enhances the speed of graft hydration. The grafted surface was further found to be durable under strong water jetting. Thus, a significant synergetic effect of the grafted PNIPAAm and micropillars delivered a durable temperature-modulated smart wetting property with a transition from the hydrophobic to hydrophilic state.

Condensation Frosting on Micropillar Surfaces - Effect of Microscale Roughness on Ice Propagation.

Microscale surface structures have been widely explored as a promising tool for antifreezing or frost avoidance on heat transfer surfaces. Despite studies of many surface feature designs, the mechanisms associated with condensation freezing and ice propagation on microstructured surfaces have yet to be thoroughly elucidated, espectially when it comes to quantitative understanding. In this work, condensation freezing on circular micropillar surfaces is investigated, with varying pillar spacing and height (layout/microscale roughness) but a constant pillar diameter. The pillar layout is found to have significant effects on both liquid nucleation and neighboring droplet interactions, as reflected by the condensation droplet distribution prior to soilidification and eventually the freezing front propagation area velocity. In general, nucleation is preferred on the pillar top rather than the bottom of the pillared surface unless there is a large distance between the pillars. Interactions between neighboring droplets solely on pillar tops (or bottom surfaces) can induce heterogeneity in the droplet distribution and slow freezing front propagation. Based on the roles the pillars play in nucleation, droplet coalescence, and ice bridging, four different condensation states are identified and related to the layout of the pillars, and the freezing front area propagation velocity is found to be different in each state. The findings provide a quantitative basis for designing antifreezing surfaces, applicable to a wide range of thermal systems.

Temperature effect on mechanical response of flash-sintered ZnO by in-situ compression tests

ZnO has been widely used for various industrial applications. Compared to the extensive investigations on the functional properties of ZnO, the mechanical behavior of ZnO is less well understood. Here we investigated temperature-dependent deformation mechanisms of flash-sintered and conventionally sintered ZnO by in-situ microcompression test up to 600 °C. When tested at room temperature, prominent transgranular cracking occurred in the flash-sintered ZnO at a flow stress of 1.2 GPa, higher than that for the conventionally sintered ZnO (0.9 GPa). A high density of dislocations formed near grain boundaries and fracture surfaces led to the high strength and work-hardening capability in the flash-sintered ZnO. At 200 °C, the flow stress of the flash-sintered ZnO decreased to 0.7 GPa, and the fracture mode evolved to intergranular cracking. When compressed at 400 °C, severe deformation localized at the pillar top was dominated by grain boundary-mediated processes. At 600 °C, plastically deformed grains and intergranular cracks increased prominently, accompanied by a decrease in the density of geometrically necessary dislocation. This study shed lights on understanding the influence of the flash sintering process on the mechanical behaviors of ZnO.

Mechanisms of picosecond laser-induced damage in common multilayer dielectric gratings.

The modifications of multilayer dielectric (MLD) gratings arising from laser-induced damage using 0.6-ps and 10-ps laser pulses at 1053 nm are investigated to better understand the damage-initiation mechanisms. Upon damage initiation, sections of the affected grating pillars are removed, thereby erasing the signature of the underlying mechanisms of laser damage. To address this issue, we performed paired studies using macroscopic grating-like features that are 5 mm in width to reveal the laser-damage morphology of the different grating sections: pillar side wall, sole, and pillar top. The results suggest that, similarly to MLD coatings, there are two damage-initiation mechanisms corresponding to the different pulse durations.

Enhancement of nucleate boiling by combining the effects of surface structure and mixed wettability: A lattice Boltzmann study

The combination of microstructures and mixed wettability for enhancing nucleate boiling has attracted much attention in recent years. However, in the existing experimental and numerical studies, the tops of microstructures are entirely subjected to wettability modification, which makes the influences of mixed wettability dependant on the characteristic length of microstructures. In order to disclose the joint effects of surface structure and mixed wettability on nucleate boiling, in this work we propose an improved type of pillar-textured surface with mixed wettability, in which the tops of square pillars are partially subjected to wettability modification. Numerical investigation of the boiling heat transfer performance on the improved mixed-wettability surface is carried out using a three-dimensional thermal multiphase lattice Boltzmann model. The numerical results show that the width of the wettability-modified region plays an important role in the boiling performance of the improved mixed-wettability surface and the best boiling performance is achieved in the situation that the width of the wettability-modified region is sufficiently large but the bubble nucleated on the pillar top still does not interfere with the coalescence-departure mechanism of the bubbles nucleated around the pillar, which optimizes the joint effects of surface structure and mixed wettability for enhancing nucleate boiling. The influences of the shape of the wettability-modified region are also studied. Among the investigated shapes, the square is found to perform better than the other two shapes.

3D numerical simulation of condensation and condensate behaviors on textured structures using lattice Boltzmann method

Condensation is one of the most widely investigated interface phenomenon in science and engineering. However the three-dimensional (3D) condensate behaviors including the initial nucleation, growth, coalescence, penetration, spreading or expansion on textured surfaces have seldom been clarified comprehensively. In this work, the 3D pseudopotential LB model with a phase change model is employed, and the condensation process on textured structures with homogeneous and inhomogeneous wettability is investigated. It is found that the nucleation position rises to the top of the structure and the nucleation time gets longer with the increase of surface hydrophobicity when condensation occurs on homogeneous textured structure, and the dropwise condensation mode transits into the film condensation. The condensation on structures with inhomogeneous surface wettability at the top, side and bottom of the pillars and structures with hybrid top (namely hydrophilic spots in the center of the top of the hydrophobic pillars) is then investigated. It is concluded that hybrid top of the textured structures can enhance condensation heat transfer, shorten the nucleation time, and at the same time maintain the condensate in the Cassie state for a long time before the condensation mode transition, leading to the best condensation performance.