Difference In Surface Free Energy Research Articles

Experimental constraints on Mg isotope fractionation during the aragonite–calcite transition and implications for seawater δ26Mg reconstruction

The linkage between the variation of the seawater Mg budget and the long-term carbon cycle can be elucidated by seawater Mg isotope composition (δ26Mg). However, obtaining primary seawater δ26Mg signatures from marine archives is challenging due to the widespread alteration of diagenesis. Aragonite, a common primary marine carbonate, can effectively record seawater δ26Mg but is prone to alteration and transformation into calcite during early diagenesis. Therefore, a comprehensive understanding of Mg isotope behavior during the aragonite–calcite transition is essential to enhance the applicability of aragonite δ26Mg. In this study, we investigate the variation of aragonite δ26Mg during diagenesis with a limited supply of Mg by conducting a series of well-controlled aragonite–calcite transition experiments in a closed system. The experimental conditions encompass temperatures of 60 and 90 °C, the presence of Ca and Na in the solution, varying Na concentrations, as well as the presence of calcite seed. Results demonstrate that the significant decrease of bulk carbonate δ26Mg is accompanied by a substantial amount of Mg released into the solution during the aragonite–calcite transition, and the amount of released Mg is controlled by fluid chemistry via altering Mg partitioning in calcite. Furthermore, Mg isotope fractionation during calcite precipitation is influenced by temperature, ionic strength, and the presence of calcite seed, while kinetics played a negligible role in our experiments. Combined with previous experiments, the temperature-dependent Mg isotope fractionation during calcite precipitation in unseeded experiments is Δ26Mgcal-sol = (−0.13 ± 0.06) × 106/T2 – (0.47 ± 0.68). This fractionation is systematically higher than that of seeded experiments by 0.3–0.6 ‰ from 15 to 90 °C and can mainly be attributed to differences in surface free energy between homogeneous and heterogeneous calcite nucleation. These findings offer fundamental understandings of the Mg isotope behavior during the aragonite–calcite transformation, providing useful insights for interpreting the variation of δ26Mg in experimental and natural carbonates and facilitating ancient seawater δ26Mg reconstruction.

Fabrication of an Organic-Inorganic Hybrid Hard Coat with a Gradient Structure Controlled by Photoirradiation.

Organic-inorganic materials have attracted attention because of the advantages of both organic and inorganic resins. Among their disadvantages, hard coating films made of organic-inorganic mixtures of resins have opacity and interface peeling problems because of organic-inorganic phase separation and surface segregation of inorganic resins. Although an organic-inorganic gradient-structured material comprising an inorganic-rich domain at the air interface and an organic-rich domain at the organic substrate has the potential to solve these problems, the fabrication of a gradient-structured material has not yet been achieved. Here, we describe the fabrication of an organic-inorganic gradient film by impeding the movement of organic and inorganic resins through radical photopolymerization of organic and inorganic oligomers. Moreover, we successfully enhanced gouge hardness by cross-linking with photobase-catalyzed sol-gel reactions of inorganic resins at the air interface. As a result, the organic-inorganic gradient coating contributed excellent gouge hardness (pencil hardness >9H), adhesion to an organic substrate such as polycarbonate, and transparency (visible light transmittance >99%T). In addition, we demonstrated that the formation of organic-inorganic gradient structures is dominated by the surface free energy and viscosity of each resin. Achieving a gradient structure required a significant difference in surface free energy (>20 mJ/m2) and high mixture viscosity (>65 mPa·s).

Mass production of superhydrophilic micropatterned copper surfaces using powder injection molding process

Hydrophilic micropatterned copper surfaces are manufactured using a powder injection molding (PIM) process. Copper powder and a wax-polymer-based binder system are utilized to prepare a feedstock. The rheological properties of the feedstock are evaluated to design the PIM process. Polymethylmethacrylate (PMMA) sacrificial mold inserts fabricated by photolithography are used to shape the micropatterns. Both PIM and photolithography processes are suitable for high-volume products; therefore, the micropatterned surfaces can be mass-produced. The wettability of the manufactured surfaces is investigated by measuring the apparent contact angle. The apparent contact angle tends to decrease as the absolute value of the difference in effective surface free energy between the wet and dry states increases. When the absolute value of the difference is equal to or exceeds 150 mJ/m 2 , the surface is fully wetted immediately and exhibits superhydrophilicity. Both high aspect ratio and small gap size are key to achieving superhydrophilicity of the micropatterned surface. • Superhydrophilic micropatterned copper surface is manufactured without any defects. • Rheological analysis of the copper feedstock indicates that it is suitable for PIM. • PMMA sacrificial mold inserts fabricated using photolithography shape micropatterns. • The combined process is suitable for mass production of superhydrophilic surfaces. • Wettability of the micropatterned surface is linked to the dimensions of the pattern.

Self-stratification studies in waterborne epoxy-silicone systems

Waterborne epoxy‑silicone coating formulations are prepared by combining selected ingredients in optimum quantities to produce ~250–275 μm films (dry film thickness, DFT) applied on polyester, sandblasted steel, smooth steel, acrylic, polypropylene and aluminum substrates. The self-stratification of the applied coatings is then evaluated using Fourier Transform Infrared spectroscopy – Attenuated Total Reflectance (FTIR–ATR) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDX) analysis. The difference in the absorption spectra of the top and bottom surfaces of these films as well as a significant difference in topography seen from the SEM images and elemental mapping through an EDX analysis of the cross-section has confirmed the occurrence of stratification on polyester substrate. The observed stratification results are subsequently compared with a theoretical model where the primary mechanism driving the separation is assumed to be the surface free energy difference of the resins and their respective wetting of the substrate. The influence of using two different theories, Wu's Harmonic Mean Method and Owens-Wendt Method for the interfacial surface tensions and the solid surface free energy computations, on the predictions from this model is also tested. The theoretical predictions support the observed results for most cases of the formulated waterborne systems; except for the case of sandblasted steel, the observed results do not match the predictions. The possible reasons for the difference in between the prediction and observation for this specific case has also been elucidated.

Organic solvent permeation characteristics of TiO2-ZrO2 composite nanofiltration membranes prepared using organic chelating ligand to control pore size and surface property

TiO2-ZrO2-(3,5-di-tert-butylcatechol, DTBC) composite membranes were fabricated via the sol–gel method under four different firing conditions: 300 °C (N2), 300 °C (Air), 350 °C (Air), and 500 °C (Air). The chemical structure of the DTBC originated organic material in the composite was controlled by setting the firing temperature. The average pore sizes of the membranes were 1.0–1.1 nm when fired at 300 °C, 1.4 nm at 350 °C, and 2.1 nm at 500 °C. The molecular weight cut-off of the membranes (in daltons) in water ranged from 480 to 535 when fired at 300 °C, 890 at 350 °C, and 1,680 at 500 °C, whose corresponding molecular diameter was in good agreement with the average pore size measured via nanopermporometery. Permeation tests of the organic solvents showed that the membrane-solvent interaction affected the permeation mechanism in addition to the solvent viscosity and the occupied area of the solvent molecules. The surface free energy difference between the membrane and the solvent expressed the interaction between the membrane and the solvent molecule. The proposed solvent permeation model was examined and showed better agreement with the experimental results compared with the model based on the solubility parameters of a solvent. The organic solvent permeation mechanism of the ceramic NF membrane was greatly affected by the membrane-solvent intermolecular interaction.

MG-63 and FetMSC Cell Response on Atomic Layer Deposited TiO2 Nanolayers Prepared Using Titanium Tetrachloride and Tetraisopropoxide

Titanium oxide nanocoatings were synthesized on the surface of monocrystalline silicon and ultra-fine-grained titanium by atomic layer deposition (ALD) using titanium tetrachloride (TiCl4) and titanium tetraisopropoxide (TTIP). The morphology of the samples was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure and composition were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle measurements, and energy-dispersive spectroscopy (EDS). The cytological response of osteosarcoma MG-63 and human fetal mesenchymal stem cells (FetMSCs) were studied by analyzing their morphology, viability, and alkaline phosphatase activity with and without the use of medium-induced differentiation in the osteogenic direction. A significant influence of the precursor type and ALD temperature on the crystal structure, morphology, composition, and surface free energy of TiO2 nanocoatings was found. The biocompatibility of amorphous non-stoichiometric and partially crystalline stoichiometric TiO2 coatings was compared. Both types of cells showed faster adhesion and improved spreading on the surface for the samples from TTIP compared to those from TiCl4 at the early stages of cultivation (2 h) due to the difference in composition and higher surface free energy. No cytotoxic effect was found on both types of coatings, nor was there a noticeable difference in cell differentiation. All ALD coatings provided excellent biocompatibility and osteoconductive properties.

Mechanistic understanding of the aspect ratio-dependent adjuvanticity of engineered aluminum oxyhydroxide nanorods in prophylactic vaccines

Aluminum oxyhydroxide (AlOOH) adjuvants are widely used in human vaccines. However, the interaction mechanisms at the material-bio interface, and further understandings on physicochemical property-dependent modulation of the immune responses still remain uncertain. Herein, a library of AlOOH nanorods with well-defined aspect ratios is designed to explore the mechanisms of adjuvanticity. The aspect ratios of AlOOH nanorods were demonstrated to be intrinsically modulated by the hydroxide supersaturation level during crystal growth, leading to the differences in surface free energy (SFE). As a result, higher aspect ratio AlOOH nanoadjuvants with lower SFE exhibited more hydrophobic surface, resulting in more membrane depolarization, cellular uptake and dendritic cell (DC) activation. By using hepatitis B surface antigen (HBsAg) virus-like particles (VLPs) or SARS-CoV-2 spike protein receptor-binding domain (RBD) as model antigens, AlOOH nanorods with higher aspect ratio were determined to elicit more potent humoral immune responses, which could be attributed to the enhanced DC activation and the efficient antigen trafficking to the draining lymph nodes. Our findings highlight the critical role of aspect ratio of AlOOH nanorods in modulating adjuvanticity, and further provide a design strategy for engineered nanoadjuvants for prophylactic vaccines.

Nonclassical Nucleation Pathways in Stacking-Disordered Crystals

The nucleation of crystals from liquid melt is often characterized by a competition between different crystalline structures or polymorphs and can result in nuclei with heterogeneous compositions. These mixed-phase nuclei can display nontrivial spatial arrangements, such as layered and onionlike structures, whose composition varies according to the radial distance, and which so far have been explained on the basis of bulk and surface free-energy differences between the competing phases. Here we extend the generality of these nonclassical nucleation processes, showing that layered and onionlike structures can emerge solely based on structural fluctuations even in the absence of free-energy differences. We consider two examples of competing crystalline structures, hcp and fcc forming in hard spheres relevant for repulsive colloids and dense liquids, and the cubic and hexagonal diamond forming in water relevant also for other group 14 elements such as carbon and silicon. We introduce a novel structural order parameter that combined with a neural-network classification scheme allows us to study the properties of the growing nucleus from the early stages of nucleation. We find that small nuclei have distinct size fluctuations and compositions from the nuclei that emerge from the growth stage. The transition between these two regimes is characterized by the formation of onionlike structures, in which the composition changes with the distance from the center of the nucleus, similar to what is seen in the two-step nucleation process.15 MoreReceived 24 June 2020Revised 28 January 2021Accepted 23 April 2021DOI:https://doi.org/10.1103/PhysRevX.11.031006Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCrystal growthCrystallizationNucleationPhysical SystemsHard sphere colloidsIceWaterPolymers & Soft MatterCondensed Matter, Materials & Applied Physics

Influence of pore structure and surface free energy on the contents of adsorbed and free methane in tectonically deformed coal

Differences in pore and surface free energy affect the occurrence of adsorbed and free methane in tectonically deformed coal (TDC), which influences coalbed methane extraction and coal mine safety. Therefore, eight middle-rank TDC samples from the Yueliangtian coal mine (Guizhou Province, Southwest China) were screened. Pore volume and specific surface area were explored via mercury intrusion, nitrogen adsorption/desorption, and carbon dioxide adsorption approaches. Based on the low-field nuclear magnetic resonance analysis for powdered TDC, the relaxation time (T2) amplitudes and the contents of adsorbed and free methane, the surface free energy reduction (SFER), and adsorption potential were measured. 1) The pore specific surface area, pore volume, T2 amplitudes and contents of adsorbed and free methane, SFER, and adsorption potential of the strongly deformed coal are obviously larger than those of the weakly deformed coal. Adsorbed methane content is dominantly affected by micropore specific surface area, and free methane content is primarily influenced by macropore volume. 2) The methane T2 spectra of the TDC contain three distinctive peaks; the first, P1 (T2 < 2 ms), represents adsorbed methane, and the second, P2 (2–40 ms), corresponds to free methane. As the pressure increases, both the T2 amplitude rate and content rate of adsorbed methane decrease, while those of free methane rise. 3) With the enhancement of tectonic deformation, the specific surface area and volume of pores increase (especially those of micropores and macropores), more adsorption positions and storage space for adsorbed and free methane become available, and the SFER and adsorption potential of the TDC are enhanced, leading to increases in the T2 amplitudes and contents of adsorbed and free methane. The present research will help improve the accuracy of coalbed methane evaluation and the prevention of coal and gas outbursts.

Relationship between the surface structure of the gate insulator and the performance of organic thin-film transistors

To investigate the impact on the device performance of different surface structures of the self-assembled monolayer (SAM) used to form the gate insulator of organic field effect transistors (OFETs), sum frequency generation spectroscopy and contact angle measurements were performed on SAM insulators with different surface structures. Furthermore, the surface structure of the SAM was varied with changing its dipping or spin coating formation method. Moreover, the electrical properties of OFETs were examined when only the surface structure of the gate insulator had changed. The results showed that compared with the dipping method, the disorder of alkyl chains (gauche defects) increased on the octadecylphosphonic acid (ODPA) SAM surface, deposited through the spin coating method. Contact angle measurements revealed that the surface free energy of ODPA-SAM increased in tandem with an increase in gauche defects on the SAM surface. Contrary to expectations, the device performance of OFETs with the SAM insulator with gauche defects improved, which is most probably due to the smaller surface free energy difference between ODPA-SAM and poly(3-hexylthiophene) (P3HT), which improved the adhesion at the ODPA-SAM/P3HT interface.

Suppressing the Ring Stain Effect with Superhydrophilic/Superhydrophobic Patterned Surfaces.

The ring stain phenomenon is a critical hindrance to the distribution of the solute during drying for biochemical assays and materials deposition. Herein, we developed a substrate, characterized with hydrophilic spots surrounded by hydrophobic areas, to suppress the ring stain effect, and fabricated four kinds of patterned surfaces to investigate the relationship between the surface free energy and ring-suppressing performance. We found that during the evaporation process, a drop was constrained on the hydrophilic spot with a pinned contact line, and the ring stain effect was suppressed significantly. The suppressing performance of the ring stain effect increases with surface free energy differences between the hydrophilic and hydrophobic regions.

Early stages of InP nanostructure formation on AlInAs

The potential of ${\mathrm{Al}}_{x}{\mathrm{In}}_{1\ensuremath{-}x}\mathrm{As}/\mathrm{InP}$ as a flexible candidate for future device applications relies on a thorough understanding of the growth mechanisms of this system during metalorganic vapor-phase epitaxy (MOVPE). We present a systematic study of the morphology of InP films grown on macroscopically lattice-matched ${\mathrm{Al}}_{x}{\mathrm{In}}_{1\ensuremath{-}x}\mathrm{As}$ during low-pressure MOVPE. InP and AlInAs alloys are often assumed to be fully compatible, as long as macroscopic lattice matching is preserved. However, thin InP films show a variety of spontaneously formed nanostructures as the growth conditions are varied. We have examined the systematic variation of individual growth conditions (temperature, V/III ratios, growth rate, and misalignment angle and direction) to obtain a comprehensive picture of the morphological evolution of this system. The analysis of these experiments is based on a kinetic model of the deposition and decomposition of polyatomic precursors and the subsequent adatom kinetics, which is used to form characteristic lengths from combinations of kinetic coefficients associated with each process. The orderings of these lengths for particular ranges of growth conditions account for many aspects of the morphological evolution on perfectly oriented and misoriented surfaces. For perfectly oriented surfaces, differences in surface free energies are suggested as the driving force for Volmer-Weber growth and the observed formation of multilayer features. Finally, we examine the transition from quantum rings to quantum dots during postgrowth recovery when the group-V source is switched from phosphine to arsine. A qualitative explanation of similar observations in InAs/InP based on As/P exchange is consistent with our findings.

Estimating the Nucleation Ability of Various Surfaces Towards Isotactic Polypropylene via Light Intensity Induction Time Measurements

Crystallization of isotactic polypropylene (iPP) at the interface with crystalline films of two commercially employed nucleating agents (sodium benzoate (NaBz) and sodium 2,2’-methylene bis-(4,6-di-tert-butylphenyl)phosphate (NA-11)) and with a glass fiber (GF) was investigated using a polarized optical microscope. The analysis of the light intensity evolution during the crystallization process enabled the successful estimation of the time at which the crystal growth began, i.e., the induction time (ti), at various crystallization temperatures. Meaningful differences in the ti values were observed between the investigated systems. Moreover, the ti data have been analyzed according to different nucleation models proposed in the literature, which consider either the time to form the first crystalline layer in contact with the substrate or the time required to grow a cluster of critical size. It has been found that the two models are applicable in different temperature ranges depending on the efficiency of the given substrate. Therefore, in order to obtain the value of the surface free energy difference function, Δσ, which is directly related to the nucleation energy barrier and useful for the definition of a universal nucleating efficiency scale, a model that considers both the above-mentioned times was fitted to the overall data. The values of Δσ for the nucleation of iPP on the surface of the different substrates are thus obtained and discussed in the framework of the literature results.

Nanoscale Behavior and Manipulation of the Phase Transition in Single-Crystal Cu2 Se.

Phase transition is a fundamental physical phenomenon that has been widely studied both theoretically and experimentally. According to the Landau theory, the coexistence of high- and low-temperature phases is thermodynamically impossible during a second-order phase transition in a bulk single crystal. Here, the coexistence of two (α and β) phases in wedge-shaped nanosized single-crystal Cu2 Se over a large temperature range are demonstrated. By considering the surface free-energy difference between the two phases and the shape effect, a thermodynamic model is established, which explicitly explains their coexistence. Intriguingly, it is found that with a precise control of the heating temperature, the phase boundary can be manipulated at atomic level. These discoveries extend the understanding of phase transitions to the nanoscale and shed light on rational manipulation of phase transitions in nanomaterials.

Experimental study on two-phase flow pressure drop during ethanol–water vapor mixture condensation in microchannels

Ethanol-water vapor mixtures condensation shows different flow patterns in microchannels due to the equivalent surface free energy differences. The transition point of streak flow pattern was introduced in the paper which was found closely related to the frictional pressure drop of ethanol–water vapor mixtures condensation flow in microchannels. Characteristics of two-phase pressure drop for ethanol–water vapor mixtures condensation flow in silicon microchannels of streak and smooth annular flow pattern were investigated. Four types of multi-port trapezoidal and triangular microchannels with hydraulic diameter in the range of 126–155 μm were employed. The pressure drop was determined under steam mass flux between 259.2 and 504.8 kg m−2 s−1 when the inlet ethanol weight concentration varied from 1% to 60%. The experimental pressure drop results were compared with existing correlations of flow condensation. The transition point basing on the streak flow pattern of binary vapor condensation was proposed to replace the traditional Reynolds number criterion of the laminar flow state to turbulent flow state for the frictional factor and the C parameter for Kim and Mudawar’s universal pressure drop model, which is in good agreement with the results the experiment results.

Initial lamellar thickness dependency of recrystallization behavior of poly(4‐methyl‐1‐pentene)

ABSTRACTThe isothermal crystallization and subsequent melting process in semicrystalline poly(4‐methyl‐1‐pentene) were investigated via temperature‐dependent small‐ and wide‐angle X‐ray scattering and Flash DSC techniques. In a phase diagram of inversed crystalline lamellar thickness and temperature, the crystallization and melting lines can be described by two linear dependencies of different slopes and different limiting temperatures at infinite lamellar thickness. Upon subsequent heating, recrystallization lines with different slopes were observed for samples with different lamellar thickness, indicating changes in surface free energy difference between stabilized crystallites and mesomorphic phase. The surface free energy of native crystallites with extended‐chain conformation decreased with increasing lamellar thickness due to a more ordered surface region and less chain ends which changes cooperatively with mesomorphic phase. The surface free energy of stabilized crystallites remained unchanged for all lamellar thickness. Therefore, the recrystallization lines with different slopes are consequences of changes in surface free energy of mesomorphic phase. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 219–224

Two-phase flow patterns for condensation of ethanol-water mixtures in triangular microchannels

An array of isosceles triangular microchannels with sidewalls inclined at 54.7° were fabricated by the wet etching method. The condensation of water and ethanol binary mixtures was visualized with additional measurements to investigate the condensation flow patterns in the silicon microchannels with hydraulic diameters of approximately 155μm. The visualization study indicated that the flow patterns were influenced by the inlet ethanol concentration and the mass flux. Annular, injection, droplet-injection and bubble flow patterns were observed along the channels. The condensation instability effects were stronger with increased equivalent surface free energy differences. The increasing equivalent surface free energy differences caused droplets to form in the microchannel that moved from the condensing surface to the top corner due to the Marangoni effect, which led to fluctuating flow patterns. The frequency of the injection flow increased with increasing Rev and input ethanol concentration. The mass flux and the steam quality during condensation were measured at various locations in the experiments. Two phase flow pattern maps were developed for various inlet ethanol concentrations.

Numerical Study of the Forced Convective Condensation on a Short Vertical Plate

ABSTRACTNumerical investigation was conducted on the effects of gravity, surface tension, and wall adhesion upon condensation on a short vertical plate. The volume of fluid method was applied to model the interaction between the liquid and vapor phases and to capture the interface. The surface tension was implemented by employing the method of continuum surface force model. A modified phase-change model, derived from basic equations related to the kinetic gas theory, was proposed and verified based on the cases of Nusselt film condensation of water vapor on a vertical flat plate, the forced convection film condensation on a horizontal flat plate, and the capillary blocking due to condensation in a horizontal miniature circular tube. The predicted results showed that a laminar capillary wavy flow regime exists and the waves enhance the heat transfer of condensation on the plate. The mean film thickness increases and the heat transfer performance becomes worse with decrease of gravity. A high value of surface tension or contact angle, representing a large surface free energy difference, leads to an enhancement of heat transfer on the plate with large-amplitude waves.

Visualization study of condensation of ethanol–water mixtures in trapezoidal microchannels

A visualization experiment is carried out to investigate the ethanol–water vapor mixtures condensation flow patterns in an array of microchannels under a wide range of concentration (2–60%). The text microchannel is a trapezoidal silicon channel with a hydraulic diameter of 165.87μm and a length of 50mm. Along the flow direction, annular, annular-streak, annular-streak-droplet, churn, injection, droplet-injection and bubble flow patterns are observed in the vapor mixtures condensation under different inlet ethanol mass concentration (60%, 31%, 20%, 6%, 4% and 2%), which is obviously different from pure steam condensation. The equivalent surface free energy differences under various vapor conditions and vapor–surface temperature differences are calculated quantitatively. The experimental results show that flow patterns are closely related to the equivalent surface free energy differences. A correlation based on the critical quality is proposed to indicate the injection two-phase flow patterns transition.

Analysis of condensation heat transfer enhancement with dropwise-filmwise hybrid surface: Droplet sizes effect

The maximum droplet radius during dropwise condensation can significantly influence the heat transfer characteristics. On the dropwise-filmwise hybrid surface, droplets on the dropwise region can remove through filmwise region spontaneously driven by the surface free energy difference between the dropwise and filmwise regions, and thus the maximum droplet radius (equivalent to the departure radius for the complete dropwise condensation) can be adjusted by the configurations of hybrid surface. The condensation heat transfer enhancement of steam with hybrid surface is investigated in this paper by integrating the dropwise and filmwise condensation heat transfer models. The influence of maximum droplet radius on heat flux of dropwise region, the liquid film thickness and heat flux of filmwise region are investigated, respectively. Accordingly, the heat transfer contributions of two regions to the heat transfer characteristics of hybrid surface are analyzed. Finally, the influences of surface subcooling degree, contact angle and contact angle hysteresis on heat transfer characteristics of hybrid surface are discussed. The results indicate that an optimum value of the maximum droplet radius exists to enhance the condensation heat transfer of steam with the hybrid surface, which is dependent on surface subcooling degree, filmwise region width and contact angle while independent on contact angle hysteresis. With the surface subcooling degree increases ranging from 1.0K to 10K, the optimum maximum radius of droplet on dropwise region increases from about 0.2mm to 0.375mm. The optimum maximum radius of droplet increases from about 0.25mm to 0.5mm when the filmwise region width increases from 0.5mm to 1.0mm. The optimum maximum radius of droplet decreases with the increase of the contact angle. Therefore, steam condensation heat transfer performance can be regulated and optimized by designing the hybrid surface appropriately. The results also indicate that heat transfer enhancement factor for the hybrid surface is larger than 1.0 for the low surface subcooling or the condensing surface with small contact angle or large contact angle hysteresis. Therefore, the hybrid surface can effectively enhance the condensation heat transfer for the special cases, such as those with low surface subcooling degree, or with small contact angle and large contact angle hysteresis. For the case discussed in this paper, the maximum enhancement factor can approach up to about 1.18.