Magnetically Induced Decrease in Droplet Contact Angle on Nanostructured Surfaces

Orthopaedic surgery comes with an inherent risk of bacterial infection, prolonged antibiotic therapy and revision surgery. Recent research has focused on nanostructured surfaces to improve the bactericidal and osseointegrational properties of implants. However, an understanding of the mechanical properties of bactericidal materials is lacking. In this work, the surface properties of hydrothermal TiO2 nanostructured surfaces are investigated for their effect on bactericidal efficiency and cellular metabolic activity of human osteoblast cells. TiO2 nanostructures, approximately 307 nm in height and 14 GPa stiffness, were the most effective structures against both gram-positive (Staphylococcus aureus) and gram-negative (Pseudomonas aeruginosa) bacteria. Statistical analysis significantly correlated structure height to the death of both bacteria strains. In addition, the surface contact angle and Young’s modulus were correlated to osteoblast metabolic activity. Hydrophilic surfaces with a contact angle between 35 and 50° produced the highest cellular metabolic activity rates after 24 hours of incubation. The mechanical tests showed that nanostructures retain their mechanical stability and integrity over a long time-period, reaffirming the surfaces’ applicability for implants. This work provides a thorough examination of the surface, mechanical and wettability properties of multifunctional hydrothermally synthesised nanostructured materials, capable of killing bacteria whilst improving osteoblast metabolic rates, leading to improved osseointegration and antibacterial properties of orthopaedic implants.

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Synthesis of Superhydrophobic Carbon Surface during Combustion Propane

Eurasian Chemico-Technological Journal ◽

10.18321/ectj94 ◽

2011 ◽

Vol 14 (1) ◽

pp. 19 ◽

Cited By ~ 4

Author(s):

Z.A. Mansurov ◽

M. Nazhipkyzy ◽

B.T. Lesbayev ◽

N.G. Prikhodko ◽

M. Auyelkhankyzy ◽

...

Keyword(s):

Contact Angle ◽

Surface Morphology ◽

Carbon Nanostructures ◽

Carbon Surface ◽

Flame Synthesis ◽

Water Droplets ◽

Sem Images ◽

Surface Carbon ◽

Nanostructured Surfaces ◽

Nonpremixed Flame

We synthesize and deposit carbon nanostructures through flame synthesis on silicon and nickel wafers at different nonpremixed flame locations to produce hydrophobic surfaces. The hydrophobicity is characterized through the contact angle for water droplets placed on the surface. The surface morphology of the nanoparticles is obtained from SEM images. The morphology and hydrohobicity of the nanostructured surfaces depends upon the deposition, which differs at various flame locations. We determine the optimum flame location for the synthesis and deposition of surface carbon nanostructures that lead to maximum hydrophobicity.

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Controlling states of water droplets on nanostructured surfaces by design

Nanoscale ◽

10.1039/c7nr06896d ◽

2017 ◽

Vol 9 (46) ◽

pp. 18240-18245 ◽

Cited By ~ 18

Author(s):

Chongqin Zhu ◽

Yurui Gao ◽

Yingying Huang ◽

Hui Li ◽

Sheng Meng ◽

...

Keyword(s):

Contact Angle ◽

Water Droplets ◽

Nanostructured Surfaces ◽

Base Angle ◽

Intrinsic Contact Angle

The transition between the Cassie and Wenzel states can be controlled via precisely designed trapezoidal nanostructures on the surface, for which the base angle of the trapezoids and the intrinsic contact angle of the surface are two possible adjustable parameters.

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Cell Growth Morphology on Nano-Structured Surface Based on Wetting

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1061-1062.575 ◽

2014 ◽

Vol 1061-1062 ◽

pp. 575-578

Author(s):

Ge Qin ◽

Hao Xue Li ◽

Meng Die Ma ◽

Juan Juan Li ◽

Ya Fei Deng

Keyword(s):

Contact Angle ◽

Solid Surface ◽

Cell Morphology ◽

Nanostructured Surface ◽

Growth Morphology ◽

Nanostructured Surfaces ◽

Microstructured Surface ◽

Solid Liquid ◽

The Impact ◽

Growth Shape

This paper studied the growth morphology of the cells on the nanostructured surfaces of the bio-electrodes implanted in human patients. A transition model of the cells on those surfaces, which is the W model or C-B model, was deduced according to the effect of the microstructures on the wetting characteristics and the solid-liquid contact angle models of the microstructured surface. According to the contact angle formula of the model of the droplet on the solid surface, the formula was derived to describe the morphology of the ells on the nanostructured surface. The results of the experiments showed the impact of nanostructured to the morphology of the cells. The changes of the cell morphology on the smooth surface and the nanostructured surface showed that the cell morphology was affected by the nanostructures of solid surface, and the growth shape of cell was different when the sizes were different.

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Metrics for Quantifying Surface Wetting Effects on Vaporization Processes at Nanostructured Hydrophilic Surfaces

Volume 2: Heat Transfer in Multiphase Systems; Gas Turbine Heat Transfer; Manufacturing and Materials Processing; Heat Transfer in Electronic Equipment; Heat and Mass Transfer in Biotechnology; Heat Transfer Under Extreme Conditions; Computational Heat Transfer; Heat Transfer Visualization Gallery; General Papers on Heat Transfer; Multiphase Flow and Heat Transfer; Transport Phenomena in Manufacturing and Materials Processing ◽

10.1115/ht2016-7203 ◽

2016 ◽

Cited By ~ 2

Author(s):

Claire M. Kunkle ◽

Van P. Carey

Keyword(s):

Contact Angle ◽

Contact Line ◽

Contact Angles ◽

Apparent Contact Angle ◽

Static Contact Angle ◽

Sensitive Indicator ◽

Nanostructured Surfaces ◽

Hydrophilic Surfaces ◽

Static Contact ◽

Spread Area

A static contact angle is most often used as a means of quantifying the wetting characteristics of the liquid phase in vaporization processes at a solid surface. This metric is often convenient to measure and intuitive in its interpretation, but when a surface is superhydrophilic, the resulting low contact angles are difficult to measure accurately from photographs of sessile droplet profiles or contact line regions. For droplets at ultra low contact angles, small changes of contact angle can produce very large changes in wetted surface area, which makes small uncertainties in contact angle result in large uncertainties in wetted area. For hydrophilic nanostructured surfaces, another disadvantage is that the relationship of the macroscopic (apparent) contact angle to the nanoscale interaction of the liquid and vapor contact line with the nanostructured surface is not always clear. In this study, a new wetting metric based on spreading characteristics of sessile droplets is proposed that can be easily measured for hydrophilic surfaces. This metric also has the advantage that it is a more direct and sensitive indicator of how a droplet spreads on the surface. The spread area directly impacts heat transfer interactions between the droplet and the surface, therefore affecting evaporation time. Consequently, a metric that more directly illustrates the spread area provides an indication of how the wetting will affect these mechanisms. Use of the proposed new metric is explored in the context of evaporation and boiling applications with superhydrophilic surfaces. Characteristics of this metric are also compared to static contact angle and other choices of wetting metrics suggested in earlier studies, such as dynamic advancing and receding contact angles, and spreading coefficients. The effects of nanoscale structure and/or roughness on the proposed wetting metric are analyzed in detail. A model is developed that predicts the dependence of the proposed wetting parameter on intrinsic material wettability for rough, nano-structured surfaces. The model results demonstrate that the proposed metric is a more sensitive indicator of macroscopic wetting behavior than apparent contact angle when the surface is superhydrophilic. This characteristic of the proposed new metric is shown to have advantages over other wetting metrics in the specific case of superhydrophilic nanostructured surfaces. Application of the proposed wetting metric is demonstrated for some example nanostructured surfaces. The results of our study indicate that this proposed new metric can be particularly useful for characterizing the effects of variable wetting on vaporization processes on highly wetted nanostructured surfaces.

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A State-of-the-Art Review on Pool Boiling on Nanostructure Surfaces

ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2015-48120 ◽

2015 ◽

Cited By ~ 4

Author(s):

Isabela Ignácio ◽

Elaine Maria Cardoso ◽

José Luiz Gasche ◽

Gherhardt Ribatski

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Contact Angle ◽

Heat Transfer Coefficient ◽

State Of The Art ◽

Porous Matrix ◽

Review Of The Literature ◽

Nanostructured Surfaces ◽

The Heat Transfer Coefficient ◽

Transfer Mechanisms

The differences in the heat transfer coefficient (HTC) and critical heat flux (CHF) behaviors between nanostructured and smooth surfaces are attributed to modifications on the surface wettability and capillarity effects through the porous matrix generated by the nanostructure layer. Both act in order of improving rewetting effects, explaining the CHF augmentation. The fact that the contact angle decreases is commonly considered to justify the HTC reduction for nanostructured surfaces. In this context, this study presents a critical review of the literature concerning the boiling phenomena on nanostructures surfaces. Care is exercised in order of characterizing the nanostructuring methods and compare heat transfer results obtained under almost similar conditions by different authors. Heat transfer mechanisms pointed in the literature as responsible for the heat transfer behaviors are also contrasted.

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Experimental Study of Aqueous Binary Mixture Droplet Vaporization on Nanostructured Surfaces

Volume 2: Advanced Electronics and Photonics, Packaging Materials and Processing; Advanced Electronics and Photonics: Packaging, Interconnect and Reliability; Fundamentals of Thermal and Fluid Transport in Nano, Micro, and Mini Scales ◽

10.1115/ipack2015-48153 ◽

2015 ◽

Author(s):

Russell J. LaBrie ◽

Jorge Padilla ◽

Van P. Carey

Keyword(s):

Heat Transfer ◽

Contact Angle ◽

Hydrothermal Synthesis ◽

Binary Mixture ◽

Synthesis Time ◽

Nanostructured Surfaces ◽

Droplet Vaporization ◽

Angle Measurements ◽

Zno Nanocrystals ◽

Contact Angle Measurements

In this study heat transfer due to vaporization is investigated for low concentration binary mixtures of 2-propanol/water on nanostructured surfaces. The surfaces are comprised of zinc oxide (ZnO) nanocrystals grown by hydrothermal synthesis on a smooth copper substrate having an average roughness of 0.06 μm. Three nanostructured surfaces used in this study differ only in the duration of the hydrothermal synthesis consisting of 4, 10, and 24 hours of surface growth. Surface geometries were observed to be a function of hydrothermal synthesis time with an increase in area coverage, length, and diameter of nanocrystals with increase synthesis time. ZnO nanocrystals exhibit mean diameter of 500–700 nm, mean length of 1.7–3.3 μm and porosities of 0.04–0.58. Individual droplets between 2.5–3.9 mm in diameter consisting of a binary mixture of 2-propanol/water with concentration of either 0.01 M or 0.03 M were deposited at a minimum distance above the surface that would be sufficient for droplets to detach on their own due to gravity onto a nanostructured surface at temperatures between 110–140 °C. High speed video was used to record the deposition and vaporization process and through image analysis it was possible to measure heat transfer coefficients based on the wetted area, as well as other parameters. Through the video analysis it was observed that droplets which are approximately spherical, impact the surface and spread into a thin film with mean film thickness between 65–400 μm which then evaporated by film evaporation without nucleate boiling. Wettability of each of the surfaces was characterized through contact angle measurements from photographs of the droplet profile when the droplet profile was discernible. When profiles were not discernible due to hydrophilicity of some surfaces, contact angles were calculated by utilizing droplet volume and spread area. Contact angle measurements were performed on the surfaces before and after each experiment in order to document changes in wettability as a result of experimentation. Results from this experiment are compared to water droplet vaporization results from a previous experiment in order to determine whether 2-propanol enhances the heat transfer, and found that the heat transfer coefficient was increased by up to 128% in some cases. Heat transfer enhancement was found to be a function of droplet diameter as well as mixture concentration with 3.9 mm 0.01 M 2-propanol/water droplets showing larger enhancement. Potential uses of heat transfer in this application are also discussed.

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Modeling and Optimization of Superhydrophobic Condensation

Journal of Heat Transfer ◽

10.1115/1.4024597 ◽

2013 ◽

Vol 135 (11) ◽

Cited By ~ 123

Author(s):

Nenad Miljkovic ◽

Ryan Enright ◽

Evelyn N. Wang

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Contact Angle ◽

Contact Angle Hysteresis ◽

Unified Model ◽

Transport Processes ◽

Superhydrophobic Surfaces ◽

Dropwise Condensation ◽

Structured Surfaces ◽

Nanostructured Surfaces

Superhydrophobic micro/nanostructured surfaces for dropwise condensation have recently received significant attention due to their potential to enhance heat transfer performance by shedding water droplets via coalescence-induced droplet jumping at length scales below the capillary length. However, achieving optimal surface designs for such behavior requires capturing the details of transport processes that is currently lacking. While comprehensive models have been developed for flat hydrophobic surfaces, they cannot be directly applied for condensation on micro/nanostructured surfaces due to the dynamic droplet-structure interactions. In this work, we developed a unified model for dropwise condensation on superhydrophobic structured surfaces by incorporating individual droplet heat transfer, size distribution, and wetting morphology. Two droplet size distributions were developed, which are valid for droplets undergoing coalescence-induced droplet jumping, and exhibiting either a constant or variable contact angle droplet growth. Distinct emergent droplet wetting morphologies, Cassie jumping, Cassie nonjumping, or Wenzel, were determined by coupling of the structure geometry with the nucleation density and considering local energy barriers to wetting. The model results suggest a specific range of geometries (0.5–2 μm) allowing for the formation of coalescence-induced jumping droplets with a 190% overall surface heat flux enhancement over conventional flat dropwise condensing surfaces. Subsequently, the effects of four typical self-assembled monolayer promoter coatings on overall heat flux were investigated. Surfaces exhibiting coalescence-induced droplet jumping were not sensitive (<5%) to the coating wetting characteristics (contact angle hysteresis), which was in contrast to surfaces relying on gravitational droplet removal. Furthermore, flat surfaces with low promoter coating contact angle hysteresis (<2 deg) outperformed structured superhydrophobic surfaces when the length scale of the structures was above a certain size (>2 μm). This work provides a unified model for dropwise condensation on micro/nanostructured superhydrophobic surfaces and offers guidelines for the design of structured surfaces to maximize heat transfer. Keywords: superhydrophobic condensation, jumping droplets, droplet coalescence, condensation optimization, environmental scanning electron microscopy; micro/nanoscale water condensation, condensation heat transfer.

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