Academic literature on the topic 'Hydrophobicity scale'

Titanium alloys with special macro-micro composite structures of directional hydrophobicity are difficult to prepare due to poor thermal conductivity and good corrosion resistance, inhibiting the wide engineering applications for aerospace, marine engineering, and biomedicine. To prepare macro-micro composite structures on the surface of titanium alloys and achieve directional hydrophobicity, the sub-millimeter structures with an edge width of 150 μm, a groove width of 250 μm, and a depth of 250 μm were fabricated on the titanium alloy by wire electrical discharge machining (WEDM) technology, and high voltage-induced weak electric arc machining (HV-μEAM) was used to fabricate micro-scale feature size micro-structures on the processed macro-structure edges. The influence of process parameters on the morphology of microstructures was studied experimentally. The smooth surface of the titanium alloy is isotropically hydrophilic, and its contact angle is 68°. After processing the macrostructure on the titanium alloy surface, it shows directional hydrophobicity after being modified by low surface energy materials. The macro-micro composite structure formed by HV-μEAM realizes a directional hydrophobic surface with contact angles (CA) of 140° (parallel direction) and 130° (perpendicular direction), respectively. This surface has been modified with low surface energy to achieve contact angles of 154° and 143°. The results of the abrasion resistance test show that under the load of 100 g, it retains directional hydrophobicity at a friction distance of 700 mm with 600# sandpaper. The existence of the sub-millimeter macrostructure is the reason for the directionality of surface hydrophobicity. The microstructure can realize the transformation of the titanium alloy surface from hydrophilic to hydrophobic. Under the combined effects of the macro and micro composite structure, the surface of the titanium alloy shows obvious directional hydrophobicity.

A superhydrophobic fabric surface was fabricated by forming a dual roughness structure in combination with lowered surface energy. The contribution of the innate micro-scale roughness resulting from the waviness of filaments and yarns in a woven fabric on hydrophobicity was investigated in comparison with a smooth film surface. Though the micro-scale roughness coming from the multi-filaments of fabric was conducive in enhancing the hydrophobicity of the surface, the micro-scale roughness itself was not enough to create superhydrophobicity. Thus a nano-scale roughness was introduced by an anisotropic etching employing oxygen plasma etching followed by plasma enhanced chemical vapor deposition. As for the nano-scale roughness, however, it was possible to achieve the superhydrophobicity only with nano-scale roughness, but with a very large aspect ratio of nano-pillar structure. In the presence of dual-scale roughness consisting of both micro- and nano-scale structures, the superhydrophobic characteristic was effectively achieved even at a small aspect ratio of nano-pillar. By adjusting the number of filaments in a yarn and by controlling the plasma process time, it was possible to control the dual-scale roughness of a woven fabric and its wettability. An excessive thinning and lengthening of nano-pillars may negatively affect the hydrophobicity by the collapse and aggregation of pillar tips, and an appropriate processing condition is critical to design a durable superhydrophobic surface.

Highly evolved, efficient and sophisticated biological systems can be used as models for scientific innovations. This research explored specific surface structures on plant leaves with respect to their hydrophobicity in the context of the often arid Australian climate. The relationships between leaf surface structures and their hydrophobicity could inform the making of artificial surfaces with specially designed hydrophobicity. Moderate hydrophobicity and strong surface adhesion were discovered on many study plant leaves. Scanning Electron Microscopy (SEM) revealed that their surface morphologies could be categorized into four groups while their water-repellent mechanisms were considered at an individual species level. Specifically, physical models were built based on the topography of several Eucalyptus species. Wetting robustness and surface free energy analyses were performed with these models to study wetting transitions on surfaces with specific microscopic features. In the fabrication component of the study, a convenient self-assembly procedure of oxysilane successfully converted a hydrophilic glass slide into a hydrophobic surface, with the measured contact angle changing from 30.8 to more than 1000. Atomic force microscope (AFM) images showed randomly distributed roughness at a micrometre scale on these self-assembled hydrophobic surfaces. Samples with square arrays of micro-posts were also fabricated following a sophisticated photo-lithography process. Wetting properties similar to some leaves, namely moderate hydrophobicity and strong surface adhesion, were observed with these fabricated samples. Anisotropic wetting, liquid-surface contact footprints and base lengths on these micro-textured surfaces were also investigated. Finally, fluorine containing diamond-like carbon (F-DLC) coatings were examined because of their chemical inertness, mechanical durability, and low surface energy. F-DLC films were prepared by closed-field, unbalanced, magnetron sputtering (CFUBMS) on silicon substrate to study their wetting and mechanical properties. The influences of CF4 and C2H2 gas addition during fabrication on these properties were explored by measuring contact angles, fluorine contents, surface roughness, Young's modulus and hardness. Simulation from Finite Element Analysis with COMSOL software was also conducted to confirm the mechanical results obtained in nano-indentation experiments. The leaf surface geometries revealed in this study could trigger further relevant research and applications. Surface free energy analysis on the built models could lead to a deeper theoretical understanding of wetting state transition for these geometries. The preliminary results on the self-assembly of oxysilane at ambient conditions could contribute to the development of cost-efficient and environmentally friendly methods for fabricating durable hydrophobic coatings. The results of F-DLC coatings could be beneificial for manipulating surface free energy and mechanical properties, to match specific requirements for certain applications.

With the dramatic expansion of pinyon-juniper woodlands over the last century, improved understanding of how these woodlands modify infiltration properties is needed, in order for land managers to make informed decisions on how to best manage their specific resources. However, current methods for measuring soil infiltration are often limited by low sample sizes and high experimental error, due to constraints associated with remote, non agricultural settings. This thesis first presents a scheme for automating and calibrating two commercially available infiltrometers, which allows collection of a large number of precise unsaturated infiltration measurements in a relatively short period of time. Secondly, a new method to precisely determine saturated hydraulic conductivity from small intact soil cores collected in the field is demonstrated. This method removes bias due to measurement error using a multiple head linear regression approach. Finally, hundreds of fine spatial scale measurements of soil sorptivity, unsaturated hydraulic conductivity, saturated hydraulic conductivity, soil water content, and other soil descriptive measurements along radial line transects extending out from the trunk of juniper (Juniperus osteosperma) and pinyon pine (Pinus edulis) trees. Within the subcanopy of these trees, interactions among litter material, root distributions, and hydrophobic soil significantly influence ecohydrologic properties by limiting and redirecting infiltration below the soil surface. Consequently, hydrophobicity appears to be a mechanism that promotes survival of woody vegetation in arid environments, through decreasing evaporation rates from the soil surface. We further demonstrate how differences in unsaturated infiltration and soil water content between the subcanopy and intercanopy zones are not discrete. Unsaturated infiltration was significantly lower within the subcanopy than in the intercanopy, and increased by eight-fold across a gradient extending outward from near the edge of the canopy to approximately two times the canopy radius. This gradient was not strongly related to soil moisture. In the intercanopy, increasing structural development of biological soil crust cover beyond this gradient was positivity correlated with infiltration capacity. Consequently, these results indicate that the spatial location of the trees should be considered in the assessment and modeling of woody plant and biological soil crust influence on infiltration capacity in a pinyon-juniper ecosystem.

Coal preparation plants use large quantities of water for cleaning processes. Upon cleaning, the spent water must be removed such that the final product moisture level meets market constraints. However, removal of free water from the surface of fine particles is difficult and costly, and often the results are less than desirable. Fine particles inherently have very large surface areas, and hence retain large amounts of water. Increased amounts of fines also cause denser particle packing, which creates relatively small capillaries in filter cakes and, thus, cause slower dewatering kinetics. As a result, dewatering costs for fine particles are much higher than for dewatering coarse particles. Considering the technical and economic issues associated with dewatering coal and mineral fines, an extensive matrix of laboratory- and pilot-scale dewatering tests have been conducted to evaluate the use of novel dewatering aids. The reagents are designed to lower the surface tension of water, increase the hydrophobicity of the particles to be dewatered, and increase the capillary radius by hydrophobic coagulation. All of these are designed to lower the moisture of the filter cakes produced in mechanical dewatering processes. Laboratory-scale dewatering tests confirmed that using the novel dewatering aids can lower the final cake moisture of coal by 20-50%, while increasing the dewatering kinetics. Several on-site, pilot-scale tests were conducted to demonstrate that the process of using the novel dewatering aids can be scaled. Based on the laboratory- and pilot-scale tests conducted, a scale-up model for the process of using the novel dewatering aids has been developed. It can predict the final cake moistures as a function of vacuum pressure, filtration time and specific cake weight. The model can be useful for the scale-up of vacuum disc filters (VDF) and horizontal belt filters (HBF). Simulation results indicate that dewatering aids can be very effective, especially when used in conjunction with HBF due to its ability to control cake thickness and drying cycle time independently. In light of the promising laboratory- and pilot-scale test results, an industrial demonstration of the novel dewatering aids has been conducted at the Smith Branch impoundment site, which contains 2.9 million tons of recoverable coal. When the reagent was used for dewatering flotation products using a VDF, the moisture content was reduced from 26 to 20% at 0.5 lb/ton of reagent addition and to 17.5% at 1 lb/ton. The use of the dewatering aid also improved the kinetics of dewatering, increased the throughput, and reduced the power consumption of vacuum pumps by 30%. The novel dewatering aids were also tested successfully for dewatering of kaolin clays. In this case, the mineral was treated with a cationic surfactant before adding the dewatering aids. This two-step hydrophobization process was able to reduce the cake moisture and also increase the throughput.
Ph. D.

Die Zielsetzung der vorliegenden Arbeit ist die Beschreibung hydrophober Bodeneigenschaften und deren Auswirkungen auf Oberflächenabfluss und Erosion auf verschiedenen Skalen. Die dazu durchgeführten Untersuchungen fanden auf einer Rekultivierungsfläche im Braunkohlegebiet Welzow Süd (Südostdeutschland) statt. Die Prozesse wurden auf drei Skalen untersucht, die von der Plotskala (1m²) über die Hangskala (300m²) bis zur Betrachtung eines kleinen Einzugsgebietes (4ha) reichen. Der Grad der hydrophoben Bodeneigenschaften wurde sowohl direkt, über die Bestimmung des Kontaktwinkel, als auch indirekt, über die Bestimmung der Persistenz, ermittelt. Dabei zeigte sich, dass der Boden im Winterhalbjahr hydrophil reagierte, während er im Sommerhalbjahr hydrophobe Bodeneigenschaften aufwies. Die Ergebnisse deuten darauf hin, dass ansteigende Bodenwassergehalte, die in der Literatur häufig als Ursache für einen Wechsel der Bodeneigenschaften angegeben werden, auf dieser Fläche nicht zu einem Umbruch der Bodenbedingungen führen. Stattdessen kam es als Folge des Auftauens von gefrorenem Boden zu hydrophilen Bodeneigenschaften, die zu einem Anstieg des Bodenwassergehalts führten. Räumliche Unterschiede zeigten sich in den geomorphologischen Einheiten. Rinnen und Rillen wiesen seltener hydrophobe Eigenschaften als die Zwischenrillenbereiche und Kuppen auf. Diese räumlichen und zeitlichen Variabilitäten wirkten sich auch auf den Oberflächenabfluss aus, der als Abflussbeiwert (ABW: Quotient aus Abfluss und Niederschlag) untersucht wurde. Der ABW liegt auf Böden mit hydrophoben Bodeneigenschaften (ABW=0,8) deutlich höher als bei jenen mit hydrophilen Eigenschaften(ABW=0,2), wie sie im Winter oder auf anderem Substrat vorzufinden sind (diese Werte beziehen sich auf die Plotskala). Betrachtet man die Auswirkungen auf unterschiedlichen Skalen, nimmt der Abflussbeiwert mit zunehmender Flächengröße ab (ABW = 0,8 auf der Plotskala, ABW = 0,5 auf der Hangskala und ABW = 0,2 im gesamten Gebiet), was in den hydrophil reagierenden Rillen und Rinnen auf der Hangskala und dem hydrophilen Substrat im Einzugsgebiet begründet ist. Zur Messung der Erosion wurden verschiedene, zum Teil neu entwickelte Methoden eingesetzt, um eine hohe zeitliche und räumliche Auflösung zu erreichen. Bei einer neu entwickelten Methode wird der Sedimentaustrag ereignisbezogen über eine Waage bestimmt. In Kombination mit einer Kippwaage ermöglicht sie die gleichzeitige Messung des Oberflächenabflusses. Die Messapparatur wurde für Gebiete entwickelt, die eine überwiegend grobsandige Textur aufweisen und nur geringe Mengen Ton und Schluff enthalten. Zusätzlich wurden zwei Lasersysteme zur Messung der räumlichen Verteilung der Erosion eingesetzt. Für die erste Methode wurde ein punktuell messender Laser in einer fest installierten Apparatur über die Fläche bewegt und punktuell Höhenunterschiede in einem festen Raster bestimmt. Durch Interpolation konnten Bereiche mit Sedimentabtrag von Akkumulationsbereiche unterschieden werden. Mit dieser Methode können auch größere Flächen vermessen werden (hier 16 m²), allerdings weisen die Messungen in den Übergangsbereichen von Rinne zu Zwischenrille große Fehler auf. Bei der zweiten Methode wird mit einer Messung ein Quadratmeter mit einer hohen räumlichen Auflösung komplett erfasst. Um ein dreidimensionales Bild zu erstellen, müssen insgesamt vier Aufnahmen von jeweils unterschiedlichen Seiten aufgenommen werden. So lassen sich Abtrag und Akkumulation sehr genau bestimmen, allerdings ist die Messung relativ aufwendig und erfasst nur eine kleine Fläche. Zusätzlich wurde der Sedimentaustrag noch auf der Plotskala erfasst. Die Messungen zeigen, korrespondierend zu den Bodeneigenschaften, große Sedimentausträge während des Sommerhalbjahrs und kaum Austräge im Winter. Weiterhin belegen die Ergebnisse eine größere Bedeutung der Rillenerosion gegenüber der Zwischenrillenerosion für Niederschlagsereignisse hoher Intensität (>25 mm/h in einem zehnminütigem Intervall). Im Gegensatz dazu dominierte die Zwischenrillenerosion bei Ereignissen geringerer Intensität (<20 mm/h in einem zehnminütigem Intervall), wobei mindestens 9 mm Niederschlag in einer Intensität von mindesten 3,6 mm/h nötig sind, damit es zur Erosion kommt. Basierend auf den gemessenen Abflüssen und Sedimentausträgen wurden Regressiongleichungen abgeleitet, die eine Berechnung dieser beiden Prozesse für die untersuchte Fläche ermöglichen. Während die Menge an Oberflächenabfluss einen starken Zusammenhang zu der Menge an gefallenem Niederschlag zeigt (r² = 0,9), ist die Berechnung des ausgetragenen Sedimentes eher ungenau (r² = 0,7). Zusammenfassend beschreibt die Arbeit Einflüsse hydrophober Bodeneigenschaften auf verschiedenen Skalen und arbeitet die Auswirkungen, die vor allem auf der kleinen Skala von großer Bedeutung sind, heraus.
The objective of the thesis is the investigation of water repellent soil conditions and their consequences on surface runoff and erosion by water on different scales. The test site is a lignite mining area situated in Welzow Süd (south east Germany). The processes are to investigate on three different scales, starting with a plot scale (1 m²), then a hill slope scale (300 m²) and, finally, with a small catchment area (4 ha). The level of water repellency was quantified by both direct (contact angle) and indirect measurement (persistence of the soil). The results show seasonal differences with hydrophilic soil conditions during winter and water repellent reactions during summer. For this change in soil conditions, the soil water content is pronounced in literature to be the most important factor. On the test site, the soil water content changed instead as a consequence of the thawing of the soil which affects the hydrophilic conditions of the soil itself. The spatial differences of the soil water content are related to rill and channel areas (hydrophillic) and to knoll areas (water repellent). Both the spatial as well as the temporal variation of the soil conditions affect surface runoff which is investigated as a runoff coefficient (RC: ratio of amount of surface runoff to amount of precipitation). The RC shows higher values on soil with water repellent conditions (RC=0.8) in comparison with the values on hydrophilic soils (RC=0.2). The hydrophilic conditions predominate in areas with different substrates and during the winter. Observations on different scales show a decreasing RC as the size of the area increases (RC = 0.8 on the plot scale, RC = 0.5 on the hill slope scale and RC = 0.2 for the entire catchment area). The reasons for this are the hydrophilic rill in the hill slope area and the hydrophilic substrate in the entire catchment area. The measurement of erosion, based on different methods, some of them just newly developed, quantifies in a good resolution sediment transport spatially as well as temporally. The central part of one of the newly developed approaches is a balance which quantifies an event based sediment output. This approach is coupled with a tipping bucket to measure surface runoff. The system has been developed for coarse textured areas with little amounts of sand and silt. Additionally, two laser systems are used to detect changes in the soil surface over the spatial distribution. The first method contains a laser which measures only a single point and has to be moved in a fixed apparatus above the soil surface in a well defined raster. The areas of sediment abrasion and the detachment areas are restricted by interpolation of the measurement results. This method enables measurements on large areas (16 m² in this project), but tends to result in a high level of errors in the transition zone between rill and interrill. The second laser system covered an area of 1 m² in high resolution. To construct a three-dimensional picture, four different pictures have to be taken from four different directions. This defines the abrasion and detachment areas in a very detailed manner, but the method is very time-consuming and covers only a small area. In addition, measurements on the plots collected the amount of sediment output on a small scale. These results show, corresponding to the water repellent soil conditions, high rates of sediment output during summer, but low rates during winter season. The results show also the dominance of rill erosion in comparison with interrill erosion during high intensity rainfall events (>25 mm/h during one interval of ten minutes). On the contrary, interrill erosion becomes more important during low intensity rainfall events (<20 mm/h during at one interval of ten minutes). At least a 9 mm amount of precipitation with a minimum intensity of 3.6 mm/h is necessary to provoke erosion on this test site. Based on the measurement results regression empirical equations were developed to quantify surface runoff and sediment output. While, surface runoff correlates well with the amount of precipitation (r² = 0,9), sediment output shows little correlation to the amount and intensity of the precipitation (r² = 0,7). In summary, the thesis described effects of water repellent soil conditions on surface runoff and erosion on different scales. The effects on the smaller scales especially are of high interest to hydrological processes.

L'objectif de l'approche des simulations moléculaires interactive (Interactive Molecular Simulations - IMS) est d'observer en direct la dynamique conformationnelle d'une simulation moléculaire en cours. Le retour visuel instantané permet un suivi instructif ainsi que l'observation des changements structurels imposés par la manipulation de l'IMS par l'utilisateur. J'ai mené une étude approfondie des connaissances pour rassembler et synthétiser l'ensemble des recherches qui ont développé l'IMS. La dynamique moléculaire interactive (Interactive Molecular Dynamics - IMD) est l'un des premiers protocoles IMS qui a posé les bases du développement de cette approche. Mon laboratoire de thèse s'est inspirée de celle-ci pour développer le moteur de simulation BioSpring basé sur le modèle de réseaux élastique. Ce modèle permet de simuler la flexibilité de grands ensembles biomoléculaires et ainsi potentiellement révéler des changements à longue échelle de temps qui ne seraient pas facilement saisis par la dynamique moléculaire. Ce moteur de simulation ainsi que le logiciel de visualisation UnityMol, développé par le biais du moteur de jeu Unity3D, et liés par l'interface de communication MDDriver ont été étendus pour les faire converger vers une suite logicielle complète. Le but est de fournir à un expérimentateur, qu'il soit expert ou profane, une boîte à outils complète pour modéliser, afficher et contrôler interactivement l'ensemble des paramètres d'une simulation. L'implémentation particulière d'un tel protocole, basé sur une communication formalisée et extensible entre les différents composants, a été pensée pour pouvoir facilement intégrer de nouvelles possibilités de manipulation interactive et des jeux de données expérimentales qui s'ajouteront aux contraintes imposées à la simulation. L'utilisateur peut donc manipuler la molécule d'intérêt sous le contrôle des propriétés biophysiques intégrés dans le modèle simulé, tout en ayant la possibilité de piloter à la volée les paramètres de simulation. Aussi, un des objectifs initiaux de cette thèse était d'intégrer la gestion des contraintes d'interaction ambigües du logiciel d'amarrage biomoléculaire HADDOCK directement dans UnityMol, rendant possible l'utilisation de ces mêmes contraintes à une variété de moteurs de simulations. Un axe principal de ces recherches était de développer un algorithme de positionnement rapide et interactif de protéines dans des membranes implicite tiré d'un modèle appelé Integrative Membrane Protein and Lipid Association Method (IMPALA) développée par l'équipe de Robert Brasseur en 1998. La première étape consistait à effectuer une recherche approfondie des conditions dans lesquelles les expériences ont été réalisées à l'époque, afin de vérifier la méthode et de valider notre propre implémentation. Nous verrons qu'elle ouvre des questions intéressantes sur la manière dont on peut reproduire les expériences scientifiques. L'étape finale qui conclue cette thèse était le développement d'une nouvelle méthode universelle d'interaction lipide-protéine, UNILIPID, qui est un modèle d'incorporation interactif de protéines dans les membranes implicites. Elle est indépendante de l'échelle de représentation, peut être appliquée à des niveaux tout atomes, gros-grains jusqu'au niveau d'un grain par acide aminé. La représentation de la dernière version Martini3[6] ainsi qu'une méthode d'échantillonnage Monte-Carlo et de simulation de dynamique des corps rigides ont été spécialement intégrés à la méthode, en plus de divers outils de préparation de systèmes. En outre, UNILIPID est une approche versatile qui reproduit précisément des termes d'hydrophobicité expérimentaux pour chaque acide aminé. En plus de membranes implicites simples, je décrirai une implémentation analytique de membranes doubles ainsi qu'une généralisation à des membranes de forme arbitraire, toutes deux s'appuyant sur des applications inédites
The goal of Interactive Molecular Simulations (IMS) is to observe the conformational dynamics of a molecular simulation in real-time. Instant visual feedback enables informative monitoring and observation of structural changes imposed by the user's manipulation of the IMS. I conducted an in-depth study of knowledge to gather and synthesize all the research that has developed IMS. Interactive Molecular Dynamics (IMD) is one of the first IMS protocols that laid the foundation for the development of this approach. My thesis laboratory was inspired by IMD to develop the BioSpring simulation engine based on the elastic network model. This model allows for the simulation of the flexibility of large biomolecular ensembles, potentially revealing long-timescale changes that would not be easily captured by molecular dynamics. This simulation engine, along with the UnityMol visualization software, developed through the Unity3D game engine, and linked by the MDDriver communication interface, has been extended to converge towards a complete software suite. The goal is to provide an experimenter, whether an expert or novice, with a complete toolbox for modeling, displaying, and interactively controlling all parameters of a simulation. The particular implementation of such a protocol, based on formalized and extensible communication between the different components, was designed to easily integrate new possibilities for interactive manipulation and sets of experimental data that will be added to the restraints imposed on the simulation. Therefore, the user can manipulate the molecule of interest under the control of biophysical properties integrated into the simulated model, while also having the ability to dynamically adjust simulation parameters. Furthermore, one of the initial objectives of this thesis was to integrate the management of ambiguous interaction constraints from the HADDOCK biomolecular docking software directly into UnityMol, making it possible to use these same restraints with a variety of simulation engines. A primary focus of this research was to develop a fast and interactive protein positioning algorithm in implicit membranes using a model called the Integrative Membrane Protein and Lipid Association Method (IMPALA), developed by Robert Brasseur's team in 1998. The first step was to conduct an in-depth search of the conditions under which the experiments were performed at the time to verify the method and validate our own implementation. We will see that this opens up interesting questions about how scientific experiments can be reproduced. The final step that concluded this thesis was the development of a new universal lipid-protein interaction method, UNILIPID, which is an interactive protein incorporation model in implicit membranes. It is independent of the representation scale and can be applied at the all-atom, coarse-grain, or grain-by-grain level. The latest Martini3 representation, as well as a Monte Carlo sampling method and rigid body dynamics simulation, have been specially integrated into the method, in addition to various system preparation tools. Furthermore, UNILIPID is a versatile approach that precisely reproduces experimental hydrophobicity terms for each amino acid. In addition to simple implicit membranes, I will describe an analytical implementation of double membranes as well as a generalization to arbitrarily shaped membranes, both of which rely on novel applications

Membrane bioreactors (MBRs) offer promising solution for wastewater treatment and reuse to address the problem of water scarcity. Nevertheless, this technology is still facing challenges associated with membrane biofouling. This phenomenon has been mainly investigated in lab-scale MBRs with little or no insight on biofouling in full-scale MBR plants. Furthermore, the temporal dynamics of biofouling microbial communities and their extracellular polymeric substances (EPS) are less studied. Herein, a multidisciplinary approach was adopted to address the above knowledge gaps in lab- and full-scale MBRs. In the full-scale MBR study, 16S rRNA gene pyrosequencing with multivariate statistical analysis revealed that the early and mature biofilm communities from five full-scale MBRs differed significantly from the source community (i.e. activated sludge), and random immigration of species from the source community was unlikely to shape the community structure of biofilms. Also, a core biofouling community was shared between the five MBR plants sampled despite differences in their operating conditions. In the lab-scale MBR studies, temporal dynamics of microbial communities and their EPS products were monitored on different hydrophobic and hydrophilic membranes during 30 days. At the early stages of filtration (1 d), the same early colonizers belonging to the class Betaproteobacteria were identified on all the membranes. However, their relative abundance decreased on day 20 and 30, and sequence reads belonging to the phylum Firmicutes and Chlorobi became dominant on all the membranes on day 20 and 30. In addition, the intrinsic membrane characteristic did not select any specific EPS fractions at the initial stages of filtration and the same EPS foulants developed with time on the hydrophobic and hydrophilic membranes. Our results indicated that the membrane surface characteristics did not select for specific biofouling communities or EPS foulants, and the same early colonizers were selected from the source community (i.e. activated sludge), and then went through significant changes to form a mature biofilm. Our findings from these studies could support future research aimed at developing enhanced biological-based strategies to control biofouling in MBRs.

碩士
國立成功大學
機械工程學系
105
To improve hydrophobicity and tribology performance of HPMC films, two different methods to produce SA/HPMC composite films, namely blending and coating have been studied in this research. Contact angle test was used to characterize the hydrophobicity of surfaces; pin-on-disk, 3D profiler and SEM images of worn surface of samples were used for tribological performance analysis. Experiment results and analysis show that WCA of blending films decrease as SA content increases due to larger surface roughness, whereas the WCA of coating films increase as SA content increases due to the surface geometry effect and hydrophobic nature of SA petal-like crystals on the surface of coating films. As to tribological properties, with addition of SA, tribological performance of blending and coating films was improved effectively, and the dominant wear mechanism of SA/HPMC composites have also be demonstrated to be formation and development of SA third bodies with appropriate size and shape during wear process. By this research, applications of HPMC films as packaging and coating materials have been strengthened, and the mechanisms of stearic acid improving hydrophobicity and tribological performance were decrypted as well, which provides a valuable reference for the design of similar cellulose derivatives/fatty acids composites.

The potential of membrane distillation (MD) in seawater desalination and high-salt wastewater treatment makes it a highly promising application in alleviating the global water crisis. However, membrane fouling and wetting are the main obstacles to the large-scale application of MD. Bio-inspired super liquid-repellent membranes offer a viable resolution to these challenges. The rapid advancement of nanotechnology has stimulated the growing attention toward electrospun nanofiber membranes (ENMs). Electrospun fibers demonstrate excellent functionalization, controllability, and hydrophobicity. Their low energy consumption and ease of preparation promote their application prospects in the construction of super liquid-repellent membranes. This article provides a comprehensive summary of electrospinning principles and influencing factors, coupled with a detailed account of the theory and preparation of super-liquid-repellent membranes via electrospinning, thus explicating the application and challenges of these membranes in MD, facilitating a deeper understanding of the ENMs application in MD for readers.

Abstract One of the resources which may be exploited in studying membrane transport proteins is the enormous (and increasing) body of genome sequence data. At the time of writing, complete genomic sequences are known for 21 prokaryotes (1), a yeast (2), and for Caenorhabditis elegans (3). Current estimates suggest that integral membrane proteins comprise about 20–30% of most genomes (4, 5). This provides a strong motivation to exploit this information in terms of trying to understand the relationship between membrane protein sequence and structure (and eventually function). Prediction of protein structure is fraught with difficulties and despite intense efforts, ab initio methods for structure prediction remain elusive (6). However, for membrane proteins (or at least those whose membrane domains are composed largely of (l-helices), the prospects of prediction are somewhat brighter as the lipid bilayer restricts the number of degrees of freedom of the system. Prediction of transmembrane (TM) Cl-helices is widespread and a number of different methods and hydrophobicity scales have been devised to aid such predictions (7). Other methods allow the prediction of preferred orientations of such TM helices, thus placing restrictions on how they may be packed together in the intact protein.

This paper aims to perform a numerical analysis of application effects of a superhydrophobic paint by completely coating the blades of a model-scale marine propeller in order to make it a superhydrophobic surface (SHS). First, a two-dimensional study was conducted. Two foils were analyzed for several hydrophobic conditions, varying the slip length. Pressure and skin friction distributions were shown. There is an increase of lift-to-drag ratio with hydrophobicity, but followed by an increase in suction pressure. In three-dimensional case, a propeller was simulated for several hydrophobic conditions, comparing thrust, torque and efficiency coefficients and pressure and friction distribution. Results with propeller showed that an increase in slip length is not always followed by an increase in efficiency, with an apparent efficiency gain limit. For the imposed simulation conditions, from the limit of gain, efficiency no longer increases with hydrophobicity, but its area of low pressure continues to grow.

Abstract Experiments indicate that hydrodynamic drag may be reduced by using ultrahydrophobic substrates to induce slip at the solid-liquid interface. The connection between drag-reduction and slip is explored, and these previously isolated fields are joined into a single, more comprehensive area of research. We present data from two experimental techniques indicating the role of hydrophobicity and size scale in drag-reduction. In one series of studies, water was directed through a channel containing two rectangular plates of smooth silicon. Flow rates for smooth non-hydrophobic plates and smooth hydrophobic plates were identical. In another series of studies, a rheometer was used to measure the relative drag experienced by a polypropylene-coated disk as it was rotated in water. The polypropylene (PP) was ultrahydrophobized (water contact angles were θa/θr = 167°/166°) by argon plasma etching in the presence of poly(tetrafluoroethylene). Drag was reduced by over 20% by using the roughened PP instead of the virgin PP. Contact angle hysteresis is isolated as a critical factor in the drag-reduction mechanism proposed.

Understanding the effects of surface nanostructures on fluid flow in micro- and nano-channels is highly desirable for micro/nano-electro-mechanical systems. By way of equilibrium and non-equilibrium molecular dynamics simulations, wetting on nano-structured surfaces and liquid flow in nano-channels with structured surfaces are simulated. The surfaces show dual effects on the boundary slip and friction of the liquid flow in nano-channels. Generally, the nanostructures enhance the surface hydrophilicity for a hydrophilic liquid-solid interaction, and increase the hydrophobicity for a hydrophobic interaction. Simultaneously, the nanostructures distort the nanoscale streamlines of the liquid flow near the channel surface and block the flow, which decreases the apparent slip length. The twofold effects of the nanostructures on the surface wettability and the hydrodynamic disturbance result in a non-monotonic dependence of the slip length on the structure’s size. However, the surface structure may lead to a very high contact angle of about 170° in some cases, which cause the surface show super-hydrophobicity and lead to a remarkable velocity slip. The surface nanostructures can thus be applied to control the friction of micro- and nano-flows. In addition, the gaseous flows in micro- and nano-channels with structured surfaces are simulated. The geometry of the surface is modeled by triangular, rectangular, sinusoidal and randomly triangular nanostructures respectively. The results show that the velocity slips, including negative slip, depend not only on the Knudsen number but also the surface structure. The impacts of the surface nanostructure and the gas rarefaction are strongly coupled. In general, the slip length of a gaseous flow over a structured surface is less than what predicted by the Maxwell model, and depends not only on the Knudsen number but also the size of the surface nanostructures.

There are several examples in nature where the biological surfaces exhibit unique functional response, such as velcro, fish scale and lotus leaves. The texture on lotus leaf exhibits super-hydrophobicity and self cleaning properties. Lotus leaf has hemispherical protrusions of 20–30 μm in diameters which are randomly distributed over the surface. This work is focused on creating similar textured surfaces on Ti6Al4V rods via a vibration assisted reverse micro Electrical Discharge Machining (R-MEDM) process. Textured surfaces containing micropillars of 40–50 μm in diameter spaced at 35 μm have been created during the process. These textured surfaces are expected to exhibit hydrophobicity and hemocompatibility. To experimentally characterize the process, a full factorial design of experiments has been conducted to analyze the effects of voltage, capacitance, amplitude and frequency of the anode (plate electrode) vibrations on the erosion rate and process stability. The process stability is expressed in terms of the percentages of the normal, open circuit and the short circuit durations in the voltage-current (VI) signature obtained during the process. It has been observed that the normal discharge durations increase with an increase in the amplitude and the frequency of the vibrations. Fabricated texture exhibits hydrophobicity and the measured contact angles in a sessile drop test with water varied between 110 and 115°. Also, the textured surface was subjected to hemotoxicity tests which yielded positive results. Based on these results, it can be seen that the machined textured surface are hydrophobic and biocompatible in nature which could potentially find applications in cardiovascular biomedical implants. In addition, this process has been used to create hierarchical structures comprising of primary and a secondary structure over it to mimic the hierarchical structures found on lotus leaves.

Abstract Bioinspired Micro/Nano textured rough topography of a surface has many applications in super-hydrophobicity, self-cleaning surface, anti-icing coatings, anti-biofouling, and drag reduction surfaces. The role of hierarchical and complex surface topography in nature is to amplify the hydrophobicity and maximize the fouling resistance. Thus, a similar micro- and nano-scale 3-D topographic surfaces inspired from the nature were fabricated using a simple and scalable two roll coating process. This process was based on the ribbing instabilities associated with the shearing of non-Newtonian fluids between two rollers. The polymer composite retains the deformed shape due to the recovery of high-viscosity after removing the shear stress. The relationship between the process conditions and the textured structure were studied with the shear rate, capillary number and the surface roughness parameters (e.g., Wenzel factor and density of peaks). The results showed that the samples’ Wenzel roughness factor increased with the increase in shear rate up to a particular value and then decreased. Similarly, the density of peaks in the sample increased with an increase in capillary number up to a particular value and then decreased. These bioinspired surfaces with hierarchical textured patterns produced using two roll coating process show a tremendous potentiality to be used in super-hydrophobic, anti-biofouling, and drag reduction applications.

Abstract A high-speed jet is formed when a pulse force acts on a concave interface of the liquid, which is due to the focus of the momentum on the center of curvature of the interface. We also found that there are fascinating jets in the experiments with a pulse acceleration imposed on the convex liquid interface while the arrangement is limited between two parallel panels. The mechanism of the convex interface jets is analyzed experimentally and numerically in this paper. A droplet with a diameter of approximately 12 mm is generated between two 0.8-mm spacing parallel plates coated with hydrophobic materials. A pulsed laser is focused at the center of the droplet through a convex lens to generate pulsed bubbles so that the movement of the interface is accelerated. The evolution of the liquid jets is observed by high-speed photography. A high-precision numerical method of the interface is established based on the volume of fluid method (VOF) and large eddy simulation (LES), which is enabled to capture the gas-liquid interface and small-scale flow structures exactly. An intriguing jet close to the plate is observed while the concave interface only forms that near the centerline. A charming entrainment phenomenon captured in the development of the jets, is mainly related to the big difference (Δθ) in contact angles between two plates, with a phase diagram given in the present work. Finally, a discussion responding to the influence of different contact angles on the tip velocity of a jet is done, concluding that the jet velocity increases gradually with the enlargement of Δθ to some extent. In addition, the hydrophobic plate, which is regarded as a mirrored plane and reflects the momentum of the fluid, plays a significant role in the formation of hydrophobic jets as well. Our findings offer a new understanding both of the formation of jets and surface cleaning.

A micro/meso scale modelling of two-phase droplets move on hydrophilic/hydrophobic surfaces with micro roughness is reported. The physical model is basically of two-phase flow interacting with the surfaces of different hydrophobicity or wettability. Numerical modelling based on the lattice Boltzmann method (LBM) is developed and applied to the computational calculation and simulation. The LBM modelling deals with surface tension dominated behaviour of water droplets in air spreading on a hydrophilic surface with hydrophobic strips of different sizes and contact angles under different physical and interfacial conditions, and aims to find quantitative data and physical conditions of the biomimetic approaches. The current LBM can be applied to simulate two-phase fluids with large density ratio (up to 1000), and meanwhile deal with interactions between a fluid-fluid interface and a partial wetting wall. In the simulation, the interactions between the fluid-fluid interface and the partial wetting wall with different hydrophobic strips such as single strip, intersecting stripes, and alternating & parallel stripes, of different sizes and contact angles are considered and tested numerically; the phenomena of droplets spreading and breaking up, and the effect of hydrophobic strips on the surface wettability or self-cleaning characteristics are simulated, reported and discussed.

The gas diffusion layer (GDL) plays a critical role in the overall performance of a polymer electrolyte fuel cell (PEFC), especially in the mass transport control regime due to suboptimal liquid water transport. Liquid water blocks the porous pathways in the catalyst layer and gas diffusion layer thereby causing hindered oxygen transport from the channel to the active reaction sites. This phenomenon is known as “flooding” and is perceived as the primary mechanism leading to the limiting current behavior in the cell performance. The pore morphology and wetting characteristics of the cathode GDL are of paramount importance in the effective PEFC water management. Typical beginning-of-life GDLs exhibit hydrophobic characteristics, which facilities liquid water transport and hence reduces flooding. Experimental data, however, suggest that the GDL loses hydrophobicity over prolonged PEFC operation and becomes prone to enhanced flooding. In this work, we present a pore-scale modeling framework to study the structure-wettability-durability interplay in the context of flooding behavior in the PEFC GDL.

Abstract Hybrid steam-CO2 flooding, mature technology to enhance oil recovery, promotes the deposition of asphaltene from heavy oil and the CO2-brine-silica interaction to change the wettability of silica surface. The asphaltene deposition can promote lipophilicity of the silica surface while the CO2-brine-silica interaction can enhance its hydrophilicity. Therefore, aiming to study the wettability alteration during hybrid steam-CO2 flooding, we explore the interaction characteristics of CO2 with oil and brine on the silica surface. In this work, a series of experiments are conducted to reveal the wettability alteration of silica by the interaction of CO2 with different fluids under different conditions. The CO2-brine-silica interaction experiments and the CO2-oil-silica experiments are carried out in the temperature and pressure-resistant vessel to comprehensively acquire the silica under the influence of various fluids in the static process. In addition, based on the core flooding experiments, computerized tomography (CT) technology is applied to realistically and automatically extract the dynamic contact angle in the dynamic process. The result of contact angle from CO2-brine-silica interaction experiments shows the interaction between CO2 and brine evidently enhances the hydrophilicity of the silica surface under high temperature, and the ability of CO2 and brine to promote the increase of hydrophilicity is much greater than that in the absence of CO2. Moreover, the result of contact angle from CO2-oil-silica experiments indicates the increase of temperature and CO2 pressure makes the silica surface covered by heavy oil present the tendency of hydrophobia. The micro-CT images from core displacement experiments are automatically processed by an intelligent algorithm to extract the remaining oil distribution and display the data of dynamic contact angle. Under the influence of steam, the remaining oil mainly performs the form of membrane oil attached to the silica surface. Furthermore, the edges of the remaining oil take on an irregular shape and the contact angle reflecting hydrophobicity reach 45.2% after steam flooding. After the stage of CO2 flooding, the obvious reduction in membrane oil thickness occurs and the number of contact angles reflecting hydrophobicity decreases to 35.3%. Moreover, the oil film gradually transforms into many oil droplets on the surface under the steam and CO2, which may be conducive to the migration of heavy oil in a porous medium. Taking static and dynamic characteristics of contact angle into account under different environments, the conditions and mechanism of wettability alteration can serve as a perspective for CO2 application in pore-scale displacement.

Original Objectives Specific objectives are to: (1) modify charge and hydrophobicity of pectins to improve emulsion stabilizing properties (2) develop emulsions that can be sterically stabilized using modified pectins and/or pectin/protein hybrids (3) obtain submicronal inner emulsion droplets (10-50 nanometers) with small and monodispersed double emulsion (1-2 μm) droplets with long-term stability (possibly by emulsified microemulsions) and (4) trigger and control the release at will. Background Methodology for encapsulation and controlled release of selected addenda, e.g. drugs, vitamins, phytochemicals, flavors, is of major impact in the food industries. Stable double emulsions with desired solubilization and release properties of selected addenda are formed using charge modified pectin or pectin-protein hybrids. Major conclusions, solutions, achievements * We developed methodology to isolate PME isozymes and prepared modified pectins in sufficient quantity to characterize, form single and double emulsions and test stability. *Amino acid sequence of PME isozymes was estimated and will facilitate cloning of PME for commercial application * The contribution of total charge and distribution of charge of modified pectin was determined *Soluble complexes or modified pectins and whey isolates are formed * Stable W/O/W double emulsions were formed that did not cream, had small particle size * Inner phase of double emulsions are nano-sized and stable. These new structures were termed emulsified microemulsions (EME) * Release of bioactives were controlled between a few days to months depending on layering on droplets by hybrids * Commercial testing by Israeli company of stability and release of Vitamin C showed good chemical stability Implications Resolved the major stability limitation of W/O/W emulsions. Resolved the questions regarding citrus PMEs and tailored pilot scale modification of pectins.