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Superhydrophobic
Ultrahydrophobic (or superhydrophobic) surfaces are highly hydrophobic, i.e., extremely difficult to wet. The contact angles of a water droplet on an ultrahydrophobic material exceed 150°. This is also referred to as the lotus effect, after the superhydrophobic leaves of the lotus plant. A droplet striking these kinds of surfaces can fully rebound like an elastic ball. Interactions of bouncing drops can be further reduced using special superhydrophobic surfaces that promote symmetry breaking, pancake bouncing or waterbowl bouncing. Theory In 1805, Thomas Young defined the contact angle ''θ'' by analysing the forces acting on a fluid droplet resting on a smooth solid surface surrounded by a gas. :\gamma_\ =\gamma_+\gamma_\cos where :\gamma_\ = Interfacial tension between the solid and gas :\gamma_\ = Interfacial tension between the solid and liquid :\gamma_\ = Interfacial tension between the liquid and gas ''θ'' can be measured using a contact angle goniometer. Wenzel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobic
In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar substances from polar compounds. Hydrophobic is often used interchangeably with lipophilic, "fat-loving". However, the two terms are not synonymous. While hydrophobic substances are usually lipophilic, there are exception ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lotus Effect
The lotus effect refers to self-cleaning properties that are a result of ultrahydrophobicity as exhibited by the leaves of '' Nelumbo'', the lotus flower. Dirt particles are picked up by water droplets due to the micro- and nanoscopic architecture on the surface, which minimizes the droplet's adhesion to that surface. Ultrahydrophobicity and self-cleaning properties are also found in other plants, such as '' Tropaeolum'' (nasturtium), ''Opuntia'' (prickly pear), '' Alchemilla'', cane, and also on the wings of certain insects. The phenomenon of ultrahydrophobicity was first studied by Dettre and Johnson in 1964 using rough hydrophobic surfaces. Their work developed a theoretical model based on experiments with glass beads coated with paraffin or PTFE telomer. The self-cleaning property of ultrahydrophobic micro-nanostructured surfaces was studied by Wilhelm Barthlott and Ehler in 1977, who described such self-cleaning and ultrahydrophobic properties for the first time as the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wetting
Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. This happens in presence of a gaseous phase or another liquid phase not miscible with the first one. The degree of wetting (wettability) is determined by a force balance between adhesive and cohesive forces. Wetting is important in the bonding or adherence of two materials. Wetting and the surface forces that control wetting are also responsible for other related effects, including capillary effects. There are two types of wetting: non-reactive wetting and reactive wetting. Wetting deals with three phases of matter: gas, liquid, and solid. It is now a center of attention in nanotechnology and nanoscience studies due to the advent of many nanomaterials in the past two decades (e.g. graphene, Carbon nano tube, carbon nanotube, boron nitride nanomesh). Explanation Adhesive forces between a liquid and solid cause a liq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cassie's Law
Cassie's law, or the Cassie equation, describes the effective contact angle θc for a liquid on a chemically heterogeneous surface, i.e. the surface of a composite material consisting of different chemistries, that is non uniform throughout. Contact angles are important as they quantify a surface's wettability, the nature of solid-fluid intermolecular interactions. Cassie's law is reserved for when a liquid completely covers both ''smooth'' and ''rough'' heterogeneous surfaces. More of a rule than a law, the formula found in literature for two materials is; \cos \theta_c = \sigma_1 \cos \theta_1 + \sigma_2 \cos \theta_2 where \theta_1and \theta_2 are the contact angles for components 1 with fractional surface area \sigma_1, and 2 with fractional surface area \sigma_2 in the composite material respectively. If there exist more than two materials then the equation is scaled to the general form of; \cos \theta_ =\sum_^N \sigma_k \cos \theta_k , with \sum_^N \sigma_k = 1. Cassie-B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contact Angle
The contact angle is the angle, conventionally measured through the liquid, where a liquid– vapor interface meets a solid surface. It quantifies the wettability of a solid surface by a liquid via the Young equation. A given system of solid, liquid, and vapor at a given temperature and pressure has a unique equilibrium contact angle. However, in practice a dynamic phenomenon of contact angle hysteresis is often observed, ranging from the advancing (maximal) contact angle to the receding (minimal) contact angle. The equilibrium contact is within those values, and can be calculated from them. The equilibrium contact angle reflects the relative strength of the liquid, solid, and vapour molecular interaction. The contact angle depends upon the medium above the free surface of the liquid, and the nature of the liquid and solid in contact. It is independent of the inclination of solid to the liquid surface. It changes with surface tension and hence with the temperature and purit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanopin Film
Nanopin film is an experimental material in nanotechnology developed in 2005 with unusual superhydrophobic properties . A droplet of water makes contact with the surface of this film and forms an almost perfect sphere with a contact angle of 178 °. This happens because it is covered with nanoscale, topped-off pins or cones perpendicular to the surface. The surface is regarded as a composite material with mostly air and a small fraction constituted by the tops of the cones. When the contact angle of the cone material is sufficiently large, Cassie's law predicts large contact angle values for the composite. This particular nanopin film is produced with borosilicate glass. A solution of CoCl2•6H2O or cobalt chloride hexahydrate is heated at 60 °C for 24 hours in a chemical bath deposition to form a brucite type cobalt(II) hydroxide layer with composition :CoOH1.13Cl0.09(CO3)0.39.0.05H20 The top coating is provided by lauric acid in a separate step. A 3 square micrometer surface n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanotechnology
Nanotechnology, also shortened to nanotech, is the use of matter on an atomic, molecular, and supramolecular scale for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal of precisely manipulating atoms and molecules for fabrication of macroscale products, also now referred to as molecular nanotechnology. A more generalized description of nanotechnology was subsequently established by the National Nanotechnology Initiative, which defined nanotechnology as the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). This definition reflects the fact that quantum mechanical effects are important at this quantum-realm scale, and so the definition shifted from a particular technological goal to a research category inclusive of all types of research and technologies that deal with the special properties of matter which occur below the given size threshold. It is therefore commo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrowetting
Electrowetting is the modification of the wetting properties of a surface (which is typically hydrophobic) with an applied electric field. History The electrowetting of mercury and other liquids on variably charged surfaces was probably first explained by Gabriel Lippmann in 1875 and was certainly observed much earlier. A. N. Frumkin used surface charge to change the shape of water drops in 1936. The term electrowetting was first introduced in 1981 by G. Beni and S. Hackwood to describe an effect proposed for designing a new type of display device for which they received a patent. The use of a "fluid transistor" in microfluidic circuits for manipulating chemical and biological fluids was first investigated by J. Brown in 1980 and later funded in 1984–1988 under NSF Grants 8760730 & 8822197, employing insulating dielectric and hydrophobic layer(s) (EWOD), immiscible fluids, DC or RF power; and mass arrays of miniature interleaved (saw tooth) electrodes with large or matching In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimer (chemistry)
A dimer () (''di-'', "two" + ''-mer'', "parts") is an oligomer consisting of two monomers joined by bonds that can be either strong or weak, covalent or intermolecular. Dimers also have significant implications in polymer chemistry, inorganic chemistry, and biochemistry. The term ''homodimer'' is used when the two molecules are identical (e.g. A–A) and ''heterodimer'' when they are not (e.g. A–B). The reverse of dimerization is often called dissociation. When two oppositely charged ions associate into dimers, they are referred to as ''Bjerrum pairs'', after Niels Bjerrum. Noncovalent dimers Anhydrous carboxylic acids form dimers by hydrogen bonding of the acidic hydrogen and the carbonyl oxygen. For example, acetic acid forms a dimer in the gas phase, where the monomer units are held together by hydrogen bonds. Under special conditions, most OH-containing molecules form dimers, e.g. the water dimer. Excimers and exciplexes are excited structures with a short life ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planta (journal)
''Planta'' is a monthly peer-reviewed scientific journal covering all areas of botany. It was established in 1925 and is published by Springer Science+Business Media. The editors-in-chief are Anastasios Melis ( UC-Berkeley) and Dorothea Bartels (Universitat Bonn). According to the ''Journal Citation Reports'', the journal has a 2012 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a scientometric index calculated by Clarivate that reflects the yearly mean number of citations of articles published in the last two years in a given journal, as ... of 3.347. References External links * Botany journals Publications established in 1925 Springer Science+Business Media academic journals Monthly journals English-language journals {{botany-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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