Patent Application
20140314991
Embodiments described herein relate generally to devices, systems and methods for producing liquid-impregnated surfaces for the inhibition of vapor or gas nucleation.
Nucleation phenomena typically occur heterogeneously (on a surface) at cracks or surface defects, where there is a significantly lower energy barrier to nucleation. On perfectly smooth surfaces, such as liquid surfaces, the energy barrier to nucleation can be very high, and nucleation may not occur even when the external environment becomes significantly supersaturated.
Carbonated or “fizzy” beverages such as soft drinks and many types of beer have a limited shelf life because they tend to go flat over time, i.e., lose a substantial portion of the dissolved carbon dioxide. Nucleation at the interior surfaces of container releases the carbon dioxide from the liquid phase which can seep out from the cap seal and diffuse through the plastic over time. By altering interior surface of the containers to increase the energy barrier to nucleation and by preventing gas from coming out of solution, the shelf life of these beverages can be extended.
Water and other liquids have a specific boiling point at atmospheric pressure. This boiling point can be altered by changing the external pressures on the liquid and by altering the vapor pressures of the liquids themselves. In certain applications, it is desirable to raise a liquid above its boiling point by increasing the external pressure on the liquid, and without altering the vapor pressure of the liquid itself.
Cavitation is the formation and then immediate implosion of cavities in a liquid usually as a result of rapid changes in pressure. Cavitation can occur on the surface of impellers or propellers. Cavitation typically begins at a nucleation site where bubbles of saturated vapor form in a low pressure area of the liquid. Cavitation can significantly reduce the efficiency of impellers or propellers of displacing the liquid, can cause noise, and wear and corrosion on the surface. During cavitation, an impeller or propeller loses thrust when the vaporous cavitation bubble forms.
Thus, there is a need for surfaces with an energy barrier to nucleation. In particular, there is a need for surfaces with reduced nucleation sites which inhibit the release of gases dissolved in liquids. There is also a need for surfaces with reduced nucleation sites which inhibit the start of the boiling process. There is also a need for surfaces with reduced nucleation sites that inhibit the formation of cavitation bubbles.
Embodiments described herein relate generally to devices, systems and methods for producing liquid-impregnated surfaces for the inhibition of vapor or gas nucleation. In some embodiments, an apparatus having a liquid-impregnated surface includes a first surface having a first roll off angle. A plurality of solid features are disposed on the first surface such that interstitial regions are defined between the solid features. An impregnating liquid is disposed in the interstitial regions which are dimensioned and configured to remain impregnated by the impregnating liquid through capillarity. The impregnating liquid disposed in the interstitial regions at least partially defines a second surface having a second roll off angle less than the first roll off angle. Furthermore, the second surface has substantially less nucleation sites for formation of bubbles in a contact liquid that includes a gas dissolved therein and is disposed on the second surface, as compared to the first surface.
a-b is a schematic diagram of a liquid droplet placed on a liquid-impregnated surface, according to an embodiment.
a shows measured roll off angles of different liquid-impregnated surfaces.
a shows measured velocities of water droplets as a function of substrate tilt angle.
a shows condensation of water droplets on a first liquid-impregnated surface that includes a 100 cSt silicon oil as an impregnating liquid.
Some known surfaces with designed chemistry and roughness, possess substantial non-wetting (hydrophobic) properties which can be extremely useful in a wide variety of commercial and technological applications. Some hydrophobic surfaces are inspired by nature, such as for example, the lotus plant which includes air pockets trapped within the micro or nano-textures of the surface, increasing the contact angle of a contact liquid (e.g., water or any other aqueous liquid) disposed on the hydrophobic surface. As long as these air pockets are stable, the surface continues to exhibit hydrophobic behavior. Such known hydrophobic surfaces that include air pockets, however, present certain limitations including, for example: i) the air pockets can be collapsed by external wetting pressures, ii) the air pockets can diffuse away into the surrounding liquid, iii) the surface can lose robustness upon damage to the texture, iv) the air pockets may be displaced by low surface tension liquids unless special texture design is implemented, and v) condensation or frost nuclei, which can form at the nanoscale throughout the texture, can completely transform the wetting properties and render the textured surface highly wetting.
Non-wetting surfaces can also be formed by disposing a liquid-impregnated surface on a substrate. Such liquid-impregnated surfaces can be nonwetting to any liquid, i.e. omniphobic (e.g. super hydrophobic, super oleophobic, or super metallophobic), can be configured to resist ice and frost formation, and can be highly durable. Liquid-impregnated surfaces can be disposed on any substrate, for example, on the inner surface of pipes, containers, or vessels, and can be configured to present a non-wetting surface to a wide variety of products, for example, food products, pharmaceuticals, over-the-counter drugs, nutraceuticals, health and beauty products, industrial greases, inks, bitumen, cement, adhesives, hazardous waste, consumer products, or any other product, such that the product can be evacuated, detached, or otherwise displaced with substantial ease on the liquid-impregnated surface.
Liquid-impregnated surfaces described herein, include impregnating liquids that are impregnated into a rough surface that includes a matrix of solid features defining interstitials regions, such that the interstitial regions include pockets of impregnating liquid. The impregnating liquid is configured to wet the solid surface preferentially and adhere to the micro-nano textured surface with strong capillary forces, such that the contact liquid has an extremely high advancing contact angle and an extremely low roll off angle (e.g., a roll off angle of about 1 degree and a contact angle of greater than about 100 degrees). This enables the contact liquid to displace with substantial ease on the liquid-impregnated surface. Therefore, the liquid-impregnated surfaces described herein, provide certain significant advantages over conventional super hydrophobic surfaces including: i) the liquid-impregnated surfaces creates a low hysteresis for the product, ii) such liquid-impregnated surfaces can include self cleaning properties, iii) can withstand high drop impact pressure (i.e., are wear resistant), iv) can self heal by capillary wicking upon damage, v) can repel a variety of contact liquids, such as semisolids, slurries, mixtures and/or non-Newtonian fluids, for example, water, edible liquids or formulations (e.g., ketchup, catsup, mustard, mayonnaise, syrup, honey, jelly, etc.), environmental fluids (e.g., sewage, rain water), bodily fluids (e.g., urine, blood, stool), or any other fluid (e.g. hair gel, toothpaste), vi) can reduce ice formation, vii) enhance condensation, viii) allow mold release, ix) prevent corrosion, x) reduce ice or gas hydrate adhesion, xi) prevent scaling from salt or mineral deposits, xii) reduce biofouling, and xiii) enhance condensation. Furthermore, the liquid-impregnated surfaces described herein can substantially reduce the number of nucleation sites. This can substantially inhibit nucleation vapor and/or gas bubbles dissolved in a contact liquid, for example, a carbonated beverage, a boiling liquid, or a flowing liquid, on the liquid-impregnated surface. In this manner, the liquid-impregnated surface can reduce fizzing and prevent carbonated beverages from going flat, inhibit boiling (e.g., because of heating or reduction in pressure), or prevent cavitation.
Examples of liquid-impregnated surfaces, methods of making liquid-impregnated surfaces and applications thereof, are described in U.S. Pat. No. 8,574,704, entitled “Liquid-Impregnated Surfaces, Methods of Making, and Devices Incorporating the Same,” filed Aug. 16, 2012, the entire contents of which are hereby incorporated by reference herein. Examples of materials used for forming the solid features on the surface, impregnating liquids, and applications involving edible contact liquids, are described in U.S. Pat. No. 8,535,779, entitled “Self-Lubricating Surfaces for Food Packaging and Food Processing Equipment,” issued Sep. 17, 2013, the entire contents of which are hereby incorporated by reference herein. Examples of non-toxic liquid-impregnated surfaces are described in U.S. Provisional Application No. 61/878,481, (the '481 application) entitled “Non-toxic Liquid-Impregnated Surfaces”, filed Sep. 16, 2013, the entire contents of which are hereby incorporated by reference herein.
In some embodiments, an apparatus having a liquid-impregnated surface includes a first surface having a first roll off angle. A plurality of solid features are disposed on the first surface such that interstitial regions are defined between the solid features. An impregnating liquid is disposed in the interstitial regions which are dimensioned and configured to remain impregnated by the impregnating liquid through capillarity. The impregnating liquid disposed in the interstitial regions at least partially defines a second surface having a second roll off angle less than the first roll off angle. Furthermore, the second surface has substantially less nucleation sites for formation of bubbles in a contact liquid that includes a gas dissolved therein and is disposed on the second surface, as compared to the first surface. In some embodiments, the contact liquid is carbonated. In some embodiments, the contact liquid is nitrogenated.
In some embodiments, a vessel for heating a liquid and having a liquid-impregnated surface includes a first surface having a first roll off angle. A plurality of solid features are disposed on the first surface such that interstitial regions are defined between the plurality of solid features. An impregnating liquid is disposed between the interstitial regions which are dimensioned and configured to remain impregnated by the impregnating liquid through capillarity. The impregnating liquid disposed in the interstitial regions at least partially defines a second surface having a second roll off angle less than the first roll off angle. Furthermore, the second surface has substantially less nucleation sites for formation of bubbles in a contact liquid that is disposed on the second surface and is heated to release a gas dissolved in the contact liquid, as compared to the first surface.
In some embodiments, an apparatus having a liquid-impregnated surface includes a hub rotatable about a central axis. At least one blade is connected to the hub. The blade include parts including a leading edge, a trailing edge, a fillet, a face, and a back. Each part includes a first surface having a first roll off angle. A plurality of solid features are disposed on the first surface of at least one part of the blade such that interstitial regions are defined between the plurality of solid features. An impregnating liquid is disposed between the interstitial regions which are dimensioned and configured to remain impregnated by the impregnating liquid through capillarity. The impregnating liquid disposed in the interstitial regions at least partially defines a second surface of the at least one part of the blade, having a second roll off angle less than the first roll off angle. Furthermore, the second surface has substantially less cavitation in a contact liquid in contact with the second surface, as compared to the first surface. In some embodiments, the apparatus can be a propeller or an impeller.
As used herein, the term “about” and “approximately” generally mean plus or minus 10% of the value stated, for example about 250 μm would include 225 μm to 275 μm, about 1,000 μm would include 900 μm to 1,100 μm.
As used herein, the term “contact liquid”, “bulk material, and “product” are used interchangeably to refer to a solid or liquid that flows, for example a non-Newtonian fluid, a Bingham fluid, a high viscosity fluids, or a thixotropic fluid and is contact with a liquid-impregnated surface, unless otherwise stated.
In some embodiments, the surface 110 can be an inner surface of a container. The container can include any suitable container such as, for example, tubes, bottles, vials, flasks, molds, jars, tubs, cups, caps, glasses, pitchers, barrels, bins, totes, tanks, kegs, tubs, syringes, tins, pouches, lined boxes, hoses, cylinders, and cans. In such embodiment, the container can be constructed in almost any desirable shape. The container can be constructed of rigid or flexible materials. Foil-lined or polymer-lined cardboard or paper boxes can also be used to form the container. In some embodiments, the surface 110 can include a surface of hoses, piping, conduit, nozzles, syringe needles, dispensing tips, lids, pumps, and other surfaces for containing, transporting, or dispensing the contact liquid CL. The surface 110 can be formed from any suitable material including, for example plastic, glass, metal, alloys, ceramics, coated fibers, any other material, or combinations thereof. Suitable surfaces can include, for example, polystyrene, nylon, polypropylene, wax, fluorinated wax, natural waxes, siliconyl waxes, polyethylene terephthalate, polypropylene, poly propylene carbonate, poly imide, polyethylene, polyurethane, graphene, polysulphone, polyethersulfone, polytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE), fluorinated ethylenepropylene copolymer (FEP), polyvinylidene fluoride (PVDF), perfluoroalkoxytetrafluoroethylene copolymer (PFA), perfluoromethyl vinylether copolymer (MFA), ethylenechlorotrifluoroethylene copolymer (ECTFE), ethylene-tetrafluoroethylene copolymer (ETFE), perfluoropolyether(PFPE), polychlorotetrafluoroethylene (PCTFE), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polyethyleneglycol (PEG), Polyvinylpyrrolidone (PVP), Polylactic acid (PLA), Acrylonitrile butadiene styrene (ABS), Tecnoflon cellulose acetate, poly(acrylic acid), polypropylene oxide), Dsorbitol, erythritol, xylitol, lactitol, maltitol, mannitol, and polycarbonate.
The solid features 112 can be disposed on the surface 110 using any suitable process. For example, in some embodiments, a top down fabrication process can be used to form the solid features 112 on the surface 110. For example, micro and/or nano-lithography (e.g., photolithography, SU-8 masks, nano imprinting, hard masking, shadow photolithography, etc.) can be used to define the solid features 112 on the surface 110, for example, silicon, glass, chromium, gold, PDMS, parylene, or any other suitable surface. In some embodiments, the micro and/or nano patterns can be used as the features of the solid features 112. In some embodiments, the micro and/or nano-patterns can be used as masks for further etching of the surface 110, for example, wet chemical etching (e.g., using buffered hydrofluoric acid, gold etchant, chromium etchant), or dry etching (e.g., reactive ion etching, deep reactive ion etching, SF6 etching, electron beam lithography, plasma beam lithography, etc.). In some embodiments, the solid features 112 can be grown in-situ on the surface, for example, using atomic layer deposition (ALD), sputtering, e-beam deposition, chemical vapor deposition, plasma enhanced chemical vapor deposition, and the likes.
In some embodiments, the solid features 112 can be disposed on the inner surface of a container (e.g., any of the containers described herein) or be integral to the surface itself (e.g., the textures of a polycarbonate bottle may be made of polycarbonate). In some embodiments, the solid features 112 may be formed of a collection or coating of particles including, but not limited to insoluble fibers (e.g., purified wood cellulose, micro-crystalline cellulose, and/or oat bran fiber), wax (e.g., carnauba wax, Japan wax, beeswax, candelilla wax, rice bran wax), shellac, fluorinated waxes, siliconyl waxes, other polysaccharides, fructo-oligosaccharides, metal oxides, montan wax, lignite and peat, ozokerite, ceresins, bitumens, petrolatuns, paraffins, microcrystalline wax, lanolin, esters of metal or alkali, flour of coconut, almond, potato, wheat, pulp, zein, dextrin, cellulose ethers (e.g., Hydroxyethyl cellulose, Hydroxypropyl cellulose (HPC), Hydroxyethyl methyl cellulose, Hydroxypropyl methyl cellulose (HPMC), Ethyl hydroxyethyl cellulose), ferric oxide, ferrous oxide, silicas, clay minerals, bentonite, palygorskite, kaolinite, vermiculite, apatite, graphite, molybdenum disulfide, mica, boron nitride, sodium formate, sodium oleate, sodium palmitate, sodium sulfate, sodium alginate, agar, gelatin, pectin, gluten, starch alginate, carrageenan, whey and/or any other edible solid particles described herein or any combination thereof.
In some embodiments, surface energy of the surface 110 and/or the solid features 112 can be modified, for example, to enhance the adhesion of the solid features 112 to the surface 110 or to enhance the adhesion of the impregnating liquid 120 to the solid features 112 and/or the surface 110. Such surface modification processes can include, for example, sputter coating, silane treatment, fluoro-polymer treatment, anodization, passivation, chemical vapor deposition, physical vapor deposition, oxygen plasma treatment, electric arc treatment, thermal treatment, any other suitable surface chemistry modification process or combination thereof.
In some embodiments, the solid features 112 can be disposed by exposing the surface 110 (e.g., polycarbonate) to a solvent (e.g., acetone). For example, the solvent may impart texture by inducing crystallization (e.g., polycarbonate may recrystallize when exposed to acetone). In some embodiments, the solid features 112 can be disposed by dissolving, etching, melting, reacting, treating, or spraying on a foam or aerated solution, exposing the surface to electromagnetic waves such as, for example ultraviolet (UV) light or microwaves, or evaporating away a portion of a surface, leaving a textured, porous, and/or rough surface behind that includes a plurality of the solid features 112. In some embodiments, the solid features 112 can be defined by mechanical roughening (e.g., tumbling with an abrasive, sandblasting, sanding), spray-coating or polymer spinning, plasma spraying, thermal spraying, deposition of particles from solution (e.g., layer-by-layer deposition, evaporating away liquid from a liquid/particle suspension contacting the surface), and/or extrusion or blow-molding of a foam, or foam-forming material (for example a polyurethane foam). In some embodiments, the solid features 112 can also be formed by deposition of a polymer from a solution (e.g., the polymer forms a rough, porous, or textured surface); extrusion or blow-molding of a material that expands upon cooling, leaving a wrinkled surface; and application of a layer of a material onto a surface that is under tension or compression, and subsequently relaxing the tension or compression of surface beneath, resulting in a textured surface.
In some embodiments, the solid features 112 can be formed by disposing a material, for example, a porous media on the surface capable of forming a layer of the material on the surface that includes pores of different sizes, and/or self-assembles on the surface 110. For example, in some embodiments, the solid features 112 are disposed through non-solvent induced phase separation of a polymer, resulting in a sponge-like porous structure. This can include, for example, a solution of polysulfone, poly(vinylpyrrolidone), and DMAc may be cast onto a substrate and then immersed in a bath of water. Upon immersion in water, the solvent and non-solvent exchange, and the polysulfone precipitates and hardens. The material can be disposed on the surface 110 by any suitable method, for example, spray coating, immersion (dip) coating, vapor deposition, pouring and/or any other suitable method to form the textured surface 110.
The solid features 112 can include micro-scale features such as, for example posts, pillars, spheres, nano-needles, pores, cavities, interconnected pores, grooves, ridges, spikes, peaks, interconnected cavities, bumps, mounds, particles, particle agglomerations, or any other random geometry that provides a micro and/or nano surface roughness. In some embodiments, the solid features 112 can include particles that have micro-scale or nano-scale dimensions which can be randomly or uniformly dispersed on a surface. Characteristic spacing between the solid features 112 can be about 1 mm, about 900 μm, about 800 μm, about 700 μm, about 600 μm, about 500 μm, about 400, μm, about 300 μm, about 200 μm, about 100 μm, about 90 μm, about 80 μm, about 70 μm, about 60 μm, about 50 μm, about 40 μm, about 30 μm, about 20 μm, about 10 μm, about 5 μm, 1 μm, or 100 nm, about 90 nm, about 80 nm, about 70 nm, about 60 nm, about 50 nm, about 40 nm, about 30 nm, about 20 nm, about 10 nm, or about 1 nm. In some embodiments, characteristic spacing between the solid features 112 can be in the range of about 100 μm to about 100 nm, about 30 μm to about 1 μm, or about 10 μm to about 1 μm. In some embodiments, characteristic spacing between solid features 112 can be in the range of about 100 μm to about 80 μm, about 80 μm to about 50 μm, about 50 μm to about 30 μm, about 30 μm to about 10 μm, about 10 μm to about 1 μm, about 1 μm to about 90 nm, about 90 nm to about 70 nm, about 70 nm to about 50 nm, about 50 nm to about 30 nm, about 30 nm, to about 10 nm, or about 10 nm to about 1 nm, inclusive of all ranges therebetween.
In some embodiments, the solid features 112, for example solid particles can have an average dimension of about 200 μm, about 100 μm, about 90 μm, about 80 μm, about 70 μm, about 60 μm, about 50 μm, about 40 μm, about 30 μm, about 20 μm, about 10 μm, about 5 μm, 1 μm, about 100 nm, about 90 nm, about 80 nm, about 70 nm, about 60 nm, about 50 nm, about 40 nm, about 30 nm, about 20 nm, about 10 nm, or about 1 nm. In some embodiments, the average dimension of the solid features 112 can be in the range of about 100 μm to about 100 nm, about 30 μm to about 10 μm, or about 20 μm to about 1 μm. In some embodiments, the average dimension of the solid feature 112 can be in the range of about 100 μm to about 80 μm, about 80 μm to about 50 μm, about 50 μm to about 30 μm, or about 30 μm to about 10 μm, or 10 μm to about 1 μm, about 1 μm to about 90 nm, about 90 nm to about 70 nm, about 70 nm to about 50 nm, about 50 nm to about 30 nm, about 30 nm, to about 10 nm, or about 10 nm to about 1 nm, inclusive of all ranges therebetween. In some embodiments, the height of the solid features 112 can be substantially uniform. In some embodiments, the surface 110 can have hierarchical features. For example the solid features can include micro-scale features that further include nano-scale features disposed thereupon.
In some embodiments, the solid features 112 (e.g., particles) can be porous. Characteristic pore size (e.g., pore widths or lengths) of particles can be about 5,000 nm, about 3,000 nm, about 2,000 nm, about 1,000 nm, about 500 nm, about 400 nm, about 300 nm, about 200 nm, about 100 nm, about 80 nm, about 50 nm, about 10 nm, or about 1 nm, inclusive of all ranges therebetween. In some embodiments, characteristic pore size can be in the range of about 200 nm to about 2 μm, or about 10 nm to about 1 μm inclusive of all ranges therebetween. Controlling the pore size, the length of pores, and the number of pores can allow for greater control of the impregnating liquid flow rates, product flow rates, and overall material yield.
The impregnating liquid 120 is disposed on the surface 110 such that the impregnating liquid 120 impregnates the interstitial regions defined by the plurality of solid features 112, for example, pores, cavities, or otherwise inter-feature spacing defined by the surface 110 such that no air remains in the interstitial regions. The interstitial regions can be dimensioned and configured such that the surface remains impregnated by impregnating liquid 120 through capillarity. The impregnating liquid 120 disposed in the interstitial regions of the plurality of solid features 112 is configured to define a second roll off angle less than the first roll of angle (i.e., the roll of angle of the unmodified surface 110. In some embodiments, the impregnating liquid 120 can have a viscosity at room temperature of less than about 1,000 cP, for example about 1 cP, 10 cP, 20 cP, 50 cP, about 100 cP, about 150 cP, about 200 cP, about 300 cP, about 400 cP, about 500 cP, about 600 cP, about 700 cP, about 800 cP, about 900 cP, or about 1,000 cP, inclusive of all ranges therebetween. In some embodiments, the impregnating liquid 120 can have viscosity of less than about 1 cP, for example, about 0.1 cP, 0.2 cP, 0.3 cP, 0.4 cP, 0.5 cP, 0.6 cP, 0.7 cP, 0.8 cP, 0.9 cP, or about 0.99 cP, inclusive of all ranges therebetween. In some embodiments, the impregnating liquid 120 can fill the interstitial regions defined by the solid features 112 such that the impregnating liquid 120 forms a layer at least about 5 nm thick above the plurality of solid features 112 disposed on the surface 110. In some embodiments, the impregnating liquid 120 forms a layer at least about 100 nm thick above the plurality of solid features 112 disposed on the surface 110. In some embodiments, the impregnating liquid 120 forms a layer at least about 1 um thick above the plurality of solid features 112 disposed on the surface 110. In some embodiments the plurality of solid features can have an average roughness, Ra, less than 0.8 um, for example, in compliance with the rules and regulations of a regulatory body (e.g., the Food and Drug Administration (FDA)).
The impregnating liquid 120 may be disposed in the interstitial spaces defined by the solid features 112 using any suitable means. For example, the impregnating liquid 120 can be sprayed (e.g., air spray, thermal spray, plasma spray) or brushed onto the textured surface 110 (e.g., a texture on an inner surface of a bottle). In some embodiments, the impregnating liquid 120 can be applied to the textured surface 110 by filling or partially filling a container that includes the textured surface 110. The excess impregnating liquid 120 is then removed from the container. In some embodiments, the excess impregnating liquid 120 can be removed by adding a wash liquid (e.g., water, surfactants, acids, bases, solvents, etc.), or a heated wash liquid to the container to collect or extract the excess liquid from the container. In some embodiments, the excess impregnating liquid may be mechanically removed (e.g., pushed off the surface with a solid object or fluid), absorbed off of the surface 110 using another porous material, or removed via gravity or centrifugal forces. In some embodiments, the impregnating liquid 120 can be disposed by spinning the surface 110 (e.g., a container) in contact with the liquid (e.g., a spin coating process), and condensing the impregnating liquid 120 onto the surface 110. In some embodiments, the impregnating liquid 120 is applied by depositing a solution with the impregnating liquid and one or more volatile liquids (e.g., via any of the previously described methods) and evaporating away the one or more volatile liquids. In some embodiments, the solid materials may be removed in a wash process, and reapplied after the wash process.
In some embodiments, the impregnating liquid 120 can be applied using a spreading liquid that spreads or pushes the impregnating liquid along the surface 110. For example, the impregnating liquid 120 (e.g., ethyl oleate) and spreading liquid (e.g., water) may be combined in a container and agitated or stirred. The fluid flow within the container may distribute the impregnating liquid 120 around the container as it impregnates the solid features 112.
In some embodiments, the impregnating liquid 120 included in the liquid-impregnated surface 100 can be saturated with the solid features 112 (e.g., any of the solid features described herein) such that the solid features 112 do not dissolve into the impregnating liquid 120.
In some embodiments, the impregnating liquid 120 can include, silicone oil, a perfluorocarbon liquid, halogenated vacuum oil, greases, lubricants, (such as Krytox 1506 or Fromblin 06/6), a fluorinated coolant (e.g., perfluoro-tripentylamine sold as FC-70, manufactured by 3M), a high temperature heat transfer fluid (e.g. Galden HT 200 or Galden HT 270, Novec fluids, etc.), an ionic liquid, a fluorinated ionic liquid that is immiscible with water, a silicone oil comprising PDMS, a fluorinated silicone oil such as, for example polyfluorosiloxane, or polyorganosiloxanes, a liquid metal, a synthetic oil, a vegetable oil, derivative of a vegetable oil, a mono- di- or triglyceride, an electro-rheological fluid, a magneto-rheological fluid, a ferro-fluid, a dielectric liquid, a hydrocarbon liquid such as mineral oil, polyalphaolefins (PAO), fluorinated glycine, fluorinated ethers, or other synthetic hydrocarbon co-oligomers, a fluorocarbon liquid, for example, polyphenyl ether (PPE), perfluoropolyether (PFPE), or perfluoroalkanes, a refrigerant, a vacuum oil, a phase-change material, a semi-liquid, polyalkylene glycol, esters of saturated fatty and dibasic acids, polyurea, grease, synovial fluid, bodily fluid, or any other aqueous fluid or any other impregnating liquid described herein. In some embodiments, the impregnating liquid 120 can include an ionic liquid. Such ionic impregnating liquids can include, for example, tetrachloroethylene (perchloroethylene), phenyl isothiocyanate (phenyl mustard oil), bromo benzene, iodobenzene, obromotoluene, alpha-chloronaphthalene, alpha-bromonaphthalene, acetylene tetrabromide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMim), tribromohydrin (1,2,3-tribromopropane), tetradecane, cyclohexane, ethylene dibromide, carbon disulfide, bromoform, methylene iodide (diiodomethane), stanolax, Squibb's liquid petrolatum, p-bromotoluene, monobromobenzene, perchloroethylene, MCT oil, carbon disulfide, phenyl mustard oil, monoiodobenzene, triacetin, triglyceride of citric acid, alpha-monochloro-naphthalene, acetylene tetrabromide, aniline, butyl alcohol, isoamyl alcohol, n-heptyl alcohol, cresol, oleic acid, linoleic acid, amyl phthalate, any other ionic liquid and any combination thereof.
In some embodiments, the liquid-impregnated surface 100 can include non-toxic materials, for example impregnating liquid 120 and/or solid 112 (e.g., solid particles used to form solid features such as, for example, wax) which are non-toxic to humans and/or animals. Such non-toxic liquid-impregnated surfaces can thereby be disposed on surfaces, for example the interior surface of containers, which are configured to house products formulated for human use or consumption. Such products can include, for example food products, drugs (e.g., FDA approved drugs), or health and beauty products.
In some embodiments, any solvents used in the processing of any components of the liquid-impregnated surface 100, for example the solid surface, may remain in the liquid-impregnated surface in some concentration, and thus the solvents can also be chosen to be non-toxic. Examples of solvents that are nontoxic in residual quantities include ethyl acetate, ethanol, or any other non-toxic solvent.
The non-toxicity requirements can vary depending upon the intended use of the product in contact with the liquid-impregnated surface. For example, liquid-impregnated surfaces configured to be used with food products or products classified as drugs would be required to have a much higher level of non-toxicity when compared with products meant to contact only the oral mucosa (e.g., toothpaste, mouth wash, etc.), or applied topically such as, for example, health and beauty products (e.g., hair gel, shampoo, cosmetics, etc.).
In some embodiments, the liquid-impregnated surface 100 can include materials that are a U.S. Food and Drug Administration (FDA) approved direct or indirect food additive, an FDA approved food contact substance, satisfy FDA regulatory requirements to be used as a food additive or food contact substance, and/or is an FDA GRAS material. Examples of such materials can be found within the FDA Code of Federal Regulations Title 21, located at “http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm”, the entire contents of which are hereby incorporated by reference herein. In some embodiments, the components of the liquid-impregnated surface 100, for example the impregnating liquid can exist as a component of the food product disposed within the container. In some embodiments, the components of the liquid-impregnated surface 100 can include a dietary supplement or ingredient of a dietary supplement. The components of the liquid-impregnated surface 100 can also include an FDA approved food additive or color additive. In some embodiments, the liquid-impregnated surface 10 can include materials that exist naturally in, or are derived from plants and animals. In some embodiments, the liquid-impregnated surface 100 for use with food products includes solids or impregnating liquid that is flavorless or have a high flavor threshold of below 500 ppm, are odorless or have high odor threshold, and/or are substantially transparent.
In some embodiments, the materials included in the liquid-impregnated surface 100 can include an FDA approved drug ingredient, for example any ingredient included in the FDA's database of approved drugs, “http://www.accessdata.fda.gov/scripts/cder/drugsatfda/index.cfm”, the entire contents of which are hereby incorporated herein by reference. In some embodiments, the liquid-impregnated surface 100 can include materials that satisfy FDA requirements to be used in drugs or are listed within the FDA's National Drug Discovery Code Directory, “http://www.accessdata.fda.gov/scripts/cder/ndc/default.cfm”, the entire contents of which are hereby incorporated herein by reference. In some embodiments, the materials can include inactive drug ingredient of an approved drug product as listed within FDA's database, “http://www.accessdata.fda.gov/scripts/cder/ndc/default.cfm”, the entire contents of which are hereby incorporated herein by reference. In some embodiments, the materials can include any materials that satisfy the requirement of materials that can be used in liquid-impregnated surfaces configured to be used with food products, and/or include a dietary supplement or ingredient of a dietary supplement.
In such embodiments, the liquid-impregnated surface 100 can include materials which are FDA approved and satisfies FDA drug requirements as are listed within the FDA's National Drug Discovery Code Directory and can also include FDA approved health and beauty ingredient, that satisfy FDA requirements to be used in health and beauty products, satisfies FDA regulatory laws included in the Federal Food, Drug and Cosmetic Act (FD&C Act), or the Fair Packaging and Labeling Act (FPLA).
In some embodiments, the liquid-impregnated surface 100 can include materials that are an FDA approved health and beauty ingredient, that satisfies FDA requirements to be used in health and beauty products, satisfies FDA regulatory laws included in the Federal Food, Drug and Cosmetic Act (FD&C Act), or the Fair Packaging and Labeling Act (FPLA). In some embodiments, the materials can include a flavor or a fragrance.
In some embodiments, the materials included in the liquid-impregnated surfaces 100 described can be flavorless or have high flavor thresholds below 500 ppm, and can be odorless or have a high odor threshold. In some embodiments the materials included in the liquid-impregnated surface 100 can be substantially transparent. For example, the solid features 112 or impregnating liquid 120 can be selected so that they have substantially the same or similar indices of refraction. By matching their indices of refraction, they may be optically matched to reduce light scattering and improve light transmission. For example, by utilizing materials that have similar indices of refraction and have a clear, transparent property, a surface having substantially transparent characteristics can be formed. In some embodiments, the materials included in the liquid-impregnated surface 100 are organic or derived from organically grown products. In some embodiments, the impregnating liquid 120 can include one or more additives. The additive can be configured, for example, to reduce the viscosity, vapor pressure, or solubility of the impregnating liquid. In some embodiments, the additive can be configured to increase the chemical stability of the liquid-impregnated surface, for example the additive can be an anti-oxidant configured to inhibit oxidation of the liquid-impregnated surface. In some embodiments the additive can be added to reduce or increase the freezing point of the liquid. In some embodiments, the additive can be configured to reduce the diffusivity of oxygen or CO2 through the liquid-impregnated surface or enable the liquid-impregnated surface to absorb more ultra violet (UV) light, for example protect the product (e.g., any of the products described herein), disposed within a container on which the non-toxic liquid-impregnated surface is disposed. In some embodiments, the additive can be configured to provide an intentional odor, for example a fragrance (e.g., smell of flowers, fruits, plants, freshness, scents, etc.). In some embodiments, the additive can be configured to provide color to the liquid-impregnated surface and can include, for example a dye, or an FDA approved color additive. In some embodiments, the non-toxic liquid-impregnated surface includes an additive that can be released into the product, for example, a flavor or a preservative.
In some embodiments, the materials included in any of the liquid-impregnated surface 100 can be organic or derived from organically grown products. For example, the impregnating liquid 120 can include organic liquids that are often or sometimes non-toxic. Such organic liquids can, for example, include materials that fall within the following classes; lipids, vegetable oils (e.g., olive oil, light olive oil, corn oil, soybean oil, rapeseed oil, linseed oil, grapeseed oil, flaxseed oil, peanut oil, safflower oil, palm oil, coconut oil, or sunflower oil), fats, fatty acids, derivatives of vegetable oils or fatty acids, esters, terpenes, monoglycerides, diglycerides, triglycerides, alcohols, and fatty acid alcohols. Examples of vegetable oils suitable for use as impregnating liquid 120 are described in Gunstone, F., “Vegetable Oils in Food Technology: Composition, Properties and Uses: 2nd Ed.”, Wiley, John and Sons Inc., Pub. May 2011, the contents of which are hereby incorporated by reference herein in their entirety.
In some embodiments, the liquid-impregnated surface '00 described herein can include organic solids and/or liquids that are non-toxic and fall within the following classes; lipids, waxes, fats, fibers, cellulose, derivatives of vegetable oils, esters (such as esters of fatty acids), terpenes, monoglycerides, diglycerides, triglycerides, alcohols, fatty acid alcohols, ketones, aldehydes, proteins, sugars, salts, minerals, vitamins, carbonate, ceramic materials, alkanes, alkenes, alkynes, acyl halides, carbonates, carboxylates, carboxylic acids, methoxies, hydroperoxides, peroxides, ethers, hemiacetals, hemiaketals, acetals, ketals, orthoesters, orthocarbonate esters, phospholipids, lecithins, any other organic material or any combination thereof. In some embodiments, any of the non-toxic liquid-impregnated surfaces described herein can include non-toxic materials that are boron, phosphorous, or sulfur containing compound. Some examples of food-safe impregnating liquids are MCT (medium chain triglyceride) oil, ethyl oleate, methyl laurate, propylene glycol dicaprylate/dicaprate, or vegetable oil, glycerine, squalene. In some embodiments, any of the non-toxic liquid-impregnated surfaces can include inorganic materials, for example ceramics, metals, metal oxides, silica, glass, plastics, any other inorganic material or combination thereof. In some embodiments, any of the non-toxic liquid-impregnated surfaces described herein can include, for example preservatives, sweeteners, color additives, flavors, spices, flavor enhancers, fat replacers, and components of formulations used to replace fats, nutrients, emulsifiers, surfactants, bulking agents, cleansing agents, depilatories, stabilizers, emulsion stabilizers, thickeners, flavor or fragrance, an ingredient of a flavor or fragrance, binders, texturizers, humectants, pH control agents, acidulants, leavening agents, anti-caking agents, anti-dandruff agents, anti-microbial agents, anti-perspirants, anti-seborrheic agents, astringents, bleaching agents, denaturants, depilatories, emollients, foaming agents, hair conditioning agents, hair fixing agents, hair waving agents, absorbents, anti-corrosive agents, anti-foaming agents, anti-oxidants, anti-plaque agents, anti-static agents, binding agents, buffering agents, chelating agents, cosmetic colorants, deodorants, detangling agents, emulsifying agents, film formers, foam boosting agents, gel forming agents, hair dyeing agents, hair straightening agents, keratolytics, moisturizing agents, oral care agents, pearlescent agents, plasticizers, refatting agents, skin conditioning agents, smoothing agents, soothing agents, tonics, and/or UV filters.
In some embodiments, the liquid-impregnated surface 100 can include non-toxic materials having an average molecular weight in the range of about 100 g/mol to about 600 g/mol. which are included in the Springer Material Landolt-Bornstein database located at, “http://www.springermaterials.com/docs/index.html”, or in the MatNavi database located at “www.mits.nims.go.jp/index_en.html”. In some embodiments, the impregnating liquid 120 can have a boiling point greater than 150° C. or preferably 250° C., such that the impregnating liquid 120 is not classified as volatile organic compounds (VOC's). In some embodiments, the impregnating liquid 120 can have a density which is substantially equal to the density of the product.
The ratio of the solid features 112 (e.g., particles) to the impregnating liquid 120, can be configured to ensure that little or no portion of the solid features 112 protrude above the impregnating liquid-contact liquid interface. For example, in some embodiments, a ratio of the solid features 112 to the impregnating liquid 120 on the surface 110 can be less than about 15%, or less than about 5%. In some embodiments, the ratio of the solid features 112 to the projected area of the liquid-impregnating liquid 120 can be less than about 50%, about 45%, about 40%, about 35%, about 30%, about 25%, about 20%, about 15%, about 10%, about 5%, or less than about 2%. In some embodiments, the ratio of the solid features 112 to the impregnating liquid 120 can be in the range of about 5% to about 50%, about 10% to about 30%, or about 15% to about 20%, inclusive of all ranges therebetween. In some embodiments, a low ratio can be achieved using surface textures that are substantially pointed, caved, or are rounded. By contrast, surface textures that are flat may result in higher ratios, with too much solid material exposed at the surface.
In some embodiments, the liquid-impregnated surface 100 can have an “emerged area fraction” q, which is defined as a representative fraction of the projected surface area of the liquid-impregnated surface 112, corresponding to non-submerged solid (non-submerged by the impregnating liquid. This portion can be in contact with a contact liquid) at room temperature, of less than about 0.50, about 0.50, about 0.30, about 0.25, about 0.20, about 0.15, about 0.10, about 0.05, about 0.01, or less than about 0.005. In some embodiments, φ can be greater than about 0.001, about 0.005, about 0.01, about 0.05, about 0.10, about 0.15, or greater than about 0.20. In some embodiments, φ can be in the range of about 0 to about 0.25. In some embodiments, φ can be in the range of about 0 to about 0.01. In some embodiments, φ can be in the range of about 0.001 to about 0.25. In some embodiments, φ can be in the range of about 0.001 to about 0.10.
In some embodiments, the liquid-impregnated surface 100 can have a spreading coefficient Soe(v)<0, where Soe(v) is spreading coefficient, defined as γev−γeo−γov, where γ is the interfacial tension between the two phases designated by subscripts, said subscripts selected from e, v, and o, where e is a non-vapor phase (e.g., liquid or semi-solid) external to the surface and different from the impregnating liquid, v is vapor phase external to the surface (e.g., air), and o is the impregnating liquid.
In some embodiments, the solid features 112 provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that θos(v),receding<θc where θc is critical contact angle. In some embodiments, the solid features 112 can provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that: (i) θos(w),receding=0; and/or (ii) θos(v),receding=0 and θos(w),receding=0, where θos(w),receding is receding contact angle of the impregnating liquid 120 (e.g., oil, subscript ‘o’) on the surface 100 (subscript ‘s’) in the presence of water (subscript ‘w’), and where θos(v),receding is receding contact angle of the impregnating liquid 120 (e.g., oil, subscript ‘o’) on the surface 100 (subscript ‘s’) in the presence of vapor phase (subscript ‘v’, e.g., air). In some embodiments, the solid features 112 provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that: (i) θos(v), receding>0; and/or (ii) θos(w), receding>0, where θos(v),receding is receding contact angle of the impregnating liquid 120 (e.g., oil, subscript ‘o’) on the surface 100 (subscript ‘s’) in the presence of vapor phase (subscript ‘v’, e.g., air), and where θos(w),receding is receding contact angle of the impregnating liquid 120 (e.g., oil, subscript ‘o’) on the surface 100 (subscript ‘s’) in the presence of water (subscript ‘w’). In some embodiments, both θos(v), receding>0 and θos(w), receding>0. In some embodiments, the solid features 112 provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that: (i) θos(v),receding<θc; and/or (ii) θos(w),receding<θc, where θc is critical contact angle. In some embodiments, the solid features 112 provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that: (i) θos(v),receding<θ*c; and/or (ii) θos(w),receding<θ*c, where θ*c=cos−1 (1/r), and where r is roughness of the solid portion of the surface 100.
In some embodiments, the solid features 112 provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that θos(v), receding<θc. where θc is critical contact angle. In some embodiments, the solid features 112 can provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that: (i) θos(e),receding=0; and/or (ii) θos(v),receding=0 and θos(e),receding=0, where θos(e),receding is receding contact angle of the impregnating liquid 120 (e.g., oil, subscript ‘o’) on the surface 100 (subscript ‘s’) in the presence of the contact liquid CL (subscript ‘e’), and where θos(v),receding is receding contact angle of the impregnating liquid 120 (e.g., oil, subscript ‘o’) on the surface 100 (subscript ‘s’) in the presence of vapor phase (subscript e.g., air). In some embodiments, the solid features 112 provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that: (i) θos(v), receding>0; and/or (ii) θos(e), receding>0, where θos(v),receding is receding contact angle of the impregnating liquid 120 (e.g., oil, subscript o) on the surface 100 (subscript ‘s’) in the presence of vapor phase (subscript ‘v’, e.g., air), and where θos(w),receding is receding contact angle of the impregnating liquid 120 (e.g., oil, subscript ‘o’) on the surface 100 (subscript ‘s’) in the presence of the contact liquid CL (subscript ‘e’). In some embodiments, both θos(v), receding>0 and θos(e), receding>θc. In some embodiments, the solid features 112 provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that: (i) θos(v),receding<θc; and/or (ii) θos(e),receding<θc, where θc is critical contact angle. In some embodiments, the solid features 112 provide stable impregnation of the impregnating liquid 120 therebetween or therewithin, such that: (i) θos(v),receding<θ*c; and/or (ii) θos(v),receding<θ*c, where θ*c=cos−1 (1/r), and where r is roughness of the solid portion of the surface 100.
In some embodiments, liquid-impregnated surface 100 can have advantageous droplet roll-off properties that minimize the accumulation of the contacting liquid CL on the surfaces. Without being bound to any particular theory, in some embodiments, a roll-off angle which is the angle of inclination of the liquid-impregnated surface 100 at which a droplet of contact liquid placed on the textured solid begins to move, can be less than about 50°, less than about 40°, less than about 30°, less than about 25°, or less than about 20° for a specific volume of contact liquid. In such embodiments, the roll off angle can vary with the volume of the contact liquid included in the droplet, but for a specific volume of the contact liquid, the roll off angle remains substantially the same.
In some embodiments, the impregnating liquid 120 can include one or more additives to prevent or reduce evaporation of the impregnating liquid 120. For example, a surfactant can be added to the impregnating liquid 120. The surfactants can include, but are not limited to, docosenoic acid, trans-13-docosenoic acid, cis-13-docosenoic acid, nonylphenoxy tri(ethyleneoxy) ethanol, methyl 12-hydroxyoctadecanate, 1-Tetracosanol, fluorochemical “L-1006”, and any combination thereof. Examples of surfactants described herein and other surfactants which can be included in the impregnating liquid can be found in White, I., “Effect of Surfactants on the Evaporation of Water Close to 100 C.” Industrial & Engineering Chemistry Fundamentals 15.1 (1976): 53-59, the content of which is incorporated herein by reference in its entirety. In some embodiments, the additives can include C16H33COOH, C17H33COOH, C18H33COOH, C19H33COOH, C14H29OH, C16H33OH, C18H37OH, C20H41OH, C22H45OH, C17H35COOCH3, C15H31COOC2H5, C16H33OC2H4OH, C18H37OC2H4OH, C20H41OC2H4OH, C22H45OC2H4OH, Sodium docosyl sulfate (SDS), poly(vinyl stearate), Poly(octadecyl acrylate), Poly(octadecyl methacrylate) and any combination thereof. Further examples of additives can be found in Barnes, G. T., “The potential for monolayers to reduce the evaporation of water from large water storages”, Agricultural Water Management 95.4 (2008): 339-353, the content of which is hereby by incorporated herein by reference in its entirety.
The liquid-impregnated surface 100 can be in contact with a contact liquid CL such that, the contact liquid CL moves easily over the liquid-impregnated surface 100. The contact liquid CL, can be any liquid or non-Newtonian fluid that is immiscible with the impregnating liquid 120 such as, for example, water, edible liquids or aqueous formulations (e.g., ketchup, mustard, mayonnaise, honey, etc.), environmental fluids (e.g., sewage, rain water), bodily fluids (e.g., urine, blood, stool), or any other fluid. In some embodiments, the contact liquid CL can be a food product or a food ingredient such as, for example, a sticky, highly viscous, and/or non-Newtonian food product. Such food products can include, for example, candy, chocolate syrup, mash, yeast mash, beer mash, taffy, food oil, fish oil, marshmallow, dough, batter, baked goods, chewing gum, bubble gum, butter, peanut butter, jelly, jam, dough, gum, cheese, cream, cream cheese, mustard, yogurt, sour cream, curry, sauce, ajvar, currywurst sauce, salsa lizano, chutney, pebre, fish sauce, tzatziki, sriracha sauce, vegemite, chimichurri, HP sauce/brown sauce, harissa, kochujang, hoisan sauce, kim chi, cholula hot sauce, tartar sauce, tahini, hummus, shichimi, ketchup, mustard, pasta sauce, Alfredo sauce, spaghetti sauce, icing, dessert toppings, or whipped cream, liquid egg, ice cream, animal food, any other food product or combination thereof. In some embodiments, the contact liquid CL can include a topical or oral drug a cream, an ointment, a lotion, an eye drop, an oral drug, an intravenous drug, an intramuscular drug, a suspension, a colloid, or any other form and can include any drug included within the FDA's database of approved drugs. In some embodiments, the contact liquid CL can include a health and beauty product, for example, toothpaste, mouth washes, mouth creams, denture fixing compounds, any other oral hygiene product, sun screens, anti-perspirants, anti-bacterial cleansers, lotions, shampoo, conditioner, moisturizers, face washes, hair-gels, medical fluids (e.g., anti-bacterial ointments or creams), any other health or beauty product, and or combination thereof. In some embodiments, the contact liquid CL can include any other non-Newtonian, thixotropic or highly viscous fluid, for example, laundry detergent, paint, oils, waxes, petroleum products, fabric softeners, industrial solutions, or any other contact liquid CL.
Interaction Between Various Phases in a Liquid-Impregnated Surface
A liquid-impregnated surface that is in contact with a contact liquid defines four distinct phases: an impregnating liquid, a surrounding gas (e.g., air), a contact liquid and a textured surface. The interactions between the different phases determine the morphology of the contact line (i.e., the contact line that defines the contact angle of a contact liquid droplet with the liquid-impregnated surface) because the contact line morphology substantially impacts the droplet pinning and therefore contact liquid mobility on the surface. There are various parameters which can play a role in defining the non-wetting performance of a liquid-impregnated surface. Key parameters include the relative contact angles of the impregnating liquid and the contact liquid, spreading coefficient, dimensions of the solid features, interfacial energies, and viscosities of the impregnating liquid and the contact liquid. Other factors include, for example, the roll off angle of contact liquid that affects how droplets are shed (whether they roll or slip), and what their shedding velocities are. Moreover, questions related to the longevity of the impregnated liquid film and its possible depletion, due to evaporation and entrainment with the droplets being shed, can have substantial bearing on the configuration of a liquid-impregnated surface, for example, the liquid-impregnated surface 100. Some of the key parameters and their impact on the liquid-impregnated surface are described below.
The contact angle, θos(e), is generally defined as the angle conventionally measured through goniometry, as the angle at which a liquid o, intersects with a surface, s, in the presence of an external phase ‘e’ (liquid or gas), at equilibrium. The contact angle can be a function of the hydrophobicity or hydrophilicity or surface energy of the liquid and the solid surface. The contact angle can also depend on the surface roughness.
A liquid-impregnated surface (e.g. the liquid-impregnated surface 100) can define two contact angles. The first is the contact angle θos(a) which is the contact angle of the impregnating liquid (subscript ‘o’) on a smooth surface of the same chemistry or material as the textured surface (subscript ‘s’) in the presence of air (subscript ‘a’). Said another way, this is the contact angle a droplet of impregnating liquid (e.g., the impregnating liquid 120) will form when disposed on a smooth solid surface of the same materials as 112 and surrounded by air. Complete submergence of the textured surface in air can happen if the contact angle θos(a)=0°, such that the impregnating liquid is able to completely cover the plurality of solid features of surface 112, reducing φ to 0. Although complete submergence may be achieved temporarily by depositing excess impregnating liquid, eventually this excess will drain or flow away (e.g., under gravity or shear stress) and the liquid-air interface may contact the textured surface 112.
The second is the contact angle θos(w) which is defined by the impregnating liquid when surrounded by a contact liquid (subscript ‘w’) such as, for example, water, an aqueous liquid, or any other contact liquid described herein. In this scenario, the textured surface can remain submerged in the impregnating liquid if the contact angle θos(w) is also equal to zero. Information on whether both θos(a)=0° and θos(w)=0° impacts the choice of an impregnating liquid, for example, the impregnating liquid 120, that can be used for a given droplet liquid and textured substrate material (e.g., the solid surface 110 that includes a plurality of solid features 112 disposed thereupon). If θos(a)=0° and θos(w)=0°, then φ=0, resulting in zero contact between the contact liquid and the surface 112. Although this condition is desirable, it is not necessarily. Alternative, less constraining requirements are described below.
The critical contact angle θc, also depends upon the interstitial spacing between the solid features included in the liquid-impregnated surface (e.g., the liquid-impregnated surface 100). The critical contact angle can be defined by
θc=cos−1((1−θ)/(r−φ)),
where φ is the emerged area fraction, as described herein. The critical contact angle θc can dictate the stability of a liquid in an liquid-impregnated surface. The spacing between the solid features can be controlled such that the critical contact angle θc is increased above the receding contact angle θrec,os(w), such that the surface 100 remains impregnated by the impregnating liquid 120. In this case, the contact liquid does not displace the impregnating liquid to impale the solid features, and easily sheds off the liquid-impregnated surface. If the interstitial spacing is too large, then the receding contact angle θrec,os(w) can be greater than the critical contact angle θc, such that the contact liquid can displace the impregnating liquid and impale the solid features, i.e. get pinned within the solid features. In the case that θrec,os(a)>0c, the impregnating liquid cannot be made to impregnate the surface 112.
Referring now to
The samples were then cleaned in a Piranha solution and treated with a low-energy silane (octadecyltrichlorosilane (OTS)) by solution deposition. The textured surface 210 was impregnated with the impregnating liquid 220 (
Table 1 shows various configuration of features formed on the textured surface 210. Table 2 includes intrinsic contact angles of impregnating liquids 220 on smooth surfaces of the same materials as the textured material 210. Note if the textured surface 210 is not coated with OTS, then θos(w)>θc for both impregnating liquids 220 and all post spacing b. Thus water droplets should displace the hydrophobic liquid 220 and get impaled by the microposts 212 leading to significant pinning, which was confirmed as such droplets did not roll-off of these textured surfaces.
In some embodiments, an impregnating liquid can “cloak” a droplet of a contact liquid. Cloaking occurs when the impregnating liquid spreads over the droplet of the contact liquid. In some embodiments, cloaking can cause the contact liquid to impale the impregnating liquid and therefore negatively impact the non-wetting characteristics of a liquid-impregnated surface (e.g., the liquid-impregnated surface 100). Furthermore, cloaking can also cause the impregnating liquid to get entrained with the contact liquid. This can lead to a loss of the impregnating liquid as the contact liquid is displaced from the liquid-impregnated surface. The degree of cloaking of the contact liquid with the impregnating liquid depends on the spreading coefficient Sow(a) of the impregnating liquid on the contact liquid in air. The spreading coefficient Sow(a) can be determined from the relative surface tension at the interface of each of the impregnating liquid, contact liquid, and air by the equation Sow(a)=γwa−γwo−γoa. Here γwa is the interfacial surface tension between the contact liquid and air, γwo is the interfacial surface tension between the contact liquid and the impregnating liquid, and γoa is the interfacial surface tension between the impregnating liquid and air. If Saw(a)>0, then cloaking will occurs, and if Sow(a)<0 then only partial cloaking or substantially no cloaking will occur. This knowledge can be used to select an impregnating liquid that provides an interfacial surface tension γwo between the contact liquid and the impregnating liquid such that Sow(a)<0, and cloaking can be reduced or substantially eliminated.
In some embodiments, cloaking can be desirable and can be used as a means for preventing environmental contamination, like a time capsule preserving the contents of the cloaked material. Cloaking can result in encasing of the material thereby cutting its access from the environment. This can be used for transporting materials (e.g., bioassays) across a length in a way that the material is not contaminated by the environment. In some embodiments, cloaking can be exploited to prevent corrosion, fouling, etc. In some embodiments, cloaking can be used for preventing vapor-liquid transformation (e.g., water vapor, metallic vapor, etc.). In some embodiments, cloaking can be used for inhibiting liquid-solid formation (e.g., ice, metal, etc.). In some embodiments, cloaking can be used to make reservoirs for carrying the materials, such that independent cloaked materials can be controlled and directed by external means (like electric or magnetic fields).
In some embodiments, the amount of cloaking can be controlled by various properties of the impregnating liquid such as, for example, viscosity and/or surface tension of the impregnating liquid. Additionally or alternatively, the de-wetting of the cloaked material can also be controlled to release the material, for example a system in which a product is disposed on the liquid-impregnated surface at one end, and upon reaching the other end is exposed to an environment that causes the product to uncloak.
Referring now to
122 ± 0.8
20 ± 5°
Table 3 shows surface and interfacial tension measurements and resulting spreading coefficients Sow(a)=γwa−γow−γoa, of 9.34, 96.4, and 970 cP Dow Corning PMX 200 Silicone oils on water in air. Values of γow were provided by Dow Corning.
As shown in
c shows an 8 μl water droplet placed on the silicone oil impregnated textured surface 210. The droplet forms a large apparent contact angle (˜100 degrees) but very close to the solid surface (arrows in
As described herein, the textured surface 210 can be completely submerged in the impregnating liquid 220 if θos(a)=0°. This condition was found to be true for silicone oil, implying that the tops of the microposts 212 should be covered by a stable thin oil film. This film was observed experimentally using laser confocal fluorescence microscopy (LCFM); the micropost 212 tops appear bright due to the presence of a fluorescent dye that was dissolved in the oil (
Stable Configuration of Contact Liquid Droplets on Liquid-Impregnated Surfaces
The relationships between the contact angles and the spreading coefficient of the impregnating liquid can be used to develop a thermodynamic framework to determine various states of the liquid-impregnated surface. The thermodynamic framework which is based on the interfacial energies of the surface, impregnating liquid, contact liquid, and ambient air can be used to ascertain a combination of a textured surface and impregnating liquid that will provide most favorable non-wetting properties for any particular contact liquid.
As described herein, a liquid-impregnated surface that includes an impregnating liquid (e.g., oil) disposed on a textured surface in the presence of air (i.e., no contact liquid) can have three possible states. These include a first state A1 in which the solid features of the surface are not impregnated with impregnating liquid (i.e., are dry), a second state A2 in which the solid features of the surface are impregnated with impregnating liquid but have emergent features, and a third state A3 in which the solid features are completely impregnated with the impregnating liquid (i.e., encapsulated). The same liquid-impregnated surface can have three separate states when a contact liquid (e.g., water) is in contact with the liquid-impregnated surface. These include a first state W1 in which the textured surface is impaled with the contact liquid, a second state W2 in which the solid features of the surface are impregnated with impregnating liquid but have emergent features, and a third state W3 in which the solid features are completely impregnated with the impregnating liquid (i.e., encapsulated). The stable state will be the one that has the lowest interfacial energy E. For example, if state W3 has the lowest interfacial energy EW3, this will be the most stable state. In this state the impregnating liquid will substantially encapsulate the solid features of the textured surface in the presence of the contact liquid and thereby, provide optimum non-wetting properties. Thus, knowledge of the interfacial energy can be used to select the best combination of the textured surface and the impregnating liquid for a given contact liquid.
E
A2
<E
A1
(γsa−γas)/γoa>(1−φ)/(r−φ) (1)
E
A2
<E
A3
γsa−γos−γoa<0 (2)
where φ is the emergent area fraction, and r is the ratio of total surface area to the projected area of the solid. In the case of square posts with width a, edge-to-edge spacing b, and height h, φ=a2/(a+b)2 and r=1+4ah/(a+b)2. Applying Young's equation, cos(θos(a))=(γsa−γos)/γoa, Eq. (1) reduces to the hemi-wicking criterion for the propagation of a oil through a textured surface: cos(θos(a))>(1−φ)/(r−φ)=cos(θc). This requirement can be conveniently expressed as θos(a)<0. In Eq. (2), γsa−γos−oa, is simply the spreading coefficient Sos(a) of oil on the textured surface in the presence of air. This can be reorganized as (γsa−γos)/γoa<1, and applying Young's equation again, Eq. (2) can be written as θos(a)>0. Expressing Eq. (1) in terms of the spreading coefficient Sos(a), yields: −γoa(r−1)/(r−φ)<Sos(a). The above simplifications then lead to the following equivalent criteria for the surface to be in state A2:
E
A2
<E
A1
,E
A3
θc>θos(a)>0
−γoa(r−1)/(r−φ)<Sos(a)<0 (3)
Similarly, state A3 would be stable if EA3<EA2, EA1. From
E
A3
<E
A2
θos(a)=0
γsa−γos−γoa≡Sos(a)≧0 (4)
E
A3
<E
A1
θos(a)<cos−1(1/r)
Sos(a)>−γoa(1−1/r) (5)
Note that Eq. (5) is automatically satisfied by Eq. (4), thus the criterion for state A3 to be stable (i.e. encapsulation) is given by Eq. (4). Following a similar procedure, the condition for state A1 to be stable can be derived as:
E
A1
<E
A2
,E
A3
θos(a)>θc
Sos(a)<−γoa(r−1)/(r−φ) (6)
The rightmost expression of Eq. (4) can be rewritten as (γsa−γos)/γoa>1. Young's equation would suggest that if θos(a)=0 degrees, then (γsa−γos)γoa=1 (i.e. Sos(a)=0). However, θos(a)=0 degrees is true also for the case that (γsa−γos)/γoa>1 (i.e. Sos(a)>0). Young's equation predicts the contact angle based on balancing the surface tension forces on a contact line, such that the equality only exists for a contact line at static equilibrium. For a spreading film (Sos(a)>0) a static contact line doesn't exist, hence precluding the applicability of Young's equation.
Referring now to the states of the liquid-impregnated surface in the presence of water as the contact liquid, the interface beneath the droplet will attain one of the three different states—W1, W2, or W3 (
E
W2
<E
W1
,E
W3
θc>θos(w)>0
−γow(r−1)/(r−φ)<Sos(w)<0 (7)
State W3 will be stable (i.e. the oil will encapsulate the texture) when:
E
W3
<E
W1
,E
W2
θos(w)≡0
γsw−γos−ow≡Sos(w)≧0. (8)
and the droplet will displace the oil and be impaled by the textures (state W1) when:
E
W1
<E
W2
,E
W3
θos(w)>θc
Sos(w)<−γow(r−1)/(r−φ) (9)
This thermodynamic framework can be combined with the cloaking criterion described herein to obtain an overall framework which can be used to predict the performance of a liquid-impregnated surface in the presence of any particular contact liquid.
Solid Feature Spacing, Hierarchical Solid Features, and Roll off Angle
In some embodiments, solid features disposed on a surface can be configured to include hierarchical features, as described herein. Such hierarchical features can enable complete impregnation and encapsulation of the solid features with an impregnating liquid that would otherwise not completely encapsulate the solid features if the hierarchical features are absent.
The effect of texture on the roll-off angle α* can be modeled by balancing gravitational forces with pinning forces. A force balance of a water droplet on a smooth solid surface at incipient motion gives ρwΩg sin α*≈2Rbγwa(cos θrec,ws(a)=cos θadv,ws(a)), where ρw is the density of the contact liquid droplet of volume Ω, g is the gravitational acceleration, Rb is the droplet base radius, and θadv,ws(a) and θrec,ws(a) are the advancing and receding contact angles of contact liquid droplet in air on the smooth solid surface. Pinning results from contact angle hysteresis of up to two contact lines: an oil-air-solid contact line with a pinning force per unit length given by γoa(cos θrec,os(a)−cos θadv,os(a)), and an oil-water-solid contact line with a pinning force per unit length given by γow(cos θrec,os(w)−cos θadv,os(w)). The length of the contact line over which pinning occurs is expected to scale as Rbφ1/2 where φ1/2 is the fraction of the droplet perimeter (˜Rb) making contact with the emergent features of the textured substrate. Thus a force balance tangential to the surface gives:
ρwΩg sin α*˜rBφ1/2[γow(cos θrec,os(w)−cos θadv,os(w))+γoa(cos θrec,os(a)−cos θadv,os(a))] (10)
Dividing Eq. (10) by Rbγwa we obtain a non-dimensional expression:
Bo sin α*f(θ)˜φ1/2[(γow(cos θrec,os(w)−cos θadv,os(w))+γoa(cos θrec,os(a)−cos θadv,os(a))]/γwa (11)
where f(θ)=Ω1/3/Rb=[(π/3)(2+cos θ)(1−cos θ)2/sin3 θ)]1/3 by assuming the droplet to be a spherical cap making an apparent contact angle θ with the surface. Bo=Ω2/3ρwg/γwa is the Bond number, which compares the relative magnitude of gravitational forces to surface tension forces. Values for θrec,os(w), θadv,os(w), θrec,os(a), θadv,os(a), γow, γoa, and γwa are provided in Tables 2 and 3.
Dynamics of Droplet Shedding—Rolling Angle and Rolling Velocity
The speed or velocity at which a contact liquid having a volume Ω disposed on a liquid-impregnated surface, rolls of the liquid-impregnated surface depends on the viscosity of the impregnating liquid and the pinning of the contact line of a droplet of the contact liquid on the liquid-impregnated surface. Once gravitational forces acting on the contact liquid droplet overcome the pinning forces, the velocity attained by the droplet determines how quickly it can be shed, which reflects the non-wetting performance of the surface. The steady-state shedding velocity V of water droplets on a liquid-impregnated surface which was substantially similar to the liquid-impregnated surface 200, was measured using a high-speed camera while systematically varying the impregnating liquid dynamic viscosity μo, post spacing b, textured surface tilt angle α, and droplet volume, Ω. These measurements are shown in
To explain these trends, it is first determined whether the water droplet is rolling or sliding. Consider the oil-water interface beneath the droplet as shown in
Since (μo/μw(hcm/t)>>1 as described herein, Vi/V<<1, i.e. the oil-water interface moves at a negligibly small velocity relative to that of the water droplet's centre of mass. This suggests that the water droplets being shed on the textured surface, for example, textured surface 210, are rolling. This was further confirmed by adding ground coffee particles to the water droplet and tracking their motion relative to the droplet with a high-speed camera as the water droplet moved across the surface. Particle trajectories, shown in
To determine the magnitude of V, the rate of change of gravitational potential energy is balanced as the droplet rolls down the incline with the total rate of energy dissipation due to contact line pinning and viscous effects. The resulting energy balance gives:
where Fg and Fp represent the net gravitational and pinning forces acting on the water droplet, the Ω terms are the volume over which viscous dissipation occurs, and the □ū terms are the corresponding velocity gradients. The form of Eq. (13) is similar to that for viscous contact liquid droplets rolling on completely non-wetting surfaces though additional terms are present due to the presence of the impregnated oil. The three terms on the right side of Eq. (13) represent the rate of viscous dissipation within the droplet (I), in the oil film beneath the droplet (II), and in the wetting ridge near the three-phase contact line (III).
The rate of viscous dissipation (i.e., the energy lost by the rolling droplet of the contact liquid due to its viscosity) within the water droplet (I) is primarily confined to the volume beneath its centre of mass and can be approximated as I˜uw(V/hcm)2Rb2hcm, where Rb is the base radius of the droplet. Applying geometrical relations for a spherical cap, Rb/hcm=g(θ)=4/3 (sin θ)(2+cos θ)/(1+cos θ)2 results in:
I˜μ
w
V
2
R
b
g(θ)
The rate of viscous dissipation within the film (II) can be approximated as II˜μo(Vi/t)2Rb2t. Since (μw/μo)(t/hcm)<<1, from Eq. (12) □ūfilm˜Vi/t˜(uw/μo)(V/hcm). Using hcm=Rb/g(θ) can be rewritten, such that:
Finally, the rate of viscous dissipation in the wetting ridge (III) can be approximated as III˜μo(V/hridge)2Rbh2ridge since fluid velocities within the wetting ridge must scale as the velocity of the centre of mass and vanish at the solid surface, giving velocity gradients that scale as □ū˜V/hridge, where hridge is the height of the wetting ridge. Thus,
III˜μ
o
V
2
R
b.
Noting that Fg=ρwg sin α and Fp=ρwΩg sin α* and dividing both sides of Eq. (13) by RbVγwa yields
Where Ca=μwV/γwa, is the capillary number, Bo=Ω2/3ρwg/γwa is the Bond number, and f(θ)=Q1/3/Rb (described before herein). Since (μw/μo)(t/Rb)<<1, and μo/μw>>g(θ) in our experiments, Eq. (14) can be simplified to:
The datasets shown in
Flow Rate of a Contact Liquid on a Liquid-Impregnated Surface
The flow rate of contact liquid on a liquid-impregnated surface depends on the viscosity of the viscosity of the contact liquid, the viscosity of the impregnating liquid, the height of the solid features, the depth of the contact liquid (e.g., the height of the contact liquid above the liquid-impregnated surface). This can be understood by studying the flow of a contact liquid through a pipe or channel that includes a liquid-impregnated surface. Typically, flow through a pipe or channel, having a liquid-impregnated surface on its interior can be described by the following equation:
Q/(Δp/L)˜(R4/μ1)(1+C(h/R)(μ1/μ2) (16)
where Q is the volumetric flow rate, R is pipe radius, h is the height of the texture, μ2 is the viscosity of the impregnating liquid, and μ1 is the viscosity of the contact liquid flowing through the pipe. C is a constant that relates to the obstruction of the flow of the impregnating liquid due to the texture. C=1 in the limit of infinitely sparse textures (no texture) approaches 0 for very tightly spaced textures. Δp/L is the pressure drop per L. Note that C*h*(μ1/μ2) defines a slip length, b. Without being bound to any particular theory, it is believed that (h/R)(μ1/μ2) is greater than 1 for this to have a significant effect and this sets the height of the texture in relation to the viscosity ratio.
Power˜(Δp/L)*Q (here “˜” means “scales as”)
So equation (16) becomes:
Then the ratio of the flow rate of a liquid without the coating to one with the coating, at the same pumping power, is:
Or the reduction in power require to achieve the same flow rate is:
If h<<R, then the flow of the product also drags the material within the film at a flow rate Qf given by:
Q
f
/Q=h/R[2b/R+(b/R)2]/[1/2+2b/R+(b/R)2] (20)
If b/R<<1 then:
Q
f
/Q˜4hb/R2 (valid for h<R and b/R) (21)
Although modeled for pipe flow, the general principals also apply to open systems, for example, product containers, where R is replaced with the characteristic depth of the flowing material. The average velocity of the flow ˜Q/A, where A is the cross-sectional area of the flowing fluid.
For example, mayonnaise, which is a Bingham plastic, has a viscosity that approaches infinity at low shear rates (it is non-Newtonian), and therefore behaves like a solid as long as shear stress within it remains below a critical value. Whereas, for honey, which is Newtonian, the flow is much slower. For both systems, h and R are of the same order of magnitude, and μ2 is the same. However, since
μhoney<<μmayonnaise, then (h/R)(μhoney/μ2)<<(h/R)(μmayonnaise/μ2)
thus mayonnaise flows much more quickly out of the bottle than honey. Therefore, to increase the flow rate of honey, an impregnating liquid can be selected that has a lower viscosity μ2 such that the ratio μhoney/μ2 increases, and thereby the flow rate of the contact liquid over the liquid-impregnated surface increases. In some embodiments, μ1/μ2 can be greater than about 1, about 10, about 103, about 106, about 109.
Liquid-impregnated surfaces have an outer surface of mostly liquid, which significantly inhibits nucleation of vapor or gas dissolved in a liquid. Similarly, liquid-impregnated surfaces can also be used to inhibit boiling by reducing nucleation sites. Similarly, liquid-impregnated surfaces can also be used to inhibit cavitation by preventing the formation of bubbles.
In some embodiments, a vessel, for example a soda can or a beer glass can include a liquid-impregnated surface. The liquid-impregnated surface is formed on a first surface, for example, an interior surface of the vessel by disposing a plurality of solid features on it, for example, using spray coating or any other method described herein. The first surface can have a first roll off angle towards a contact liquid. The plurality of solid features are configured to define interstitial regions between the solid features. An impregnating liquid is disposed in the interstitial regions and on the solid features to form a substantially continuous layer and furthermore, the impregnating liquid adheres to the solid features and the interstitial regions. The interstitial regions are dimensioned and configured to remain impregnated by the impregnating liquid. The impregnating surface can at least partially define a second surface having a second roll off angle less than the first roll off angle. The second surface defined by the liquid-impregnated surface of the vessel is configured so that the vessel has less nucleation sites for the formation of gas and vapor bubbles when compared with a similar vessel that does not include a liquid-impregnated surface thereon. In some embodiments, the impregnating liquid can be immiscible with the liquid disposed in the vessel. The impregnating liquid can be non toxic, for example, formulated from edible materials. In some embodiments, a low energy coating, for example, OTS or any other low energy coating (e.g., hydrophobic coatings such as silanes) can be disposed between the plurality of solid features and the impregnating liquid, for example, to promote adhesion. The liquid disposed in the vessel can be any liquid which has a dissolved gas included in it, for example, a carbonated or a nitrogenated liquid, such as, for example, a beverage, beer, soft drink, or any other liquid with a gas dissolved in it.
In some embodiments, a vessel for heating a liquid and having a liquid-impregnated surface includes an interior surface. The vessel can be any heating vessel, for example, cookware, tank, or any other heating vessel. The vessel can be made from any suitable material including but not limited to metal, plastic, ceramic, or any other material. A plurality of solid features are disposed on a first surface, for example, an interior surface of the vessel, having first roll off angle such that the plurality of solid features define interstitial regions between them. An impregnating liquid, for example, any of the impregnating liquids described herein, is disposed in the interstitial regions and on the solid features, such that the impregnating liquid forms a substantially continuous layer and furthermore, adheres to the solid features and the interstitial regions. The interstitial regions are dimensioned and configured to remain impregnated by the impregnating liquid. The impregnating surface can at least partially define a second surface having a second roll off angle less than the first roll off angle. The second surface of the liquid-impregnated surface can have substantially less nucleation sites for formation of bubbles in a contact liquid that is disposed on the second surface and is heated to release a gas (e.g., air) dissolved in the contact liquid, as compared to the first surface. The impregnating liquid is formulated to be immiscible with a fluid disposed in the internal volume defined by the container, for example, a liquid to be heated by the container. The liquid-impregnated surface of the vessels is configured to have less nucleation sites for the formation of gas and vapor bubbles compared to a similar vessel that does not include the liquid-impregnated surface. For example, liquid water normally boils at 100° C. at atmospheric pressure. Water in a vessel with liquid-impregnates interior surfaces can be superheated above 100° C. due to a lack of nucleation sites to initiate the boiling process.
In some embodiments, active surface of impellers and propellers include a liquid-impregnated surface. As the propeller rotates within the liquid and creates regions of high and low pressure, the liquid-impregnated surface inhibit the formation of cavitation bubbles. For example, the propeller or impeller includes a hub with at least one blade disposed on it. The blade has parts including the leading edge, trailing edge, face, back, and fillet. Each part includes a first surface having a first roll off angle. A liquid-impregnated surface can be disposed on the first surface, for example, by forming solid features on at least one or more parts of the blade such that the solid features define interstitial regions within which an impregnating liquid is disposed. The interstitial regions can be dimensioned and configured to remain impregnated by the impregnating liquid. The impregnating liquid can at least partially define a second surface having a second roll off angle less than the first roll off angle. Furthermore, the second surface can have substantially less cavitation in a contact liquid in contact with the second surface, as compared to the first surface. The roll off angle of the liquid-impregnated surface can be the same or can differ on separate parts of the blade. For example, the roll off angle of liquid-impregnated surface on the leading edge and face can be less than the roll off angle of liquid-impregnated surface on the trailing edge and back. This can, for example, prevent cavitation from occurring on those parts of the blade. In some embodiments, only some parts of the blade of the propeller can be preferentially configured to define the liquid-impregnated surface, for example, to restrict cavitation to only the parts without the liquid-impregnated surface. This can, for example, be used to create turbulence only at certain parts, for example, to aid propulsion.
The following examples show performance of various liquid-impregnated surfaces towards inhibition condensation, performance of various liquid impregnated surfaces towards various contact liquids, and inhibition of nucleation of beverages in contact with the liquid-impregnated surfaces. These examples are for illustrative purposes only and are not intended to limit the scope of this disclosure.
a shows a first liquid-impregnated surface that includes a 100 cSt silicone oil as the impregnating liquid.
This example demonstrates results of a series of experiments that included flowing a number of different external phases on a number of different solid surfaces impregnated with different impregnating liquids. The results of the conducted experiments are shown in Table 3 below. In Table 3 below, θos(a),receding is the receding contact angle of the impregnating liquid (e.g., silicone oil, subscript ‘o’) on the surface (subscript ‘s’) in the presence of air (subscript ‘a’), and where θos(e),receding is the receding contact angle of the impregnating liquid (e.g., silicone oil, subscript ‘o’) on the surface (subscript ‘s’) in the presence of the external phase (subscript ‘e’), θ*c=Cos−1 (1/r) is the critical contact angle on the textured substrate and α* is the roll-off angle.
Slide off angles were measured using 500 μL volumes of the external fluid, except for water, for which 5 μL droplets were used. It was observed that in experiments where θos(e),rec<θc*, the roll-off angles, α*, were low (e.g., less than or equal to 20°), whereas in cases where θrec,os(e)>θc*, the roll-off angles, α*, were high (e.g., greater than or equal to 40°).
The silicon surfaces used in the experimental data shown in Table 3 above were 10 lam square silicon posts (10×10×10 μm) with 10 μm interpillar spacing. The 10 μm square silicon microposts were patterned using photolithographic and etched using deep reactive ion etching (DRIE). The textured substrates were cleaned using piranha solution and were coated with octadecyltrichlorosilane (OTS from Sigma-Aldrich) using a solution deposition method.
The “WPTFE” surfaces shown in Table 3 above were composed of a 7:1 spray-coated mixture of a mixture of Teflon particles and Toko LF Dibloc Wax, sprayed onto a PET substrate. The carnauba wax (CW) surfaces were composed of PPE CW spray-coated onto a PET substrate. The impregnating liquids were propylene di(caprylate/caprate) (“PDC”), Krytox 1506, DOW PMX 200 silicone, oil, 10 cSt (“Silicone oil”) and Christo-lube EXP 101413-1 (“CL”). The external phases used were mayonnaise, toothpaste (e.g., Crest extra whitening), and red water based paint. Wenzel roughness, r, was measured using a Taylor hobson inferometer. Although precise estimates of φ could not be easily obtained, it was observed in the inferometer that φ was much less than 0.25 for all the impregnated surfaces described in the table, and tested, and using 0.25 as an upper bound on φ for our surfaces we determine that cos−1 ((1−φ)/(r−φ))=θc, is no more than 5° greater than the values for θ*c.
A liquid-impregnated surface was prepared similar to the preparation method for the embodiment 200 show in
Referring now to
A few drops of the diet coke were now disposed on the liquid-impregnated surface described herein, as shown in
A commercially available beer glass was configured to define a liquid-impregnated surface, by spray coating. The nucleation characteristics of the liquid-impregnated glass was compared with an untreated glass with a commercially available beer disposed in each of the glass.
While various embodiments of the system, methods and devices have been described above, it should be understood that they have been presented by way of example only, and not limitation. Where methods and steps described above indicate certain events occurring in certain order, those of ordinary skill in the art having the benefit of this disclosure would recognize that the ordering of certain steps may be modified and such modification are in accordance with the variations of the invention. Additionally, certain of the steps may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above. The embodiments have been particularly shown and described, but it will be understood that various changes in form and details may be made.
This application claims priority to U.S. Provisional Patent Application No. 61/794,335, entitled “Methods and Articles for Liquid-Impregnated Surfaces for Inhibition of Vapor and Gas Nucleation,” filed Mar. 15, 2013 the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61794335 | Mar 2013 | US |
