A COMPONENT FOR LIQUID HANDLING WITH SELF-CLEANING PROPERTIES

Abstract

The invention concerns a super hydrophobic surface for handling a liquid and/or able to be contacted by a liquid, said surface comprising at least one hydrophobic liquid contact surface portion, wherein said hydrophobic liquid contact surface portion presents a micro- and nano-meter hierarchical patterned structure, the structure comprising: —homogeneously distributed micrometre-sized pillars (1), and—homogeneously distributed nanometre-sized pillars (2), preferably said pillars (2) having a dimension below 1 micrometer, at the upper surface of the micrometre-sized pillars, and—nanometre-sized protrusions (3) at the upper surface of the nanometre-sized pillars, the protrusions being positioned in a non-periodic, irregular pattern. The invention also relates to the use of such surfaces with micro- and nano-meter hierarchical patterned structure, for example in handling hot liquids, and a corresponding manufacturing process, e.g. using an injection moulding process for producing the component in polymer.

Claims

1. A component configured for handling a liquid and/or being able to be contacted by a liquid, said component comprising at least one liquid contact surface portion, the component being integrally formed with the liquid contact surface portion, wherein said liquid contact surface portion presents a micro- and nano-meter hierarchical patterned structure, said structure comprising: homogeneously distributed micrometre-sized pillars, homogeneously distributed nanometre-sized pillars, said pillars having a dimension below 1 micrometer, at the upper surface of the micrometre-sized pillars, and nanometre-sized protrusions at the upper surface of the nanometre-sized pillars, said protrusions being positioned in a non-periodic, irregular pattern.

2. The component according to claim 1, wherein the micro- and nano-meter hierarchical patterned structure comprises at least one of: homogeneously distributed micrometre-sized pillars presenting a height of at least 3 μm, homogeneously distributed nanometre-sized pillars at the upper surface of the micrometre-sized pillars presenting a height comprised between 500 nm and 1000 nm, or nanometre-sized protrusions at the upper surface of the nanometre-sized pillars presenting a height comprised between 50 and 400 nm.

3. The component according to claim 1, wherein the micro- and nano-meter hierarchical patterned structure comprises at least three different height levels above the surface of the component, each of said homogeneously distributed micrometre-sized pillars, said homogeneously distributed nanometre-sized pillars, and said nanometre-sized protrusions thereby being positioned in substantively separate and non-overlapping height intervals above and across the surface of the component.

4. The component according to claim 1, wherein the nanometre-sized protrusions have a density of at least 105 protrusions/mm2 and the non-periodic, irregular pattern originates from a moulding, an embossing or a casting form, said moulding, embossing or casting form having the corresponding non-periodic, irregular pattern from a semiconductor material with the equivalent nano-grass surface structure in this non-periodic, irregular pattern.

5. The component according to claim 1, wherein the component is made, at least partly, of a polymer, and is preferably produced by injection molding embossing, or roll-to-roll imprinting.

6. The component according to claim 1, wherein the micro- and nano-meter hierarchical patterned structure is imprinted at the surface of the component during an injection molding operation, an embossing, or a roll-to-roll imprinting.

7. Use of a hydrophobic liquid contact surface portion presenting a micro- and nano-meter hierarchical patterned structure in at least one component for handling a liquid having a temperature of at least 35 degrees Celsius, said component being integrally formed with said hydrophobic liquid contact surface portion, said structure comprising: homogeneously distributed micrometre-sized pillars, and homogeneously distributed nanometre-sized pillars at the upper surface of the micrometre-sized pillars, and nanometre-sized protrusions at the upper surface of the nanometre-sized pillars, said protrusions being positioned in a non-periodic, irregular pattern.

8. Use according to claim 7, wherein the component for handling a liquid is applied for: liquid processing, transport, handling or storage, the liquid being water or one or more water-based liquids, including any microfluidic devices, transparent surfaces and components with at least one-transparent surface, medical devices, or food and beverages handling including packaging.

9. A manufacturing process for manufacturing a polymer component, the process comprises: micro and nano-lithographic processing a semiconductor wafer having a three-level micro- and nano-meter hierarchical patterned structure, an upper-most level having a nano-meter structure being produced by a process resulting in a nano-grass surface structure with a non-periodic, irregular pattern, transferring said hierarchical patterned structure into an injection molding tool, embossing tool, or roll-to-roll imprinting tool, forming a polymer component for liquid handling, said polymer component having a liquid contact surface portion presenting a micro- and nano-meter hierarchical patterned structure, the polymer component being integrally formed with the liquid contact surface portion, said structure comprising: homogeneously distributed micrometre-sized pillars, homogeneously distributed nanometre-sized pillars having a dimension below 1 micrometer, at the upper surface of the micrometre-sized pillars, and nanometre-sized protrusions at the upper surface of the nanometre-sized pillars, said protrusions being positioned in a non-periodic, irregular pattern.

10. The manufacturing process according to claim 9, wherein the transferring of said hierarchical patterned structure into an injection molding tool, embossing tool, or roll-to-roll imprinting tool is performed with an intermediate metal insert, attached to an inner surface of the tool prior to manufacturing.

11. The manufacturing process according to claim 9, wherein the injection molding tool, the embossing tool, or the roll-to-roll imprinting tool is made of steel, or steel alloys.

12. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The characteristics and advantages of the invention will be better understood in relation to the following figures wherein:

[0094] FIGS. 1a-1c illustrates a first micro- and nano-meter hierarchical patterned structure used as a hydrophobic liquid contact surface portion according to the invention,

[0095] FIG. 2 illustrates a second micro- and nano-meter hierarchical patterned structure used as a hydrophobic liquid contact surface portion according to the invention,

[0096] FIG. 3 illustrates a third micro- and nano-meter hierarchical patterned structure used as a hydrophobic liquid contact surface portion according to the invention,

[0097] FIG. 4 illustrates a micro- and nano-meter hierarchical patterned structure used as a hydrophobic liquid contact surface portion according to the state of the art,

[0098] FIG. 5 is a sketch of the self-cleaning effect of the super hydrophobic surface, and

[0099] FIG. 6 shows the drag reduction of the super hydrophobic surface

DETAILED DESCRIPTION OF THE DRAWINGS

[0100] FIGS. 1a-1c illustrate a first micro- and nano-meter hierarchical patterned structure used as a hydrophobic liquid contact surface portion in the components of beverage dispensing apparatuses according to the invention. In order to test the property of the structure, said structure was manufactured in polypropylene foil. Ni stamps presenting the reverse design were used for embossing the structure in the plastic foil. The process for manufacturing the Ni stamps and embossing polypropylene plastic is known and described in WO 2013/131525, which is incorporated by reference in its entirety, for two levels with a microstructure and, on top thereof, a nanostructure from nano-grass.

[0101] FIGS. 1a-1c show SEM (Scanning Electron Microscope) images of the hierarchical structure. In these images, the view are tilted meaning that, depending on the angle taken for the view, the pillars and protrusions can appear slightly larger than in the reality or of smaller height than in the reality.

[0102] FIG. 1a is a tilted SEM image showing the micrometre-sized square pillars 1 homogeneously distributed along a matrix of lines and columns. The pillars are identical and present a height H.sub.m of 40 μm and a width W.sub.m of 40 μm. The pillars are separated one from the others by a pitch D.sub.m (distance centre to centre) of 115 μm.

[0103] FIG. 1b is a magnified tilted SEM view of one pillar of FIG. 1a: it illustrates nanometre-sized pillars 2 positioned at the upper surface of the micrometre-sized pillars 1. These nanometre-sized pillars are homogeneously distributed along a matrix of lines and columns. Next lines are offset one to the other. The pillars are identical.

[0104] FIG. 1c is a magnified photo of several nano-sized pillars of FIG. 1b: the nano-sized pillars 2 present a round section with a height h.sub.n of 750 nm. The pillars are slightly conical, the round shape at the base stretching at the top of the pillars. The width w.sub.n at the base is of 500 nm. The pillars are separated one from the others at the base by a maximal pitch d.sub.n of 750 nm.

[0105] The photo of FIG. 1c shows the upper surface of the nano-sized pillars. The upper surface comprises nanometre-sized protrusions 3: these nanometre-sized protrusions present irregular heights, yet these heights remain comprised between 100 and 400 nm. The density of these nanometre-sized protrusions at the upper surface of the pillars is of about 10.sup.7 protrusions/mm.sup.2. However, density can be at least 10.sup.5 protrusions/mm.sup.2, at least 10.sup.6 protrusions/mm.sup.2, at least 10.sup.7 protrusions/mm.sup.2, at least 10.sup.8 protrusions/mm.sup.2. These protrusions are positioned in a non-periodic, irregular pattern.

[0106] FIG. 2 is a photo showing a second micro- and nano-meter hierarchical patterned structure used as a hydrophobic liquid contact surface portion in the components of beverage dispensers according to the invention.

[0107] FIG. 2 is a magnified tilted SEM view of cylindrical micrometre-sized pillars 1 with cylindrical nano-sized pillars 2 rising from their top surface. These micrometre-sized pillars 1 are homogeneously distributed along a matrix of lines and columns. Next lines are offset one to the other. The pillars are identical. The nanometre-sized protrusions at the top of the nano-sized pillars 2 are not visible in the photo at this magnification, yet they are present. These nanometre-sized protrusions present the same features as those present in the structure of FIG. 1c.

[0108] The micrometre-sized cylindrical pillars 1 are homogeneously distributed along a matrix of lines and columns. The pillars 1 are identical and present a height H.sub.m of 20 μm and a width W.sub.m of 5 μm. The pillars are separated one from the others by a pitch D.sub.m (distance centre to centre) of 15 μm.

[0109] The nanometre-sized cylindrical pillars 2 are homogeneously distributed along a matrix of lines and columns. The pillars 2 are identical and present a height h.sub.n of 750 nm and a width w.sub.m of 500 nm. The pillars are separated one from the others by a pitch d.sub.n (distance centre to centre) of 750 nm.

[0110] FIG. 3 is a photo showing a third micro- and nano-meter hierarchical patterned structure used as a hydrophobic liquid contact surface portion in the components of beverage dispensers according to the invention.

[0111] FIG. 3 is a magnified tilted SEM view of cylindrical micrometre-sized pillars 1 with slightly visible cylindrical nano-sized pillars 2 rising from their top surface. These micrometre-sized pillars 1 are homogeneously distributed along a matrix of lines and columns. Next lines are offset one to the other. The pillars are identical. The nanometre-sized protrusions at the top of the nano-sized pillars 2 are not visible in the photo at this magnification, yet they are present. These nanometre-sized protrusions present the same features as those present in the structure of FIG. 1c.

[0112] The micrometre-sized cylindrical pillars 1 are homogeneously distributed along a matrix of lines and columns. The pillars 1 are identical and have been manufactured from an Ni stamp presenting a reverse design to produce pillars 1 presenting a height H.sub.m of 30 μm and a width W.sub.m of 5 μm. Yet, during the step of removing the propylene foil from the Ni stamp, pillars 1 were stretched resulting in pillars with a slightly higher final height. Pillars are separated one from the others by a pitch D.sub.m (distance centre to centre) of 15 μm.

[0113] The nanometre-sized cylindrical pillars 2 are homogeneously distributed along a matrix of lines and columns. The pillars 2 are identical and, similarly to pillars 1 have been stretched during the manufacturing step; the Ni stamp was configured to produce pillars 2 of a height h.sub.n of 750 nm and a width w.sub.m of 500 nm. The pillars are separated one from the others by a pitch do (distance centre to centre) of 750 nm.

[0114] FIG. 4 is a photo showing a micro- and nano-meter hierarchical patterned structure used as a hydrophobic liquid contact surface portion according to the state of the art. FIG. 4 is a tilted SEM image showing the micrometre-sized round pillars 1 homogeneously distributed along a matrix of lines and columns in an hexagonal array. All the pillars are identical and present a height H.sub.m of 16 μm and a diameter W.sub.m of 18 μm. The pillars are separated one from the others by a pitch D.sub.m of 50 μm.

[0115] Nanometre-sized protrusions 3 at the top of the micro-sized pillars 1 are not visible in the illustrated figure at this magnification, yet they are present. Nanometre-sized protrusions presenting a height comprised between 200 and 400 nm at a density of 10.sup.7 protrusions/mm.sup.2 were measured. These protrusions are positioned in a non-periodic, irregular pattern.

[0116] FIG. 5 is a sketch of the self-cleaning effect of the super hydrophobic surface. On classical surfaces the droplets are more or less immobilized on the surface. On the super hydrophobic surface, the droplets rolls along the surface. Dirt particles are captured by the droplets and transported to the edges of the surface, where they escape from the surface and leave the surface clean.

[0117] FIG. 6 shows the drag reduction of the super hydrophobic surface. The figure shows the velocity profile of a liquid flowing past a surface. On a classical surface the velocity of the liquid close to the surface will be zero or close to zero. On the super hydrophobic surface, the contact area between the liquid and the surface is very small. This causes the liquid to slip on the surface with a non-vanishing velocity of the liquid close to the surface. This results in reduced drag on objects moving through the liquid and reduce flow resistance when liquid is moving past the surface.

EXAMPLES

[0118] The hydrophobic properties of the foils of plastic describes in FIGS. 1a-1c, 2, 3 and 4 were tested with hot beverages.

[0119] The procedure of the test consisted in: [0120] cleaning the foil with ethanol and then deionized water, [0121] positioning the foil according to an inclined angle of 5° or 45° with horizontal, that is reproducing a very small inclination inside a component of a beverage dispenser, [0122] depositing manually a drop (volume of 50 uL) of hot beverage on the foil. The hot beverage presented a temperature of 70° C. and consisted in water, coffee, skimmed milk, fat milk or chocolate, and [0123] observing the movement of the drop on the surface of the foil.

TABLE-US-00001 Type of patterned structure Result of the test According to the invention micro + nano + drops of hot water rolled nano-meter immediately hierarchical from the foil inclined at 5°, patterned drops of hot skimmed milk and structure of fat milk rolled immediately FIGS. 1a-1c from the foil if the foil was inclined by 45°. drops of coffee and chocolate did not roll off even inclined at 45°. micro + nano + drops of hot water rolled nano-meter immediately from hierarchical the foil inclined at 5°, patterned drops of hot skimmed milk, structures of fat milk, coffee and chocolate FIGS. 2 and 3 rolled immediately from the foil if the foil was inclined by 45°. According to the prior art micro + drops of hot water rolled nano-meter immediately from the hierarchical foil inclined at 5°, patterned drops of hot beverages did structure not roll off from the of FIG. 4 foil inclined by 45°.

[0124] The results of the present invention are clearly better than the prior art solutions, such as WO 2013/131525. This structure increases the hydrophobic properties of the surface, but does not in general provide a self-cleaning surface for hot liquids. The three level structures of the present invention results in a much higher contact angle, lower roll-off angles and a surface which is more stable towards immersion in water and impinging droplets.

[0125] Uses of the Super Hydrophobic Surface.

[0126] In general, super hydrophobic surfaces possess characteristics of self-cleaning, drag reduction, anti-condensation and anti-bacterial. The value of these characteristics is important in a range of different application areas:

[0127] 1. Medical: medical devices including glasses, prescription lenses, watches, hearing aids, ostomy pouching systems, endoscopes, patches, bandages, and a prosthesis

[0128] 2. Water transport including surfaces of boats and ships. In this area drag reduction is directly coupled to fuel reduction of increased speed. The drag reduction comes both from the low drag coefficient of the surface itself and the self cleaning effect that continues to keep the surface clean and smooth.

[0129] 3. Water distribution systems including tubes, pipes, and microfluidic systems. In these systems, the reduced drag coefficient increases the flow capacity of the systems and the self cleaning effect ensures the system to stay clean without deposits. Also the antibacterial effect prevents the systems from being contaminated by e.g. harmful bacteria.

[0130] 4. Water sports including reduced friction in equipment and clothing. In this area the value of the surfaces is mainly to reduce drag in order to improve performance. Surf boards, swim suits etc. with lower friction will inevitably result in improved performance.

[0131] 5. Water containers including tanks, bottles, cans, barrels etc. In this area mainly the self cleaning and antibacterial effects are important to keep the containers clean and un contaminated by bacteria.

[0132] 6. Industrial equipment including heaters, boilers, heat exchangers, pumps, compressors: For these uses it is important to reduce deposits from the water that could limit performance. Also friction reduction is important for capacity and energy use in e.g. pumps and compressors. In some instances prevention of condensation, by the anti-condensation characteristic will improve the efficiency of heat exchangers and compressors because they can run closer to or even beyond the condensation limit.

[0133] 7. Appliances including washing machines, dishwashers, fridges etc.: Self-cleaning of surfaces will help keeping the machines clean and tidy both on the visual surfaces and inside. Clean machines are known to have a longer lifetime and use less energy.

[0134] 8. Transparent surfaces including mirrors, displays, dashboards, windows (also automotive): All these uses rely on a clean and transparent surface. Anti condensation reduces formation moisture to reduce transparency, the reduced friction will allow droplets to roll off the surface easily and the self-cleaning effect will ensure that dirt in the surface will be removed with the droplets.

[0135] 9. Food equipment including industrial equipment: self-cleaning surfaces are important to limit the energy use associated with cleaning of the machines and will prevent contamination by harmful bacteria. Trays, baskets, crates for storage, transportation and serving of food can become easier to clean.

[0136] 10. Beverage dispensers incl. storage of liquid, particular the internal wall of a storage.

[0137] 11. Packaging: In some instances it is desirable to apply packaging that reduces the risk for access of humidity, moisture and water. A packaging material with an anti-condensation surface will help prevent this.

[0138] 12. Toys including baby toys and water toys: These toys often has a tendency to form a biofilm that may contain harmful bacteria. A self-cleaning surface will help to prevent this.

[0139] 13. Outdoor lighting (including automotive): these uses rely on a clean and transparent surface for light to escape undisturbed from the device. Anti condensation reduces formation moisture to reduce transparency, the reduced friction will allow droplets to roll off the surface easily and the self-cleaning effect will ensure that dirt in the surface will be removed with the droplets.

[0140] 14. Lab-on-chip systems or microfluidic devices for biomedical or liquid analysis: superhydrophobic surface properties can help to control the flow of liquid.

[0141] 15. Waste reduction and recyclability: Medical containers can be emptied more easily there by ensuring that the patient receives all the prescribed medication. Food containers can be more easily emptied which reduces food waste and makes the container more suitable for recycling since it is clean.

[0142] Although the invention has been described with reference to the above illustrated embodiments, it will be appreciated that the invention as claimed is not limited in any way by these illustrated embodiments.

[0143] Variations and modifications may be made without departing from the scope of the invention as defined in the claims. Furthermore, where known equivalents exist to specific features, such equivalents are incorporated as if specifically referred in this specification. As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”.

LIST OF REFERENCES IN THE DRAWINGS

[0144] micro-sized pillar 1 [0145] nano-sized pillar 2 [0146] nanometre-sized protrusion 3