WO2018108645A2

WO2018108645A2 - Anti-fouling system with upconversion for generating uv radiation

Info

Publication number: WO2018108645A2
Application number: PCT/EP2017/081603
Authority: WO
Inventors: Bart Andre Salters; Eduard Matheus Johannes Niessen; Elvira Johanna Maria Paulussen; Roelant Boudewijn HIETBRINK
Original assignee: Koninklijke Philips N.V.
Priority date: 2016-12-16
Filing date: 2017-12-06
Publication date: 2018-06-21
Also published as: WO2018108645A3; TW201834700A

Abstract

The invention provides an anti-fouling device (10) comprising a window (100), a radiation concentrator optical element (200) and an upconversion element (300), wherein: said window (100) comprises an anti-fouling surface (110) for transmission of at least part of anti-fouling radiation (11) to the external of the device (10), wherein the window (100) is further transmissive for at least part of one or more of visible and IR radiation (1) from external of the device (10); the radiation concentrator optical element (200) is configured for concentrating at least part of said one or more of visible and IR radiation (1); and the upconversion element (300) is configured within the device (10), and is configured for upconverting at least part of said one or more of visible and IR radiation (1) into said anti- fouling radiation (11), wherein said anti-fouling radiation (11) comprises UV radiation.

Description

Anti-fouling system with upconversion for generating UV radiation

FIELD OF THE INVENTION

The invention relates to an anti-fouling device, for instance for providing a surface on which bio fouling cannot easily grow or accumulate. The invention further relates to an object comprising such device, as well as to a method for applying such device to an object.

BACKGROUND OF THE INVENTION

Antimicrobial upconversion systems are known in the art. US2010/0297206, for instance, describes antimicrobial articles, systems, and methods used for killing, inactivating, and/or inhibiting microorganisms. The antimicrobial articles and systems utilize up-conversion luminescence wherein a phosphor or luminescent material is capable of absorbing visible, infrared light, or longer wavelength radiation and emitting antimicrobial ultraviolet radiation via upconversion thus inhibiting the growth of, inhibiting the

reproduction of or killing or otherwise inactivating microorganisms such as, but not limited to, spores, bacteria, fungi, mildew, mold, and algae. Embodiments of the antimicrobial article or system may comprise such a luminescent material and thus will have antimicrobial activity when exposed to natural or artificial light.

SUMMARY OF THE INVENTION

Bio fouling or biological fouling is the accumulation of microorganisms, plants, algae, etc. on wetted surfaces, such as on boats, underwater inspection equipment in offshores, water in-and outlets, propellers on ships and generators, etc.. The consequences of bio fouling on surfaces of these equipment's are of major impact (financially, operationally and safety). Oceanographic companies are already investing large amounts of money in anti- fouling solutions for offshore technology.

Hence, it is an aspect of the invention to provide an alternative device that can be used for preventing and/or reducing bio fouling, which preferably further at least partly obviates one or more of above-described drawbacks. Anti-fouling systems can be equipped with UV LEDs or UV sources.

However, these sources are expensive. Hence, it might be an option to make use of solar energy for producing UV radiation by means of upconversion (UC) in phosphor materials. However, most phosphors used for upconversion appear to have poor conversion at low powers, which will be the case when solar energy is used. Further, it is not straightforward to use upconversion phosphors in such a way that a surface can easily be protected from bio fouling.

Therefore it is herein proposed to use upconverters in combination with an optical system to increase irradiance levels on the conversion phosphors, and configure the device such that bio fouling can be reduced and/or prevented.

Hence, in a first aspect the invention provides an anti-fouling device

("device") comprising a window, a radiation concentrator optical element and an

upconversion element, wherein:

said window comprises an anti-fouling surface for transmission of at least part of anti-fouling radiation (generated by the device) to the external of the device, wherein the window is further transmissive for at least part of one or more of visible and IR radiation from external of the device (such as solar radiation);

the radiation concentrator optical element ("optical element" or "concentrator") is configured for concentrating at least part of said one or more of visible and IR radiation; and

the upconversion element (may also be indicated as "upconverter" or

"upconverter element" or "upconversion element") is configured within the device, and is configured for upconverting at least part of said one or more of visible and IR radiation into said anti-fouling radiation, wherein said anti-fouling radiation comprises UV radiation.

In this way, the device can transform light from external of the device, such as

UV and/or visible and/or IR from solar light, into anti-fouling radiation. Especially, the anti- fouling radiation comprises UV radiation. This can prevent bio fouling adhering to the window, i.e. the surface of the window, herein also indicated as anti-fouling surface, and or reduce growth of such biological material on the window, or even reduce already available bio fouling on (the anti-fouling surface of) the window.

The device allows concentration of the external radiation such that the upconversion process may be much more efficient. Upconversion processes are especially dependent upon the excitation intensity or excitation density. By concentrating the light, the (UV) radiation provided via upconversion can substantially be enhanced. For instance, the intensity of the upconversion light can be dependent upon the square of the intensity of the incoming light. Therefore, by concentrating the light with the optical element a much higher excitation density can be provided to the upconversion element. Further, the design of the device may in embodiments allow the use of the device as a skin or hull to another device, element, apparatus, etc., which are herein in general indicated as "object". In this way, an external surface is provided to the object that may not substantially suffer from biofouling. This may be of especially interest for outdoor applications, like outdoor applications subject to rain or (surface) water.

Therefore, in yet a further aspect the invention provides an object comprising an object surface and the anti-fouling device as defined herein, wherein the anti-fouling surface of said anti-fouling device is configured as at least part of said object surface. Hence, on part of the surface of the object, the device may be arranged, by which part of the original object surface is now replaced by the device, thereby providing the window of the device as (substitute) object surface of the object. Hence, in specific embodiments the object is selected from the group consisting of an immobile marine object, a motorized marine object, an infrastructural element, a windmill, etc..

The anti-fouling surface provided by the device may be provided indoor, but especially outdoor. Further, the anti-fouling surface for such object may be provided above the water level or even below the water level, as the device may also harvest solar light under the water level, especially until depths of about 10 m under the water level. Of course, the efficiency may depend upon the depth, the pollution of the water, the turbidity of the water, but this will be known to a person skilled in the art.

Hence, in some embodiments the object during use may be at least partly submerged in water. As indicated herein, the object may especially be selected from the group consisting of a vessel and an infrastructural object. Herein, the phrase "object that during use is at least partly submerged in water" especially refers to objects such as vessels and infrastructural objects that have aquatic applications. Hence, during use such object will be in general in contact with the water, like a vessel in the sea, a lake, a canal, a river, or another waterway, etc.. The term "vessel" may e.g. refer to e.g. a boat or a ship, etc., such as a sail boat, a tanker, a cruise ship, a yacht, a ferry, a submarine, etc. etc.. The term

"infrastructural object" may especially refer to aquatic applications that are in general arranged substantially stationary, such as a dam, a sluice, a pontoon, an oilrig, etc. etc..

Especially, the object is an object configured for marine applications, i.e. application in or near to a sea or an ocean. Such objects are during their use at least temporarily, or substantially always, at least partly in contact with the water. The object may be at least partly below the water (line) during use, or may substantially be all of its time below the water (line), such as for submarine applications. The invention may e.g. be applied for marine anti-fouling, keeping wetted surfaces clean, for off-shore applications, for (sub) sea applications, for drilling platforms, etc.. Due to this contact with the water or with (outdoor) air and rain, biofouling may occur, with the above indicated disadvantages. Biofouling will occur at the surface of an external surface ("surface") of such object. The surface of an (element of the) object to be protected may comprise steel, but may optionally also comprise another material, such as e.g. selected from the group consisting of wood, polyester, composite, aluminium, rubber, hypalon, PVC, glass fiber, etc. Hence, instead of a steel hull, the hull may also be a PVC hull or a polyester hull, etc. Instead of steel, also another iron material, such as an (other) iron alloys may be used.

The term "external surface" especially refers to the surface that may be in physical contact with water or with (outdoor) air and rain. Instead of the term "external surface" also the term "fouling surface" may be applied. Further, in such embodiments the term "water line" may also refer to e.g. filling level. Herein, also the term "anti-fouling surface" is applied, to indicate a surface that receives the anti-fouling radiation, and is thus less subject to biofouling or can even remove biofouling due to the anti-fouling radiation.

Herein, the term "fouling" or "biofouling" or "biological fouling" are interchangebly used. Above, some examples of fouling are provided. Biofouling may occur on any surface in water, or close to water and being temporarily exposed to water, (outdoor) air and/or rain. On such surface biofouling may occur when the element is in, or near water, such as (just) above the water line (like e.g. due to splashing water, such as for instance due to a bow wave) , or when in contact with (outdoor) air and rain. The surface or area on which fouling may be generated is herein also indicated as fouling surface.

As indicated above, the invention provides an anti-fouling device ("device") comprising a window, a radiation concentrator optical element and an upconversion element. This device is especially configured to provide anti-fouling radiation when the device, more especially its window, is irradiated with radiation, such as visible and/or IR radiation. Hence, the device when receiving solar light at the anti-fouling surface may concentrate the solar light and upconvert (within the device) into anti-fouling radiation, which again is offered at the anti-fouling surface where it may escape from the window or, when biofouling is available, may be absorbed by the biofouling leading to a destruction of the biofouling, and thereby removal. The window comprises an anti-fouling surface for transmission of at least part of anti-fouling radiation (generated by the device) to the external of the device, wherein the window is further transmissive for at least part of one or more of visible and IR radiation from external of the device (such as solar radiation). Hence, the window is chosen such that visible and/or IR radiation may enter the device via the window and further chosen such that at least UV radiation may escape from the device via the window.

Hence, the window especially comprises a radiation transmissive material, such as glass, quartz, (fused) silica, silicone, etc.. The window is not necessarily transmissive for all wavelengths and is also not necessarily entirely transmissive for all radiation. Hence, the window is transmissive for at least part of the visible and/or IR radiation and is at least transmissive for at least part of the UV radiation generated by the upconverter element.

Especially, the window is adapted to transmit at least 10%, such as at least 20%>, like at least 35%), such as especially at least 50%>, such as at least 75%, like at least 90%> of the anti- fouling radiation. Further, 10%, the window is adapted to transmit at least 10%, such as at least 20%>, like at least 35%, such as especially at least 50%>, such as at least 75%, like at least 90% of at least part of the visible and/or IR radiation. The transmission or radiation permeability can be determined by providing radiation at a specific wavelength with a first intensity to the material and relating the intensity of the radiation at that wavelength measured after transmission through the material, to the first intensity of the radiation provided at that specific wavelength to the material (see also E-208 and E-406 of the CRC Handbook of Chemistry and Physics, 69th edition, 1088-1989).

In specific embodiments, a material may be considered transmissive when the transmission of the radiation at a wavelength or in a wavelength range, especially at a wavelength or in a wavelength range of radiation generated by a source of radiation (here especially the radiation provided by the upconversion element), through a 1 mm thick layer of the material, especially even through a 5 mm thick layer of the material, under

perpendicular irradiation with said radiation is at least about 80%, such as at least about 85%, such as even at least about 90%>.

The device is especially a closed device, especially in the sense that it is essentially impermeable to water in a closed state or in a state that the device can be used for providing the anti-fouling radiation when being irradiated with e.g. solar light. Hence, the window may essentially be the only part where radiation may enter the device and where radiation may escape from the device. The term "window" may also refer to a plurality of windows, such as a 2D array of windows (comprised by the same device). The window is thus especially impermeable for water. Further, the device (and thus also the window) may especially be impermeable to air when the device is in a closed state.

Further, the device comprises a radiation concentrator optical element. As indicated above, such optical element is especially configured for concentrating at least part of said one or more of visible and IR radiation. Hence, such optical element may be configured to concentrate (effectively) one or more wavelengths selected from the visible range or infrared range. The concentrator may have a focal point, or a focal plane (i.e. a plurality of focal points) which may coincide with the upconversion element, though this is not necessarily the case. Any concentration may already improve the output of the converter element. Hence, especially the optical element is configured such that concentrated light (i.e. light with a larger power per cross-sectional area than the light provided from an external source, such as the sun, at the anti-fouling surface) is provided at the upconversion element.

Further, the device comprises the upconversion element, which is especially configured within the device, and is configured for upconverting at least part of said one or more of visible and IR radiation into said anti-fouling radiation, wherein said anti-fouling radiation comprises UV radiation. Hence, the optical element and the upconversion element are radiationally coupled. The term "radiationally coupled" especially means that the optical element and the upconverter element are associated with each other so that at least part of the radiation concentrated by the optical element is received by the upconverter element (and at least partly converted into anti-fouling radiation. Further, the anti-fouling radiation also leaves the device via the optical element. Hence, the beam path is from external via the anti- fouling surface through the window, via the optical element to the upconverter element, with anti-fouling radiation escaping from the upconverter element, via the optical element through the window, and escaping from the device at the anti-fouling surface. Hence, the optical element may further be optimized for an (efficient) outcoupling of the anti-fouling radiation from the device. As an even distribution of the anti-fouling light over the anti-fouling surface may be desirable, the optical element may thus be configured to provide an (essentially parallel) beam escaping from the optical element (at a side opposite of the side where the upconverter element is configured). This already shows that an optimization of the optical element may be a balance between incoming and escaping radiation. Further, also the window may further be optimized for an (efficient) transmission of the anti-fouling radiation from the device.

Hence, the anti-fouling radiation is especially generated by the upconversion element. The up-conversion element is especially configured for upconverting at least part of said one or more of visible and IR radiation concentrated by the optical element into said anti-fouling radiation.

Even though UV and IR radiation is described herein, the term "light" may also refer to such radiation, and of course visible light.

Below, some further more specific embodiments are described.

In embodiments, the radiation concentrator optical element has one or more focal points for said one or more of visible and IR radiation, wherein the device is configured with said one or more focal points coinciding with said upconversion element. The term "one or more focal points" may e.g. refer to a focal point or a focal area. In general, the

upconversion element and optical element are such, that the one or more focal points may be at the upconverter element, or close to the upconverter element, such as within about 2 cm, like within about 1 cm. Further, these one or more focal points may be chosen for visible radiation of infrared radiation. Especially, these one or more focal points may be chosen close to the upconverter element ( for radiation having a wavelength selected from the range of 200-800 nm, especially at least 400-600 nm).

Especially, the upconverter element (see further also below) is configured to upconvert visible or IR radiation into UV radiation, especially UV radiation in the range of 100-300 nm. Ultraviolet (UV) is that part of electromagnetic light bounded by the lower wavelength extreme of the visible spectrum and the X-ray radiation band. The spectral range of UV light is, by definition between about 100 and 400 nm (1 nm=10^"9 m) and is invisible to human eyes. Using the CIE classification the UV spectrum is subdivided into three bands: UVA (long-wave) from 315 to 400 nm; UVB (medium- wave) from 280 to 315 nm; and UVC (short-wave) from 100 to 280 nm. In reality many photobiologists often speak of skin effects resulting from UV exposure as the weighted effect of wavelength above and below 320 nm, hence offering an alternative definition. The terms "visible", "visible light" or "visible emission" refer to light having a wavelength in the range of about 400-780 nm.

A strong germicidal effect is provided by the light in the short-wave UVC band. In addition, erythema (reddening of the skin) and conjunctivitis (inflammation of the mucous membranes of the eye) can also be caused by this form of light. Because of this, when germicidal UV-light lamps are used, it is important to design systems to exclude UVC leakage and so avoid these effects. In case of immersed light sources, absorption of UV light by water may be strong enough that UVC leaking is no problem for humans above the liquid surface. Hence, in an embodiment the UV radiation (anti-fouling light) comprises UVC light. In yet another embodiment, the UV radation comprises radiation selected from a wavelength range of 100-300 nm, especially 200-300 nm, such as 230-300 nm. Hence, the UV radation may especially be selected from UVC and other UV radiation up to a wavelength of about 300 nm. Good results are obtained with wavelengths within the range of 100-300 nm, such as 200-300 nm, or even more especially in the range of 230-300 nm.

Hence, in embodiments the optical element may be configured to provide concentrated radiation that can be upconverted by the upconversion element and configured to provide (essentially parallel) rays of upconverted radiation to the anti-fouling surface. The rays are not necessarily provided parallel.

The term optical element may also refer to a plurality of optical elements which may be configured to provide concentrated radiation at the upconverter element. In specific embodiments, the term optical element may also refer to a plurality of different optical elements which may be configured to provide concentrated radiation at the upconverter element.

The upconverter element may comprise a lens. The upconverter element may also comprise a compound parabolic concentrator (CPC). However, compound parabolic concentrator like concentrators may also be used, e.g. CPC with one or more planar section may also be applied, as will be clear to a person skilled in the art. Hence, optics similar in shape to CPCs may also be applied.

Hence, in embodiments the radiation concentrator optical element comprises a lens. Such lens may be configured downstream from the window (when seen from external). However, the lens may also be partially comprised by the window. Therefore, in

embodiments the lens is comprised by said window. For instance, this may allow (the use of) micro lens arrays. Further, this may also allow a device with some flexibility (when the window is flexible).

The terms "upstream" and "downstream" relate to an arrangement of items or features relative to the propagation of the light from a light generating means (e.g. the sun), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is "upstream", and a third position within the beam of light further away from the light generating means is "downstream". Note that in fact in this invention there may be two light generating means: the external source and the upconverter element. For solar light, the window is configured upstream of the upconverter element; however, for anti-fouling light, the window is configured downstream of the upconverter. In specific embodiments the device comprises a plurality of lenses and a plurality of upconversion elements, wherein each lens is configured to provide concentrated radiation to a respective upconversion element. As indicated above, the plurality of lenses may be at least partially comprised by the window (i.e. each lens may partially be comprised by the window). Such configuration allows a 2D array of the lenses and (thus also) a 2D array of the upconverter elements. In specific embodiments, the window may (thus) comprise micro lens optics configured for concentrating at least part of said one or more of visible and IR radiation, with in specific variants the window comprises a flexible material. A flexible material may e.g. be silicone. Such configuration may allow a plate like device having flexibility, for a conformal layer to an object. The term "flexible" especially refers to bendable.

In yet other embodiments, which may be combined with the former embodiment(s) of the lens(es), the radiation concentrator optical element comprises a compound parabolic concentrator. Such CPC may be configured downstream from the window (when seen from external), even at some (non-zero) distance from the window. However, in other embodiments the compound parabolic concentrator has a concentrator exit, wherein said concentrator exit is comprised by said window. This may allow a CPC array with the window as common element. Further, this might also allow a device with some flexibility (when the window is flexible).

In specific embodiments, the device comprises a plurality of compound parabolic concentrators and a plurality of upconversion elements, wherein each compound parabolic concentrator is configured to provide concentrated radiation to a respective upconversion element. As indicated above, the plurality of CPCs may be at least partially comprised by the window, more especially, the concentrator exits may be at least partially comprised by the window (i.e. each CPC exit may partially be comprised by the window). Such configuration allows a 2D array of the CPCs and (thus also) a 2D array of the upconverter elements. In specific embodiments, the window may comprise a flexible material. A flexible material may e.g. be silicone. Such configuration may allow a plate like device having flexibility, for a conformal layer to an object. The term "flexible" especially refers to bendable.

The phrase "at least partly comprised by the window" may refer to embodiments wherein the indicated element, such as the lens being at least partly embedded in the window or the concentrator exit being embedded in the window, but also to

embodiments wherein the indicated element is attached to the window, such that e.g. a lens face and window face coincide, or such that an concentrator exit face (essentially) coincides with a window face.

For instance, an anti-fouling surface of the window may be shaped to provide one or more lenses, e.g. to provide a lens array, such as a micro lens array. Alternatively or additionally, a device surface of the window may be shaped to provide one or more lenses, e.g. to provide a lens array, such as a micro lens array.

For instance, a concentrator exit may be in physical contact with the device surface of the window, such that essentially the concentrator exit and the device surface coincide.

The window of the device is thus especially a two-way window, for transmission of (visible and/or IR) radiation from external of the device into the device, for conversion by the upconversion element into anti-fouling radiation, wherein at least part of the anti-fouling radiation again is transmitted through the same window. In this way, biofouling at the side of the anti-fouling surface of the window may receive UV radation. Hence, the window is especially configured to transmit at least part of the radiation generated by the upconversion element.

The upconverter element is especially configured within the CPC, such as at or close to the one or more focal points.

Hence, the compound parabolic concentrator comprises a concentrator cavity defined by one or more reflective surfaces and a concentrator optical axis (O), wherein the device further comprises a cavity element comprising said upconversion element, wherein the cavity element is configured at least partly within said concentrator cavity and configured to occupy a part of said concentrator cavity, and wherein in specific embodiments said cavity element is configured parallel to said optical axis (O). Such embodiments allow an easy arrangement of the upconverter element in the CPC. In specific embodiments, the cavity element is configured in contact with one or more of said one or more reflective surfaces. The cavity element may especially fit to the CPC cavity. Hence, in embodiments the cavity element may be have clearance fit, or a transition fit, or an interference fit to the cavity, especially a transition fit or interference fit, such as an interference fit. The cavity element may essentially consist of the upconverter element, but may in embodiments also refer to e.g. a support coated with the upconverter element, or a frame enclosing the upconverter element. Parts of the cavity element that may not be in contact with the reflective surfaces and which are not upconverter element may be reflective or transmissive. As indicated above, the cavity element is configured to occupy a part of said concentrator cavity. In order not to have detrimental impact on the light output, the volume % of the cavity occupied by the cavity element may be less than about 15%, such as less than about 10%, such as in the range of 1-15%.

The term reflective especially refers to reflectivity, especially specular reflective to one or more of UV, visible and IR, especially at least UV and visible, even more especially at least to wavelengths in the range of 200-800 nm, especially at least 400-600 nm. Especially, the term reflective refers to reflectivity (especially specular reflective) to wavelengths in the range of 200-800 nm.

The device may also comprise a plurality of such cavity elements. This may allow e.g. arranging in a stable way the upconversion element in the CPC cavity. For instance, two cavity elements may be configured perpendicular to each other and may be associated to each other, thereby providing a cross-shaped cavity element. Therefore, in specific embodiments the device comprises a plurality of cavity elements configured at least partly within said concentrator cavity and configured to occupy a part of said concentrator cavity, and wherein said cavity elements have mutual angles (a) larger than 0° and equal to or smaller than 120°, especially equal to or smaller than 90°. When a plurality of cavity elements is applied, these cavity elements are especially associated to each other. This may effectively provide a cavity element including different planes or wings, having mutual angles (a). Cavity elements that are associated to each other may thus provide planes, essentially parallel to the optical axis, and having mutual angles larger than 0° and equal to or smaller than 120°, especially equal to or smaller than 90°, such as 120°, 90° or 60 °.

As yet further indicated above, the device comprises an upconversion element. The upconversion element comprises an upconversion material (or "upconverter material"), which can convert two (or more) photons into a single photon of a second energy. In some systems, this may include an upconversion of two photons of the same energy. In yet other systems, this may include an upconversion of two photons of different energies. Once in the upconverted state, radiative relaxation may occur, optionally accompanied with non-radiative relaxation. Anyhow, the photon that is emitted has an energy higher than any of the absorbed photons. Upconversion materials are specific examples of luminescent materials or phosphors.

Photon upconversion (UC) may for instance be based on triplet-triplet annihilation (TTA). For instance, the upconversion material may comprise Ir(C6)₂(acac), with C6 = coumarin 6 and acac = acetylacetone. Upconversion (luminescent) materials are known in the art, and are e.g. described in US2010/0297206, US2010/0297207, US2011/0171062, or US2016237343, which are herein incorporated by reference, especially with respect to the upconversion (luminescent) materials indicated therein. Especially, the upconverter element is configured to convert visible (and/or IR) radiation into one or more of UVA, UVB and UVC radiation. The term "upconversion element" may also refer to a plurality of different upconversion elements. Especially, the term "upconversion material" especially refers to a plurality of different upconversion materials. In this way, different spectral parts may be absorbed and converted into anti-fouling radiation.

As indicated above, the invention also provides an object comprising an object surface and the anti-fouling device as defined herein, wherein the anti-fouling surface of said anti-fouling device is configured as at least part of said object surface. In yet a further aspect, the invention also provides a method of applying an anti-fouling device as defined herein to an object comprising an object surface, wherein the anti-fouling device is configured to said object to provide with the anti-fouling surface of said anti-fouling device at least part of said object surface.

The device may include one or more concentrators, such as a parabolic concentrators, and/or one or more lenses. In general, each (such) radiation concentrator optical element addresses an upconversion element. When more than one radiation concentrator optical element is available, each radiation concentrator optical element may in other embodiment address different parts of an (extended) upconversion element, such as a layer comprising an upconversion material

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figs, la-lc schematically depict some aspects of the device and object;

Figs. 2a-2c schematically depict some embodiments; and

Figs. 3a-3b schematically depict some variants.

The schematic drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. la schematically depicts an embodiment of an anti-fouling device 10 comprising a window 100, a radiation concentrator optical element 200 and an upconversion element 300. The window 100 comprises an anti-fouling surface 110 for transmission of at least part of anti-fouling radiation 11 to the external of the device 10. This anti-fouling radiation is generated by the uponversion element 300 see also below. Further, the window 100 is transmissive for at least part of one or more of visible and IR radiation 1 from external of the device 10. The window comprises radiation transmissive material, with the anti-fouling surface 110 and a device surface 113 (i.e. the surface of the window directed to the device). In between, the radiation transmissive material is configured, such as glass, quartz, etc.. The window is essentially not permeable for water. The window 100 can be flat, but may also be curved. Radiation from external, indicated with reference 1 , such as solar radiation, is at least partially transmitted through the window, and may reach the radiation concentrator optical element 200.

The radiation concentrator optical element 200 is configured for concentrating at least part of said one or more of visible and IR radiation 1. Further, the device 10 comprises an upconversion element 300, which receives at least part of the concentrated radiation 1. The upconversion element 300 is configured within the device 10, and is configured for upconverting at least part of said one or more of visible and IR radiation 1 into said anti-fouling radiation 11 , wherein said anti-fouling radiation 11 comprises UV radiation. To this end, the upconversion element 300 may comprise upconversion material 310.

The radiation concentrator optical element 200 has one or more focal points 201 for said one or more of visible and IR radiation 1, wherein in embodiments the device 10 is configured with said one or more focal points 201 coinciding with said upconversion element 300. Here, there are a plurality of focal points 201, i.e. a focal plane, the coincides with the upconversion element 300. However, the focal point(s) may also be configured at some distance, such as within a distance of about 2 cm from the upconversion element 300.

Fig. la very schematically also depicts an object 1000 comprising an object surface 1110 and the anti-fouling device 10, wherein the anti-fouling surface 110 of said anti- fouling device 10 is configured as at least part of said object surface 1110. Here, by way of example part of the object surface 1110 is the original surface and part of this original object surface 1110 is replaced by the device, more especially at least the anti-fouling surface 110. Note that the height of the device 10, indicated with h may be in the range of 0.1-100 mm, such as 2-100 mm.

Fig. la (and lb and lc) schematically depict embodiments wherein the device includes a device cavity 13 wherein the upconversion element 300 and at least part of the optical element 200 is configured. Fig. lb schematically depicts an embodiment wherein the radiation

concentrator optical element 200 comprises a lens 210. Here, by way of example the lens 210 is comprised by said window 100. Reference O indicates an optical axis of the device.

Fig. lc schematically depicts an embodiment wherein the radiation concentrator optical element 200 comprises a compound parabolic concentrator 220. The compound parabolic concentrator 220 has an concentrator exit 221. In the schematically depicted embodiment the concentrator exit 221 is comprised by said window 100 though this is not necessarily the case. The compound parabolic concentrator 220 comprises a

concentrator cavity 222 defined by one or more reflective surfaces 223. Further, the device 10 comprises concentrator optical axis O.

Note that in Figs, la and lb, the optical element is comprised by the device cavity 13, and in Fig. lc, the device cavity 13 is (at least partially) enclosed by the optical element.

Fig. 2a schematically depicts an embodiment wherein the device comprises a plurality of lenses 210 and a plurality of upconversion elements 300, wherein each lens 210 is configured to provide concentrated radiation 1 to a respective upconversion element 300. Fig.

2b schematically depicts an embodiment wherein the window 100 comprises micro lens optics 215 configured for concentrating at least part of said one or more of visible and IR radiation 1. Further, Fig. 2b schematically depicts an embodiment wherein the window 100 comprises a flexible material. Note that the lenses are in this embodiment configured at the anti-fouling surface. However, they may also be comprised at the device surface 113, or may be entirely embedded in the window 100.

Fig. 2c schematically depicts an embodiment wherein the device comprises a plurality of compound parabolic concentrators 220 and a plurality of upconversion elements 300, wherein each compound parabolic concentrator 220 is configured to provide

concentrated radiation 1 to a respective upconversion element 300.

In Figs. 2a-2c the upconversion elements 300 are indicated as separate elements, each addressed by different radiation concentrator optical elements 200. In yet other embodiments, a layer may be provided comprising the upconversion element 300. Then, each radiation concentrator optical element 200 may address part of such layer. Such upconversion element may be an extended upconversion element.

Combinations of different embodiments, such as e.g. depicted in Figs. 2a-2c may also bee applied, such as a device with lenses and CPCs, with each lens or CPC addressing a specific (part of the (extended)) upconversion element. Fig. 3a further schematically depicts two variants of compound parabolic concentrators 220 or similar structures, wherein left the CPC has an essentially circular cross- section and the right CPC-like concentrator has an essentially square cross-section.

Further, by way of example the device 10 further comprises a cavity element 224 comprising said upconversion element 300, wherein the cavity element 224 is configured at least partly within said concentrator cavity 222 and configured to occupy a part of said concentrator cavity 222, and wherein said cavity element 224 is configured parallel to said optical axis O. Here, the cavity element 224 is configured in contact with one or more of said one or more reflective surfaces 223. Actually, the device 10 comprises a plurality of cavity elements 224 configured at least partly within said concentrator cavity 222 and configured to occupy a part of said concentrator cavity 222, and wherein said cavity elements 224 have mutual angles a larger than 0° and equal to or smaller than 90°. A specific variant is very schematically shown in Fig. 3b, wherein two disks with each a notch can be used to provide the cavity element(s) 224 as schematically depicted in Fig. 3a (left). Of course, the plates (here disks) may have other shapes such as to conform to the respective CPC cavity shape.

In embodiments, the invention provides an antifouling / antimicrobial system comprising an upconversion material to convert visible radiation into UV radiation for achieving an antifouling / antimicrobial action, and an optical element having an optical effect with respect to the visible radiation and/or the UV radiation for enhancing the antifouling / antimicrobial action. The system is herein also indicated as "device".

Especially, the system comprises an optical element to increase the conversion efficiency of the visible to UV conversion.

Further, the system may especially comprise an upconversion material positioned in the focal point of an optical solar collector to increase the irradiance onto the upconversion material and consequently increasing conversion efficiency.

In specific embodiments, the antifouling/antimicrobial system may include a collection system comprising compound parabolic concentrators (CPC's) and the phosphor material is in the focal point of each CPC. Especially, the exit surface of the CPC is the anti-fouling surface. In embodiments, the upconversion material is configured as (two) phosphor discs, interconnected as in schematically depicted in Figs. 3a-3b. Conservative estimations on the devices depicted in Fig. 3a already gave relatively good upconversion results. Alternatively or additionally, the antifouling/antimicrobial may include a collection system comprising a lens array and the phosphor material is in the focal point of each lens. Especially, the exit surface of the lens is the anti-fouling surface.

In specific embodiments, the upconversion is a visible -to-UV conversion. In embodiments, the photon upconversion (UC) is based on sensitized triplet-triplet annihilation (TTA), for instance, the upconversion material is of the type Ir(C6)₂(acac).

In specific applications, the exit surface coincides with the under-water surface of a ship hull, buoyancy module, wind mill or other marine part, etc..

Hence, amongst others the invention may include embodiments of a device wherein a window is configured for transmission of external light and the same window is configured for transmission of upconverted light. Hence, during use light from external of the device may penetrate through the window, may be concentrated by the concentrator (which may at least partly be comprised by the window), and upconverted light (generated by the upconverter element by upconverting at least part of the concentrated light), penetrates through the window (again) to the external of the device. The upconversion element is especially contained in a closed cavity. The cavity may at least be closed by the window.

The term "substantially" herein, such as in "substantially all light" or in "substantially consists", will be understood by the person skilled in the art. The term

"substantially" may also include embodiments with "entirely", "completely", "all", etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term "substantially" may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term "comprise" includes also embodiments wherein the term "comprises" means "consists of. The term "and/or" especially relates to one or more of the items mentioned before and after "and/or". For instance, a phrase "item 1 and/or item 2" and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species".

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

Claims

CLAIMS:

1. An anti-fouling device (10) comprising a window (100), a radiation concentrator optical element (200) and an upconversion element (300), wherein:

said window (100) comprises an anti-fouling surface (110) for transmission of at least part of anti-fouling radiation (11) generated by the upconversion element (300) to the external of the device (10), wherein the window (100) is further transmissive for at least part of one or more of visible and IR radiation (1) from external of the device (10);

the radiation concentrator optical element (200) is configured for concentrating at least part of said one or more of visible and IR radiation (1); and

the upconversion element (300) is configured within the device (10), and is configured for upconverting at least part of said one or more of visible and IR radiation (1) concentrated by the radiation concentrator optical element (200) into said anti-fouling radiation (11), wherein said anti-fouling radiation (11) comprises UV radiation.

2. The device (10) according to claim 1, wherein the radiation concentrator optical element (200) has one or more focal points (201) for said one or more of visible and IR radiation (1), wherein the device (10) is configured with said one or more focal points (201) coinciding with said upconversion element (300).

3. The device (10) according to any one of the preceding claims, wherein the radiation concentrator optical element (200) comprises a lens (210).

4. The device (10) according to claim 3, wherein the lens (210) is comprised by said window (100).

5. The device (10) according to any one of the preceding claims 3-4, wherein the device comprises a plurality of lenses (210) and a plurality of upconversion elements (300), wherein each lens (210) is configured to provide concentrated radiation (1) to a respective upconversion element (300).

6. The device (10) according to claim 5, wherein the window (100) comprises micro lens optics (215) configured for concentrating at least part of said one or more of visible and IR radiation (1), and wherein the window (100) comprises a fiexible material.

7. The device (10) according to any one of the preceding claims, wherein the radiation concentrator optical element (200) comprises a compound parabolic concentrator (220).

8. The device (10) according to claim 7, wherein the compound parabolic concentrator (220) has an concentrator exit (221), wherein said concentrator exit (221) is comprised by said window (100).

9. The device (10) according to any one of the preceding claims 7-8, wherein the compound parabolic concentrator (220) comprises a concentrator cavity (222) defined by one or more reflective surfaces (223) and a concentrator optical axis (O), wherein the device (10) further comprises a cavity element (224) comprising said upconversion element (300), wherein the cavity element (224) is configured at least partly within said concentrator cavity (222) and configured to occupy a part of said concentrator cavity (222), and wherein said cavity element (224) is configured parallel to said optical axis (O).

10. The device (10) according to claim 9, wherein said cavity element (224) is configured in contact with one or more of said one or more reflective surfaces (223).

11. The device (10) according to any one of the preceding claims 9-10, wherein the device (10) comprises a plurality of cavity elements (224) configured at least partly within said concentrator cavity (222) and configured to occupy a part of said concentrator cavity (222), and wherein said cavity elements (224) have mutual angles (a) larger than 0° and equal to or smaller than 90°.

12. The device (10) according to any one of the preceding claims 7-11, wherein the device comprises a plurality of compound parabolic concentrators (220) and a plurality of upconversion elements (300), wherein each compound parabolic concentrator (220) is configured to provide concentrated radiation (1) to a respective upconversion element (300).

13. An object (1000) comprising an object surface (1110) and the anti-fouling device (10) according to any one of the preceding claims 1-12, wherein the anti-fouling surface (110) of said anti-fouling device (10) is configured as at least part of said object surface (1110).

14. The object (1000) according to claim 13, wherein the object (1000) is selected from the group consisting of a immobile marine object, a motorized marine object, an infrastructural element, and a windmill.

15. A method of applying an anti-fouling device (10) according to any one of the preceding claims 1-12 to an object (1000) comprising an object surface (1110), wherein the anti-fouling device (10) is configured to said object (1000) to provide with the anti-fouling surface (110) of said anti-fouling device (10) at least part of said object surface (1110).