METHODS AND APPARATUS FOR CREATING

PHOTONIC STRUCTURED ICE CUBE

Field of the Invention

The present invention relates to ice production. More particularly, the invention relates to methods and apparatus for coloring ice cubes by producing photonic structured ice cubes.

Background of the Invention

Ice cubes are widely used for cooling beverages, wherein the beverage can be a soft drink, water, an alcoholic beverage, a cocktail, a milk shake and many other beverages.

There are many different types of ice, including, for example, ice cube, half- ice cube, nugget ice, flake ice, crescent ice, gourmet ice and ice tube that is formed on the inner surface of vertical tubes and is produced in the form of small hollow cylinders. The production techniques of the clear ice types involve a slow cooling that results in a layer-by-layer solidification from the cold surface/interface toward the periphery.

Ice cubes are sometimes preferred over crushed ice, because they melt more slowly; they are standard in mixed drinks that call for ice, in which case the drink is said to be "on the rocks".

While commercial ice cubes can come in different sizes and shapes, to date there is no industrial solution for coloring the ice without damaging the color or the taste of the drink. Coloring the ice cube, or creating a visible pattern inside the ice cube, may make a beverage more appealing and visually interesting to the user, and therefore may stand out when a client needs to choose between various otherwise similar beverages. It may also be used for delivering commercial messages or for "branding" the ice cubes. Therefore, techniques for coloring or for creating visible patterns in ice cubes are commercially desirable.

The standard coloring method of ice cubes is by the use of food coloring and/or other colored edible materials. However, such materials are mixed with the beverage when the ice melts and affect the color and/or the taste of the beverage. The use of food coloring is also considered by many users to be unhealthy and therefore undesirable.

Photonic structures or crystals are periodic or quasi-periodic optical structures, typically nano- or micro-structures, that affect the motion of photons and may generate coloration by producing various interference patterns. Photonic structures might be composed of pillars, conical shapes, spherical shapes, or any series of geometric structures, combinations or arrangements, protrusions or niches. The height, diameter and spacing between the features (i.e. peak-to-peak distance minus the size of said features), which are also referred to as the dimensions of photonic structures, or "feature size", are in the range of 50 - 5000 nm. Dimensions of 300 - 800 nm are suitable for intensive light diffraction in the visible range of the spectrum. Another condition for achieving coloration, is refractive index difference between the ice, (with refractive index of 1.31) and the material that comes in contact with it, which in case of air, the refractive index is almost 1. Photonic structures are common in nature (for examples of naturally occurring photonic structures, see: Pete Vukusic & J. Roy Sambles, Nature 424, 852-855, 14 August 2003, doi:10.1038/nature01941) and are used in a range of applications.

Some processes of producing clear ice having photonic structure on its surface, present unique challenges. Cheap method for introduction of photonic structure into the ice cube is the main challenge, which is strongly influenced by the nanostructure templates production cost. The templates, which in some cases are used for the molding, are made of organic polymers and duplicated using embossing techniques, in order to have cheap molds replication, high durability and food compatibility. However, such templates produce hydrophobic surfaces, thus water would not penetrate/enter into the nano-metric features of the mold, and would not wet the surface. As a result, the desired micro/nano-structured ice surface would not be achieved.

Summary of the Invention

The present invention allows adding a new and unique color to ice cubes, without any influence on the color or the taste of beverages as a result of the ice cube melting, by the use of photonic structures embedded in the ice cube to generate the visual effects. The photonic structures are within the volume of the ice cube, and therefore melt only after the surrounding exterior ice already has already melted.

According to one embodiment of the invention an apparatus for the production of an ice cube of the invention comprises: a flat back with ice mold base, wherein the ice mold base comprises photonic structures, and wherein at the lower half of the back, the ice mold base is an elevated ice mold base with photonic structures; a peripheral ice mold base which is a flat surface that can be heated; a grid, which can be folded exactly to half with the use of rails and can pass gas or water through internal channels; a cooling system; an ultrasonic oscillator; and a surface treating device.

A method for the production of colored ice cubes according to the invention, using the above-described apparatus consists of:

a) flowing water through a grid while cooling with the use of a cooling system to produce ice;

b) detaching the grid, together with the formed patterned ice, from the mold, by heating the peripheral ice mold base and pumping compressed air through the air piping;

c) folding the grid on the rails to bring the two halves of the ice cube into contact and binding the two halves or flowing water through the grid, into the slot between two ice cubes halves, freezes and binding the two halves.; and

d) ejecting the colored ice cube from the folded grid.

An apparatus according to another embodiment of the invention, which is suitable for the production of colored ice cubes, comprises: a mold base having mold fingers on the bottom side, wherein the mold fingers consist of surfaces with photonic structures; a cooling system on the top side of the apparatus; ejectors for ejecting the ice at the end of its production; an ultrasonic oscillator; and a surface treating device.

A method according to another embodiment of the invention, for the production of colored ice cubes using the above-described apparatus, consists of:

a) immersing the bottom side of the apparatus in water and cooling the apparatus using the cooling system;

b) empting the excess water and ejecting the perforated ice using the ejectors;

c) optionally, placing the perforated ice produced in step b in an ice cube mold;

d) optionally, filling the ice cube mold with water and freezing; and

e) optionally, ejecting the ice cube from the mold.

According to yet another embodiment of the invention there is provided an apparatus for the production of colored ice cube, comprising: a piston head inside a chamber, wherein the top surface of the piston head consist of an ice mold base having a photonic structure surface on top of a cooling system, and wherein the chamber walls have filling holes to allow water to go inside the chamber; and a surface treating device.

A method according to still a further embodiment of the invention, for the production of colored ice cubes using the above-described apparatus, consists of: a) immersing the chamber in water and lowering the piston head one notch to allow water to go into the channel through the holes in the walls;

b) cooling the ice mold base, using the cooling system, to bring the water in the chamber into freezing;

c) repeating steps a - b several times; and

d) ejecting the ice cube by pushing the piston head to its upper passion.

Brief Description of the Drawings

In the drawings:

Fig. 1 illustrates a glass of a beverage with photonic ice cubes presenting text;

Fig. 2 shows a top view (2A) and a cross section (2B), taken along the C-C plane of Fig. 2A, of a photonic ice cube of Fig. 1;

Fig. 3 is an example of two molds for photonic structures. Fig. 3A has a diffraction grating structure (ID structure) and Fig. 3B has a pillars structure (2D structure);

Fig. 4 is an isometric view (4A) and side view (4B) of a moth-eye anti-reflective structure;

Fig. 5 illustrates the dynamics of a freezing process, wherein the major heat flow is from the top, as it is usually the case with home-made ice cubes. When the upper part of the water freezes, air bubbles are trapped (5A), and eventually destruct the photonic structure (5B);

Fig. 6 illustrates two options for dynamics of freezing processes, wherein the major heat flow is perpendicular to the mold surface, as shown in Fig. 6A, that exemplifies the issues with local heat gradients which in some cases may cause dissociation between the ice and the mold, and Fig. 6B exemplifies potential issues when the mold is on top and the expansion of ice in the freezing process pushes against the top of the chamber and causes dissociation;

Fig. 7 illustrates a proper freezing process for making transparent crystalline ice having nano or micro structure patterning on its surface, wherein the cooling is from the bottom surface (the mold surface) and is uniform across the surface;

Fig. 8 illustrates apparatus suitable for the production of photonic ice cubes;

Fig. 9 is a side view of the apparatus of Fig. 8 (9A) during ice production and a closer look on one chamber in that apparatus (9B);

Fig. 10 shows the apparatus of Fig. 8, after the process of the production of ice cubes is over;

Fig. 11 shows the de-molding process of apparatus of Fig. 8;

Fig. 12 shows the bonding process of the two halves of the colored ice cube, using the apparatus of Fig. 8;

Fig. 13 shows the ejection step of the apparatus of Fig. 8;

Fig. 14 is an example of an ice cube (14A) made by the apparatus of Fig. 8, and a cross section (14B) thereof;

Fig. 15 illustrates other photonic ice cubes according to the invention. Fig. 15A shows an ice cube having homogenous photonic structure (no indicia) and Fig. 15B shows a photonic ice cube wherein the photonic structure is arranged in a letters shape;

Fig. 16 illustrates the advantage of adding a moth-eye structure for minimizing reflections and enlarging the critical angle; Fig. 17 is an overview of apparatus according to another embodiment of the invention for the production of the photonic ice cubes;

Fig. 18 is a bottom view of the apparatus of Fig. 17;

Fig. 19 shows the water immersion step using the apparatus of Fig. 17;

Fig. 20 shows the ice forming step using the apparatus of Fig. 17;

Fig. 21 shows the water empting step using the apparatus of Fig. 17;

Fig. 22 shows the ice ejecting step (22A) using the apparatus of Fig. 17, and a scheme of the perforated ice formed by said apparatus (22B);

Fig. 23 shows the placement of the perforated ice into the ice cube mold, according to an embodiment of the invention;

Fig. 24 shows the step of ice cube mold closing and water filling, according to the same embodiment of the invention;

Fig. 25 shows the freezing process inside the ice cube mold, according to the same embodiment of the invention;

Fig. 26 shows a photonic ice cube which is the product of the apparatus and method illustrated in Figs. 17 - 25, having small voids caring photonic structures;

Fig. 27 illustrates apparatus for the production of photonic ice cubes, according to another embodiment of the invention;

Fig. 28 is a cross section of the apparatus of Fig. 27, taken along the A-A axis shown at the top of the figure;

Fig. 29 shows the water pumping step in the apparatus of Fig. 27;

Fig. 30 shows the water freezing step in the apparatus of Fig. 27;

Fig. 31 shows the second water pumping step in the apparatus of Fig. 27; Fig. 32 shows the second water freezing step in the apparatus of Fig. 27; Fig. 33 shows the third water pumping step in the apparatus of Fig. 27; Fig. 34 shows the third water freezing step in the apparatus of Fig. 27; Fig. 35 shows the ejecting step in the apparatus of Fig. 27;

Fig. 36 shows a isometric view of photonic ice cube produced by the apparatus and method of Figs. 27 - 35; and

Fig. 37 illustrates an easy and inexpensive way to produce a diffraction grating mold having text and symbols, according to another embodiment of the invention.

Detailed Description of the Invention

The invention relates to apparatus and methods for producing ice cubes with internal photonic structure. With reference to Fig. 1, such colored ice cubes (103) can be used for serving beverages (102) with a textual message (104) embedded in them. The beverage (102) is served in a glass or a cup (101), optionally coated with a reflective material, or made from a polarizer material.

Fig. 2 shows one embodiment of the invention, wherein the photonic structure is arranged in a letters shape, producing a readable text, (104) and embedded inside an ice cube (103). The photonic structure is embedded in a small void volume inside the center of the ice cube and it is thermally isolated from the body of the ice cube as long as the ice cube is not fully melted, as well as reduces ice sublimation by hermetically sealing the void.

The heat flow from the external environment to the photonic structure follows the equation:

Q/A=k*(Tl-T2)/L,

Wherein Tl is the external temperature (typically T1>0°C), T2 is the internal temperature (typically T2≤0°C), L is the distance from the external surface to the void volume and k is the ice heat conduction coefficient equal to 2.18 W/(m*K). Latent-heat released during the melting of ice (334 J/gr) also contributes to slow down the ice cube melting process.

Fig. 3 illustrates some mold structure for creating a photonic structure in the ice, according to an embodiment of the invention. The mold structure can be any periodic or quasi-periodic nanostructure, microstructure or hierarchical structure composed from micro and/or nano structures, that affects the motion of photons, and can be composed, for example, of a linear diffraction grating (301) (as shown in Fig. 3A), pillars (302) (as shown in Fig. 3B), conical shapes, spherical shapes, square shapes, grooves, rows or any other repeating geometric structure, combination or arrangement, protrusions or niches. According to an embodiment of the invention Blaze diffraction grating, Echelle grating, Immersion grating, prism array or Grism are some examples of photonic structure that can be apply on ice. Some examples of hierarchical structures that can function as photonic structures are micro/millimetric size prisms pattern, covered with nanostructure or photonic structure covered with moth-eye structure.

The material of the mold ('structured mold') can be any organic polymer, such as derivatives of polysiloxanes (dimethyle siloaxne, H methyl siloaxne and etc.), derivatives of epoxy-based photoresists (SU-8 and etc.), derivatives of polyethyelen (PE, PET and etc.) , derivatives of polycarbonate (PC), any Hygroscopic polymer, such as dry or wet derivatives of polyamide (PA6), or dry or wet cellulose-containing material (for example Cellulose Acetate). An additional approach is to use inorganic materials, such as metal oxides (titanium dioxide, zinc oxides and etc.) dielectric materials (silicon dioxide, aluminum oxide and etc.) and metals (aluminum, copper, zinc and etc.).

In order to obtain a faster freezing process, high conductive polymers can be used, such as derivatives of polythiophene (poly(3,4-ethylenedioxythiophene) (PEDOT), polymethylthiophene (PMT), etc.), derivatives of polyphenylene (poly(p-phenylene sulfide) (PPS), Poly(p-phenylene vinylene) (PPV), etc.). Heat conductive additives can be added into the structured mold polymer, like heat conductive nano/micro particles such as carbon, gold, etc. , heat conductive nano wires or tubes made from carbon, gold, silver, etc. using nodes welding techniques to increase conduction, heat conductive micromesh or milimetric net made from steel, copper, etc.

According to an embodiment of the invention a moth-eye structure (401) is employed, as shown in Fig. 4, on the interface between the bulk ice and the internal void, where the photonic structure is located. The effect of the addition of such structure to the internal surface of the ice cube is illustrated in Fig. 16. Fig. 16A schematically shows that when the light hits the ice surface at the critical angle, in the interface between the bulk ice cube and the internal void, a total internal reflection of the light may occur and no light would reach the photonic structure. The moth-eye structure on the surface of that interface allows some light to penetrate the interface hence increasing the desired visual effect of the photonic structure.

Fig. 5 illustrates the dynamics of a freezing process. When the main heat flow is through the upper face of the cube, namely when there is a little or no heat flow from the walls of the ice mold (504) (a typical situation in the case of homemade ice cubes, using a standard plastic trail). Because of the low density, ice (501) is formed from the upper surface to the bottom. Without the degassing of water (502) before reaching to the freezing point, lower gas solubility in the ice will result in the appearance of air bubbles in the ice crystal (505) and eventually deposited on the surface of the structured mold (301) and produce air bubbles inside the ice photonic structure (503). Such process destroys the photonic structures as well as the ice cube clarity.

Fig. 6A shows another possible faulty process for the production of photonic structures on ice. In the case illustrated in the figure, the heat flow is from the lower surface, perpendicular to the structured mold surface (604), while the other walls of the ice mold are surrounded with a thermal isolator (603). In such process, the ice (501) is produced from the bottom of the cube, and air bubbles (602) are floated and emitted from the water (502). However, small temperature differences between the ice (501) and the water (502) might cause separation of the already formed ice from the structured mold carrying the photonic structure (604) to create a gap (601). Water from the upper phase penetrates the gap and might destroy the photonic structure.

Fig. 6B exemplifies potential issues when the main heat flow is through the upper face of the ice mold (504) and the structured mold (604) is located on top of the ice mold. The expansion of ice (501) during the freezing process pushes against the top of the chamber and causes structured mold dissociation (601);

Fig. 7 illustrates a suitable freezing process for the production of a transparent crystalline ice having nano or micro structure patterning on its surface, which can function for example as a photonic structure (301). The freezing is from the lower face of the ice mold (504), due to the peripheral isolation (603), wherein the structured mold (604) is located (i.e. the structured mold is placed on top of the surface with the highest heat flow). The heat flow from the lower phase is uniform and freezing occurs along the whole area of the lower surface. The optimal freezing temperature is between -1°C to -5 ^° C, which allows for a slow freezing process, preventing the air bubbles (602) from being trapped in the formed ice (501). The air bubbles eventually leave the water (502), through the upper face, and the ice on the template is free of defects. The process described herein can be implemented on homemade ice cubes, using a standard trail with the methods #1, #2 and #3, which are described hereinafter.

The process described in Fig. 7 and in reference to all the methods and apparatus of the invention in which water is frozen on structured mold, is equivalent to the process wherein a structured mold is placed on ice, heated, melts the ice and then the ice is frozen again.

The ways for adding water, or any water based solution (e.g. water with sugar to increase the ice refractive index), that are described herein, include purring, flowing, injection, adding water layer-by-layer, with spray or by a dripper, etc. (i.e. 'adding water techniques'), apply to all the methods and the apparatus of the invention. Three different apparatus and methods for the production of colored ice cubes according to the invention will described hereinafter:

Apparatus and method #1

One embodiment of the invention is described in Figs. 8 - 15. Fig. 8 describes an apparatus, comprising a flat back having a structured mold base (801) with photonic structures (301) and a peripheral mold base (806) which is a flat surface that can be heated, wherein at the lower half of the back, the ice mold base is an elevated ice structured mold base (802) with photonic structures; a grid (805), which can be folded exactly to half with the use of rails (803); a cooling system (804); and a surface treatment device (807).

The grid (805) can be optionally heated for wet ejection of the formed ice cubes. The heating can be done by passing a hot gas or water through internal channels in the grid or by applying electrical current through heating bodies in the grid.

The peripheral ice mold base (806) can be heated, for example, by using a thin heating lines that selectively heat the peripheral ice mold base (806) without heating the elevated ice structured mold base (802).

The surface treatment device (807) can be a UV-ozone surface treating device, a corona treatment device, atmospheric pressure plasma or any other surface treating device.

Fig. 9A is a side view of the apparatus described in Fig. 8. Water flows from top to bottom. An ultrasonic oscillator is optionally connected to the grid via the dedicated ultrasonic oscillator connector (906), which can help achieve better structured mold wetting properties. Fig. 9B shows a detailed structure of one chamber of the grid (805) of the apparatus. The ice (901) is formed on the mold base (905) located on a carrying board (904), preferably made of a metal with high heat conduction. To achieve optically clear ice crystals, water supercooling should be avoided and ice nucleation should be initiated at the highest possible temperature. There are many techniques for ice nucleation on the structured mold, including acoustic or electric pulse, induction of local freezing (seeding), sonication, changing temperature profile (i.e. start with relatively low temperatures, (for example, around. -5 ^° C) after the first ice layer was created, and then raising the temperature (for example, up to -1 ^° C), changing the heat flow rate, and inserting ice particles to the water solution. A pre- treatment of water, such as a process that results in purified water, or initially boiling the water, etc., can improve the ice accumulation rate without losing the ice clarity. In the case in which the mold base is made of water-absorbing polymer, like hygroscopic polymers, for example, such as nylon PA-6 or cellulose acetate, an optional antifreeze water layer (907) is located between the mold base and the carrying board in order to keep the polymer wet during the whole process. The antifreeze water layer should not freeze at the working temperature (typically -1 °C to -5°C) and can consists of salt water or any other suitable water based antifreeze. The water from the antifreeze water layer penetrates the polymer of the structured mold base and keeps it wet for better wetting of the surface. The back surface of mold base (905) can also carry a nano or micro structures pattern, in order to increase its surface area and improving water penetration rate. The apparatus can control the water level in the antifreeze water layer and can compensate for the absorbed water. The antifreeze water layer (907) increases the flexibility of mold base (905) and can help enlarge the de-molding angle between the structured mold base and ice during de-molding process, which is described later in Fig. 11. The apparatus further comprises an air piping (902) for dry ejection of the formed ice, and a peripheral canal (903) in the grid for distributing the compressed air coming from the air piping.

A structured mold made from hygroscopic polymers is simple, inexpensive, high durability and food computability solution for producing nano structures on ice, as it doesn't involve any complex surface treatments or physical forces. Other example are: polymers having hydrophilic coatings to producing hydrophilic structured mold surfaces, which usually suffer from delamination problem which cause low durability and can lead to coating residues in the ice cubes (i.e. problems with food compatibility). Glass or metal oxides can also be used for producing hydrophilic structured mold surfaces, but its production cost is very high.

Figs. 10 - 13 illustrate the final stages of the colored ice production, using the apparatus of Fig. 8. Fig. 10 shows the apparatus at the end of the molding process. The upper half of the grid is full with flat bottom half photonic ice cubes (1001) and the lower half of the grid is full with middle elevated bottom half photonic ice cubes (1002).

Fig. 11 and Fig. 12 show the apparatus at the end of the de-molding process. The ice cubes are detached from the mold base surface, the grid if folded on its center to bring the flat bottom half photonic ice cubes (1001) in contact with the middle elevated bottom half photonic ice cubes (1002), in order to bring them into contact with each other and bind the two halves into a complete ice cube. The de-molding process can be carried out under any temperature below zero, preferably at a temperature between -1 ^° C to -5 ^° C. Below this temperature the ice becomes more brittle and the connection between the ice and the structured mold becomes stronger, which can lead to ice photonic structure damage. The whole process is performed inside a cold chamber, having a temperature below the freezing point, and can be even below the de-molding temperature, and can be filled with any gas. The low temperature inside the humidity-sealed chamber keeps the chamber dry, without humidity which might be deposited on the newly formed structured face of the two halves ice cubes and destroy the fine structure. Further, in the case where a wet ejection (using heat or water adding) is used, the low temperature allows the binding of the two halves without the need of additional step. Another alternative option for bonding the two ice cubes halves is by pumping water through internal channels in the grid, after the folding completes. The water flows into the slot between two halves ice cubes, freezes and binds them together. The same result would be achieved when hot gas is passed through the grid or electrical heating is applied for a short time, and melts the area near the slot between the two half ice cubes. The final step in the production of colored ice cubes using the apparatus of Fig. 8 is to eject the cubes from the grid, as described in Fig. 13. Heating the grid (805) can help with the ejection of the newly formed colored ice cubes (1301).

Fig. 14 is a schematic top view (14A) and a cross section (14B) of a colored ice cube (1301) formed by the apparatus of Fig. 8. As one of the molds is elevated in the middle, a thin void volume with air (1402) or any other gas like C0 ₂ , in order to reduce convection or for other purposes, is formed between the two photonic structured ice surfaces (1401) that can function independently or function as one optical system like Echelle Spectrometer optical system for example. The shape of the void (1402), the colored ice cube (1301) cross section, outside ice cube surfaces and internal void surfaces are not limited and can be flat, convex, concave, tilted at any angle or shaped in any 3D shape. This includes all the methods and all the apparatus of this invention.

Fig. 15 illustrates other photonic ice cubes, according to the invention. Fig. 15A shows an ice cube having a homogenous photonic structure (1501) and Fig. 15B shows a photonic ice cube wherein the photonic structure is arranged in a letters shape (1502).

Fig. 16 illustrates the effect of the moth-eye structure. In the case of an ice cube having two photonic structured ice surfaces (1401) separated by air (1402), as shown in Fig. 16A, a total internal reflection would occur when the light hits the ice-air interface in the critical angle or larger, hence reducing the light hitting the photonic structures and reducing the observable visual effect of the structured ice. When one of the surfaces is a moth-eye surface (1601), as shown in Fig. 16B, even at critical angle or larger, a partial light transmission would occur. Alternative, the total internal reflection that shown in Fig. 16A, can be used for creating ice reflective diffraction grating.

The hygroscopic wetting technique that includes using antifreeze water layer (907), a freezing process including temperature profile, a pre-treatment of water, de-molding techniques, and all other methods and techniques that are described herein, can be used in the same way in apparatus and methods #2 and #3, and vice versa as well.

Apparatus and method #2

An alternative embodiment of the invention is described in Figs. 17 - 26.

Fig. 17 shows a apparatus, comprising a refrigerant piping (1701) attached to a mold base (1704), wherein structured mold fingers (1703) are located on the other side of the mold base. The apparatus further comprises ejectors (1702) to eject the formed structured ice at the end of the process. A surface treatment device (1705) is facing the mold fingers side of the mold base. The surface treatment device can be a UV- ozone surface treating device, a corona treatment device, atmospheric pressure plasma or any other surface treating device.

Fig. 18 is a bottom view of the apparatus of Fig. 17. The inset shows the tip of the mold fingers, having a photonic structure surface (1801), which can cover all the structured mold finger (1703) surfaces, not only on the mold finger bottom surface, as shown in the figures. The mold fingers arrangement can be within any shape including letters or indicia. Mold finger diameter, length or cross-section shape is not limited, as long as water doesn't get into the ice voids during the freezing process described in Fig. 24.

The method of production of colored ice cubed, using the apparatus of Fig. 17, involves immersing the mold fingers in a water tank (1905), which is full with water (1901) and optionally attached to an ultrasonic oscillator (1904), as described in Fig. 19. The photonic structure surface (1801) on the tip of the mold fingers is filled with water (1901). The mold fingers core (1902) can be made from any material, preferably from a material with high heat conduction.

Fig. 20 shows the step of cooling the mold fingers, using the refrigerant piping (1701) and forming a perforated photonic ice (2001). Fig. 21 shows the newly formed perforated photonic ice after empting the water. Fig. 22 shows the ejection process of the perforated photonic ice (2001), using the ejectors (1702), to give the perforated photonic ice (2001) having the embedded photonic structure ice surface (2201). There are some options to producing mechanical ejection (i.e. dry ejection, can be done in several optional ways) including, but not limited to, using mechanical force, changing mold dimension (i.e. increases dimension before freezing process and decreases it after process ends) in order to separate the mold from the ice, using mold draft, using high passion's ratio material, etc. The same dry ejecting principles can be implemented in methods and apparatus #1 and #3, where it is required.

The temperature after perforated photonic ice elements (2001) are ejected during handling, and until the cold water is added at the end of its production process, should be below zero, and the environment should be dry.

Several perforated photonic ice elements (2001) are then placed inside an ice mold tank (2301), as shown in Fig. 23, and the tank is then filled with cold water (2402) (close to the freezing point) and covered with a cover (2401), as shown in Fig. 24. The cover (2401) optionally has a water inlet, and the ice mold tank optionally have holes to allow continuous running water throughout the freezing process.

The structure of Fig. 24 is then frozen to produce a photonic ice cube (2501) having small voids carrying photonic surfaces (2201), as shown in Fig. 25.

To ensure that the photonic structures last for the same period of time that the ice remains frozen, air or gas is need to isolate the photonic structures from being refilled with ice during the production process and from being in contact with water during the melting of the ice when in use. In order to test whether this is the case, a 3 and 4 millimeter diameter and 15 millimeter depth hole was drilled into clear ice cube. The ice cube was then inserted into a glass of water and it was spun. The trapped air remained inside the 3 and 4 millimeter holes until the ice was melted, keeping the inner surfaces of the hole dry. A schematic illustration of the final colored ice cube, produced by using the apparatus of Fig. 17, after removing the photonic ice cube (2501) from the ice mold tank (2301) is shown in Fig. 26.

Another option is to use perforated photonic ice elements (2001) directly with the drink, without the steps describes in Figs. 23 to 26.

Apparatus and method #3

A further embodiment of the invention is illustrated in Figs. 27 - 36.

Figs. 27 and 28 show a apparatus comprising a water tank structure (2707) having a central cylinder having incoming water holes (2804) and comprising a piston head (2801) surrounded by a flat surface (2704), wherein the top of the piston head comprises an elevated ice structured mold base having photonic structure surface (2701) and an income compressed air hole (2702) and wherein a refrigerant piping (2803) and a compressed air piping (2802) are embedded in the center of the piston head (2801). The apparatus further comprises an ultrasonic oscillator (2705). A surface treatment device (2706) is facing the elevated ice structured mold base having photonic structure surface (2701). The surface treatment device can be a UV- ozone surface treating device, a corona treatment device, atmospheric pressure plasma or any other surface treating device. The elevated ice structured mold base cross-section shape as well as the elevation length, can be of any shape or length, having a photonic structure surface (2701) on all its surfaces, and not only on top of it, as shown in the figures.

The first step of the production of colored ice cubes using the apparatus mentioned above is filling the water tank structure (2707) with water (2703), that it's at a temperature as close as possible to the freezing point, and pulling the piston head (2801) one notch down to pump water to the central cylinder through the incoming water holes (2804) and bring the water into contact with the elevated ice structured mold base having photonic structure surface (2701), as described in Fig. 29. The mechanism for piston movement (not shown in the figures) can be pneumatic, hydraulic, electric or other.

The water inside the cylinder is then cooled to produce ice (3002), producing a photonic structure surface (3001) in the interface between the ice structured mold and the ice, as shown in Fig. 30.

Next, air is supplied through compressed air piping (2802) for the de-molding process. The piston head (2801) is pulled another notch down, to allow water (2703) to fill the void volume through the incoming water holes (2804). Compressed air piping (2802) functions now as an air inlet pipe that enables the air to enter from air hole (2702), during piston movement, through the void volume, up to the alcove (3101) and get trapped inside it. The alcove has a bigger volume than the ice expansion below, and the air inside it keeps the photonic structure ice surface dry, as shown in Fig. 31.

When the water inside the cylinder is froze, a new photonic structure surface (3001) is produced in the interface between the ice structured mold and the ice, while the older photonic structure surface (3001) remains dry thanks to the internal void (3201), as described in Fig. 32.

The temperature in the void, after the de-molding process ends, and until water is added, should be below zero, and the environment should be dry.

Figs. 33 - 34 describe another repeat of the above process to produce another photonic structure surface (3001) in the formed ice cube. The process can be repeated typically between 0 to 25 times. Alternatively, with an appropriate device, a continuous process can be applied in order to produce long photonic ice rods having repeats of the photonic structure surfaces. The photonic ice rods may be cut afterwards into separate ice cubes, wherein each ice cube typically contains 1 to 5 photonic structure surfaces. In such process, the repeats number is unlimited.

Fig. 35 shows the end of the process, wherein the piston head (2801) is pushed up, pushing the newly formed colored ice cube (3002) out of the production apparatus. The internal voids (3201) trap air between the photonic structure surface (3001) and the flat ice surface (3501).

The final photonic ice cube (3601), produced by using the apparatus of Figs. 27 and 28, is schematically shown in Fig. 36.

Fig. 37 shows an example of easy and inexpensive way to produce diffraction grating structured mold having text and symbols, according to an embodiment of the invention. Diffraction grating with horizontal elements (3701) and diffraction grating with vertical elements (3703) can be cut into letters with horizontal diffraction grating elements (3702) and letters with vertical diffraction grating elements (3704), respectively. A company logo (3705) can also be cut. Then a combined mold with horizontal letters and logo and vertical background (3706) can be produced. Another inexpensive way to produce a diffraction grating mold having text and symbols is by local removal of elements by laser marking for example.

An optional way to enhance the visual effect is to serve the beverage with the crystalline photonic ice in a glass or cup coated with reflective layer, such as metal, on the inner or outer (in case the glass is transparent) surface of the glass, or glass made from polarizer material.

Polymers are attractive materials for the realization of optical devices in a wide range of applications. Their fast and easy processing technologies allow for cost- effective mass production, while their tunable properties provide high flexibility in design. Processing of thermoplastic polymers has experienced a continuous development over the past decades and injection molding nowadays plays a key role in cost-effective high volume nano/micro structures master mold replication, as well as hot embossing, roll-to-roll techniques, and many more. Chemical mold replication, using the material solubility property, e.g. using acetone to replicate a mold structure into cellulose acetate, is another possible method for cost-effective mass production of polymeric based master mold.

Producing photonic structure ice makers in mass-production volumes for ice plants factories, restaurants, cafes, hotels, pubs, cinemas and many more business, requires large consideration at the end-price of a single ice cube, as well as structured mold durability, and food compatibility. Using nano/micro structures embossing replications or chemical mold replication on polymers molds together with the simple and inexpensive methods described herein, can make this technology relevant.

However, such surfaces are not suitable for producing nano structures in ice as the liquid water would not penetrates the nano structures in the template and not wet the surface completely i.e. Cassie state.

Manufacturing Examples

In an attempt to have water embossing with features size that is smaller than 1500nm, one or more of the following methods were tested:

A. Using hydrophilic mold material, such as:

a. Hydrophilic metals such as metal oxides (titanium dioxide, zinc oxides and etc.);

b. Hydrophilic polymers such as PA 6, PA 6/6, PET, etc.;

c. Hydrophilic rubbers by hydrophilic polymers grafting process / techniques such as graft polyacrylonitrile on cellulose;

d. Glass.

B. Apply surfaces treatments, such as:

a. UV-ozone cleaning;

b. Corona treatment;

c. Dielectric barrier discharge;

d. Water (H ₂ 0) plasma;

e. Atmospheric-pressure plasma;

f. Water impregnation using high water absorption materials, e.g. hygroscopic polymers, such as: PA6, Cellulose Acetate (CA) and Ethylene vinyl alcohol (EVOH); g. Hydrophilic food compatible surface coating like metal oxides coating using dip coating or spin coating, metal coating using the same techniques and then oxidation the coating;

h. Wet solution treatment like Basic acid washing.

C. Using physical force, such as:

a. Hydraulic pressure;

b. Sonication (ultrasonic);

c. Vacuum;

d. Electrical surface charging (induced dipole).

D. Adding surfactant to the water, such as:

a. Edible surfactant like E432 to E436;

b. Natural surfactant like E322;

c. Mold coating using water with surfactant;

d. Thin water layer having surfactant freezing on the diffraction grating mold, and then continues with regular water (without surfactant) freezing.

The various surfaces and modifications, and combinations of them, were tested in 2 simple tests:

1. Ice photonic structuring - the visual effect expected from a successfully structured ice is tested. A "Good" mark is given for a process that yields a visual effect and a "Failed" mark is given in case no visual effect is presented. In some cases, no visual effect is expected (for example, when testing the moth eye structure) or when the test was not performed, the "N/A" mark is given.

2. Water-break test (ASTM International, Standard Test Method for Hydrophobic Surface Films by Water-Break Test, F22-02) - mold surface is dipped in reverse osmose (RO) water and withdrawn in a vertical position. When the draining water remains as a film over the surface, a hydrophilic is indicated and a "Pass" mark is given. When the water film breaks up into a discontinuous film within 1 minute, a hydrophobic surface is indicated and a "Failed" mark is given. The strong correlation between the water-break test results and the ice photonic structuring results, as indicated in the results in tables 1 - 5 below, suggests that the water-break test can be used to quickly test whether a surface is suitable for a mold for structures ice cubes.

The results of the tests of the different surfaces, with or without different treatments, are summarized in tables 1 - 5 below:

Table 1: Linear diffraction grating 1000 lines / mm

TWEEN20

Water with 0.01%

PE Good Pass None

TWEEN20

Table 2: Blaze diffraction grating 1800 Grooves / mm

Table 3: Linear diffraction grating 330 lines / mm

Table 4: Square pillar mold: feature size 1500 nm

Table 5: Moth-eye mold

Water

Material Treatment I Ice

1 Sonication structuring break test

Acrylic resin None 1 Failed Failed None

NA

Acrylic resin Plasma 20 min Pass None

(colorless)

Table 6: DVD Mold

I ice Water

Material Treatment Sonication structuring break test

PE None I Failed Failed None

Silver None 1 Failed Failed None

Silver plasma 20 min 1 Good Pass None

Polycarbonate None Failed Failed None

PE None Failed Failed None

All the above description has been provided for the purpose of illustration and is not meant to limit the invention in any way.