WO2018138719A1

WO2018138719A1 - Continuous release device for water soluble solids and uses thereof

Info

Publication number: WO2018138719A1
Application number: PCT/IL2018/050075
Authority: WO
Inventors: Zeev Birger
Original assignee: Neotop Water Systems Ltd.
Priority date: 2017-01-24
Filing date: 2018-01-22
Publication date: 2018-08-02

Abstract

A device for continuous release of bio-active materials, and compositions comprising same into an aqueous environment, the device comprising: an upper container configured for containing at least one bio-active material; and a lower container comprising at least one open cell medium and at least one orifice allowing access and egress of aqueous solutions between the environment and the lower container, wherein said upper container is having a distal face and a proximal face, such that, the proximal face is facing the lower container..

Description

CONTINUOUS RELEASE DEVICE FOR WATER SOLUBLE SOLIDS AND

USES THEREOF

FIELD OF THE INVENTION The present disclosure generally relates to devices for sustained release of water soluble active ingredients, such as, fertilizers and disinfectants etc.

BACKGROUND OF THE INVENTION

Water-soluble fertilizers driven into the ground, or mixed with the soil, around plants or trees initially provide an abundance of nutrients but progressively lower amount of the nutrients are provided with time.

Certain water-insoluble fertilizers, such as, urea-formaldehyde reaction products - a relatively expensive source of nitrogen, seldom provide the desired plant growth as the fertilizer is not released in accordance with plant needs.

Sustained release formulations are mainly used in the pharmaceutical industry and are designed to release the pharmaceutically active ingredients at a predetermined rate in order to maintain a stable drug concentration in the body for a specific period of time with minimum side effects.

Some slow release fertilizer compositions were developed to date. For example U.S. Patent No. 4,052,190 discloses a controlled-release fertilizer composition comprising a water-soluble fertilizer; a material having the property of reversibly swelling into a water-insoluble permeable gel surface layer in the presence of water; a gel promoter; and a sequestering agent.

U.S. Patent No. 4,321 ,078 discloses to a fertilizer composition comprising a substantially balanced plant nutrient composition in which each of the plant nutrients dissolve at a controlled rate. The fertilizer composition provides, in a slow release form, the primary nutrients, namely, nitrogen, phosphorus, calcium, sulfur, magnesium and potassium. The composition further provides iron, manganese, zinc, copper and boron. All nutrients are combined in the composition such that each dissolves at a controlled rate over a prolonged period of time, thereby providing the amounts of plant nutrients required for optimal plant growth.

U.S. Patent No. 8,617,284 discloses cellulose based sustained release macronutrient compositions for use as fertilizers. The compositions include a macronutrient compound adsorbed on the surface of a hydroxyapatite phosphate nanoparticles; and a medium containing cellulose and/or lignin, having a plurality of cavities, wherein said nanoparticles are dispersed within the cavities of said medium.

Slow release devices for delivery of fertilizers currently known in the art are based on manual or automatic gates, valves and/or pumps, which are designed to deliver fertilizers upon demand. These devices, however, require a control unit, and are usually expensive.

Slow release compositions may also be beneficial for decontamination of water reservoirs, as shown, for example, in McKnight et al. (Water Resources Division, M.S. 407 The U.S. Geological Survey). McKnight et al. disclose that slow delivery of copper(II) sulfate disinfectant to a water reservoir in low concentrations results with better extermination of nuisance algae, without the side-effects often witnessed when providing the entire amount of disinfectants at one shot.

There is still a need for devices enabling efficient and cost effective slow release of active ingredients to planters and water reservoirs.

SUMMARY OF THE INVENTION

The present invention relates to devices that allow controlled release of water soluble active agent(s) into an aqueous environment over a prolonged period of time while avoiding exposure of the environment to harmful levels of the active agent(s), as may occur when the total amount of the active ingredient(s) is released at a single release. Thus, according to some aspects there are provided herein devices and uses thereof for controlled release, continuous release, extended release and/or sustained release of compositions comprising active ingredients, wherein the release is induced by exposure to water. In some embodiments, the device may comprise an upper (or top) container and a lower (or bottom) container. In some embodiments, the upper and lower containers may be connected to one another. The upper container is configured to contain at least one active agent, or a composition comprising same, and the lower container is configured to retard or prolong the release of said active agent from the device, according to some embodiments. The upper container comprises an external enclosure, enclosing an internal cavity, which contains said active agent, or the composition comprising same, according to some embodiments. In some embodiments the lower container comprises at least one orifice and an open cell medium, such that, solutions can flow through the at least one orifice into, or from, the lower container. The open cell medium comprises water absorbent properties, which enable controlled access and egress of aqueous solutions from the lower container through the orifice, according to some embodiments. Thus, the lower container is configured to allow a prolonged release of water therefrom and this respect, the lower container acts as a dropper in an aqueous environment, according to some embodiments.

Due to its hydrophilic and water absorption properties, the open cell medium may absorb water from the vicinity of the device, thereby attracting water into the lower container through the orifice.

Without being bound by any theory or mechanism, the water molecules enter, optionally, in the form of water vapors, into the upper container through the open cell medium within the lower container, by capillary motion. Water vapors condensing within the internal cavity of the upper container dissolve fractions of the one or more active ingredients enclosed within the upper container. Therefore, the dissolved active ingredient(s), or composition(s) comprising same, is delivered to the environment at the vicinity of the device by flowing through the open cell medium in the lower container and then through the orifice.

In some embodiments the open cell medium may slow down the flow rate of the water and the dissolved active ingredient(s), or composition(s) comprising same, within the device, thereby providing slow release of the active ingredient(s) from the device into the environment in the vicinity of the device. In some embodiments there is provided a device for continuous release of bio- active materials, and compositions comprising same into an aqueous environment, the device comprising an upper container configured for containing at least one bio-active material; and a lower container comprising at least one open cell medium and at least one orifice allowing access and egress of aqueous solutions between the environment and the lower container, wherein said upper container is having a distal face and a proximal face, such that, the proximal face is facing the lower container.

In some embodiments said at least one open cell medium comprises an open cell sponge. In some embodiments the open cell sponge comprises open cell melamine- formaldehyde resin.

In some embodiments at least one open cell medium is water absorbent open cell medium.

In some embodiments the at least one open cell medium is configured to absorb water in an amount equals to at least 50% of its weight.

In some embodiments the proximal face is in contact with the lower container.

In some embodiments the upper container comprises at least one breather pipe extending from the distal face inwards.

In some embodiments the lower container comprises an external enclosure and an internal cavity, wherein said enclosure is having a distal segment and a proximal segment, such that the proximal segment is facing the upper container.

In some embodiments the proximal segment has a truncated cone-shaped structure.

In some embodiments the device further comprises an internal fixation element located at the proximal segment of the lower container and configured to prevent the at least one open cell medium from expanding outside the lower container. In some embodiments the lower container further comprises an additional sponge, said additional sponge is located at the proximal segment thereof, extending between the at least one open cell medium and the fixation element.

In some embodiments the additional sponge is in the form of a disk.

In some embodiments the additional sponge is made of hydrophilic material.

In some embodiments the upper container is connected to the lower container.

In some embodiments the upper container is irreversibly connected to the lower container.

In some embodiments the upper container contains said at least one bio-active material.

In some embodiments the at least one bio-active material is selected from the group consisting of pesticides, insecticides, fertilizers, disinfectants, plant protection agents, antibiotics and combinations thereof.

In some embodiments the at least one bio-active material comprises one or more fertilizers.

In some embodiments the at least one bio-active material comprises one or more disinfectants.

In some embodiments the at least one bio-active material has an aqueous solubility of at least 50 gr/L at 25°C.

In some embodiments the at least one open cell medium comprises pores having a mean diameter ranging from about 1 to about 500 μπι.

In some embodiments the device further comprises a floating element configured to maintain the device floating upon immersion thereof in liquids.

In some embodiments the aqueous environment comprises a solid substrate and the device further comprising an external fixation element configured to attach the device to a solid substrate. In some embodiments the solid substrate is soil.

In some embodiments the device is configured to continuously release the at least one active material to the aqueous environment.

In some embodiments there is provided a method for fertilizing plants comprising contacting the device of the present invented with the aqueous environment, thereby providing a continuous release of the at least one bio-active material into the aqueous environment, wherein the aqueous environment comprises soil and one or more plants, and wherein the at least one bio-active material comprises one or more fertilizers. In some embodiments the aqueous environment is a planter comprising soil and one or more plants.

In some embodiments there is provided a method for purification of water reservoirs comprising contacting the device disclosed herein with the aqueous environment, thereby providing a continuous release of the at least one bio-active material into the aqueous environment, wherein the aqueous environment is a water reservoir and wherein the at least one bio-active material comprises one or more disinfectants.

In to some embodiments, there are provided devices and uses thereof for timed release, continuous release, extended release and/or sustained release of active ingredients and compounds to their vicinity, upon exposure to water.

In some embodiments, the device comprises a top or upper container and a bottom or lower container, which are connectable to one another. The upper container is configured to contain the active agent and the lower container is configured to retard or prolong the release of said active agent from the device. The top container comprises an external enclosure, enclosing an internal cavity, which contains said active material. In some embodiments the bottom container comprises at least one orifice and contains a plurality of layers of materials allowing controlled exposure of the active agent to water. The plurality of layers of materials comprise at least one layer comprising water absorbent material and at least one layer comprising a porous material configured to allow access and egress of water from the bottom container through the orifice. In some embodiments the layer closest to or adjacent to the orifice is a layer of porous material, which allows access or egress of water to the bottom container. In some embodiments the layers comprise at least one layer of a water absorbent material located between at least two layers of the porous material. Due to its adhesion properties, the porous material may absorb water from the vicinity of the device into the bottom container through the orifice. The water molecules progress in the form of water vapors to the internal cavity of the top container through the layers by capillary motion. Condensation of water vapors in the internal cavity may fractionally dissolve the active material, and the dissolved material may pass through the layers out of the orifice to the vicinity of the device. In some embodiments the water absorbent material may diminish the rate of flow of water molecules and the dissolved active material within the device, thereby enabling slow release of the active material therefrom.

In some embodiments there is provided a device for sustained release of an active material into an aqueous environment, the device comprises a top container comprising an external enclosure and an internal cavity configured for containing the active material; and a bottom container comprising at least one first layer comprising a first porous material and least one second layer comprising a water absorbent material configured to absorb water at least 150% its weight; and at least one orifice allowing access and egress of water between the environment and the bottom container. In some embodiments the upper container is tapered toward the bottom so that the area of the cross section of the opening at the bottom of the upper container is smaller than the cross section at the widest dimension. In some embodiments the upper container enclosing the internal cavity comprises a truncated cone-shaped structure.

In some embodiments the top container is configured to be reversibly connected to the bottom container. In some embodiments the top container contains said active material. In some embodiments the active material is selected from the group consisting of a pesticide, an insecticide, a fertilizer, a disinfectant, a plant protection agent and a combination thereof. In some embodiments the active ingredient comprises a fertilizer. In some embodiments the active material comprises a disinfectant. In some embodiments the active ingredient has an aqueous solubility of at least

50 gr/L at 25°C. In some embodiments the first porous material enables capillary motion, of water within the material.

In some embodiments the first porous material comprises felt.

In some embodiments the water absorbent material comprises a material having a specific gravity of not more than 0.95 gr/ml. In some embodiments the water absorbent material has a specific gravity of in the range of 0.5 to 0.8 gr/ml.

In some embodiments the water absorbent material comprises polyacrylate. In some embodiments the polyacrylate comprises an anionic polyacrylate. In some embodiments the polyacrylate comprises a polyacrylate copolymer. In some embodiments the polyacrylate copolymer comprises a crosslinked polyacrylate copolymer. In some embodiments the crosslinked polyacrylate copolymer comprises a salt of crosslinked polyacrylic acid/polyacrylamide copolymer.

In some embodiments the second layer further comprises a second porous material. In some embodiments the second layer comprises a mixture of the second porous material with said water absorbent material. In some embodiments the second porous material comprises felt. In some embodiments the second layer comprises a super absorbent polymer/ felt mixture. In some embodiments the super absorbent polymer/ felt mixtures comprises between 0.5% to 10% super absorbent polymer. In some embodiments the super absorbent polymer / felt mixtures comprises between 1 % to 5% super absorbent polymer. In some embodiments the super absorbent polymer is configured to absorb water at least 50 times its weight.

In some embodiments the bottom container comprises at least two first layers. In some embodiments at least one second layer is positioned between two layers of said at least two first layers. In some embodiments the at least one orifice is configured for bidirectional passage of water.

In some embodiments the external enclosure is transparent. In some embodiments the device further comprises a floating element. In some embodiments the floating element is connected to the external enclosure. In some embodiments the floating element is connected to the bottom container.

In some embodiments the device further comprises a fixation element. In some embodiments the fixation element is connected to the external enclosure. In some embodiments the fixation element is connected to the bottom container

In some embodiments there is provided a device for sustained release of a water soluble material into an aqueous environment, the device comprising a first container comprising at least one first layer of a first porous material and least one second layer of a water absorbent material configured to absorb water at least 150% its weight; and at least one orifice, wherein the container is adapted to be connected to a second container.

In some embodiments the first container is adapted to be connected to the second container through screwing.

In some embodiments there is provided use of any one of the devices disclosed herein for fertilizing plants.

In some embodiments the plants are in a planter.

In some embodiments there is provided a use of any of one the devices disclosed herein for release of an active agent for purification of water reservoirs.

In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples illustrative of embodiments are described below with reference to figures attached hereto. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with a same numeral in all the figures in which they appear. Alternatively, elements or parts that appear in more than one figure may be labeled with different numerals in the different figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown in scale. The figures are listed below.

Fig. 1A schematically illustrates a continuous release device according to some embodiments.

Fig. IB schematically illustrates an open-cell sponge according to some embodiments.

Fig. 1C schematically illustrates an additional sponge according to some embodiments.

Fig. 2 schematically illustrates an upper container according to some embodiments.

Fig. 3 schematically illustrates an upper container according to some embodiments.

Fig. 4 schematically illustrates an internal fixation element according to some embodiments.

Fig. 5 schematically illustrates an internal fixation element according to some embodiments.

Fig. 6 schematically illustrates a lower container element according to some embodiments.

Fig. 7 schematically illustrates a lower container element according to some embodiments.

Fig. 8 schematically illustrates a lower container element according to some embodiments.

Fig. 9 schematically illustrates a lower container element according to some embodiments.

Fig. 10 schematically illustrates a lower container element according to some embodiments. Fig. 11 schematically illustrates a sustained release device according to some embodiments.

Fig. 12 schematically illustrates a sustained release device according to some embodiments. Fig. 13 schematically illustrates a sustained release device according to some embodiments.

Fig. 14 schematically illustrates sustained release device according to some embodiments.

Fig. 15 schematically illustrates sustained release device according to some embodiments.

Fig. 16 schematically illustrates sustained release device located inside a planter according to some embodiments.

Fig. 17 schematically illustrates three tubes filled with salt and with three flow- blocking matrices used in Example 1. Fig. 18 is a photo of a tube filled with salt and with layers of felt and SAP, which was used in Example 1.

Fig. 19 is a graph plotting the measured conductivity ^S/cm) versus the time measured in days for aqueous solutions comprising a tube, which includes a layer of SAP (triangles); a tube, which includes an air layer (squares); and a tube, which includes an layer of felt (straight line).

Fig. 20 is a graph plotting the measured conductivity ^S/cm) versus the time measured in days for aqueous solutions comprising five tubes, which include mixtures of 0% SAP/ felt (squares); 1 % SAP/ felt (diamonds); 2% SAP/ felt (triangles); 3% SAP/ felt (X marks); 4% SAP/ felt (circles); and 5% SAP/ felt (straight line). Fig. 21 is a graph plotting the measured conductivity ^S/cm) versus the time measured in days for aqueous solutions comprising: a device with a single ChemPosite disc (diamonds), a device with two ChemPosite discs (triangles), a device with three ChemPosite discs (circles), a device felt discs only (squares), only water (no device; straight line).

DETAILED DESCRIPTION OF THE INVENTION

In the following description, various aspects of the disclosure will be described. For the purpose of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the different aspects of the disclosure. However, it will also be apparent to one skilled in the art that the disclosure may be practiced without specific details being presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the disclosure. In some embodiments there are provided herein devices and uses thereof for continuous release of active ingredients at the vicinity outside the device, when exposed to water. In some embodiments the device comprises an upper container and a lower container, which are connectable to one another. In some embodiments the lower container contains at least one orifice and a filling made of at least one open cell medium, preferably an open-cell sponge, and the upper container comprises an external enclosure, enclosing an internal cavity, which contains an active ingredient.

Due to its hydrophilic properties, the at least one open cell medium may absorb water from the vicinity of the device, and even attract water from the vicinity outside the device into the lower container, through the orifice located at the distal face of the lower container. The water flows, e.g. in the form of water vapors, into the internal cavity of the upper container through the at least one porous material, e.g. by capillary motion. The active ingredient in the upper container may be in a solid/crystal form. Water in the internal cavity may dissolve parts of the active ingredient. As a result, the dissolved active ingredient can pass through the at least one open cell medium out the orifice to the external environment at the vicinity of the device. In some embodiments the at least one open cell medium is water absorbent, and thus it may slow down the flow rate of the solution comprising water and the dissolved active ingredient. This proposed mechanism enables slow release of the active ingredient from the device to the external environment. Advantageously, relatively small quantities of the active ingredient are released over time, thereby preventing exposure of the external environment to possibly hazardous high contents of the active ingredient. In some embodiments there is provided a device for continuous release of an active composition into an aqueous environment, the device comprises an upper container configured for containing said active composition; and a lower container comprising at least one open cell medium and at least one orifice allowing access and egress of aqueous solutions between the environment and the lower container.

The term "continuous release" refers to devices which enable delivery of compositions comprising bio-active materials over an extended period. Such devices release the active ingredient(s) at a relatively constant rate, and further avoid high concentrations of the active ingredient(s), which may be detrimental to the recipient or to its environment. Thus, the bio-active materials concentrations remain substantially invariant with time and within the desired range. The term encompases "prolonged release", "extended release", "modified release", "delayed release" and "sustained release".

The term "active composition" as used herein refers to a composition comprising at least one active ingredients, in accordance with the embodiments disclosed herein. Active ingredients include, but are not limited to, fertilizers, disinfectants, pesticides and/or herbicides among others.

In some embodiments upper container is configured to be connected to the lower container. In some embodiments upper container is connected to the lower container. In some embodiments upper container is configured to be irreversibly connected to the lower container. In some embodiments the upper container is irreversibly connected to the lower container. In some embodiments the upper container is configured to be reversibly connected to the lower container. In some embodiments upper container and the lower container are interconnected by a connector. The term "connected" as used herein refers to a physical attachment and includes, but is not limited to, mechanical attachments either through means, such as, nuts and bolts, or by being manufactured connected. Alternatively, connection may be established through adhesive materials and the like.

In some embodiments the upper container contains said active material. In some embodiments the active material is located in the internal cavity of the upper container. In some embodiments the active material is selected from the group consisting of pesticides, insecticides, fertilizers, disinfectants, plant protection agents, antibiotics and combinations thereof. In some embodiments the active material comprises a fertilizer. In some embodiments the active material comprises a disinfectant. In some embodiments the active material has a specific gravity higher than that of water. In some embodiments the active material has an average density higher than that of water.

In some embodiments the upper container comprises an external enclosure and an internal cavity. In some embodiments the external enclosure encloses the internal cavity.

The term "enclosure" as used herein means a chamber or compartment used to surround or partially surround at least a part of a certain cavity or space, which may be either empty or at least partially filled with materials, such as, an active composition in accordance with some embodiments. Typically, an enclosure would include walls, which separate the cavity within the enclosure from the environment outside the enclosure. The term "enclosure" is not intended to be limited to enclosures which completely surround the cavity. For example, the enclosure of the current disclosure may allow flow of fluids between the upper container and the lower container, but does not allow the direct flow of material, such as air, from the external environment to the cavity, formed inside the enclosure. Similarly, the term "enclose" as used herein means at least partially surround a cavity or space, which is formed inside the enclosure.

In some embodiments the upper container is having a distal face and a proximal face, such that the proximal face is facing the lower container. In some embodiments the proximal face is in contact with the lower container. In some embodiments the upper container comprises at least one breather pipe.

The term "extending from the distal face inwards" refers to the element being extended from the distal face towards the proximal face, but not necessarily, reaching and/or being in contact with the proximal face. Thus, in some embodiments, the length of the breather pipe is smaller than the distance between the proximal and distal faces of the upper container.

In some embodiments, the at least one breather pipe has two ends, wherein one end is attached to, or in contact with, the distal face of the upper container. In some embodiments the at least one breather pipe is configured to allow passage of air. In some embodiments the at least one breather pipe is configured to prevent passage of solid material therethrough. In some embodiments the at least one breather pipe is configured to prevent passage of dust therethrough.

Generally, breather pipes may be included in closed or partially closed devices in order to allow free passage of air in- and out of the device. Specifically, in devices, which require access and egress of fluids, such as aqueous solutions, a complementary breather pipe may be useful for maintaining substantially constant pressure inside the device. One of the obstacles of maintaining a device, which includes such a breather pipe is that substances or objects other than air may also reach the breather pipe and block the passage of air and/or contaminate the interior of the device. An air-permeable plug may allow passage of air, while preventing the entrance of contaminants into the device. Other contaminating factors, such as bacteria, mold and fungi may be eliminated from the system by using an antibacterial or biocidal plug, located at the distal face of the upper container, such as, but not limited to, plugs made of polyurethane and/or plugs comprising an antibacterial agent. Such antibacterial agents may include, for example an active chlorine agent, such as calcium hypochlorite, which is typically used as a decontaminant in swimming pools.

In some embodiments the device further comprises an air permeable plug configured to partially block the opening of the at least one breather pipe, preventing entrance of contaminants to the device through the breather pipe.

In some embodiments, the upper container further comprises at least one groove along the distal face thereof. In some embodiments, the breather pipe is extending from the groove inwards.

In some embodiments the device further comprises a plug configured to be harbored within the groove. The term 'harbored' as used herein includes, but is not limited to, contained with, encompassed, and the like. It refers to a structure of a groove that includes a plug therein, wherein the plug partially or completely prevents transfer of solid material, such as dust and other contaminants into the device, while it enables air flow therethrough, as required in substantially closed systems.

In some embodiments the at least one groove is configured to be plugged by an air permeable plug. In some embodiments the at least one groove is plugged by an air permeable plug. In some embodiments the upper container further comprises an air permeable plug. In some embodiments the air permeable plug comprises a sponge. In some embodiments the air permeable plug is an air permeable open-cell plug. In some embodiments the air permeable plug is configured to absorb water in an amount equals to at most 50% of its weight. In some embodiments the air permeable plug comprises a polyurethane sponge. In some embodiments the air permeable plug is an antibacterial air permeable plug. In some embodiments the lower container further includes at least one antibacterial agent. In some embodiments the upper container further includes at least one antibacterial agent. In some embodiments the at least on open cell medium is made of an antibacterial material.

As bacterial and/or fungal cultures may develop on water containing devices, incorporation of a biocide in the materials forming the device or included within the device (e.g. the open cell medium). The biocide comprising an antibacterial agent may be favorable. Addition of calcium hypochlorite powder to the upper container of devices of the current invention was found to slowly release small amounts of chlorine gas, which disinfected the interior of the device. It was also found that chlorine sank at the bottom of the upper container. This observation may be attributed to the fact that chlorine is heavier than air. Advantageously, as chlorine is lighter than water, it remained within the device and was not released to the environment at the vicinity of the device.

In some embodiments the at least one open cell medium is water absorbent open cell medium. In some embodiments the at least one open cell medium is configured to absorb water in an amount equals to at least 50% of its weight. In some embodiments the at least one open cell medium is configured to absorb water in an amount equals to at least 75% of its weight. In some embodiments the at least one open cell medium is configured to absorb water in an amount equals to at least 100% of its weight.

In some embodiments the at least one open cell medium is made of a water absorbent porous material. In some embodiments the open cell medium is a porous open cell medium.

In some embodiments the at least one open cell medium enables capillary motion, upon contact with water. In some embodiments the at least one open cell medium enables capillary motion of water within the material. As used herein, the terms "porous" and "porous material" are interchangeable and refer to any material that includes one or more of pores, cracks, fissures, vugs and voids extending into the material from external surfaces thereof. Further, the term "pore" includes and encompasses cracks, fissures, vugs and voids. Porous materials may include, for example, sponge, felt, paper, sand, cotton-wool silica, concrete, alumino- silicates, metals, minerals, polymers, ceramics, composites, asphalt, brick and mortar. Typically, the pores allow a fluid flow therethrough, including liquid materials, such as water and aqueous solutions. As a result, a porous material may give rise to capillary motion of water. The term "porous" should be understood both in a microscopic and in a macroscopic sense; that is, the porous material could have elements which in themselves are not porous to fluids. Accordingly, internal micro-pores, cavities between carrier particles, channels inside or through the porous material, and related structures are all included within the scope of "pores". As used herein, the term "adhesion" is the tendency of dissimilar particles or surfaces to cling to one another.

The terms "capillary motion" and "capillary action" as used herein are interchangeable and refer to the ability of a liquid, such as, but not limited to water, to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. Such action may be witnessed upon contacting water with hair of a paintbrush, with porous materials such as paper cotton-wool and felt.

Without wishing to be bound by any theory or mechanism, water may be introduced into the device through the orifice(s), which is located on the lower container remote from the upper container, which includes the active material. The water molecules are absorbed into the at least one open cell medium and proceed through capillary action towards the upper container, where they may be contacted with the active material. The term "open-cell" is intended to indicate a structure having a series of interconnected passageways that define a substantially open porosity. The term "open cell medium" is to be understood as a porous medium with interconnecting porosity. The porous medium is understood to be a two-phase product with voids and solid portions, wherein the voids are interconnected, and the solid portions, which define the voids, are also interconnected. As a result, such structures have a plurality of pores where inner surfaces of individual pores are accessible from neighboring pores in contrast to a closed-cell structure where individual pores may be self- contained. Open cell materials include, but are not limited to, foam and foam-like materials, cloth and cloth-like materials and polymeric material. The term "plurality" refers to two or more individual items.

In some embodiments the at least one open cell medium comprises pores having a mean diameter ranging from about 1 to about 500 μπι. In some embodiments the at least one open cell medium comprises pores having a mean diameter ranging from about 5 to about 400 μπι. In some embodiments the at least one open cell medium comprises pores having a mean diameter ranging from about 10 to about 100 μπι. In some embodiments the at least one open cell medium comprises pores having a mean diameter ranging from about 100 to about 400 μπι.

In some embodiments the at least one open cell medium comprises an open cell sponge. In some embodiments the at least one open cell medium is made of a material selected from the group consisting of open cell melamine foam, open cell melamine- formaldehyde resin, open cell polyurethane foam, open cell urea-formaldehyde resin, open-cell polyether foam, open-cell polyester foam, open cell unsaturated polyester resin, open cell epoxy resin, open-cell phenol-formaldehyde resin, open-cell polyvinyl acetal foam, open-cell polyvinyl acetate foam, open-cell vinyl foam, open-cell acrylic foam, open-cell polystyrene foam, open-cell nylon foam, open-cell cyanoacrylate foam, open-cell silicone foam, open-cell polyethylene foam, open-cell polyvinyl butyral foam, open-cell polyvinyl neoprene foam, open-cell polyvinyl alcohol foam, open-cell latex foam, open-cell polyisoyanate foam, open-cell cellulose, open-cell cotton, open-cell paper, open-cell starch, open-cell felt, open-cell polyvinyl alcohol and any combination thereof. Each possibility is a separate embodiment of the invention. In some embodiments the at least one open cell medium comprises open cell melamine-formaldehyde resin. In some embodiments the at least one open cell medium consists of open cell melamine-formaldehyde resin.

In some embodiments the at least one open cell medium has specific gravity lower than that of water. In some embodiments the at least one open cell medium comprises a material having a specific gravity of not more than about 0.95 gr/ml. In some embodiments the at least one open cell medium comprises a material having a specific gravity of not more than about 0.75 gr/ml. In some embodiments the at least one open cell medium comprises a material having a specific gravity of not more than about 0.5 gr/ml. In some embodiments the at least one open cell medium has a specific gravity of in the range of about 0.01 to about 0.5 gr/ml. In some embodiments the at least one open cell medium has a specific gravity of in the range of about 0.03 to about 0.3 gr/ml. In some embodiments the at least one open cell medium has a specific gravity of in the range of about 0.05 to about 0.2 gr/ml.

As used herein, the term "about" refers to a range of values ± 20%, or ± 10% of a specified value. For example, the phrase "a specific gravity of in the range of about 0.01 to about 0.5 gr/ml" includes ± 20% of both 0.01 gr/ml and 0.5 gr/ml.

In some embodiments the lower container comprises an approximately cylindrical shape, having a substantially elliptic cross section. In some embodiments the at least one open cell medium is approximately the shape of a rectangular cuboid having a substantially quadrangular cross section. In some embodiments the open cell medium is inserted into the cylindrical lower container through the round cross section. In some embodiments the surface of the quadrangular cross section is larger than the surface of the elliptic cross section, when the at least one open cell medium is not inserted in the lower container. In some embodiments the at least one open cell medium is compressed when inside the lower container. In some embodiments the at least one open cell medium is compressed when inside the lower container. In some embodiments the at least one open cell medium enables better capillary motion to water when compressed compared to its expanded state. It was found that compression of an open cell sponge provides an enhanced capillary motion capability. This can be achieved with a standard open cell sponge, which is usually provided in rectangular blocks, when compressed in a cylindrical container or dropper, where the surface of the cylindrical container is smaller than the corresponding surface of the sponge. It was specifically witnessed that the capillary motion of water in such systems is faster in the corners of the sponge.

In some embodiments the lower container comprises an external enclosure and an internal cavity. In some embodiments the external enclosure of the lower container is having a distal segment and a proximal segment, such that the proximal segment is facing the upper container. In some embodiments the proximal segment has a truncated cone shaped structure. In some embodiments the proximal segment tapered toward the bottom such that the area of the cross section at the proximal segment is larger than the cross section at the distal segment. In some embodiments the proximal segment has a truncated cone shaped structure, such that the lower container is configured to provide the water into a central position of the at least one open cell medium.

The term 'central position' as used herein, refers to a two-dimensional center, rather than to a three dimensional center. For example, a three dimensional shaped medium, such as a sponge, comprises a surface comprising length and width, and depth. A central position of this medium would is considered as a center of the surface, or in other words, an area, which is located substantially in the middle of both the length and the width of the medium. An illustration is presented in Figs. 1 and 9 (where open cell sponges 175 and 975 include two dimensional centers 192 and 992 respectively). In some embodiments the upper container is configured to provide the water into a central position of the at least one open cell medium. In some embodiments the upper container is configured to provide the water into a central position of the lower container. In some embodiments the internal cavity is configured to provide the water into a central position of the at least one open cell medium. In some embodiments the internal cavity is configured to provide the water into a central position of the lower container. In some embodiments the cone shape comprises a base and a vertex, wherein the base is in proximity to the upper container and has a larger diameter than that of the vertex, which is located remote from the upper container.

The terms "cone" and "cone shaped" as used herein are interchangeable and refer to a structure which enables provision of a fluid through a relatively narrow orifice. Cones are typically round three dimensional shapes. This term includes, but not limited to shapes having a base and a vertex, wherein the base has a larger diameter than that of the vertex. This term includes, but not limited to frusta, such as truncated cones. With relation to the current disclosure the terms "cone" is meant to describe such a shape that allows gravitational flow of water from the internal cavity, which under operation is located above the lower container, to the at least one open cell medium of the lower container. This is achieved by a wider diameter of the top of lower container than the diameter of its body. It is to be understood that a body, which comprises a truncated cone-shaped structure may be conically truncated all along its length or over part of its length, for example as portrayed in Figs. 1, 6, 7, 8 and 9 elements 165, 665, 765, 865 and 965.

Without wishing to be bound by any theory or mechanism, the water vapors, which reach the internal cavity of the upper container, create a humid environment, which facilitates a condensation of water drops in the internal cavity. These water drops may slowly drip on the walls of the upper container, dissolve some active material, which is present therein and gravitate towards the lower container. This would result in a high concentration of the active material in the internal bounds of the device, relative to low concentration of active material its interior. Moreover, due to the intrinsic properties of compressed open-cell media, liquid flow would be faster in the periphery next to the walls, than in the center. As a result, the total flow of the solution containing the active material, would increase. It was found that when constructing the device, such that the lower container is configured for dripping the solution to the center of the at least one open cell medium in lower container, the solution flows slowly down the medium, thereby retarding the release of the active material and providing slow release thereof from the device through the orifice(s). In some embodiments the upper container is tapered toward the bottom so that the area of the cross section of the opening at the bottom of the upper container is smaller than the cross section at the widest dimension. In some embodiments the upper container enclosing the internal cavity of the upper container comprises a truncated cone-shaped structure.

In some embodiments the internal cavity of the upper container is cone-shaped. In some embodiments the external enclosure is cone-shaped. In some embodiments the internal cavity comprises a cone-shaped structure. In some embodiments the external enclosure comprises a cone-shaped structure. In some embodiments the lower container comprises a truncated cone-shaped structure.

In some embodiments the cone shape comprises a base and a vertex, wherein the base is remote from the lower container and has a larger diameter than that of the vertex, which is located in proximity to the lower container.

In some embodiments the device further comprises an internal fixation element configured to prevent the at least one open cell medium from expanding outside the lower container. In some embodiments the device further comprises an internal fixation element configured to prevent the at least one open cell medium from expanding towards the upper container. In some embodiments the internal fixation element is located at the proximal segment of the lower container. In some embodiments the device further comprises an internal fixation element configured to fix the at least one open cell medium to the lower container. In some embodiments the internal fixation element comprises at least one orifice. In some embodiments the internal fixation element comprises a plurality of orifices. In some embodiments the at least one orifice of the internal fixation element is configured for bidirectional passage of water. In some embodiments the internal fixation element is configured for bidirectional passage of water.

Without wishing to be bound by any theory or mechanism, an open cell sponge may expand upon absorption of water. When inserted into a container having an open end, such as the lower container of the current invention, the open cell sponge may expand out of the opening. A fixation element at the open end of the container may prevent such expansion and keep the integrity of the device. Such fixation element should not prevent the free passage of water. Also, the fixation element should fit in the open end of the container. In some embodiments the internal fixation element comprises a truncated cone-shaped structure.

The term "located" is interchangeable with the term '"placed" usually referring to the position of the element relative to structural elements within the device. Located does not necessarily refer to an irreversible connection.

In some embodiments the lower container further comprises an additional sponge. In some embodiments the additional sponge is in the form of a disk. In some embodiments the additional sponge is located at the proximal segment of the lower container, extending between the at least one open cell medium and the internal fixation element. In some embodiments the additional sponge is located between the at least one open cell medium and the internal fixation element. In some embodiments the additional sponge is compressed between the at least one open cell medium and the internal fixation element. In some embodiments the additional sponge is in contact with the at least one open cell medium. In some embodiments additional sponge is in contact with the internal fixation element. In some embodiments the additional sponge is made of hydrophilic materials. In some embodiments the additional sponge is made of a water absorbent material. In some embodiments the additional sponge is made of an open cell melamine-formaldehyde resin. It is to be understood that the active material is located in the upper container, and is therefore, above both the at least one open cell medium and the additional sponge. In case the additional sponge is located over of the at least one open cell medium, the active material will be first dissolved on or in the additional sponge. As the active material may be dissolve on or in the additional sponge, it is preferable that the disk is remained wet throughout the operation period of the device. Therefore, a water absorbent and hydrophilic materials are beneficial for this application. It is also to be understood that the internal fixation element may fix the additional sponge, such that the additional sponge is placed between the upper container and the at least one open cell medium In some embodiments the active material is selected from the group consisting of pesticides, insecticides, fertilizers, disinfectants, minerals, antibiotics, hormones, plant protection agents and combinations thereof. Each possibility represents a separate embodiment of the present disclosure.

In some embodiments the active material comprises a fertilizer. In some embodiments the fertilizer is selected from the group consisting of potassium nitrate, urea, monopotassium phosphate, ammonium sulfate, potassium sulfate, ammonium phosphate, a straight N fertilizer, a Calcium ammonium nitrate fertilizer (CAN fertilizer), an NPK fertilizer, an NP fertilizer, an NK fertilizer, a high N-NPK fertilizer and a combination thereof. Each possibility represents a separate embodiment of the present disclosure. In some embodiments the fertilizer comprises an NPK fertilizer. The term "NPK fertilizer" refers to fertilizer mixtures, which may comprise active inorganic macro nutrients comprising the chemical elements nitrogen (N), phosphorous (P) and potassium (K). The names and classification of NPK fertilizers are based on the relative amounts of chemicals comprising each of these elements in the mixture. For example, a fertilizer composition, which includes 20% nitrogenous compounds, such as amines, ureas and nitrates; 20% phosphorus compounds, such phosphorus pentoxide; and 20% potassium compounds, such AS potassium oxide and potash, would be classified as a 20-20-20 or 20:20:20 fertilizer. In case only some of the element are present in the fertilizer, any of the notations may be zero. Typically, NPK fertilizer are water soluble and heavier than water. As a result, aqueous solutions containing NPK fertilizers typically also have higher densities than that of water.

In some embodiments the fertilizer is provided in a granular form.

In some embodiments the active material comprises a disinfectant. In some embodiments the active material comprises a plant protection agent.

The terms "active ingredient" and "active material" as used herein are interchangeable and refer to an ingredient that is chemically active and/or biologically active in origin. Active materials include, but are not limited to fungicides insecticides, fertilizers and a plant protection agent, which may be used for fertilizing, protecting and augmenting the growth of plants, for example in planters. Disinfectant are also under the scope of active materials and are typically used in purification of water reservoirs. In some embodiments the active material is water soluble. In some embodiments the active material has an aqueous solubility of at least 10 gr/L. In some embodiments the active material has an aqueous solubility of at least 20 gr/L. In some embodiments the active material has an aqueous solubility of at least 50 gr/L. In some embodiments the active material has an aqueous solubility of at least 100 gr/L. In some embodiments the active material has an aqueous solubility of at least 200 gr/L. In some embodiments the active material has an aqueous solubility in the range of 50 to 600 gr/L or 100 to 500 gr/L.

In some embodiments the active material form an aqueous solution upon contact with water. In some embodiments the aqueous solution has a higher density than that of water. In some embodiments the aqueous solution in heavier than water.

In some embodiments the lower container comprises a single open cell medium.

In some embodiments the orifice is configured for bidirectional passage of water. In some embodiments the external enclosure is transparent.

It is to be understood by a person skilled in the art that devices for sustained or continuous release of active materials may be either disposable or reused when the active material is consumed. In any of these case a user may visually monitor the consumption of the active material, which is located in the internal cavity through the transparent external enclosure.

In some embodiments the device further comprises a floating element, such that the device is floating upon immersion in an aqueous solution. In some embodiments the floating element comprises at least one float. In some embodiments the floating element is connected to the lower container. In some embodiments the floating element is connected to upper container. In some embodiments the floating element is connected to the external enclosure of the upper container.

In some embodiments, the floating element comprises one or more floats giving buoyancy to the device. In some embodiments, the floating element comprises multiple air-filled structures giving buoyancy to the device.

In some embodiments the device further comprises an external fixation element, configured to fix the device to the ground. In some embodiments the external fixation element is connected to the lower container. In some embodiments the external fixation element is connected to the upper container. In some embodiments the external fixation element is configured to be inserted into the ground.

In some embodiments the external fixation element is selected from the group consisting of screwing threads, stop rings, pegs, wedges, tent-pegs, pickets, pins, spikes, stakes, struts, studs, brads, chocks, cotters and combinations thereof. Each possibility represents a separate embodiment of the present disclosure. In some embodiments the external fixation element comprises a stake. In some embodiments the external fixation element comprises a stop ring. In some embodiments the external fixation element comprises screwing threads. Without wishing to be bound by any theory or mechanism, small sustained release devices according to the present disclosure may be especially beneficial for continuous release delivery of active materials to plants located in domestic planter upon exposure to water.

The term planter, as used herein includes, but not limited to, a flowerpot, a jardiniere, a flowerbox, a window box, a pot vase, a plant stand, a Cachepot and the like.

In some embodiment the device comprises a handling element. In some embodiment the upper container comprises a handling element.

In some embodiments there is provided a use of the disclosed device for plant protection. In some embodiments there is provided a use of any one of the disclosed devices for treatment of plant diseases or disorders. In some embodiments the plant diseases or disorders are selected from the group consisting of blight, wilt, Fire Blight, Alternaria Blight, Phytophthora Blight, Bacterial Blight, Cytospora Canker, Nectria Canker, Fruit Rots, Stem Rots, root rots, mushroom rots, wood rots, Asparagus Rust, Stewart's Wilt, Verticillium Wilt, Fusarium Wilt, Anthracnose, Club Root, Damping off, Downy Mildew, Galls, Leaf Blisters, Leaf Spots, Molds, Powdery Mildew, Scabs, Smuts and a combination thereof. Each possibility represents a separate embodiment of the present disclosure.

In some embodiments there is provided a use of any one of the disclosed devices for purification of water reservoirs.

In some embodiments the at least one orifice of the lower container is configured for bidirectional passage of water.

In some embodiments there is provided a method for fertilizing a plant a planter, the method comprising locating a device according to the present disclosure in the planter; adding a fertilizer to the internal cavity of the device; and watering the plant.

In some embodiments there are provided herein devices and uses thereof for sustained release of active ingredients and compounds to their vicinity, when exposed to water. The device comprises a top container and a bottom container, which are connectable to one another. In some embodiments the bottom container contains at least one orifice and a plurality of layers, and the top container comprises an external enclosure, enclosing an internal cavity, which contains an active material.

In some embodiments the layers comprise at least one layer comprising a water absorbent material located between at least two layers comprising a porous material. Due to its adhesion properties, the porous material may absorb water from the vicinity of the device into the bottom container through the orifice. The water progresses, e.g. in the form of water vapors to the internal cavity of the top container through the layers by capillary motion. Condensation of water vapors in the internal cavity may fractionally dissolve the active material, and the dissolved material may pass through the layers out the orifice to the vicinity of the device. In some embodiments the water absorbent material may down regulate the rate of passing of water molecules and the dissolved active material, thereby enabling slow release of the active material from the device. Such slow release prevents exposure of the environment to possibly hazardous high contents of the active material.

In some embodiments there is provided a device for sustained release of an active material into an aqueous environment, the device comprises a top container comprising an external enclosure and an internal cavity configured for containing said active material; and a bottom container comprising at least one first layer of a first porous material and least one second layer of a water absorbent material configured to absorb water at least 150% its weight and at least one orifice. In some embodiments top container is configured to be connected to the bottom container. In some embodiments top container is configured to be reversibly connected to the bottom container. In some embodiments top container is reversibly connected to the bottom container. In some embodiments top container and the bottom container are screwed to one another. In some embodiments top container and the bottom container are reversibly screwed to one another. In some embodiments top container and the bottom container are interconnected by a connector.

In some embodiments the external enclosure encloses the internal cavity.

In some embodiments the internal cavity is configured to provide the water into a central position of the first layer. In some embodiments the internal cavity is configured to provide the water into a central position of the bottom container. The term 'central position' as used herein, refers to a two-dimensional center, rather than to a three dimensional center. For example, a three dimensional object, such as a layer, comprises a surface comprising length and width, and depth. A central position of the object would is considered as a center of the surface, or in other words, an area, which is located substantially in the middle of both the length and the width of the object. An illustration is presented in Fig. 11 (object 1160).

In some embodiments the internal cavity is cone-shaped. In some embodiments the external enclosure is cone-shaped. In some embodiments the internal cavity comprises a cone-shaped structure. In some embodiments the external enclosure comprises a cone-shaped structure.

In some embodiments the cone shape comprises a base and a vertex, wherein the base is remote from the bottom container and has a larger diameter than that of the vertex, which is located in proximity to the bottom container.

In some embodiments the internal cavity is truncated cone-shaped. In some embodiments the external enclosure is truncated cone-shaped. In some embodiments the internal cavity comprises a truncated cone-shaped structure. In some embodiments the external enclosure comprises a truncated cone-shaped structure.

In some embodiments the truncated cone shape comprises a top base and a bottom base, wherein the top base is remote from the bottom container and has a larger diameter than that of the bottom base, which is located in proximity to the bottom container.

In some embodiments the top container comprises a base. In some embodiments the base adjacent to the bottom container, when the bottom container and top container are connected. In some embodiments the base comprises a barrier and at least one opening. In some embodiments the barrier is configured to block passages of fluids, such as water. In some embodiments the at least one opening is configured to allow passages of fluids, such as water therethrough. In some embodiments the opening is located in a center of the base, thereby enabling access and egress of water to a center of the bottom container. In some embodiments the base comprises a diameter. In some embodiments the opening comprises a diameter. In some embodiments the barrier comprises a diameter. In some embodiments the diameter of the base is at least twice larger than the diameter of the opening. In some embodiments the diameter of the base is at least four times larger than the diameter of the opening. In some embodiments the diameter of the base is at least six times larger than the diameter of the opening. In some embodiments the diameter of the base is at least ten times larger than the diameter of the opening.

Without wishing to be bound by any theory or mechanism, the water vapors, which reach the internal cavity of the top container, create a humid environment, which facilitates a condensation of water drops in the internal cavity. These water drops may slowly drip on the walls of the top container, dissolve some active material, which is present therein and gravitate towards the bottom container. This would result in a high concentration of the active material in the internal bounds of the device, relative to low concentration of active material its interior. Moreover, due to the intrinsic properties of porous materials, liquid flow would be faster in the periphery next to the walls, than in the center. As a result, the total flow of the solution containing the active material, would increase. It was found that when constructing the top container, such that the internal cavity is configured for dripping the solution to the center of the bottom container, the solution flows slowly down the layers, thereby retarding the release of the active material and providing slow release thereof from the device through the orifice.

In some embodiments the top container contains said active material. In some embodiments the active material is located in the internal cavity.

In some embodiments the active material is heavier than water. In some embodiments the active material has a specific gravity higher than that of water. In some embodiments the active material has an average density higher than that of water.

In some embodiments the active material is selected from the group consisting of a pesticide, an insecticide, a fertilizer, a disinfectant, minerals, antibiotics, hormones, a plant protection agent and a combination thereof. Each possibility represents a separate embodiment of the present disclosure.

In some embodiments the active material comprises a fertilizer. In some embodiments the fertilizer is selected from the group consisting of potassium nitrate, urea, monopotassium phosphate, ammonium sulfate, potassium sulfate, ammonium phosphate, a straight N fertilizer, a Calcium ammonium nitrate fertilizer (CAN fertilizer), an NPK fertilizer, an NP fertilizer, an NK fertilizer, a high N-NPK fertilizer and a combination thereof. Each possibility represents a separate embodiment of the present disclosure. In some embodiments the fertilizer comprises an NPK fertilizer. In some embodiments the fertilizer is provided in a granular form.

In some embodiments the active material is water soluble. In some embodiments the active material has an aqueous solubility of at least 10 gr/L. In some embodiments the active material has an aqueous solubility of at least 20 gr/L. In some embodiments the active material has an aqueous solubility of at least 50 gr/L. In some embodiments the active material has an aqueous solubility of at least 100 gr/L. In some embodiments the active material has an aqueous solubility of at least 200 gr/L. In some embodiments the active material has an aqueous solubility in the range of 50 to 600 gr/L or 100 to 500 gr L.

In some embodiments the first porous material enables capillary motion, upon contact with water.

Without wishing to be bound by any theory or mechanism, water may be introduce into the device through the orifice(s), which is located on the bottom container remote from the top container, which includes the active material. The water molecules are absorbed into the first porous material and proceed through capillary action towards the top container, where they may be contacted with the active material.

In some embodiments the first porous material comprises felt. In some embodiments the first porous material consists of felt. In some embodiments the water absorbent material comprises a material having specific gravity lower than that of water. In some embodiments the water absorbent material comprises a material having specific gravity lower than 0.95 gr/ml. In some embodiments the water absorbent material comprises a material having specific gravity lower than 0.9 gr/ml. In some embodiments the water absorbent material comprises a material having specific gravity lower than 0.85 gr/ml. In some embodiments the water absorbent material comprises a material having specific gravity lower than 0.80 gr/ml. In some embodiments the water absorbent material comprises a material having specific gravity lower than 0.75 gr/ml.

In some embodiments the water absorbent material comprises a specific gravity of not more than 0.95 gr/ml. In some embodiments the water absorbent material comprises a specific gravity of not more than 0.90 gr/ml. In some embodiments the water absorbent material comprises a specific gravity of not more than 0.85 gr/ml. In some embodiments the water absorbent material comprises a specific gravity of not more than 0.80 gr/ml. In some embodiments the water absorbent material comprises a specific gravity of not more than 0.75 gr/ml. In some embodiments the water absorbent material comprises a specific gravity in the range of 0.4 to 0.9 gr/ml. In some embodiments the water absorbent material comprises a specific gravity in the range of 0.5 to 0.8 gr/ml. In some embodiments the water absorbent material comprises a specific gravity in the range of 0.6 to 0.7 gr/ml. In some embodiments the water absorbent material comprises polyacrylate. In some embodiments the water absorbent material comprises an anionic polyacrylate. In some embodiments the water absorbent material comprises alkali polyacrylate. In some embodiments the water absorbent material comprises sodium polyacrylate. In some embodiments the water absorbent material comprises potassium polyacrylate. In some embodiments the water absorbent material comprises polyacrylamide. In some embodiments the water absorbent material comprises a polyacrylate copolymer. In some embodiments the water absorbent material comprises a crosslinked polyacrylate copolymer. In some embodiments the water absorbent material comprises a salt of crosslinked polyacrylic acid/polyacrylamide copolymer. The terms "polyacrylate" and "acrylate polymer" as used herein are meant to describe any polymer prepared from at least one monomer which is acrylic acid, it salts or derivatives. Some non-limiting examples of monomers for production of polyacrylate include acrylic acid, deprotonated acrylic acid, such as sodium of potassium acrylate, alkyl acrylate, such as methyl acrylate and ethyl acrylate, methacrylic acid, deprotonated methacrylic acrylic acid, such as sodium of potassium methacrylic acrylate, alkyl methacrylic acrylate, such as methyl methacrylic acrylate and ethyl methacrylic acrylate, acrylamide, methacrylamide, acrylonitrile and methacrylonitrile. Copolymers of such monomers with other acrylic or non- acrylic monomers are also in the scope of polyacrylates. The term "anionic polyacrylate" as used herein refers to any polyacrylate having a plurality of negatively charged carboxylate moieties. Some non-limiting examples of such polymers are alkali acrylate polymers, such as sodium acrylate polymer and potassium acrylate polymer and the like. Copolymers prepared from appropriate monomers with other acrylic or non-acrylic monomers are also in the scope of anionic polyacrylates. In some embodiments the second layer further comprises a second porous material. In some embodiments the second layer consists of the water absorbent material and the second porous material. In some embodiments the second layer consists of the water absorbent material. In some embodiments the second layer comprises a mixture of said second porous material with the water absorbent material. In some embodiments the mixture is a uniform mixture.

In some embodiments the second layer consists of a mixture of said second porous material with the water absorbent material. In some embodiments the mixture comprises between 0.1% to 20% w/w of the water absorbent material. In some embodiments the mixture comprises between 0.5% to 15% w/w of the water absorbent material. In some embodiments the mixture comprises between 0.5% to 12% w/w of the water absorbent material. In some embodiments the mixture comprises between 0.5% to 12% w/w of the water absorbent material. In some embodiments the mixture comprises between 0.5% to 10% w/w of the water absorbent material. In some embodiments the mixture comprises between 0.5% to 7% w/w of the water absorbent material. In some embodiments the mixture comprises between 0.5% to 5% w/w of the water absorbent material. In some embodiments the mixture comprises between 0.5% to 4% w/w of the water absorbent material. In some embodiments the mixture comprises between 0.8% to 4% w/w of the water absorbent material. In some embodiments the mixture comprises between 1% to 4% w/w of the water absorbent material.

In some embodiments the water absorbent material is configured to absorb water at least 200% its weight. In some embodiments the water absorbent material is configured to absorb water at least 300% its weight. In some embodiments the water absorbent material is configured to absorb water at least 500% its weight. In some embodiments the water absorbent material is configured to absorb water at least 1000% its weight. In some embodiments the water absorbent material is configured to absorb water at least 2000% its weight. In some embodiments the water absorbent material is configured to absorb water at least 5000% its weight. In some embodiments the water absorbent material is configured to absorb water at least 10000% its weight. In some embodiments the water absorbent material is configured to absorb water at least 15000% its weight.

In some embodiments the second porous material comprises felt. In some embodiments the second porous material consists of felt. In some embodiments the second porous material enables capillary motion, upon contact with water.

In some embodiments the water absorbent material comprises a super absorbent polymer. In some embodiments the water absorbent material consists of a super absorbent polymer. In some embodiments the second layer comprises a super absorbent polymer/ felt mixture. In some embodiments second layer consists of a super absorbent polymer/ felt mixture.

Some mixtures of super absorbent polymer and felt are known in the art and are typically employed for water absorption applications, such as medical and surgical pads, diapers and the like. Non limiting examples of such mixtures include the commercial Chem-Posite™ l lC-560 and Chem-Posite™ l lC-450 marketed by Emerging Technologies.

In some embodiments the super absorbent polymer is configured to absorb water at least 10 times its weight. In some embodiments the super absorbent polymer is configured to absorb water at least 30 times its weight. In some embodiments the super absorbent polymer is configured to absorb water at least 50 times its weight. In some embodiments the super absorbent polymer is configured to absorb water at least 70 times its weight. In some embodiments the super absorbent polymer is configured to absorb water at least 90 times its weight. In some embodiments the super absorbent polymer is configured to absorb water at least 120 times its weight. In some embodiments the super absorbent polymer is configured to absorb water at least 160 times its weight.

As used herein the term "super-absorbent polymer" (SAP) means materials that form hydrogels on contact with water. One preferred type of hydrogel-forming, absorbent gelling material is based on polyacrylic acid. Hydrogel-forming polymeric materials of this type are those which, upon contact with liquids such as water, imbibe such fluids and thereby form hydrogels. Some of these absorbent gelling materials include, but not limited to, substantially water-insoluble, partially cross-linked, hydrogel forming polymeric or co-polymeric materials prepared from polymerizable, unsaturated monomers of acrylate or its derivatives. Further examples of such super-absorbent polymers are hydrolyzed starch-acrylonitrile graft copolymers, starch acrylic acid graft copolymers, saponified vinyl acetate- acrylic ester copolymers, hydrolyzed acrylonitrile copolymers, hydrolyzed acrylamide copolymers, anionic acrylate copolymers, ethylene maleic anhydride copolymers, isobutylene-maleic anhydride copolymers, poly- (vinylsulfonic acid), poly(vinylphosphonic acid), poly(vinylphosphoric acid), poly(vinylsulfuric acid), sulfonated polystyrene, poly(aspartic acid), polylactic acid, and any combination thereof. The super-absorbent polymers may be in any form, for example as beads, granules, a foam, fibers, threads, and/or a film. In some embodiments, the water absorbent material forms a gel upon contact with water. In some embodiments the gel has a specific gravity lower than that of water. In some embodiments the gel has a gravity lower than 0.95 gr/ml. In some embodiments the gel has a specific gravity lower than 0.9 gr/ml. In some embodiments the gel has a specific gravity lower than 0.85 gr/ml. In some embodiments the gel has a specific gravity lower than 0.80 gr/ml. In some embodiments the gel has a specific gravity lower than 0.75 gr/ml.

Without wishing to be bound by any theory or mechanism, a super absorbent polymer, which form a gel lighter than water may allow the 'floating' of the gel preventing it from gravitating down the bottom container through the first layer. Moreover, such polymer may enable blocking of water, while allowing limited passage of water vapors, thus diminishing the rate of flow of water molecules and the dissolved active material within the device, thereby enabling slow release of the active material therefrom. On the other hand, an active material heavier than water may slowly sink and pass through the formed gel, as both the material and its aqueous solution are heavier than the gel. In some embodiments the bottom container comprises at least two first layers. In some embodiments the bottom container comprises two first layers. In some embodiments the bottom container comprises a single second layer.

In some embodiments the bottom container comprises two first layers and a single second layer. In some embodiments the second layer is positioned between the two first layers. In some embodiments the single second layer is positioned between the two first layers.

In some embodiments the least one second layer is positioned between two layers of the at least two first layer. In some embodiments the first layers and the second layers are alternately aligned.

In some embodiments the orifice is configured for bidirectional passage of water.

In some embodiments the external enclosure is transparent.

It is to be understood by a person skilled in the art that devices for sustained release of active materials may be either disposable or reused when the active material is consumed. In any of these case a user may visually monitor the consumption of the active material, which is located in the internal cavity through the transparent external enclosure.

In some embodiments the device further comprises a floating element. In some embodiments the device further comprises a float. In some embodiments the floating element is connected to the bottom container. In some embodiments the floating element is connected to the external enclosure.

In some embodiments the device further comprises a fixation element. In some embodiments the fixation element is connected to the bottom container. In some embodiments the fixation element is connected to the external enclosure.

In some embodiments the fixation element is configured to be inserted into the ground. In some embodiments the fixation element is configured to be inserted into the ground thereby affixing the device to the ground.

In some embodiments the fixation element is selected from the group consisting of a stop ring, a peg, a wedge, a tent-peg, a picket, a pin, a spike, a stake, a strut, a stud, a brad, a chock, a cotter and a combination thereof. Each possibility represents a separate embodiment of the present disclosure. In some embodiments the fixation element comprises a stake. In some embodiments the fixation element comprises a stop ring. In some embodiments there is provided a device for sustained release, the device comprising a first container comprising at least one first layer of a porous material and least one second layer of a water absorbent material configured to absorb water at least 150% its weight; and an orifice, wherein said container is adapted to be connected to a second container. In some embodiments the first container is adapted to be connected to the second container through screwing.

In some embodiments there is provided a use of the disclosed device for fertilizing plants.

In some embodiments there is provided a use of the disclosed device for fertilizing plants in planters.

Without wishing to be bound by any theory or mechanism, small sustained release devices according to the present disclosure may be especially beneficial for sustained release delivery of active materials to plants located in domestic planter upon exposure to water. In some embodiments there is provided a use of the disclosed device for plant protection. In some embodiments there is provided a use of the disclosed device for treatment of plant diseases or disorders. In some embodiments the plant diseases or disorders are selected from the group consisting of blight, wilt, Fire Blight, Alternaria Blight, Phytophthora Blight, Bacterial Blight, Cytospora Canker, Nectria Canker, Fruit Rots, Stem Rots, root rots, mushroom rots, wood rots, Asparagus Rust, Stewart's Wilt, Verticillium Wilt, Fusarium Wilt, Anthracnose, Club Root, Damping off, Downy Mildew, Galls, Leaf Blisters, Leaf Spots, Molds, Powdery Mildew, Scabs, Smuts and a combination thereof. Each possibility represents a separate embodiment of the present disclosure. In some embodiments there is provided a use of the disclosed device for purification of water reservoirs.

Reference is now made to Figs. 1A, IB and 1C which schematically illustrate an exploded view of continuous delivery device 100 comprising an upper container 105, which comprises distal face 110 and proximal face 115; a lower container 155, which comprises a proximal segment 160, a distal segment 165 and an orifice 190; an internal fixation element 125, an open-cell sponge 175 and an additional sponge 170.

Lower container 155 includes an external enclosure 158 and an internal cavity 159 configured to include open-cell sponge 175. Lower container 155 is having a distal segment 165 and a proximal segment 160, such that proximal segment 160 is facing upper container 105. Lower container 155 is configured to be connected to upper container 105, such that an integral sealed device is formed during operation of device 100. Lower container 155 further includes orifice 190 located at the bottom of the distal segment 165 for allowing passage of aqueous solutions into and from device 100. Lower container 155 is configured to contain open cell sponge 175.

Upper container 105 is having distal face 110 and proximal face 115, such that, the proximal face is facing lower container 155. Upper container 105 is configured to be connected to lower container 155, such that an integral sealed device is formed during operation of device 100. Upper container 105 is configured to contain at least one bio- active material, such as a fertilizer, including granular fertilizer.

Open-cell sponge 175 is configured to be inserted into lower container 155, and is contained within internal cavity 159 of lower container 155 during operation of device 100. Open-cell sponge 175 is made of open cell foam, such as an open-cell melamine-formaldehyde foam. It is water absorbent, and is configured to absorb water in an amount equals to at least 50% of its weight.

Open-cell sponge 175 is located inside lower container 155 and below additional sponge 170, and therefore it is the first to absorb water from the environment outside device 100, and the last to release aqueous solutions to the environment outside device 100. Open-cell sponge 175, includes an open cell material having pores having a mean diameter ranging from about 1 to about 500 μπι. The pores enable capillary motion, upon contact with water. Therefore, upon passage of water into continuous release device 100, the water contacted with open-cell sponge 175 may elevate through capillary motion and reach additional sponge 170 at proximal segment 160 of lower container 155.

Open-cell sponge 175 may also absorb aqueous solutions from additional sponge 170 and/or from upper container 105 and transfer the solutions to distal segment 165 and subsequently to the environment outside of device 100 through orifice 190. Due to the high absorption potential of open cell foams, open-cell sponge 175 enables slow passage of aqueous solutions through lower container 155 of continuous release device 100.

Additional sponge 170 is configured to be inserted into proximal segment 160 of lower container 155, such that it is located above open-cell sponge 175 during operation of device 100. Additional sponge 170 is made of a hydrophilic material and is therefore able to absorb aqueous solutions. It is the first to absorb aqueous solutions of the active material approaching from upper container 105, and it may provide these solutions to the adjacent open-cell sponge 175. Additional sponge 170 is shaped in the form of a disk in accordance with the cross section shape of proximal segment 160 of lower container 155.

Orifice 190 is located in the bottom of lower container 155 and is configured for bidirectional passage of water. Stated otherwise, orifice 155 allows passage of water from the environment outside device 100 into lower container 155, where it is absorbed in open-cell sponge 175; and passage of aqueous solutions from device 100 to its exterior environment.

When water arrives from open-cell sponge 175 and/or from additional sponge 170, to upper container 105 a humid environment may form, which may lead to condensation of water droplets. Said droplets may dissolve any water-soluble matter, such as the granular active material, contained in upper container 105 and drop back as an aqueous solution to open-cell sponge 175 at proximal segment 160 of lower container 155.

Proximal segment 160 of lower container 155 comprises a truncated cone- shaped structure, whereby said solution drops to open-cell sponge 175 at its center 192. By the center of open-cell sponge 175, it is meant the two center dimensional thereof, i.e. the center top surface of open-cell sponge 175. This type of structure represses the flow of the aqueous solution to the perimeter of lower container 155, where material flow is faster. Therefore the cone shape of proximal segment 160 of lower container 155 allows slower release of the aqueous solution from continuous release device 100. Internal fixation element 125 is located at proximal segment 160 of lower container 155 and is configured to prevent open cell sponge 175 from expanding outside lower container 155. Internal fixation element 125 is further configured to fix additional sponge 170 such that additional sponge 170 is located at proximal segment 160, extending between open cell sponge 175, and such that additional sponge 170 it is in contact with open cell sponge 175. Internal fixation element 125 comprises orifices 130, thus allowing flow of aqueous solutions therethrough from upper container 105 to open- cell sponge 175 in lower container 155.

Reference is now made to Fig. 2, which schematically illustrates an upper container 205₄which is an alternative to upper container 105 of continuous release device 100. Upper container 205 may therefore be assembled with other elements of device 100. Upper container 205 comprises distal face 210, breather pipe 214, proximal face 215, a plug 213, a conical groove 211 and a cylindrical groove 212.

Upper container 205 is having distal face 210 and proximal face 215, such that, proximal face 215 is facing a lower container of a continuous release device. Upper container 205 is configured to contain an active material, such as a pesticide, an insecticide, a fertilizer, a disinfectant, a plant protection agents, an antibiotic etc.

When water arrive to the internal civility of upper container 205 through proximal face 215 and/or through breather pipe 214 ,a humid environment may form, which may lead to condensation of water droplets. Said droplets may dissolve any water-soluble matter, such as the active material, contained in upper container 205 and drop as an aqueous solution through proximal face 215.

Breather pipe 214 extends from distal face 210 inwards into the internal cavity of upper container 205. It is configured to allow passage of air therethrough and thus avoid pressure fluctuation when a continuous release device operates.

Cylindrical groove 212 is located along distal face 210 of upper container 205. It is connected to breather pipe 214 and is configured to be plugged with plug 213.

Plug 213 is an air permeable plug configured to partially block the opening of breather pipe 214, preventing entrance of contaminants to the device through breather pipe 214. Plug 213 is configured to be harbored within cylindrical groove 212. Plug 213 is preferably made of a sponge having moderate water absorption properties, such as polyure thane sponge.

Conical groove 211 is located along distal face 210 of upper container 205. It is connected to cylindrical groove 212. The cone shape of conical groove 211 allow pouring of water by a user into the internal cavity of upper container 205. For example, in case that a continuous release device comprising upper container 205 is dry, a user may remove plug 213 and pour water in to the device through cylindrical groove 212 and breather pipe 214. Plug 213 is configured to absorb water in an amount equals to at most 50% of its weight, thereby allowing the intentional filling of conical groove 211 with water by a user, resulting in slow dripping of water into upper container 205.

Reference is now made to Fig. 3, which schematically illustrates an upper container 305₄which is an alternative to upper container 105 of continuous release device 100. Upper container 305 may therefore be assembled with other elements of device 100. Upper container 305 comprises distal face 310, breather pipe 314, proximal face 315, a plug 313, a conical groove 311, a cylindrical groove 312 and grasping stripes 320.

Upper container 305 is having distal face 310 and proximal face 315, such that, proximal face 315 is facing a lower container of a continuous release device. Upper container 305 is configured to contain an active material, such as a disinfectant. When water arrive to the internal civility of upper container 305 through proximal face 315 and/or through breather pipe 314 ,a humid environment may form, which may lead to condensation of water droplets. Said droplets may dissolve any water-soluble matter, such as the active material, contained in upper container 305 and drop as an aqueous solution through proximal face 315.

Breather pipe 314 extends from distal face 310 inwards into the internal cavity of upper container 305. It is configured to allow passage of air therethrough and thus avoid pressure fluctuation when a continuous release device operates.

Cylindrical groove 312 is located along distal face 310 of upper container 305. It is connected to breather pipe 314 and is plugged with plug 313.

Plug 313 is an air permeable plug configured to partially block the opening of breather pipe 314, preventing entrance of contaminants to the device through breather pipe 314. Plug 313 is harbored within cylindrical groove 312. Plug 313 is preferably made of a sponge having moderate water absorption properties, such as polyurethane sponge.

Conical groove 311 is located along distal face 310 of upper container 305. It is connected to cylindrical groove 312. The cone shape of conical groove 311 may allow pouring of water by a user into the internal cavity of upper container 305. For example, in case that a continuous release device comprising upper container 305 is dry, a user may remove plug 313 and pour water in to the device through cylindrical groove 312 and breather pipe 314. Plug 313 is configured to absorb water in an amount equals to at most 50% of its weight, thereby allowing the intentional filling of conical groove 311 with water by a user, resulting in slow dripping of water into upper container 305.

Grasping stripes 320 are located along the perimeter of upper container 305. They enable better grasp of the upper container 305, and therefore a better grasp of an entire continuous release device having upper container 305.

Reference is now made to Fig. 4, which schematically illustrates an internal fixation element 425, which is an alternative to internal fixation element 125 of continuous release device 100. Internal fixation element 525 may therefore be assembled with other elements of device 100. Internal fixation element 425 comprises orifices 430, allowing flow of aqueous solutions therethrough from an upper container to a lower container of continuous release devices. Similarly, internal fixation element 425 comprises a central orifice 426, allowing flow of aqueous solutions therethrough from an upper container to a lower container of continuous release devices.

Internal fixation element 425 further comprises fixation slits 431, which are configured to connect internal fixation element 425 to a lower container, through the insertion of fixing pins (such as fixing pins 861 of lower container 855) into fixation slits 431. Reference is now made to Fig. 5 which schematically illustrates an internal fixation element 525₄which is an alternative to internal fixation element 125 of continuous release device 100. Internal fixation element 525 may therefore be assembled with other elements of device 100.

Internal fixation element 525 comprises a central orifice 526, allowing flow of aqueous solutions therethrough from an upper container to a lower container of continuous release devices.

Reference is now made to Fig. 6, which schematically illustrates a lower container 655₄which is an alternative to lower container 155 of continuous release device 100. Lower container 655 may therefore be assembled with other elements of device 100. Lower container 655 comprises a proximal segment 660, a distal segment 665, external fixation element 656, a sealing ring 672, a barrier ring 674, a stopping ring 676, a bottom orifice 690 and side orifices 691.

Lower container 655 includes an external enclosure and an internal cavity. Lower container 655 is having distal segment 665 and proximal segment 660, such that proximal segment 660 may face and connect to an upper container of a continuous release device. Lower container 655 further includes orifice 690 located at the bottom of its distal segment 665 for allowing passage of aqueous solutions into and from lower container 655. Lower container 655 is configured to contain at least one open cell sponge, such as open-cell sponge 175; an internal fixation element, such as internal fixation element 125, internal fixation element 425 or internal fixation element 525; and an additional sponge, such as additional sponge 170.

Bottom orifice 690 is located in the bottom of lower container 655 and is configured for bidirectional passage of aqueous solutions. In other words, orifice 655 allows access and egress of aqueous solutions from and to the outside of lower container 655. Side orifices 691 are located at the sides of lower container 655 and function similarly. Water and aqueous solutions may pass into and from lower container 655 through side orifices 691.

Proximal segment 660 of lower container 655 comprises a truncated cone- shaped structure.

Sealing ring 672 is located at the proximal segment 660 of lower container 655. It is configured to seal a continuous delivery device, such as continuous delivery device 100, when used with lower container 655 as a lower container, such that when lower container 655 is connected to an upper container, the device is sealed at the contact point between the upper container and sealing ring 672. Barrier ring 674 is located at the proximal segment 660 of lower container 655. When lower container 655 is used as a part of a delivery device, such as continuous delivery device 100, it may be connected to an upper container, such as an upper container 105. In such formation barrier ring 674 may prevent lower container 655 from penetrating into upper container 105 deeper than desirable. Stopping ring 676 is located at the proximal segment 660 of lower container 655. When lower container 655 is inserted into the ground as a part of a of a continuous delivery device, stopping ring 676 is configured to prevent the sinking of the device into the ground.

External fixation element 656 is connected to the exterior of lower container 655. External fixation element 656 is configured to be inserted into the ground. It is shaped as screwing threads, such that it enables the fixing of continuous release devices having lower container 655 to the ground. This feature makes such continuous release devices suitable for slow release of active materials to planters, where the entire device is to be held vertically with respect to the ground. Reference is now made to Fig. 7, which schematically illustrates a lower container 755₄which is an alternative to lower container 155 of continuous release device 100. Lower container 755 may therefore be assembled with other elements of device 100. Lower container 755 comprises a proximal segment 760, a distal segment 765, external fixation element 756 and an orifice 790;

Lower container 755 includes an external enclosure and an internal cavity. Lower container 755 is having distal segment 765 and proximal segment 760, such that proximal segment 760 may face and connect to an upper container of a continuous release device. Lower container 755 further includes orifice 790 located at the bottom of its distal segment 765 for allowing passage of aqueous solutions into and from lower container 755. Lower container 755 is configured to contain at least one open cell sponge, such as open-cell sponge 175; an internal fixation element, such as internal fixation element 125, internal fixation element 425 or internal fixation element 525; and an additional sponge, such as additional sponge 170. Orifice 790 is located in the bottom of lower container 755 and is configured for bidirectional passage of aqueous solutions. In other words, orifice 755 allows access and egress of aqueous solutions from ant to the outside of lower container 755.

Proximal segment 760 of lower container 755 comprises a truncated cone- shaped structure. External fixation element 756 is connected to the exterior of lower container

755. External fixation element 756 is configured to be inserted into the ground and into water reservoirs. It is shaped as screwing threads, such that it enables the fixing of continuous release devices having lower container 755 to the ground. This feature makes such continuous release devices suitable for slow release of active materials to planters, where the entire device is to be held vertically with respect to the ground. The screwing threads further enables screwing of a nut 757, to continuous release devices having lower container 755. Nut 755 may be connected to, or a part of an additional element, which enables the mounting of continuous release devices having lower container 755. For example nut 757 may be a part of a floating element in case that the device is used in water reservoirs. This may make continuous release devices having lower container 755 suitable for slow release of active materials to water reservoirs, where the entire device may act as a buoy.

Reference is now made to Fig. 8, which schematically illustrates a lower container 855₄which is an alternative to lower container 155 of continuous release device 100. Lower container 855 may therefore be assembled with other elements of device 100. Lower container 855 comprises a proximal segment 860, a distal segment 865, external fixation element 856, opening 862, fixing pins 861 and an orifice 890;

Lower container 855 includes an external enclosure and an internal cavity. Lower container 855 is having distal segment 865 and proximal segment 860, such that proximal segment 860 may face and connect to an upper container of a continuous release device, such as upper container 105, 205 or 305. Lower container 855 further includes orifice 890 located at the bottom of its distal segment 865 for allowing passage of aqueous solutions into and from lower container 855. Lower container 855 is configured to contain at least one open cell sponge, such as open-cell sponge 175; an internal fixation element, such as internal fixation element 125, internal fixation element 425 or internal fixation element 525; and an additional sponge, such as additional sponge 170.

Orifice 890 is located in the bottom of lower container 855 and is configured for bidirectional passage of aqueous solutions. In other words, orifice 855 allows access and egress of aqueous solutions from and to the outside of lower container 855.

External fixation element 856 is connected to the exterior of lower container 855. External fixation element 856 is configured to be inserted into the ground. It is shaped as screwing threads, such that it enables the fixing of continuous release devices having lower container 855 to the ground. This feature makes such continuous release devices suitable for slow release of active materials to planters, where the entire device is to be held vertically with respect to the ground.

Fixing pins 861 are located at the top of proximal segment 860. They are configured to connect an internal fixation element (such as internal fixation element 425) to lower container 855, through the insertion of fixing pins 861 into matching fixation slits (such as fixation slits 431 of fixation element 425). Opening 862 is located at proximal segment 860 of lower container 855. It is configured for an insertion of at least one open cell sponge, such as open cell sponge 175 of continuous release device 100.

Proximal segment 860 of lower container 855 comprises a truncated cone- shaped structure. When at least one open cell sponge is inserted through opening 862, a pouring or dripping of aqueous solutions into lower container 855 from its top end will result in arrival of these solutions to the two dimensional center of lower container 855, through opening 862.

Reference is now made to Fig. 9, which schematically illustrates a lower container 955₄which is an alternative to lower container 155 of continuous release device 100. Lower container 955 may therefore be assembled with other elements of device 100. Lower container 955 comprises a proximal segment 960, a distal segment 965, external fixation element 956, opening 962, open cell sponge 975, fixing pins 961 and an orifice 990;

Lower container 955 includes an external enclosure and an internal cavity. Lower container 955 is having distal segment 965 and proximal segment 960, such that proximal segment 960 may face and connect to an upper container of a continuous release device, such as upper container 105, 205 or 305. Lower container 955 further includes orifice 990 located at the bottom of its distal segment 965 for allowing passage of aqueous solutions into and from lower container 955. Lower container 955 contains open-cell sponge 975; an internal fixation element, such as internal fixation element 125, internal fixation element 425 and internal fixation element 525; and an additional sponge, such as additional sponge 170.

Orifice 990 is located in the bottom of lower container 955 and is configured for bidirectional passage of aqueous solutions. In other words, orifice 990 allows access and egress of aqueous solutions from and to the outside of lower container 955.

External fixation element 956 is connected to the exterior of lower container 955. External fixation element 956 is configured to be inserted into the ground. It is shaped as screwing threads, such that it enables the fixing of continuous release devices having lower container 955 to the ground. This feature makes such continuous release devices suitable for slow release of active materials to planters, where the entire device is to be held vertically with respect to the ground.

Fixing pins 961 are located at the top of proximal segment 960. They are configured to connect an internal fixation element (such as internal fixation element 425) to lower container 955, through the insertion of fixing pins 961 into matching fixation slits (such as fixation slits 431 of fixation element 425).

Opening 962 is located at proximal segment 860 of lower container 855. Open cell sponge 975 is squeezed into lower container 955 through opening 962.

Lower container 955 and opening 962 comprise approximately cylindrical shapes, having a substantially elliptic cross section, whereas open cell sponge 975 is approximately the shape of a rectangular cuboid having a substantially quadrangular cross section. In some embodiments the surface of the quadrangular cross section of open cell sponge 975 is larger than the surface of the elliptic cross section of opening 962, when open cell sponge 975 is not inserted in the lower container. Therefore, open cell sponge 975 is in a compressed state when inside lower container 955.

In some embodiments open cell sponge 975 enables better capillary motion to water when compressed compared to its expanded state. It was found that compression of an open cell sponge provides an enhanced capillary motion capability. It was specifically witnessed that the capillary motion of water in such systems is faster in the corners of sponges, such as open cell sponge 975.

Proximal segment 960 of lower container 955 comprises a truncated cone- shaped structure. Due to this structure a pouring or dripping of aqueous solutions into lower container 955 from its top end will result in arrival of these solutions to the two dimensional center 992 of open cell sponge 975. This construction represses the flow of the aqueous solution to the perimeter of lower container 955, where liquid flow is faster. Therefore, the cone shape of proximal segment 960 of lower container 955 allows slower release of the aqueous solution from continuous release devices having lower container 955. Reference is now made to Fig. 10, which schematically illustrates a cross section view of lower container 155 of continuous release device 100, when internal fixation element 125, an open-cell sponge 175 and an additional sponge 170 are inserted therein.

Orifice 190 is located in the bottom of lower container 155 and is configured for bidirectional passage of aqueous solutions. Stated otherwise, orifice 190 allows access and egress of aqueous solutions from and to the outside of lower container 955.

Lower container 155 comprise an approximately cylindrical shape, having a substantially elliptic cross section, whereas open cell sponge 175 is approximately the shape of a rectangular cuboid having a substantially quadrangular cross section. In some embodiments the surface of the quadrangular cross section of open cell sponge 175 is larger than the surface of the elliptic cross section of lower container 155, when open cell sponge 175 is not inserted in the lower container (as in Figs 1A and IB). Therefore, open cell sponge 175 is in a compressed state when inside lower container 155.

In some embodiments open cell sponge 175 enables better capillary motion to water when compressed compared to its expanded state. It was found that compression of an open cell sponge provides an enhanced capillary motion capability. It was specifically witnessed that the capillary motion of water in such systems is faster in the corners of sponges, such as open cell sponge 175.

Proximal segment 160 of lower container 155 comprises a truncated cone- shaped structure. Due to this structure a pouring or dripping of aqueous solutions into lower container 155 from its top end will result in arrival of these solutions to the two dimensional center 192 of open cell sponge 175. This construction represses the flow of the aqueous solution to the perimeter of lower container 155, where liquid flow is faster. Therefore, the cone shape of proximal segment 160 of lower container 155 allows slower release of the aqueous solution from continuous release devices having lower container 155.

It can also be seen that due to the cone shapes of both proximal segment 160 and when internal fixation element 125, additional sponge 170 is squeezed into a matching structure, allowing the delivery of aqueous solutions to two dimensional center 192 of open cell sponge 175. Reference is now made to Fig. 11, which schematically illustrates a sustained release device 1000 comprising a top container 1020, which comprises an external enclosure 1022 and internal cavity 1024, and a bottom container 1050, which comprises a top layer of porous material 1052, a layer of water absorbent material 1054, a bottom layer of porous material 1056 and an orifice 1058.

Bottom container 1050 is configured to be reversibly connected to top container 1020 through screwing, such that an integral sealed device is formed.

Bottom container 1050 is configured to contain top layer of porous material 1052, layer of water absorbent material 1054 and bottom layer of porous material 1056. Bottom container 1050 also includes orifice 1058 for allowing passage of aqueous solutions into and from sustained release device 1000.

Bottom layer of porous material 1056 is located inside bottom container 1050, and below layer of water absorbent material 1054, and therefore it is the first layer to absorb water from the exterior of sustained release device 1000, and the last layer to release aqueous solutions to outside sustained release device 1000. Bottom layer of porous material 1056, includes a material, such as felt, which enables capillary motion, upon contact with water. Upon passage of water into sustained release device 1000, the water contacted with bottom layer of porous material 1056 may elevate through capillary motion and reach layer of water absorbent material 1054. Layer of water absorbent material 1054 is located inside bottom container 1050, above bottom layer of porous material 1056 and below top layer of porous material 1052. It is therefore may absorb water from bottom layer of porous material 1056, and transfer it to top layer of porous material 1052. It also may absorb aqueous solutions from top layer of porous material 1052 and transfer it to bottom layer of porous material 1056. Layer of water absorbent material 1054 includes a uniform mixture of a porous material, such as felt, with a water absorbent material, such as a super absorbent polymer. Non limiting examples of such mixtures include Chem-Posite™ l lC-560 and Chem-Posite™ l lC-450 marketed by Emerging Technologies. Due to the high absorption potential of these mixtures, layer of water absorbent material 1054 enables slows passage of aqueous solutions through sustained release device 1000. The mixture comprises between 0.1 % to 20% w/w of super absorbent polymer, which is configured to absorb water at least 100 times its weight. The water absorbent material in layer of water absorbent material 1054 has specific gravity lower than that of water. Such a specific gravity prevents the water absorbent material to be swept with the flow of water towards bottom layer of porous material 1056 and orifice 1058. Top layer of porous material 1052 is located inside bottom container 1050, and above layer of water absorbent material 1054. It may absorb aqueous solutions formed in external enclosure 1022 and transfer it to layer of water absorbent material 1054. Top layer of porous material 1052, includes a material, such as, but not limited to, felt, which enables capillary motion, upon contact with water. Orifice 1058 is located in the bottom of bottom container 1050 and is configured for bidirectional passage of water. In other words, orifice 1050 allows passage of water from outside sustained release device 1000 into bottom container 1050, where it is absorbed in bottom layer of porous material 1056; and passage of aqueous solutions from sustained release device 1000 to its exterior environment. Top container 1020 is configured to be reversibly connected to bottom container

1050 through screwing, such that an integral sealed device is formed.

External enclosure 1022 encloses internal cavity 1024. External enclosure 1022 is transparent, thereby it enables visual monitoring of the capacity within internal cavity 1024. Internal cavity 1024 is confined within external enclosure 1022. It is configured to contain an active material, such as, but not limited to, a granular fertilizer. When water arrive from top layer of porous material 1052, to internal cavity 1024 a humid environment may form, which may lead to condensation of water droplets. Said droplets may dissolve any water-soluble matter contained in internal cavity 1024 and drop back as an aqueous solution to top layer of porous material 1052. Internal cavity 1024 comprises a truncated cone-shaped structure, whereby said aqueous solution drops to top layer of porous material 1052 at its center 1060. By the center of top layer of porous material 1052, it is meant the two dimensional center of the layer, i.e. the center top surface of top layer of porous material 1052. This type of structure represses the flow of the aqueous solution to the perimeter of bottom container 1050, where material flow is faster. Therefore the cone shape of internal cavity 1024 allows slower release of the aqueous solution from sustained release device 1000.

Reference is now made to Fig. 12, which schematically illustrates a sustained release device 1100 comprising a top container 1120, which comprises an external enclosure 1122 and internal cavity 1124; a bottom container 1150, which comprises a top layer of porous material 1152, a layer of water absorbent material 1154, a bottom layer of porous material 1156 and an orifice 1158; and a floating element 1162.

Bottom container 1150 is configured to contain top layer of porous material 1152, layer of water absorbent material 1154 and bottom layer of porous material 1156. Bottom container 1150 also includes orifice 1158.

Floating element 1162 is connected to the exterior of bottom container 1150. It includes a material lighter than water, which enables the floating of sustained release device 1100, which makes it suitable for slow release of active materials to water reservoirs, where the entire device may act as a buoy. Such a material lighter than water may be a uniform material, such as foamed polystyrene, or may be a material inflated by air.

Bottom layer of porous material 1156 is located inside bottom container 1150, and below layer of water absorbent material 1154.

Layer of water absorbent material 1154 is located inside bottom container 1150, above bottom layer of porous material 1156 and below top layer of porous material 1152. Layer of water absorbent material 1154 includes a uniform mixture of a porous material, such as felt, with a water absorbent material, such as a super absorbent polymer. The water absorbent material in layer of water absorbent material 1154 has specific gravity lower than that of water. Top layer of porous material 1152 is located inside bottom container 1150, and above layer of water absorbent material 1154.

Orifice 1158 is located in the bottom of bottom container 1150 and is configured for bidirectional passage of water. External enclosure 1122 encloses internal cavity 1124. External enclosure 1122 is transparent, thereby it enables visual monitoring of the capacity within internal cavity 1124.

Internal cavity 1124 is confined within external enclosure 1122. It is configured to contain an active material, such as, but not limited to, a disinfectant and comprises a truncated cone-shaped structure.

Reference is now made to Fig. 13, which schematically illustrates a sustained release device 1200 comprising a top container 1220, which comprises an external enclosure 1222 and an internal cavity 1224 containing an active material 1226; a bottom container 1250, which comprises a top layer of porous material 1252, a layer of water absorbent material 1254, a bottom layer of porous material 1256 and orifices 1258; and a fixation element 1262.

Bottom container 12501250 is configured to contain top layer of porous material 1252, layer of water absorbent material 1254 and bottom layer of porous material 1256. Bottom container 1250 also includes orifices 1258.

Fixation element 1262 is connected to the exterior of bottom container 1250. It is shaped such that it enables the fixing of sustained release device 1200 to the ground. This feature makes sustained release device 1200 suitable for slow release of active materials to planters, where the entire device is to be held vertically with respect to the ground.

Bottom layer of porous material 1256 is located inside bottom container 1250, and below layer of water absorbent material 1254.

Layer of water absorbent material 1254 is located inside bottom container 1250, above bottom layer of porous material 1256 and below top layer of porous material 1252. Layer of water absorbent material 1254 includes four layers 1264. Each one of layers 1264 includes a uniform mixture of a porous material, such as felt, with a water absorbent material, such as a super absorbent polymer. The water absorbent material in layers 1264 has specific gravity lower than that of water. Layers 1264 may be identical to one another or different from one another, so long that each includes a uniform mixture of a porous material, with a water absorbent material. Non limiting examples of such uniform mixtures include Chem-Posite™ l lC-560 and Chem-Posite™ l lC-450 marketed by Emerging Technologies. Due to the high absorption potential of these mixtures, layer of water absorbent material 1254 enables slows passage of aqueous solutions through sustained release device 1200, thereby allowing a sustained release of the active material therefrom. Typically, the uniform mixture comprises between 0.1 % to 20% w/w of super absorbent polymer, which is configured to absorb water at least 100 times its weight. The water absorbent material in layers 1264 has specific gravity lower than that of water. Such a specific gravity prevents the water absorbent material to be swept with the flow of water towards bottom layer of porous material 1256 and orifices 1258.

Top layer of porous material 1252 is located inside bottom container 1250, and above layer of water absorbent material 1254.

Orifices 1258 are located in the bottom and in the sides of bottom container 1250 and are configured for bidirectional passage of water. External enclosure 1222 encloses internal cavity 1224. External enclosure 1222 is transparent, thereby it enables visual monitoring of the capacity of active material 1226 within internal cavity 1224.

Internal cavity 1224 is confined within external enclosure 1222. It contains active material 1226. When water arrive from top layer of porous material 1252, to internal cavity 1224 a humid environment may form, which may lead to condensation of water droplets therein. Said droplets may dissolve active material 1226 and drop back as an aqueous solution of active material 1226 to top layer of porous material 1252. Internal cavity 1224 comprises a truncated cone-shaped structure, whereby said aqueous solution drops to top layer of porous material 1252 at its center. By the center of top layer of porous material 1252, it is meant the two dimensional center of the layer, i.e. the center top surface of top layer of porous material 1252. This type of structure represses the flow of the aqueous solution of active material 1226 to the perimeter of bottom container 1250, where fluid flow is faster. Therefore the cone shape of internal cavity 1224 allows slower release of the active material 1226 from sustained release device 1200. Active material 1226 is located inside internal cavity 1224. It is provided in a granular form and may include, for example a pesticide, an insecticide, a disinfectant, a plant protection agent and/or a fertilizer, such as an NPK fertilizer. Active material 1226 is water soluble, and therefore it dissolves upon contact with the water droplets in internal cavity 1224.

Reference is now made to Fig. 14, which schematically illustrates a sustained release device 1300 comprising a top container 1320, which comprises an external enclosure 1322 and an internal cavity 1324 containing an active material 1326; a bottom container 1350, which comprises a layer of porous material 1352, a layer of water absorbent material 1354, a layer of porous material 1356, a layer of water absorbent material 1364, a layer of porous material 1366 and an orifice 1358; and a stop ring 1362.

Bottom container 1350 is configured to contain layer of porous material 1352, layer of water absorbent material 1354, layer of porous material 1356, layer of water absorbent material 1364 and layer of porous material 1366. Bottom container 1350 also includes orifice 1358.

Stop ring 1362 is connected to the exterior of bottom container 1350. It is shaped such that it prevents the submergence of sustained release device 1300 in the ground. This feature makes sustained release device 1300 suitable for slow release of active materials to planters, where the entire device is to be held vertically with respect to the ground of the planter.

Layer of porous material 1366 is located inside bottom container 1350, and below layer of water absorbent material 1364, and therefore it is the first layer to absorb water from the exterior of sustained release device 1300, and the last layer to release aqueous solutions to outside sustained release device 1300. Layer of porous material 1366, includes a material, such as, but not limited to, felt, which enables capillary motion, upon contact with water. Upon passage of water into sustained release device 1300, the water contacted with layer of porous material 1366 may elevate through capillary motion and reach layer of water absorbent material 1364. Layer of water absorbent material 1364 is located inside bottom container 1350, above layer of porous material 1366 and below layer of porous material 1356. It is therefore may absorb water from layer of porous material 1366, and transfer it to layer of porous material 1356. It also may absorb aqueous solutions from layer of porous material 1356 and transfer it to layer of porous material 1366. Layer of water absorbent material 1364 includes a uniform mixture of a porous material, such as felt, with a water absorbent material, such as a super absorbent polymer. Non limiting examples of such mixtures include Chem-Posite™ l lC-560 and Chem-Posite™ l lC-450 marketed by Emerging Technologies. Due to the high absorption potential of these mixtures, layer of water absorbent material 1364 enables slows passage of aqueous solutions through sustained release device 1300, thereby enabling a sustained release of the active material therefrom. Typically, the mixture comprises between 0.1 % to 20% w/w of super absorbent polymer, which is configured to absorb water at least 100 times its weight. The water absorbent material in layer of water absorbent material 1364 has specific gravity lower than that of water. Such a specific gravity prevents the water absorbent material to be swept with the flow of water towards layer of porous material 1366 and orifice 1358.

Layer of porous material 1356 is located inside bottom container 1350, above layer of water absorbent material 1364 and below layer of water absorbent material 1354. Layer of porous material 1356, includes a material, such as, but not limited to, felt, which enables capillary motion, upon contact with water. Upon passage from layer of water absorbent material 1364, the water contacted with layer of porous material 1356 may elevate through capillary motion and reach layer of water absorbent material 1354. Layer of water absorbent material 1354 is located inside bottom container 1350, above layer of porous material 1356 and below layer of porous material 1352. It is therefore may absorb water from layer of porous material 1356, and transfer it to layer of porous material 1352. It also may absorb aqueous solutions of active material 1326 from layer of porous material 1352 and transfer it to layer of porous material 1356. Layer of water absorbent material 1354 includes a uniform mixture with similar characteristics to those describe for layer of water absorbent material 1364, although the two layers are not necessarily identical. Layer of water absorbent material 1354 enables slows passage of aqueous solutions through sustained release device 1300, thereby enabling a sustained release of the active material therefrom.

Layer of porous material 1352 is located inside bottom container 1350, above layer of water absorbent material 1354 and below top container 1320. Layer of porous material 1352, includes a material, such as, but not limited to, felt, which enables capillary motion, upon contact with water. Upon passage from layer of water absorbent material 1354, the water contacted with layer of porous material 1352 may elevate through capillary motion and reach internal cavity 1324.

Orifice 1358 is located in the bottom of bottom container 1350 and is configured for bidirectional passage of water.

External enclosure 1322 encloses internal cavity 1324. External enclosure 1322 is transparent, thereby it enables visual monitoring of the capacity of active material 1326 within internal cavity 1324.

Internal cavity 1324 is confined within external enclosure 1322. It contains active material 1326. When water arrive from layer of porous material 1352, to internal cavity 1324 a humid environment may form, which may lead to condensation of water droplets therein. Said droplets may dissolve active material 1326 and drop back as an aqueous solution of active material 1326 to layer of porous material 1352. Internal cavity 1324 comprises a truncated cone-shaped structure, whereby said aqueous solution drops to layer of porous material 1352 at its center.

Active material 1326 is located inside internal cavity 1324. It is provided in a granular form and may include, for example a pesticide, an insecticide, a disinfectant, a plant protection agent and/or a fertilizer, such as an NPK fertilizer. Active material 1326 is water soluble, and therefore it dissolves upon contact with the water droplets in internal cavity 1324.

Reference is now made to Fig. 15, which schematically illustrates a sustained release device 1400 comprising a stop ring 1462 and a first container 1450, which comprises a top layer of porous material 1452, a layer of water absorbent material 1454, a bottom layer of porous material 1456 and an orifice 1458. First container 1450 is configured to be reversibly connected to a second element (not shown), such as a second container through screwing.

Bottom container 1450 is configured to contain top layer of porous material 1452, layer of water absorbent material 1454 and bottom layer of porous material 1456. Bottom container 1450 also includes orifice 1458 for allowing passage of aqueous solutions into and from sustained release device 1400.

Bottom layer of porous material 1456 is located inside container 1450, and below layer of water absorbent material 1454. Bottom layer of porous material 1456, includes a material, such as, but not limited to, felt, which enables capillary motion, upon contact with water. Upon passage of water into container 1450, the water contacted with bottom layer of porous material 1456 may elevate through capillary motion and reach layer of water absorbent material 1454.

Layer of water absorbent material 1454 is located inside bottom container 1450, above bottom layer of porous material 1456 and below top layer of porous material 1452. Layer of water absorbent material 1454 includes a uniform mixture of a porous material, such as felt, with a water absorbent material, such as a super absorbent polymer. Non limiting examples of such mixtures include Chem-Posite™ l lC-560 and Chem-Posite™ l lC-450 marketed by Emerging Technologies. Due to the high absorption potential of these mixtures, layer of water absorbent material 1454 enables slows passage of aqueous solutions container 1450. Typically, the mixture comprises between 0.1% to 20% w/w of super absorbent polymer, which is configured to absorb water at least 100 times its weight. The water absorbent material in layer of water absorbent material 1454 has specific gravity lower than that of water. Such a specific gravity prevents the water absorbent material to be swept with the flow of water towards bottom layer of porous material 1456 and orifice 1458.

Top layer of porous material 1452 is located inside bottom container 1450, and above layer of water absorbent material 1454. Top layer of porous material 152, includes a material, such as, but not limited to, felt, which enables capillary motion, upon contact with water. Orifice 1458 is located in the bottom of bottom container 1450 and is configured for bidirectional passage of water.

Stop ring 1462 is connected to the exterior of bottom container 1450. It is shaped such that it prevents the submergence of sustained release device 1400 in the ground.

Reference is now made to Fig. 16, which schematically illustrates a sustained release device 1500 inserted into a planter 1580. Sustained release device 1500 comprises a top container 1520, which comprises an external enclosure 1522 and an internal cavity 1524 containing fertilizer 1526; a bottom container 1550, which comprises a top layer of porous material 1552, a layer of water absorbent material 1554, a bottom layer of porous material 1556 and orifices 1558. Device 1500 further comprises a stop ring 1562 and a fixation element 1562.

Planter 1580 contains ground 1582, into which flowers 1584 are planted and sustained release device 1500 is inserted. Typically, watering flowers 1584 in planter 1580 will allow their growth. Advantageously, growth of flowers 1584 will be further enhanced by exposing them to fertilizer 1526 for prolonged periods of time.

Bottom container 1550 is configured to contain top layer of porous material 1552, layer of water absorbent material 1554 and bottom layer of porous material 1556. Bottom container 1550 further includes orifice 1558. Fixation element 1563 is connected to the exterior of bottom container 1550. It is shaped such that it enables the fixing of sustained release device 1500 to ground 1582. This feature makes sustained release device 1500 suitable for slow release of fertilizer 1526 to flowers 1584 in planter 1580, where the entire device is to be held vertically with respect to ground 1582. Stop ring 1562 is connected to the exterior of bottom container 1550. It is shaped such that it prevents the submergence of sustained release device 1500 in ground 1582.

Bottom layer of porous material 1556 is located inside bottom container 1550, and below layer of water absorbent material 1554. Layer of water absorbent material 1554 is located inside bottom container 1550, above bottom layer of porous material 1556 and below top layer of porous material 1552.

Top layer of porous material 1552 is located inside bottom container 1550, and above layer of water absorbent material 1554.

Orifice 1558 is located in the bottom of bottom container 1550 and is configured for bidirectional passage of water. Water originated in the watering of planter 1580 may flow into device 1500 through orifice 1558 and aqueous solutions of fertilizer 1526 may flow out device 1500 through orifice 1558 to ground 1582, and lead to fertilizing flowers 1584.

External enclosure 1522 encloses internal cavity 1524. External enclosure 1522 is transparent, thereby it enables visual monitoring of the capacity of fertilizer 1526 within internal cavity 1524.

Internal cavity 1524 is confined within external enclosure 1522. It contains fertilizer 1526.

Fertilizer 1526 is located inside internal cavity 1524. It is provided in a granular form and may include, for example an NPK fertilizer. Fertilizer 1526 is water soluble, and therefore it dissolves upon contact with water in internal cavity 1524.

While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, additions and subcombinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced be interpreted to include all such modifications, additions and sub-combinations as are within their true spirit and scope.

EXAMPLES Example 1- blocking flow of salt solutions by SAP

In order to test the flow of water soluble materials through a matrix, which includes a super absorbent polymer (SAP), three tubes were filled with salt and with three flow-blocking matrices, as exemplified in Fig. 17. Tube 1600 was filled with salt 1608, layer of felt 1606, layer of SAP 1604 and layer of felt 1602. Granular table salt was used in the experiment and the SAP used was commercial LiquiBlock™ 42K powder provided by Emerging Technologies Tube 1620 was filled with salt 1628, layer of felt 1626, air layer 1624 and layer of felt 1622. Tube 1640 was filled with salt 1648, and layer of felt 1642.

The three tubes were opened in the ends proximal to the felt layers (layer 1602, layer 1622 and layer 1642) and submerged in water glasses (glass 1610, glass 1630 and glass 1650). As a result, the material in each tube gradually absorbed some of the water in each glass. In order to evaluate the flow of salt through the tube, the conductivity of the solutions in the glasses (solution 1612, solution 1632 and solution 1652) were monitored prior to the submergence of the tubes and for the next six days, once daily. An increase of salt concentration in a solution would result in an increase of the measured conductivity, therefore the flow rate of salt solutions in each glass can be monitored by conductivity. A table plotting typical sodium chloride concentrations versus the resultant conductivity may be found in the art, for example in CN 101713785.

Fig. 18 is a photograph of a tube 1700 corresponding to tube 1600, which was used in the experiment. Tube 1700 is filled with salt 1708, layer of felt 1706, layer of SAP 1704 and layer of felt 1702 and is immersed in water 1712 inside glass 1710.

Table 1 depicts the measured conductivity in μ8/ϋπι in each one of the three tubes before the experiment (day 0) and in the following six days of the experiment.

Fig. 19 is a corresponding graph plotting the measured conductivity ^S/cm) versus the time measured in days for tube 1600, which includes layer of SAP 1604 (triangles); tube 1620, which includes air layer 1624 (squares); and tube 1640, which includes layer of felt 1642 (straight line). Table 1 : Changes in conductivity during six days

From Table 1 and Fig. 19 it is seen that the conductivity of the solution with the tube that includes a continuous matrix of felt (tube 1640) is gradually increasing from about 300 μ&/θΏΐ to about 5100 μ8/αη. In other words, the salt concentration therein is increasing rapidly. On the other hand the solutions of the two other tubes which include an air block (tube 1620) or a SAP block (tube 1600) remain with substantially unchanged conductivities in the range of 300-340 μ&/θΏΐ, which are approximately the original conductivities of the water used in the experiment. It can be understood that, whereas the felt allows free flow of aqueous salt solutions, air-block as well as the felt- block used in the experiment prevent the flow of salt trough the tube.

Example 2- blocking flow of salt solutions by varying concentrations of SAP

After establishing that a layer consisting of pure SAP would lead to a substantially complete blocking of the flow aqueous NaCl solutions, a second experiment was conducted in order to better understand the relation of flow rate to concentration of SAP in similar devices comprising layers of SAP/felt mixtures.

In the experiment, six tubes similar to the tubes of Example 1 were filed with granulated sodium chloride salt; a first layer of felt, a layer comprising SAP/felt mixture; and another layer of felt. The tested tubes were similar to tube 1600 of Fig. 7, with the exception that SAP/felt mixtures were used instead of pure SAP. The SAP/felt mixtures were uniform and were prepared by mixing LiquiBlock¹"¹ SAP 42K powder and felt in ratios of 1 %, 2%, 3% 4% and 5% of SAP. A sixth tube, in which the central layer did not include SAP was used for reference. The six tubes were opened in the ends proximal to the felt layers and submerged in water glasses. As a result, the material in each tube gradually absorbed some of the water in each glass. In order to evaluate the flow of salt through the tube, the conductivity of the solutions in the glasses were monitored prior to the submergence of the tubes and for the next seven days, once daily.

Table 2 depicts the measured conductivity in μ8/ϋπι in each one of the six tubes before the experiment (day 0) and in the following seven days of the experiment.

Fig. 20 is a corresponding graph plotting the measured conductivity ^S/cm) versus the time measured in days for tubes, which include mixtures of 0% SAP/ felt (squares); 1 % SAP/ felt (diamonds); 2% SAP/ felt (triangles); 3% SAP/ felt (X marks); 4% SAP/ felt (circles); and 5% SAP/ felt (straight line).

Table 2: Conductivity changes during seven days with varying SAP concentration

From Table 2 and Fig. 20 it is seen that the conductivities of the solutions into which tubes that include up to 3% SAP/felt mixture are inserted, are gradually increasing with time. The solution into which a tube with no SAP was inserted exhibits a steep rise of conductivity from 400 μ8/αη to 10350 μ8/αη. The solution into which a tube with 1% SAP/ felt mixture was inserted exhibits a more moderate rise of conductivity from 405 μ8/αη to 4447 μ8/αη. The solution into which a tube with 2% SAP/ felt mixture was inserted exhibits a yet more moderate rise of conductivity from 402 μ8/ϋπι to 1573 μ8/αη. The solution into which a tube with 3% SAP/ felt mixture was inserted exhibits slow rise of conductivity from 401 μ8/ϋπι to 933 μ8/ϋπι.

A trend of slower release of salt is observed in accordance to increasing the ratio of SAP in the SAP/ felt mixture forming the SAP/ felt mixture layer. As a result, mixtures of 4% and 5% SAP/ felt lead to essentially blocking the flow of aqueous salt solution through the tube.

Example 3- blocking flow of fertilizer solutions in sustained release devices

In this experiment three sustained release devices were prepared similar to sustained release device 1500 in Fig. 16, wherein the active material consisted of a red 20:20:20 fertilizer and layer of water absorbent material 1554 comprised one (device A), two (device B) or three (device C) disks of commercial ChemPosite 11C-560 provided by Emerging Technologies, which includes a uniform SAP/ felt mixtures. A fourth sustained release device (device D) included felt instead of a ChemPosite 11C- 560.

Devices A through D were put into water tubs, which are accordingly denominated tubs A, B, C and D. A fifth tube E was a reference tub into which no device was inserted. The conductivity of the solution in each tub was measured before the experiments and once a day for ten days. Table 3 depicts the measured conductivity in μ8/αη in each one of the five tubs before the experiment (day 0) and in the following ten days of the experiment.

Fig. 21 is a corresponding graph plotting the measured conductivity ^S/cm) versus the time measured in days for tubs A (device A, a single ChemPosite disc; diamonds), B (device B, two ChemPosite discs; triangles), C (device C, three ChemPosite discs; circles), D (device D, only felt discs; squares) and E (no device; straight line). Table 3: Conductivity changes ten seven days with sustained release devices

From Table 3 and Fig. 21 it is seen that the conductivities of the solutions into which any king of device is inserted, are gradually increasing with time. For example, device D, which included felt filling, which excluded felt, gave rise to a rapid increase of the fertilizer concentration in water tub D, and therefore to a rapid increase of the conductivity of the solution therein from about 600 μ8/αη to about 13000 μ 8/αη within the ten days of the experiment.

Another trend which may be concluded from Table 3 and Fig. 21 is that insertion of discs comprising felt/ SAP mixtures (ChemPosite 1 lC-560 discs), leads to a slower rate of increase of the fertilizer concentration in the appropriate tubs. As more discs are inserted the rate is slower. For example, device A, which included a single ChemPosite 11C-560 disc gave rise to an increase of the conductivity of the solution in water tub A from about 600 μ&/θΏΐ to about 11000 μ8/αη within the ten days of the experiment. This increase rate of fertilizer concentration is a little slower than the corresponding rate in tub D. A more prominent slowing of conductivity increase was witnessed when using device B, which included two ChemPosite 11C-560 discs. This device gave rise to an increase of the conductivity of the solution in the corresponding water tub from about 600 μ&/θΏΐ to about 6300 μ8/αη in the ten days of the experiment. A yet more prominent slowing of conductivity increase was witnessed when using device C, which included three ChemPosite l lC-560 discs. The device gave rise to an increase of the conductivity of the solution in the corresponding water tub from about 600 μ8/αη to about 4000 μ8/αη in the ten days of the experiment.

The conductivity of the solution in tub E also gradually increased although additional electrolyte was not inserted. This result in a consequence of salt concentration increase resulting from gradual evaporation of water in this tube during the experimental period. As mentioned, a further advantage of the disclosed devices is the transparency of the external enclosures, which enabled visual inspection of the red fertilizer during the experiment.

The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without undue experimentation and without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. The means, materials, and steps for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention.

Claims

A device for continuous release of bio-active materials, and compositions comprising same into an aqueous environment, the device comprising: an upper container configured for containing at least one bio-active material; and a lower container comprising at least one open cell medium and at least one orifice allowing access and egress of aqueous solutions between the environment and the lower container, wherein said upper container is having a distal face and a proximal face, such that, the proximal face is facing the lower container.

The device of claim 1 , wherein said at least one open cell medium comprises an open cell sponge.

The device of claim 2, wherein said open cell sponge comprises open cell melamine-formaldehyde resin.

The device of claim 1, wherein at least one open cell medium is water absorbent open cell medium.

The device of claim 1 , wherein said at least one open cell medium is configured to absorb water in an amount equals to at least 50% of its weight.

The device of claim 1 , wherein the proximal face is in contact with the lower container.

The device of claim 1, wherein said upper container comprises at least one breather pipe extending from the distal face inwards. The device of claim 1 , wherein said lower container comprises an external enclosure and an internal cavity, wherein said enclosure is having a distal segment and a proximal segment, such that the proximal segment is facing the upper container.

The device of claim 8, wherein the proximal segment has a truncated cone- shaped structure.

The device of claim 8, further comprising an internal fixation element located at the proximal segment of the lower container and configured to prevent the at least one open cell medium from expanding outside the lower container.

The device of claim 10, wherein said lower container further comprises an additional sponge, said additional sponge is located at the proximal segment thereof, extending between the at least one open cell medium and the fixation element.

The device of claim 10, wherein said additional sponge is in the form of a disk.

The device of claim 10, wherein said additional sponge is made of hydrophilic material.

The device of claim 1 , wherein said upper container is connected to the lower container.

The device of claim 14, wherein said upper container is irreversibly connected to the lower container. The device of claim 1 , wherein said upper container contains said at least one bio-active material.

The device of claim 1, wherein said at least one bio-active material is selected from the group consisting of pesticides, insecticides, fertilizers, disinfectants, plant protection agents, antibiotics and combinations thereof.

The device of claim 17, wherein said at least one bio-active material comprises one or more fertilizers.

The device of claim 17, wherein said at least one bio-active material comprises one or more disinfectants.

The device of claim 17, wherein said at least one bio-active material has an aqueous solubility of at least 50 gr/L at 25°C.

The device of claim 1 , wherein the at least one open cell medium comprises pores having a mean diameter ranging from about 1 to about 500 μπι.

The device of claim 1 , further comprising a floating element configured to maintain the device floating upon immersion thereof in liquids.

The device of claim 1, wherein the aqueous environment comprises a solid substrate and the device further comprising an external fixation element configured to attach the device to a solid substrate.

The device of claim 23, wherein the solid substrate is soil.

The device of claim 24, configured to continuously release the at least one active material to the aqueous environment. A method for fertilizing plants comprising contacting the device of claim 1 with the aqueous environment, thereby providing a continuous release of the at least one bio-active material into the aqueous environment, wherein the aqueous environment comprises soil and one or more plants, and wherein the at least one bio-active material comprises one or more fertilizers.

The method of claim 26, wherein said aqueous environment is a planter comprising soil and one or more plants.

A method for purification of water reservoirs comprising contacting the device of claim 1 with the aqueous environment, thereby providing a continuous release of the at least one bio-active material into the aqueous environment, wherein the aqueous environment is a water reservoir and wherein the at least one bio-active material comprises one or more disinfectants.

A device for sustained release of an active material into an aqueous environment, the device comprising: a top container comprising an external enclosure and an internal cavity configured for containing the active material; and a bottom container comprising at least one first layer comprising a first porous material and least one second layer comprising a water absorbent material configured to absorb water in an amount which is at least 150% of its weight; and at least one orifice allowing access and egress of water between the environment and the bottom container.

30. The device of claim 26, wherein said at least one active material comprises one or more fertilizers.

31. The device of claim 26, wherein said first porous material comprises felt.

32. The device of claim 26, wherein said water absorbent material comprises polyacrylate.

33. The device of claim 26, wherein said second layer comprises a mixture of super absorbent polymer and felt.

34. A device for sustained release of a soluble material into an aqueous environment, the device comprising a first container comprising: at least one first layer of a first porous material and least one second layer of a water absorbent material configured to absorb water in an amount which is at least 150% of its weight; and at least one orifice, wherein said container is adapted to be connected to a second container.