Timing system and device and method for making the same

Abstract

A timing device for visually indicating the passage of a duration of time is disclosed. The timing device and system, in accordance with the embodiments of the invention, is sectioned into zones with different rates of reactivity and/or sensitivity, such that the zones change color or darken over a range of times. The timing device, in accordance with further embodiments of the invention, comprises a film, that is a color film, a black and white film or a combination thereof, with a photographic layer and a developer layer, which when brought together activate the device. The photographic film can be pre-exposed to light or heat to control the rate that the film changes color or darkens after being activated. Pieces of timing film, in accordance with further embodiments of the invention, have adhesion layers for attaching the pieces of timing film to perishable articles or packages containing perishable articles and are preferably configured to be dispensed from a roll or stack of the timing film.

Description

FIELD OF THE INVENTION

[0002] The invention relates to timing systems and devices and a method for making the same. More specifically, the invention relates to systems and devices for and methods of indicating the passage of a duration time.

BACKGROUND OF THE INVENTION

[0003] There are a number of different timing systems and devices, generally referred to as time-temperature indicators (TTIs) which can be used to monitor the exposure of objects to a range of temperatures over a specified period of time. In an early example, Witonsky, in U.S. Pat. No. 3,942,467 describes a time-temperature indicator with an encapsulated inner container and a pH sensitive dye solution contained therein. The device of Witonsky further has an encapsulated outer container containing an organic material which undergoes solvolysis. The outer container and the inner container are separated by a membrane. When the membrane between the inner and the outer container is broken, the contents of the containers mix and over a period of time change color thus providing an indication of the passage of a duration of time. A number of other time-temperature indicators utilize wicking techniques (such as described in U.S. Pat. No. 5,709,472 and U.S. Pat. No. 6,042,264, both issued to Prusik et al.) or diffusion layer techniques (such as described in U.S. Pat. No. 4,629,330 issued to Nichols and U.S. Pat. Nos. 5,930,206 and 5,633,835 both issued to Haas et al.). In U.S. Pat. No. 6,198,701 issued to De Jonghe et al., an electrochemical timing device is described, whereby consumption of an electrode is used to provide an indication of the passage of a duration of time.

[0004] Time-temperature indicators can have a number of different applications for indicating when an event or activity needs to take place. For example, time-temperature indicators have applications for indicating when the perishable materials have expired and need to be thrown out. Time-temperature indicators also have applications for general inventory management, for monitoring projects, activities and a host of other time and/or temperature dependent events. Therefore, there is a continued need to develop reliable timing systems and devices which can be used for a variety of different applications.

SUMMARY OF THE INVENTION

[0005] The present invention is directed to a device and system for indicating the passage of a duration of time and a method of making the same. While, the present invention is referred to herein as a timing device, it is understood that the timing device of the present invention is also sensitive to temperature. While a timing device, in accordance with the embodiments of the invention, can be configured to be more or less sensitive to temperature, the timing device will generally react, or change, at a faster rate at higher temperatures.

[0006] A timing device, in accordance with the embodiments of the present invention is a chemical-based timing device, electrochemical-based timing device, or a combination thereof. The timing device, when actuated, provides a visual indication of a passage of time. The timing device is configured as a “stand alone” indicator or, alternatively, is configured to be coupled with any number of circuits which also provide an audible signal or otherwise sense and/or store information regarding the operation of the device.

[0007] The device preferably comprises a lens, a base and means for altering the visibility of the base through the lens and thereby indicating the passage of a duration of time. The means for altering the visibility of the base through the lens preferably comprises an optical medium positioned between the lens and the base. The optical medium comprises chemicals and/or elements of a battery that react or otherwise change over time and, thereby alters the visibility of the base through the lens. For example, one or more of the materials, layers or components of the optical medium are converted from opaque to transparent or, alternatively, from transparent to opaque, thereby increasing or decreasing the visibility of the base through the lens, respectfully. Alternately, one or more of the materials, layers or components of the optical medium are dissolved or depleted, thereby altering the visibility of the base through the lens.

[0008] In accordance with the embodiments of the invention, the optical medium comprises a solid layer positioned between the lens and the base, also referred to herein as a lens coating layer, and a fluid layer positioned between the solid layer and the base. The fluid layer contains gel, water and any suitable chemical(s) required to change the solid layer from opaque to transparent, change the layer from transparent to opaque, deplete the solid layer or dissolve the solid layer, as explained in detail below. In the preferred embodiment of the invention, the solid layer is opaque and when the device is actuated, the fluid layer dissolves the solid layer over a duration of time, thereby making the base visible through the lens and indicating the passage of a duration of time.

[0009] In further embodiments of the invention, a timing device comprises an indicator between the lens and the lens coating layer to enhance the visual indication of the passage of time. Suitable indicators are fluids or solid, and can include, but are not limited to pH indicators and reactive dye indicators, which generate a color change when reacted with the fluid layer, after the fluid layer sufficiently depletes or dissolves the lens coating layer. Alternatively, the lens coating layer is a semi-porous membrane layer, wherein the indicator provides a color change when a sufficient amount of the reactive species from the fluid medium migrates through the membrane layer.

[0010] In still further embodiments of the invention, a timing device comprises a battery, wherein at least a portion of the optical medium between the solid layer and the base actively participates in an electrochemical process resulting in a visual change indicating the passage of a duration of time. In accordance with this embodiment of the invention, the battery is a galvanic cell and the optical medium comprises an electrolyte. A galvanic cell is a battery where reduction and oxidation of species within the battery will occur spontaneously as long as there is a conductive path from a first electrode of the cell to a second electrode of the cell. In operation a material within the electrolyte is plated between the base and the lens, thereby reducing the visibility of the base through the lens. Alternatively, an opaque electrode positioned between the lens and the base is depleted, thereby increasing the visibility of the base through the lens.

[0011] In still further embodiments of the invention, the battery is an electrolytic cell. An electrolytic cell requires a current from another battery, or other current source, to drive the reduction and oxidation of species within the battery. In accordance with this embodiment, a current from an external battery, or current source, flows through the battery and a material within the electrolyte is plated out between the lens and the base, thereby reducing the visibility of the base through the lens. Alternatively, an opaque electrode positioned between the lens and the base is depleted, thereby increasing the visibility of the base through the lens.

[0012] A timing device, in accordance with the embodiments of the invention, is actuated using any number of different mechanisms or combination of mechanisms. For example, where the timing device is a chemical-based timing device, the timing device is preferably formed in parts, wherein a first part comprises a first reactive region and a second part comprises a second reactive region. To form an activated device, the first part and the second part are brought together and the first reactive region and the second reactive region are held eclipsed and in contact. Alternatively, a chemical-based timing device comprises a membrane or a removable structure separating the reactive regions of the device, wherein the membrane is broken or the structure is removed to activate the device.

[0013] Where the timing device is an electrochemical-based timing device, the device is preferably actuated by a switch mechanism that closes a circuit between electrode elements of a galvanic or an electrolytic cell. Alternatively, the device is fabricated in parts as described above, wherein the parts have contact features, which when brought together close a circuit between the electrode elements of a galvanic or an electrolytic cell. An actuator switch, in accordance with further embodiments of the invention, is in electrical communication with a thermosensor, wherein the thermosensor instructs the actuator switch to close a circuit between electrode elements of a galvanic or an electrolytic cell within a range of temperatures.

[0014] In accordance with yet further embodiments of the invention, a timing device and system comprises a photo-sensitive component, element or film. For example, a timing device comprises a piece of photographic film, which is color film, black and white film or a combination thereof. The photographic film is formed from a base with a photographic medium coated or deposited thereon, wherein the photographic film is capable of being activated to change color or shade and thereby indicate the passage of a duration of time. The photographic material is any photographic medium, but preferably comprises a silver-based material including, but not limited to, silver chloride, silver fluoride, silver iodide and/or combinations thereof. In yet other embodiments of the invention the photographic medium comprises a silver-soap (Ag+ cations in a fatty acid such as stearic acid) often used in thermally-activated films. Where the photographic medium is a silver halide, the silver halide is mixed with a binder, such as cellulose or gelatin, to hold the silver halide material on the base.

[0015] The photographic material, in accordance with the embodiments of the invention, is made to be thermally and/or light sensitive using any number of techniques known in the art, including the addition of sulfur and gold and/or a dye, such as an infrared absorbing dye. To activate the photographic medium a developer is applied to the film. There are a number of materials that can be used for developing photographic materials, such as hydroquinone-based developers. Generally, all developers contain chemicals that assist in the reduction of silver halide or silver cations to form a darkened or colored image.

[0016] In accordance with the embodiments of the invention, a developer is incorporated into the construction of the film and a timing device is thermally activated or is activated by removing a barrier between the photographic material and the developer. Alternatively, the photographic material and the developer are included on separate parts or regions of a timing device and are activated by bringing together a part or region of the film with the photographic material with a part or region of the film with the developer.

[0017] In accordance with yet further embodiments of the invention, a device comprises a film with zones that change color at different rates and, therefore, provide an indication of the passage of a range of times. Each of the zones comprises a photographic material, as explained above, or other chemical and/or electrochemical materials that can be activated to change color at different rates. When the zones comprise photographic materials, the zones are made to have different reaction rates by using photographic materials with different sensitivities to heat, light and/or developer, and/or by varying the thickness of diffusion layers deposited over the zones. In accordance with further embodiments of the invention, the zones are made to have different rates of reaction and/or sensitivity to a developer by pretreating the zones to a range of different light and/or heat exposures, wherein the zones with longer exposures will develop and change color faster than zones with shorter exposures.

[0018] A system, in accordance with the embodiments of the invention, comprises a timing film, such as described above, and further comprises an adhesion layer for attaching pieces of film to consumer articles, such as containers of leftover food. The system also preferably comprises a dispenser for conveniently dispensing pieces of film from a stack or roll of the timing film and means, such as a magnet, for attaching the dispenser to a household appliance.

BRIEF DESCRIPTION OF THE DRAWING

[0019] FIGS. 1A-B show a schematic representation of a timing device, in accordance with the embodiments of the invention.

[0020] FIG. 2 shows a schematic representation of a timing device, in accordance with a preferred embodiment of the invention.

[0021] FIGS. 3A-C show systems for assembling timing devices, in accordance with the method of the present invention.

[0022] FIGS. 4A-C show schematic cross sectional views of several timing device configurations, in accordance with the embodiments of the invention.

[0023] FIG. 5 shows a piece of timing film with a plurality of zones for indicating the passage of a range of times, in accordance with the embodiments of the invention.

[0024] FIG. 6 is a cross-sectional representation of a section of timing film, in accordance with the embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Referring to FIGS. 1A-B, a timing device 100, in accordance with the embodiments of the invention is a chemical-based timing device, an electrochemical-based timing device, or a combination thereof. The timing device 100 comprises a transparent lens 101, a base 105 and an optical medium 103 therebetween. When the device 100 is actuated, the optical medium 103 is changed to a modified medium 103′, thereby altering the visibility of the base 105 through the lens 101 indicating the passage of a duration of time. The lens 101 and base 105 are formed from any suitable material, or combination of materials, including, but not limited to polymers and plastic materials.

[0026] Still referring to FIGS. 1A-B, the optical medium 103 comprises any number of different chemicals or elements which over the duration of time alter the visibility of the base 105 through the lens, as explained in detail below. Preferably, however, the base 105 becomes more visible through the lens 101 when the device 100 has expired. In order to enhance the visibility of the base 105 through the lens 101, when the device 100 has expired, the base 105 is preferably brightly colored and/or has indicia printed thereon, such that the bright color and/or the indicia are visible through the lens 101 when the device is expired.

[0027] Referring now to FIG. 2, in accordance with a preferred embodiment of the invention, a timing device 200 comprises a lens 201, a base 211 and an optical medium 204, as described above. The optical medium 204 preferably comprises a fluid layer 207. The fluid layer 207 can be comprised of any number of fluid materials, but preferably comprises a transparent gel material, which is either acid or basic and which is either conductive or insulating, depending on the application at hand. The optical medium 204 also preferably comprises an opaque layer 205, also referred to herein as a lens coating layer, which does not imply that the opaque layer 205 is necessarily coated directly on the lens 201. The lens coating 205 is preferably formed from a material which will react with the fluid layer 207, when the device 200 is activated. For example, the lens coating layer 205 is formed from a hardened gel, such as gelatin and thiosulfate. Preferably, the liquid layer 207 dissolves the lens coating layer 205 when the device 200 is activated, thereby increasing the visibility of the base therebelow and indicating the passage of a duration of time.

[0028] Still referring to FIG. 2, in further embodiments of the invention, a timing device 200 comprises an activation layer 203. The activation layer 203 comprises an indicator, such as a pH indicator which reacts with the fluid layer 207, when the fluid layer 207 sufficiently depletes or dissolves the lens coating layer 205. Alternatively, an indicator is incorporated into the lens coating layer 205 and is dissolved or leached by the fluid layer 207, such that when the concentration of the indicator in the fluid layer 207 becomes sufficiently high, the fluid layer 207 changes color.

[0029] In still further embodiments of the invention, the lens coating layer comprises a reactive species that reacts with an indicator in the fluid layer 207. For example, the lens coating layer 205 comprises a base material, such as sodium bicarbonate, which is leached from the lens coating layer 205 or is dissolved into the fluid layer 207 from the lens coating layer 205. The fluid layer 207 comprises a pH indicator and an acid material and when a sufficient amount of base material is dissolved into the fluid layer 207, then the acid material is naturalized and the pH indicator changes color, indicating the passage of a duration of time.

[0030] In still further embodiments of the invention, a timing device 200 comprises a diffusion material 209. When the device 200 is activated, the diffusion material 209 begins to diffuse through the fluid layer 207, as indicated by the arrows 215. When the diffusion material 209 reaches the lens coating layer 205, the diffusion material 209 reacts with the lens coating layer 205 to provide a color change, dissolve the lens coating layer 205 and react with the indicator layer 203, or any combination thereof, to indicate the passage of a duration of time.

[0031] Still referring to FIG. 2, a timing device 200, in accordance with the embodiments of the present invention also comprises an attaching means 213 for attaching the timing device 200 to a product or an object (not shown). The attaching means 213 is any suitable attaching means, and preferably comprises an adhesive layer for sticking the device 200 onto the product or object.

[0032] Now referring to FIG. 3A, a timing system 300, in accordance with a preferred method of the invention, is fabricated in parts 310 and 320. A first part 310 of the system 300 comprises a first reactive region 307 formed on a suitable base 301. A second part 320 oft the system 300 comprises a second reaction region 305 formed on a clear lens 303. One or both of the parts 310 and 320 comprise adhesive rings 311 and 309. To actuate the system 300, the parts are brought together such that the first reactive region 307 and the second reactive region 305 are eclipsed and in contact with each other. The adhesive rings 311 and 309 hold the first part 310 and the second part 320 together with the reactive regions 305 and 307 eclipsed and in contact. While in contact with each other, the first reactive region 307 and the second reactive region 305, undergo a chemical, physical or electrochemical process which alters the visibility of the base 310 through the lens 303, as described above. Each of the parts 310 and 320 of the system 300, in accordance with further embodiments of the invention, comprise a protective covering (not shown), such as a cellophane, which acts protective of the reactive regions 307 and 305, and is removed prior to use.

[0033] Now referring to FIG. 3B, a system 320, in accordance with the embodiments of the invention, is formed by fabricating a plurality of first reactive regions 322 on a first piece of tape 321 and a plurality of second reactive regions 324 on a second piece of tape 323. The tapes 321 and 323 preferably have perforations 326 and 328 between each of the first reactive regions 322 and the second reactive regions 324. The tapes 321 and 323 are preferably configured to be dispensed from a roll dispenser (not shown) or any other suitable dispenser. The dispenser can be dispenser configured to attach to a household appliance using a magnet or any other suitable attachment means.

[0034] In use, an activated device is formed by removing a first part 327 comprising a first reactive region 322 and a second part 329 comprising a second reaction region 324 from the tapes 321 and 323 through the perforations 326 and 328, respectively. The first part 327 and the second part 329 are then combined with the first reactive region 322 and the second reactive region 324 eclipsed and in contact, as explained in detail above.

[0035] Now referring to FIG. 3C, in accordance with alternative embodiments of the invention, a system 340 comprises a plurality of first reactive regions 342 and second reactive regions 344 formed in an alternating fashion on single piece of tape 343. In use, an activated device is formed from a section 349 comprising a first reactive region 342 and a second reactive region 344 that is separated from the tape 343 through a perforation 348. The section 349 is then folded over onto itself through a seam 346, such that the first reactive region 342 and the second reactive region 348 are eclipsed and in contact with each other. While FIG. 3C, shows the first reactive regions 342 and the second reactive regions 344 being formed in an alternating fashion on single piece of tape 343 such that an active device is formed by folding one of the first reactive regions 342 and one of the second reactive regions 344 in an end-to-end fashion, it will be clear to one skilled in the art that a system can alternatively be formed on single piece of tape with first reactive regions and second reactive regions formed in rows, such that an active device is formed by folding one of the first reactive regions 342 and one of the second reactive regions 344 in a side-to-side fashion.

[0036] FIG. 4A shows a cross sectional view of a timing device 400, in accordance with the embodiments of the invention. As described previously, the device 400 comprises a lens 405 and a base 401. The device 400 also comprises an optical medium with one or more fluid layers 411 and 411′ and a membrane structure 412 therebetween. The device 400 further comprises a lens coating layer 403 and a reactive material 413 that is capable of reacting with the lens coating layer 403. To activate the timing device 400, the membrane structure 403 is ruptured allowing the reactive material 413 to mix with the fluid layers 411 and 411′s and react with the lens coating layer 403, thereby indicating the passage of a duration of time.

[0037] Referring now to FIG. 4B, a timing device 420, in accordance with further embodiments of the invention, comprises a lens, a metal base structure 421 and an ionic fluid medium 431, therebetween. The metal base structure 421 is formed from a first metal layer 424 with a first reduction potential and a second metal layer 422 with a second reduction potential that is substantially different from the first metal layer 424. The device 420 also has metal lens coating layer 423 with a reduction potential that is also substantially different from the first metal layer 424, but can be the same or nearly the same as the reduction potential of the second metal layer 422. To actuate the device the metal lens coating layer 423 and the second metal layer 422 are placed in electrical communication with each other. The potential difference between the first metal layer 424 and the second metal layer 422 will drive a current to flow and cause the metal lens coating layer 423 to become depleted over time, and plate out over the first metal layer, thereby indicating the passage of a duration of time.

[0038] In accordance with yet further embodiments of the invention, a timing device 440 is coupled to a circuit 450, as shown in FIG. 4C. The device 440 comprises a lens 443, a metal base 441, a reactive medium 451 and a lens coating layer 445. The ionic reactive medium 451 is capable of depleting or dissolving the lens coating layer 445, either chemically or electrochemically as explained previously, when the device 440 is activated. After the device is activated and the lens coating layer 445 is sufficiently depleted or dissolved, the ionic reactive medium 451 provides an electrical path to close the circuit 450 between the leads 447 and 448. The circuit 450, in accordance with the embodiments of the invention, comprises a battery 446 and a piezo-electric element that generate an audible signal when the device 440 expires and the circuit 450 is closed.

[0039] In still further embodiments of the invention, a timing device comprises a galvanic cell or an electrolytic cell, wherein one or more electrochemically active materials between a transparent lens and a base, such as metal ions and/or electrodes, are configured to be plated out or depleted and alters the visibility of the base through the lens and indicating the passage of a duration of time. Where a timing device is an electrochemical-based timing device, an actuator switch mechanism comprising electrical contacts can be used to actuate the device. The timing device, in accordance with still further embodiments of the invention, is in electrical communication with a thermosensor (not shown), wherein the thermosensor instructs the actuator switch to close a circuit between electrode elements of a galvanic or electrolytic cell within a range of temperatures.

[0040] Referring to FIG. 5, in accordance with yet further embodiments of the invention, a device comprises a film 500 with a plurality of zones (shown as 1-10). The zones can be arranged in any geometric pattern, but are preferably arranged in a linear fashion from a first end 510 to a second end 520 of the film 500. The zones are configured to change color at different rates and, therefore, provide an indication of the passage of a range of times. For example, when each of the zones represents one hour, then the film 500 as shown, indicates the passage of approximately 7 hours. In approximately one more hour, the next zone will change color and indicate the passage of approximately 8 hours.

[0041] Still referring to FIG. 5, each of the zones, in accordance with the embodiments of the invention, comprises a photographic, chemical and/or electro-chemical material, as described in detail above. When the zones (shown as 1 -10) comprise photographic materials, the zones can be made to have different rates of reaction by using photographic materials with different sensitivities to heat, light and/or developer and/or by varying the thickness of diffusion layers deposited over each of the zones, such as described below. In accordance with an embodiment of the invention, the zones are made to have different rates of reaction and/or sensitivity to a developer by pre-treating the zones to a range of different light and/or heat exposures, wherein the zones with longer exposures will develop and change color faster than zones with shorter exposures after being activated.

[0042] Still referring to FIG. 5, when the zones (shown as 1-10) comprise chemical and/or electro-chemical material(s), as described in detail above and in accordance with the embodiments of the invention, the zones are made to have different rates of reactivity and/or sensitivity. Accordingly, each zone has a different expiration time and indicated passage of a different amount of time and the zones viewed collectively indicate passage of a total time. This embodiment has particular applications for managing inventories of food items in a household refrigerator by indicating how long the food items have been in the refrigerator, regardless of whether or not the food items have spoiled or aged past a freshness date.

[0043] FIG. 6 is a cross-sectional representation of a section of timing film 600, in accordance with the embodiments of the invention. The section of timing film 600 is formed by coating or depositing a photographic layer 605, which can include silver, silver halide, gelatin, cellulose, fatty acids, developers or combinations thereof, onto a base structure 603. The base structure 603 is preferably formed from a polymeric material, such as polyester, and can also include an adhesive layer (not shown) for attaching the section of timing film 600 to a consumer article (also not shown).

[0044] Still referring to FIG. 6, the section of film 600, in accordance with the embodiments of the invention, further comprises a diffusion layer 615 comprising a diffusion material and a developer layer 611 comprising a developer. The diffusion material is any material that will allow the developer in the developer layer 611 to migrate to the photographic layer 605 causing the photographic layer 605 to change color or darken and indicate the passage of time. Suitable diffusion materials include, but are not limited to, gelatin, cellulose and combinations thereof.

[0045] In accordance with still further embodiments of the invention, the section of film 600 further comprises a barrier layer 613 that can be pulled out or removed to activate the device and allow the developer layer 611 to diffuse through the layer 615 and cause the photographic layer 605 to change color or darken and indicate the passage of time. Alternatively, the photographic layer 605 and the developer layer 611 are formed as separate parts that can be brought together to activate the device, as explained in detail above with reference to FIGS. 3A-C.

[0046] The current invention has applications for marking when any number of different events need to take place and/or for timing the duration of any number of different events. For example, the timing device of the present invention has applications for indicating when perishable materials have expired and need to be thrown out, indicating the age of inventory and managing when the inventory needs to be rotated, tracking a deadline and a host of other time and/or temperature dependent events. One advantage of the present invention is that the timing device can be fabricated in two or more reactive parts, wherein the device is not activated, or sensitive to the environment (such as temperature), until the parts are coupled together, as explained in detail above. Accordingly, the shelf life of the timing device prior to use is enhanced and the sensitivity of the device to environmental conditions prior to use is reduced.

[0047] While the present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of the principles of construction and operation of the invention. As such, references, herein, to specific embodiments and details thereof are not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modifications can be made in the embodiment chosen for illustration without departing from the spirit and scope of the invention.

Claims

1. A device comprising b. a base; and c. a photographic medium that is capable of being activated to change color thereby indicating a passage of time.

2. The device of claim 1, wherein the photographic medium comprises zones that are capable of being activated at different rates.

3. The device of claim 1, wherein the photographic medium comprises a silver halide.

4. The device of claim 3, wherein the reactive medium further comprises an infrared absorbing dye.

5. The device of claim 3, wherein the photographic medium further comprises a binder material for securing the silver halide to the base.

6. The device of claim 5, wherein the binder comprises a gelatin.

7. The device of claim 1, wherein the reactive medium is activated by applying a developer.

8. The device of claim 2, wherein the zones are treated to a range of exposures with a selected radiation to generate latent images within the zones.

9. The device of claim 2, further comprising a protective layer over the photographic medium wherein the photographic medium is activated by removing a protective layer.

10. A system comprising a plurality of timing zones that change color at different rates and which collectively indicate a duration of time.

11. The system of claim 10, wherein the plurality of timing zones each comprises media activated by applying developer.

12. The system of claim 10, wherein the photographic medium comprises a photo-sensitive material.

13. The system of claim 12, wherein the photo-sensitive material comprises silver halide.

14. A timing system comprising: a. sections of photographic film configured for indicating a passage of time; and b. a means for attaching the sections of photographic film to an article.

15. The system of claim 14, wherein the sections of photographic film are thermally activated.

16. The system of claim 14, wherein the means for attaching the sections of photographic film to an article comprises an adhesive backing coupled to the sections of photographic film.

17. The system of claim 14, further comprising a dispenser for dispensing the sections of photographic film.

18. The system of claim 17, wherein the dispenser comprises a housing with an attachment means for attaching the dispenser to a household appliance.

19. The system of claim 18, wherein the attachment means comprises a magnet.

20. The system of claim 14, further comprising means for activating the sections of photographic film.

21. The system of claim 20, wherein the means activating the sections of photographic film comprises a developer.

22. The system of claim 14, wherein each section of photographic film is pre-exposed to a gradient of light exposures.

23. A method of making a timing system, comprising: a. providing a substrate; and b. forming zones of a reactive medium on the substrate, the zones being capable of being activated at different rates to indicate passage of a range times.

24. The method of claim 23, wherein forming zones comprises depositing a photographic materials on the substrate.

25. The method of claim 23, further comprising exposing the zones to radiation.

26. A timing device for monitoring an age of perishable items within a refrigerator, the device comprising: a. strips of reactive zones, the zones configured to change color at a different time after being activated and being geometrically arranged to collectively indicate a total passage of time; and b. a means to activate the reactive zones.

27. The device of claim 26, wherein a portion of the reactive zones comprises a photosensitive medium that as developed changes color.

28. The device of claim 26, wherein a portion of the reactive zones comprise a diffusion layer and a dye that migrates through the diffusion layer to change color.

29. The device of claim 26, wherein a portion of the reactive zones comprises a electro-chemical material that is reduced or oxidized to change color.

30. The device of claim 26, further comprising a dispenser for dispensing the strip, the dispenser being configured to attach to the refrigerator.