60/256,832, filed December 19,2000.

BACKGROUND OF THE INVENTION This invention is generally in the field of the use of time delayed ink messaging systems useful in a variety of applications, including in kits for determining when to stop/begin administering a drug.

Time-delayed ink message systems are described in U. S. Patent No.

5,633,836, to Langer et al. Langer uses Red 60 ink in the pH sensitive message systems. This ink is colored, with a pink tint. Thus Red 60 ink does not work on white paper since a printed message will always be visible, even before an activator migrates to the layer that contains the ink.

It is therefore an object of the present invention to provide a time- delayed in the system which is colorless and durable.

BRIEF SUMMARY OF THE INVENTION A device comprising at least five different layers displays a message after a time delay of up to 14 days. pH sensitive inks, volatile acids and bases, and iodine vapors can be used to display the message. The main layers include: (1) a clear film, (2) an indicator (which can be part of the clear film), (3) a diffusion barrier, (4) an activator, and (5) a backing.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of time in minutes versus mass diffused.

Figure 2a is a graph of time in days versus weight of film in grams for measuring the diffusion of water (0.1 ml) through a diffusion barrier (layer 3) formed of S225 R film.

Figure 2b is a graph of time in days versus weight loss of film in grams for measuring the diffusion of water (0.1 ml) through a diffusion barrier (layer 3) formed of S225 R film.

Figure 3a is a graph of time in days versus weight of film in grams for measuring the diffusion of water (0.05 ml) through a diffusion barrier (layer 3) formed of S225 R film.

Figure 3b is a graph of time in days versus weight loss of film in grams for measuring the diffusion of water (0.05 ml) through a diffusion barrier (layer 3) formed of S225 R film.

Figure 4a is a graph of time in days versus weight of film in grams for measuring the diffusion of water (0.05 ml) through a diffusion barrier (layer 3) formed of S225 R film. The back of each layer of film in the diffusion barrier contained aluminum foil.

Figure 4b is a graph of time in days versus weight loss of film in grams for measuring the diffusion of water (0.05 ml) through a diffusion barrier (layer 3) formed of S225 R film. The back of each layer of film in the diffusion barrier contained aluminum foil.

Figure 5a is a graph of time in days versus weight of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of S225 R film.

Figure 5b is a graph of time in days versus weight loss of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of S225 R film.

Figure 6a is a graph of time in days versus weight of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of ZW44 film.

Figure 6b is a graph of time in days versus weight loss of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of ZW44 film.

Figure 7a is a graph of time in days versus weight of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of ELV400 film.

Figure 7b is a graph of time in days versus weight loss of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of ELV400 film.

Figure 8a is a graph of time in days versus weight of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of CV600 film.

Figure 8b is a graph of time in days versus weight loss of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of CV600 film.

Figure 9a is a graph of time in days versus weight of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of white polypropylene (PP) film, without an adhesive.

Figure 9b is a graph of time in days versus weight loss of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of white polypropylene (PP) film, without an adhesive.

Figure 1 Oa is a graph of time in days versus weight of film in grams for measuring the diffusion of water (0.05 ml) through a diffusion barrier (layer 3) formed of white polypropylene (PP) film, without an adhesive.

Figure 1 Ob is a graph of time in days versus weight loss of film in grams for measuring the diffusion of water (0.05 ml) through a diffusion barrier (layer 3) formed of white polypropylene (PP) film, without an adhesive.

Figure 11 a is a graph of time in days versus weight of film in grams for measuring the diffusion of water (0.05 ml) through a diffusion barrier (layer 3) formed of Tevlar film, without an adhesive.

Figure 1 lb is a graph of time in days versus weight loss of film in grams for measuring the diffusion of water (0.05 ml) through a diffusion barrier (layer 3) formed of Tevlar film, without an adhesive.

Figure 12a is a graph of time in days versus weight of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of Tevlar film, without an adhesive.

Figure 12b is a graph of time in days versus weight loss of film in grams for measuring the diffusion of ammonia (0.05 ml) through a diffusion barrier (layer 3) formed of Tevlar film, without an adhesive.

DETAILED DESCRIPTION OF THE INVENTION I. Description of Device The basic device consists of multiple layers of materials. The main layers include: (1) a clear film, (2) an indicator, (3) a diffusion barrier, (4) an activator, and (5) a backing. The clear film is at the top of the device and allows a user to view the message. The indicator contains the message. The diffusion barrier controls the time delay. The activator contains a volatile agent which diffuses through the diffusion barrier to the activator. The backing layer is at the bottom of the device and is impermeable to al of the contents within the device.

The devices can be designed to be activated as soon as they are manufactured. Optionally, the devices may be designed to be selectively activated. Selectively activated devices contain additional peelable backing layers and adhesive layers. Such devices contain layers in the following order: (1) a clear film, (2) an indicator, (3) a diffusion barrier, (4) a peelable backing, (5) an adhesive, (6) an activator, (7) a backing, (8) an adhesive, and (9) a peelable backing. Layers 1-3 form an indicator pack, while layers 6-9 form an activator pack. To activate this device, the user peels layer 4 away, and then sticks the indicator pack (layers 1-3) to the adhesive layer (5) on the activator pack (layers 6-9). The entire device may then be adhered to any surface by peeling away layer 9.

Layer 1 : Clear Film The top layer of the device is a clear film that allows the user to view the underlying message printed on the top of layer 2. Layer 1 should be as impermeable as possible to both moisture, needed in the indicator layer (layer 2), and to the volatile agent found in the activator layer (layer 4). Suitable films for Layer 1 include Mylar (polyester) (FLEXMARK PM 100 Clear P/T/P No PS), fluorinated ethylene propylene (FEP), clear polypropylene (PP) (FLEXMARE PP 200 H Clear), and fluorinated vinyl (Tevlar) (OT 100 Clear No PS). In the preferred embodiment, layer 1 is formed from clear polypropylene. Clear polypropylene is highly impermeable to moisture and the

volatile agents that are used in the activator layer. Additionally, polypropylene film heat-seals well to the other components of the device (see Table 2).

Minimizing diffusion of water is critical to the selection of the top layer material. A small amount of moisture is needed in the pH ink, which may be used in the indicator layer (layer 2). If this moisture can diffuse through layer 2 into the atmosphere, the indicator layer will dry out, and the pH ink will not change color. Results from permeability studies indicate that most of the moisture is lost from the four films listed above within the first few days. The clear polypropylene has better water retention properties than the other films.

Fluorinated vinyl (Tevlar) film did not performe as well as clear PP in the permeability studies described in Example 1.

Other films which may be suitable for use as layer 1 include PVdC coated films, which, for example, are available from DUPONT (e. g., Saran Coated PE) and Mobil (e. g., BICOR 85 AXT and BICOR 110 ASB-X).

The Mobil films have a polypropylene base with an acrylic layer on one side and a PVdC coating on the other, and are clear. The acrylic side of the Mobil films accepts water-based inks Optionally, the message may be printed directly on the underside of layer 1 and layer 2 may be omitted from the device.

Layer 2 : Indicator Layer A suitable material for layer 2 has the following properties: (1) a message can be printed on it, and (2) the volatile agent diffuses freely through it. White filter paper with a printed message in special pH sensitive ink may be used for Layer 2.

Another important property of layer 2 is color, since the layer needs to mask the message until it changes. Thus the selection of paper and ink is important. pH sensitive ink Suitable inks include pH sensitive inks, such as phenolphthalein or phenol red inks. The preferred ink is phenolphthalein ink. Phenolphthalein ink is almost colorless and there is no problem hiding an image made with it on white paper. For hydrophobic inks, it is preferable to print the message directly

on the top of the diffusion barrier (layer 3). The pH sensitive inks are made with ethanol and water, and they do not print well on the hydrophobic polymers used as the diffusion barriers (layer 3).

Adding glycerol to the ink allows one to produce devices with longer time delays, regardless of the water permeability properties of the top layer (layer 1).

One pH sensitive ink is an aqueous solution of phenol red, which produces a dark red ink at neutral pH (approximately 7.0). Two main problems exist with the phenol red indicator: (1) the ink always has some color regardless of the pH, and (2) the phenol red ink requires a bit of moisture to be active.

Because of the color, the message is always visible when it has been printed on a white paper background. A yellow ink (for bases), formed with the addition of acid, can be used to make a hidden message if it is printed on yellow paper that will mask the message. When the ink is activated it turns dark red/purple and the message can clearly be seen. In contrast, a purple ink (for acids), formed with the addition of base, is not as useful because it does not show up on a purple background after it has turned yellow. pH sensitive litmus paper (Precision Laboratories, West Chester, Ohio) may be used as the indicator. Red paper can be used to indicate bases (turns blue), and blue paper can be used to indicate acids (turns red). The litmus paper is easy to use. It contains no written message. The litmus paper requires moisture to work. Thus, the paper strips are moistened before they are placed in the device. For example, an electric humidifier can be used to moisten the paper strips immediately before they are laminated between layers 1 and 3.

A 1% phenolphthalein solution, which is almost completely colorless, turns a very distinct dark red when activated. Messages, in the form of words or pictures, can be written on white paper with the 1.0% ink and are invisible until activated with the volatile base. However, the 1% phenolphthalein is not quite dark enough in printed form. The maximum amount of phenolphthalein that will dissolve in a standard printing solution containing 9 parts 70% ethanol (EtOH) and 1 part glycerol is 2.5%, which also was not dark enough.

Therefore in the preferred embodiment, the indicator is formed from 9 parts

100% EtOH and 1 part glycerol with 5% (w/v) phenolphthalein. This solution results in a darker and more vibrant printed message when activated. The phenolphthalein indicators require moisture to work.

Anhydrous System Anhydrous systems can be formed. In these devices, the message on layer 2 is written with oil or a polymer-based"ink". When reacted with a iodine, the ink changes to reddish brown.

Layer 3 : Diffusion Barrier Layer 3 acts as a diffusion barrier. This layer is used to control the time delay of the message activation. Layer 3 may actually consist of multiple layers of the same film, depending on how long of a time delay is required.

Generally, the greater the total thickness of layer 3, whether using one layer or a combination of layers, the longer the time delay. In the preferred embodiment, a single thick film, instead of multiple thinner ones, is used.

Several different films have been evaluated as diffusion barriers.

These films include: vinyls, such as Cling Vinyl CV-600 (50% plasticizers), Extra-Life Vinyl ELV-400 (40% plasticizers), V-325, and S225 ; polypropylenes, such as Optiflex S 225 R White TC-391 44PP-8, ZW44 Optiflex EZWhite 44PP-8 (PP with EVA skin), and FLEXMARK PP 240 F White No PS; and polyethylenes, such as FLEXMARK PE 350 F White No PS (FLEXICON@).

Some of the test films such as the adhesive-backed ZW44 film or FLEXMARK"PP 240 (No PS) in Table 1 had an adhesive backing on one side, which makes it easier to manufacture the devices. A heat-sealer can also be used to manufacture the devices. Films without an adhesive layer were used in these tests, because the adhesive layer resulted in unpredictable heat-seals (see Table 1). Polypropylene films provided the longest delay under most circumstances (see Table 1).

Layer 4 : Activator Layer The activator layer can be formed of any number of different thin films or reservoirs containing the active agent, which usually is a volatile acid or base. The primary functions of the activator layer are to contain the volatile

agent, protect it from manufacturing conditions, and in some cases retard release of the agent to further slow message activation.

Two types of activator layers are generally used: (1) solvent-cast films, and (2) filter-paper reservoirs. In most cases, the volatile agent is in the form of a liquid, which generally can be difficult to handle. Both the solvent-cast film and filter-paper techniques are designed to make the volatile agent easy to incorporate into the finished product. Additionally, both techniques result in an activator layer that easily can be laminated between other layers of the finished device. The activator layer may be a film made from a polymer, such as polycaprolactone (PCL). PCL films are solvent-cast in a solvent such as methylene chloride.

The volatile agent can be a volatile base, such as triethylamine or amylamine, a volatile acid, such as acetic or butyric acid, ammonia, or ammonium carbonate. In the preferred embodiment, the volatile agent is ammonium carbonate.

Triethylamine and amylamine are very volatile and highly toxic. Thus films cast with these bases dry quickly. Acetic acid or butyric acid take longer to dry than the than films cast with the organic bases. Thus by the time the films have dried, and can be peeled off of the glass plate, the butyric acid has almost completely evaporated. However, the acetic acid film retains enough of its original loading to quickly turn a phenol red indicator bright yellow.

Ammonia is preferred as the volatile agent, since it is relatively inexpensive, compatible with the PCL film casting technique, highly volatile, and less toxic than the other two organic bases.

Volatile Gas FormingAgents An alternative activating agent is a volatile gas forming or releasing agent such as ammonium carbonate, commonly used as the active ingredient in "smelling salts."Ammonium carbonate, which is 30% by weight ammonia, provides a compact reservoir of active ammonia vapors, eliminating the requirement to absorb liquid ammonium hydroxide onto solid matrices, such as filter paper. Ammonium carbonate solid sublimes, producing ammonia (base) and carbon dioxide gases that can diffuse through polymer membranes and

activate a pH-sensitive indicator message. However, carbon dioxide can recombine on the message side of the system to form the Lewis base, carbonic acid, which can, in turn, inhibit activation of the pH sensitive ink.

Introducing carbon dioxide adsorbent materials in the greatly enhances the efficiency of the device. Carbon dioxide adsorbent materials may be either mixed directly with the ammonium carbonate agent or introduced as a separate layer between the ammonium carbonate (layer 4) and pH sensitive message (layer 3) layers. Carbon dioxide adsorbent materials include carbon dioxide "scrubbing agents". Examples of carbon dioxide scrubbing agents are alkali hydroxides, such as barium hydroxide, lithium hydroxide, sodium hydroxide, and aluminum hydroxide. Collins C02 absorbent Granules (Warren E. Collins Inc., Braintree, Massachusetts), which are commonly used to absorb carbon dioxide in spirometer device, is particularly effective. This product contains barium hydroxide and an indicator dye to show the status of the absorptive pellets. Addition of a one-to ten-fold excess of scrubbing agent by weight, with respect to ammonium carbonate, greatly increases the diffusion of ammonia through the polymer membranes, lowering the amount of volatile solid required to activate the message.

A significant advantage of an ammonium carbonate system is that small amounts of the material, either laminated between polymer membranes or encapsulated as solids in a polymer film, can generate tremendous quantities of ammonia gas. Working quantities of 25-50 mg can activate a 2"by 3"message packet. Consequently, small loses during storage are essentially unimportant.

Such a message system offers substantial benefits in product shelf-life applications.

Iodine Vapor : Anhydrous System Anhydrous systems which do not require water for activation of a hidden message, can be used in layer 4. Metallic iodine crystals, either enclosed in plastic"pouches"or encapsulated in polymer films (PCL) were formed. Iodine metal"sublimes"into a gas phase and has the additional property of reacting and binding to compounds with unsaturated double bonds in their chemical structure. Some examples of unsaturated compounds are oils

(corn, safflower, olive oil) and polymers (polystyrene, polybutadiene, etc).

Iodine vapor reacts with colorless unsaturated compounds and turns them either brown or red. This reaction does not depend on water.

The principle of the system remains the same: delay the diffusion of iodine vapor by interposing polymer film barriers until iodine reacts with the message written with oil or polymer-based"inks". A slight drawback of the system is the"non-specificity"of iodine binding, i. e., iodine binds to many of the polymer films and adhesives and discolors them in the process. Optionally the device may contain an opaque masking layer surrounding the message to hide the discoloration of the device.

A great advantage of the system is that a small amount of iodine metal or encapsulated film generates substantial amounts of iodine vapor, so consequently small losses during storage are not significant. This offers a great benefit for product shelf-life. Additionally, iodine has low toxicity and can be used as an antiseptic, a food additive and a dietary supplement.

Layer 5 : Backing Layer The purpose of the backing layer (layer 5) is to serve as a diffusion barrier to both the volatile agent and moisture. Ideally, layer 5 should be completely impermeable to the volatile agent. Suitable films include Extra-Life Vinyl (ELV-400), Fluorinated Ethylene Propylene (FEP), Fluorinated Vinyl (Tevlar), and Peelable Foil (PE backed aluminum foil).

Previously, many of the devices were made with ELV-400 backings simply because the extra life vinyl (ELV) had the lowest percentage of plasticizers of all the films being used at the time. In early experiments, the ELV-400 films also appeared to be the best barrier. Since it soon became apparent that the vinyl films were rather permeable to both the organic bases and moisture, FEP was laminated between the adhesive ELV film and the activator layer (layer 4), in the following order: (i) Activator Layer (layer 4), (ii) FEP (layer 4a), and (iii) Backing Layer (adhesive up) (layer 5).

FEP is highly impervious to most solvents, and was assumed to be a much better diffusion barrier than the ELV film alone. However, the FEP film does not have an adhesive layer, nor can it be heat-sealed. Consequently, there

is no easy way to test the permeability of the film to moisture or to the volatile agents.

The peelable foil is the preferred material for the backing layer, since foil containing films are often used commercially in applications where a barrier layer is required. The films used in our experiments have a PE backing that enables them to be heat-sealed. A number of devices manufactured with heat-sealed foil backings currently are being studied.

Devices Table 1 provides a summary of the different layers in each film that was tested, the loadings, the barriers, and the time delays. Films which did not contain an adhesive layer are designated"No PS". Packets that have not turned, but are expected to do so are indicated in Table 1 with an asterisk (*).

Table 1 Layer 4 Encap-Layer 3 Layer Layer 5 Layer 2 Expiration Active sulated Of layers) I Indicator Contmeitis Agent Amyl 10% PCL CV600W (1) Mylar CV600W Phenol Red 2 hrs 1 : 1 Tnethanol 10% PCL CV600W (1) Mylar CV600W Phenol Red 2 hrs amine 1: 1 Control-10% PCL CV600W (1) Mylar CV600W Phenol Red no change blank Amyl 10% PCL CV600W (1) FEP CV600W Phenol Red 1 day 1 : 1 +PCL Blank Film acetic acid 10% PCL CV600W (1) FEP CV600W Phenol Red 2 day 1: 1 (4 | films) acetic acid 10% PCL CV600W (1) FEP CV600W Phenol Red 2 day 1: 1 (1 film) Amyl 10% PCL CV600W (1) FEP CV600W pH strip 1 day 20% amyl Amyl 10% PCL CV600W (1) + FEP CV6000 pH strip 1 day 20% amyl PCL Blank W + FEP Film (1) Amyl 10% PCL CV600W FEP CV600W pH strip 2 day 20% amyl (1) + PCL +FEP (1) Blank (2) Control-10% PCL CV600W (1) + FEP CV600W pH strip no change blank PCL Blank (2) Amyl 10% PCL ELV400 (1) FEP CV600W pH strip no change 20% amyl Amyl 10% PCL ELV400 (1) + FEP CV600W pH strip 7 day 20% amyl PCL Blank + FEP Film (1) Amyl 10% PCL ELV400(1)+ FEP CV600W pH strip no change 20% amyl PCL Blank +FEP (1) Film Control-10% PCL ELV400 (1) + FEP CV600W pH strip no change blank PCL Blank (2) NH40H+F None ELV400 (1) FEP ELV400 pH strip Ihr ilter (satd) W + FEP (1) NH40H+F None ELV400 (2) FEP ELV400 pH strip 18 hr ilter (satd) W + FEP (1) NH40H+F None ELV400 (3) FEP ELV400 pH strip 18 hr ilter (satd) W + FEP (1) Filter None ELV400 (1) FEP ELV400 pH strip no change (control) W+FEP (1) Acetic None ELV400 (1) FEP ELV400 congo red 18 hr Acid (25 W+FEP strip µL) (1) + Filter Acetic None ELV400 (2) FEP ELV400 congo red 24 lir Acid (25 W+FEP strip µL) (1) + Filter Acetic None ELV400 (3) FEP ELV400 congo red 3 days Acid W+FEP strip (25fol) (1) + Filter Amyl None ELV400 (1) FEP ELV400 red litmus 10 min (25µL) W + + FEP (1) Filter Amyl None ELV400 (2) FEP ELV400 red litmus 24 hrs (25µL) W + + FEP (1) Filter Amyl None ELV400 (3) FEP ELV400 red litmus 3 days (25µL) W + + FEP (1) Filter Amyl 10% PCL V325 (1) FEP CV600W Phen-FP 2 hrs 20% amyl + FEP (1) Amyl 10% PCL V325 (2) FEP CV600W Phen-FP 3 hrs 20% amyl + FEP (1) Amyl 10% PCL V325 (3) FEP CV600W Phen-FP 10 days 20% amyl + FEP (1) Ammonia 10% PCL V325 (1) FEP CV600W Phen-FP 1 day 20% +FEP NH40H (1) Ammonia 10% PCL V325 (2) FEP CV600W Phen-FP no change 20% + FEP indicator NH40H (1) dry Ammonia 10% PCL V325 (3) FEP CV600W Phen-FP no change 20% + FEP indicator NH40H (1) dry NH40H None S225 (4) Mylar S225+m Phen-FP no change (50 uL) + ylar (1) Humidified Filter Open System by 4.28 NH40H None S225 (3) Mylar S225+m Phen-FP no change (50 µL) + ylar (1) Humidified Filter Open System by 4.28 NH40H None S225 (2) Mylar S225 + Phen-FP 14 days (50 pL) + mylar (1) Humidified Filter NH40H None ZW44 (4) Mylar ZW44 + Phen-FP 12 days (50 pLL) + mylar (1) Humidified Filter NH40H None ZW44 (3) Mylar ZW44 + Phen-FP 5 days (50 ptL) mylar (1) Humidified +Filter NH40H None ZW44 (2) Mylar ZW44 + Phen-FP 4 days (50 E, tL) + mylar (1) Humidified Filter NH40H PCL S225 (5) Mylar S225+ Phen-FP no change (50 µL) + pouch mylar (1) Humidified Filter heat seal Open System by 4.23 NH40H PCL S225 (4) Mylar S225+ Phen-FP no change (50 iL) + pouch mylar (1) Humidified Filter heat seal Open System by 4.23 NH40H hot wax S225 (4) Mylar S225+ Phen-FP no change (50 µL) + dip seal mylar (1) Humidified Filter Open System by 4.23 NH40H None S225 (4) Mylar S225+ Phen-FP 24 hrs (50 µL) + mylar (1) Humidified Filter 3 x 3 cm 8 ton press seal edge NH40H None S225 (4) Mylar S225+ Phen-FP 24 hrs (50 µL)+ mylar (1) Humidified Filter 3 x 3 cm 8 ton press seal edge NH40H None S225 (4) Mylar S225 + Phen-FP 12 hrs (50 pL) + mylar (1) Humidified Filter 3 x 3 cm 8 ton press seal edge NH40H None S225 (4) Mylar S225+ Phen-FP 2. 5 days (50 µL) + mylar (1) Humidified Filter 3 x 3 cm 8 ton press seal edge NH40H None S225 (4) Mylar S225+ Phen-FP 1 day (50 µL) + mylar (1) Humidified Filter 3 x 3 cm 8 ton press seal edge NH4OH None S225 (4) Mylar S225+ Phen-FP no change (50 p. L) + mylar (1) Humidified Filter 3 x 3 cm 8 ton press seal edge NH40H None ZW44 (3) Mylar S225+ Plien-FP no change (50 µL) + Foil (1) Humidified Filter Impulse heat sealed NH40H None ZW44 (3) Tevlar S225 + Phen-FP no change (50 I1L) + Foil (1) Not Filter humidified Impulse heat sealed NH40H None ZW44 (3) Tevlar S225+ Phen-FP no change (50 µL) + Foil (1) Not Filter humidified Impulse heat sealed NH40H None ZW44 (3) Tevlar ZW44 + Phen-FP no change (50 µL) + Foil (1) Not Filter humidified Impulse heat sealed Iodine 20% ZW44 (2) Tevlar Tevlar Safflower no change Iodine in oil-FP Not 10% PCL humidified Impulse heat sealed Iodine 20% ZW44 (2) Tevlar Tevlar safflower no change Iodine in oil-FP Not 10% PCL humidified Impulse heat sealed Iodine 20% ZW44 (2) Tevlar Tevlar safflower 9 days Iodine in oil-FP Not 10% PCL humidified Impulse heat sealed Iodine 20% ZW44 (3) Tevlar Tevlar safflower no change Iodine in oil-FP Not 10% PCL humidified Impulse heatsealed Iodine 20% ZW44 (3) Tevlar Tevlar safflower no change Iodine in oil-FP Not 14 10% PCL humidified Impulse heat sealed Iodine 20% ZW44 (3) Tevlar Tevlar safflower no change Iodine in oil-FP Not 10% PCL humidified Impulse heat sealed Iodine 20% ZW44 (2) PP (1) PP (1) safflower no change Iodine in oil-FP Not 10% PC humidified Impulse heat sealed Iodine 20% ZW44 (2) PP (1) PP (1) safflower no change Iodine in oil-FP Not 10% PC humidified Impulse heat sealed Iodine 20% ZW44 (2) PP (1) PP (1) safflower no change Iodine in oil-FP Not 10% PC humidified Impulse heat sealed NH40H PE pouch ZW44 (1) PP (1) Foil Gly/Phen-no change (50 Vol) + heat seal FP Not Filter humidified Impulse heat sealed NH40H None ZW44 (3) PP (2) Foil Gly/Phen-no change (50 µL) + FP Not Filter humidified Impulse heat sealed NH40H None ZW44 (4) PP (2) Foil Gly/Phen-no change (50 vol) + FP Not Filter humidified Impulse heat sealed NH40H None ZW44 (5) PP (2) Foil Gly/no change (50 I1L) + Phen-FP Not Filter humidified, Impulse heat sealed NH40H PP pouch ZW44 (1) PP (1) Foil Gly/no change (50 IlL) + heat seal Phen-FP Not Filter humidified, Impulse heat sealed None-None ZW44 (1) PP (1) Foil Gly/no change control Phen-FP Not humidified, Impulse heat sealed NH40H None ZW44 (1) PP (I) Foil Gly/1 day (50 µL) + Phen-FP Not Filter humidified Impulse heat sealed NH40H None ZW44 (1) PP (1) Foil Gly/1 day (50 µL) + Phen-FP Not Filter humidified Impulse heat sealed NH40H None ZW44 (1) PP (1) Foil Gly/1 day (50 uL) + Phen-FP Not Filter humidified Impulse heat sealed NH40H ZW44 (4) PP (4) Foil Gly/Phen-no change (50 aL) + FP Not Filter humidified Impulse heat sealed -50 mg PE pouch ZW44 (1) PP (1) Foil PS message 1 day Iodine heat seal Impulse crystals heat sealed -50 mg PE pouch none PP (1) Foil PS message 2 hrs Iodine heat seal Impulse crystals heat sealed -50 mg PP PE film no PP (1) Foil PS message 5 days Iodine pouch (2) adhesive Impulse crystals heat seal heat sealed NH40H PP pouch ZW44 (3) Mobil ZW44 Phen-FP no change (50 u. L) + heat seal Bicor (1) Not Filter 85pouc humidified h Impulse heat sealed NH40H none ZW44 (2) PP (1) Foil Phen-FP 3 days (500aL) Not + humidified Thick Impulse Filter heat sealed NH40H none ZW44 (2) PP (1) Foil Phen-FP 1 day (500 µL) Not + humidified Thick Impulse Filter heat sealed NH40H none ZW44 (2) PP (1) Foil Phen-FP 3 days (500 ttL) Not + humidified Thick Impulse Filter heat sealed NH40H none ZW44 (2) PP (1) Foil Phen-FP 3 days (500 µL) Not + humidified Thick Impulse Filter heat sealed 70-90 mg none ZW44 (2) PP (1) Foil Phen-FP 1 day (NH4) 2CO Not 3 humidified Impulse heat sealed 70-90 mg none ZW44 (2) PP(1) Foil Phen-FP no change (NH4)2CO Not 3 humidified Impulse heat sealed 70-90 mg none ZW44 (2) PP (1) Foil Phen-FP 1 day (NH4) 2CO Not 3 humidified Impulse heat sealed -50 mg PE pouch none PP (1) Foil Phen-FP 1 day (NH4) 2CO heat Not 3 sealed humidified Impulse heat sealed 500µL none S225 (2) PP (1) Foil 10% 1 day NH40H + Gly/Phen Not FP Printed-FP humidified Impulse heat sealed 500µL none S225 (2) PP (1) Foil 10% 1 day NH40H + Gly/Phen Not FP Printed-FP humidified Impulse heat sealed 500gL none S225 (2) PP (1) Foil 10% 1 day NH40H + Gly/Phen Not FP Printed-FP humidified Impulse heat sealed 500µL none S225 (2) PP (1) Foil 10% 1 day NH40H + Gly/Phen Not FP Printed-FP humidified Impulse heat sealed 500JJLnoneS225 (2) PP (1) Foil 10% 1 day NH40H + Gly/Phen Not FP Printed-FP humidified Impulse heat sealed 300µL none ZW44 (3) PP (1) Foil 10% 4 days NH40H + Gly/Phen Not FP Printed-FP humidified Impulse heat sealed 300gel none ZW44 (3) PP (1) Foil 10% 4 days NH40H + Gly/Phen Not FP Printed-FP humidified Impulse heat sealed 300µL none ZW44 (3) PP (1) Foil 10% 4 days NH40H + Gly/Phen Not FP Printed-FP humidified Impulse heat sealed 300piu none ZW44 (3) PP (1) Foil 10% 4 days NH40H + Gly/Phen Not FP Printed-FP humidified Impulse heat sealed none ZW44 (3) PP (1) Foil 10% no change NH4OH+ Gly/Phen Not FP Printed-FP humidified Impulse heat sealed - 150 mg PP heat- ZW44(1) PP (1) Foil z no change (NH4) 2CO sealed to Not 3 foil humidified Impulse heat sealed - 150 mg PP heat ZW44(1) PP (1) Foil 10% no change (NH4) 2CO sealed to Gly/Phen Not 3 foil Printed-FP humidified Impulse heat sealed - 150 mg PP heat- ZW44(1) PP (1) Foil 10% OVEN (NH4) 2CO sealed, to Gly/Phen Not 3 foil Printed-FP humidified Impulse heat sealed 70-90 mg none ZW44 (1) Mobil Mobil 10% 5 days (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified h Impulse heat sealed 70-90 mg none ZW44(1) Mobil Mobil 10% 5 days (NH4) zC0 Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified h Impulse heat sealed 70-90 mg none ZW44 (1) Mobil Mobil 10% 5 days (NH4)2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified h Impulse heat sealed 70-90 mg noen S225(1) Mobil Mobil 10% 1 day (NH4) 200 Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified h # Impulse heat sealed 70-90 mg none S225 (1) Mobil Mobil 10% 1 day (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified h Impulse heat sealed 70-90 mg none S225 (1) Mobil Mobil 10% 1 day (NH4)2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified h Impulse heat sealed 250 mg none S225 (1) Mobil Mobil 10% 30 min (NH4) 2CO Bicor Bicor Gly/Phen N 3 85pouc 85pouch Printed-FP ot + h humidified, 250 gm Impulse Ba (OH)2 heat sealed 250 mg none S225 (l) Mobil Mobil 10% 30 min (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 250 mg none S225 (1) Mobil Mobil 10% 30 min (NH4)2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 250 mg none ZW44 (2) Mobil Mobil 10% 1 day (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 250 mg none ZW44 (2) Mobil Mobil 10% 1 day (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 250 mg none ZW44 (2) Mobil Mobil 10% 1 day (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 10 mg none ZW44 (2) Mobil Mobil 10% no change (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 10 mg none ZW44 (2) Mobil Mobil 10% no change (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 25 mg none ZW44 (2) Mobil Mobil 10% 1 day (NH4) co Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed BaOH 25 mg none ZW44 (2) Mobil Mobil 10% 1 day (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 50 mg none ZW44 (2) Mobil Mobil 10% 1 day (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 50 mg none ZW44 (2) Mobil Mobil 10% 1 day (NH4) 2CO Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified, + h Impulse 250 gm heat sealed Ba (OH) Z 100 mg Bicor ZW44 (1) Mobil Mobil 10% 1 day (NH4) 2CO pouch Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified, + h Impulse 250 gm heat sealed Ba (OH) 2 100 mg Bicor ZW44 (1) Mobil Mobil 10% Gly/ 1 day (NH4) 2CO pouch Bicor Bicor Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) Z 100 mg Bicor none Mobil Mobil 10% 1 day (NH4) 2CO pouch Bicor Bicor Gly/Phen Not 3 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2 100 mg Bicor ZW44 (2) Mobil Mobil 10% no change (NH4) zCO pouch + Bicor Bicor Gly/Phen Not 3 Bicor (2) 85pouc 85pouch Printed-FP humidified + h Impulse 250 gm heat sealed Ba (OH) 2

Key : Gly = Gly Phen = phenolphthalein (NH4) 2CO3 = ammonium carbonate Ba (OH) 2 = barium hydroxide FP = FP PS = PS Amyl= amyl Satd = saturated Methods of making the Devices Layer 1 The clear layer is applied using standard techniques.

Layer 2 pH sensitive inks The ink was either drawn onto filter paper squares with the tip of a glass pipette or the filter paper squares were simply dipped in the ink solution and allowed to air dry. (The dried paper had to be remoistened before it could be used in the devices.) To make the color change associated with the volatile agent more noticeable, the phenol red ink was titrated with HCL to turn it bright yellow or NH4OH to turn it dark purple. The yellow indicator ink was

used with volatile bases (it turns dark red or purple) and the dark purple with acids (turns bright yellow or orange).

If many indicator squares are made at one time and allowed to dry so they could be used at a later date, the squares must be moistened prior to placement in the device. pH sensitive inks require a small amount of moisture to change color. If the filter paper squares were allowed to dry completely then the pH inks would not change color when exposed to the volatile agent from layer 4. Consequently, when devices are made with the dried filter paper squares, the indicators are moistened slightly, e. g., using an electric humidifier or spray gun, before they are laminated between layers 1 and 3.

Ink can be applied to the filter paper using inkjet printing. In one embodiment, the black ink is flushed from a cartridge of an inkjet printer, such as one made by Hewlett Packard, and the cartridge is loaded with pH sensitive ink, such as phenolphthalein ink. Using this method, words and messages can be printed in the"invisible"ink directly onto plain white printer paper. The messages are then cut out and placed in the device. Printer paper works as well as filter paper.

A method for printing phenolphthalein ink with a Hewlett Packard inkjet printer is described below. An inkjet cartridge was washed out with distilled water to remove all remaining traces of the black ink. A 1.0% phenolphthalein solution was made with 70% EtOH so that there would be a small amount of water in the indicator. In addition to the water, glycerol was added to the ink to increase its viscosity slightly and minimize the chance of the printed ink bleeding into the paper. The final concentration of the ink was 1.0% phenolphthalein dissolved in 10% glycerol, 27% water, and 63% EtOH.

The ink printed very well with this technique. Furthermore, the glycerol acts as a humectant, and it retains a sufficient amount of moisture to render the printed ink active with out any additional humidification. For example, one of the indicator paper strips exposed to atmospheric air for over a week still changed color upon exposure to NH40H. Since the glycerol retained sufficient moisture, the device does not have to rely on the water barrier

properties of layer 1 to work effectively. Allowing for a broader range of materials to be used in layer 1.

Methods of Forming layer 4 PCL film casting techniques can be used. However, the PCL film casting technique is very time consuming. Further, a large percentage of the ammonia was lost as the film dried.

In a second manufacturing technique for producing the activator layer, ammonia was loaded onto small squares of filter paper to form the activator layer. A known quantity (typically 50 ui) of ammonia was placed on a 1 cm2 piece of filter paper immediately before it was laminated between layers 3 and 5. The filter paper technique saved a considerable amount of time, and unlike the PCL film casting technique, a known quantity of volatile agent could be placed in each device. Knowing the quantity of volatile agent loaded is important since it enables one to accurately assess permeability/barrier properties of the films through weight loss experiments. It also permits one to determine when all of the volatile agent has been lost to the environment (see Example 1).

Examples Example 1: Film Permeability Studies.

A number of film permeability studies were performed to test the barrier properties of the top (layer 1), diffusion barrier (layer 3), and backing (layer 5) layers to water and ammonia. The films were made into double- sided pouches by using two layers of each film and either sealing using adhesive layer or heat-sealing the films together, if the film did not have an adhesive layer.

The pouches were loaded with a filter paper square (lcm2) containing 50 uL of water or ammonia. The filter paper was placed between the two layers of film. The pouches were weighed immediately after they were sealed, and again at later time points. Table 2 contains the data for each type of film tested and the amount of time for the water or ammonia to pass through the film. Data and graphs of the individual permeability studies is shown in Figures 2-12.

Table 2: Layer 3 Film Permeability Film Water Ammonia Seal S225 7 days 5 days Adhesive S225 w/Foil Back 7 days Adhesive ZW44 (PP) * >12 days Adhesive ELV-400 5 days Adhesive CV-600 5 days Adhesive FLEXMARKW 21 days 21 days Heat White PP Tevlar 4 days 5 days Heat

* No data taken Example 2: Studies of Layer 2 with Phenolphthalein Inks.

For the majority of the pH experiments, a phenolphthalein indicator was used. Two pH sensitive dyes, were used: Direct Yellow #4 and phenolphthalein, supplied as dry powder. The Direct Yellow changes only very slightly when exposed to a strong base (NH40H), but the phenolphthalein changes from an almost colorless solution in water to a dark purple.

Phenolphthalein is somewhat soluble in water, but it is much more soluble in ethanol (EtOH). Phenolphthalein was dissolved in EtOH at varying concentrations to determine the optimal concentration needed to produce an indicator that was both colorless and produced a distinct color change with pH.

Table 3 below illustrates results obtained using 0.1% (10 mg/ml EtOH), 1% (100 mg/ml EtOH), and 5% (500 mg/ml EtOH) phenolphthalein solutions, which were tested on I cm2 pieces of white filter paper. The filter paper squares were dipped in the respective solutions and then air-dried. Neither the 0.1% or 1.0% solutions resulted in any noticeable tint, but the 5.0% solution left a slight yellow/orange tint on the white paper. Next, the filter paper squares were humidified and exposed to NH40H. The 0.1 % squares turned a light shade of pink, and the 1.0% and 5.0% squares turned a very distinct dark purple. There was no distinguishable difference between activated color of the 1% and 5% indicators.

Table 3: Phenolphthalein Inks Concentration Color Activated Color Requires Moisture 0.1% Colorless Lt. Pink Yes 1.0% Colorless Dark pinlc/red Yes 5.0% Lt. Yellow Dark pinlUred Yes 1.0% w/ glycerol Colorless Dark pink/red *No

Does not require additional Humidification Example 3: Properties of Volatile Agents.

A number of different volatile agents have been used with varying degrees of success. Table 4 lists agents and their corresponding properties.

Table 4: Volatile Agents Agent Volatility Toxicity Layer 4 Overall Success Triethylamine Very High High PCL-Film Poor Amylamine High High PCL-Film Good Acetic Acid Moderate Low Paper & Film Good Ammonia High Moderate Paper & Film Excellent Butyric Acid High Low PCL Film Poor The activator layer (layer 4) was originally conceived as a thin film of poly (caprolactone) (PCL) containing the active agent. PCL is generally solvent-cast using methylene chloride (MeCl2), so the active agent must be miscible in the MeCl2 for it to be distributed evenly throughout the PCL film.

The first volatile agent tested was triethylamine, a highly volatile organic base. Unfortunately, triethylamine is so volatile, that, most of the amine had evaporated from the PCL film by the time the solvent was gone and the film was ready to be cut.

The next agent tested was amylamine, another organic base with a lower volatility than triethylamine. The amylamine was cast in 50% (by weight) films of PCL on a glass plate. To minimize losses of the amylamine, the films were incorporated into the devices as soon as they were dry enough to be peeled from the glass plate and cut to size (10-15 minutes).

Two volatile acids, acetic acid and butyric acid, were identified as compatible with the PCL/MeCl2 film-casting technique. Films cast with both

of these acids take significantly longer to dry. A few devices were manufactured using the acetic acid loaded PCL films with CV-600 diffusion barriers. The acetic acid prototype resulted in time delays of 2-3 days.

Results In general, the organic bases performed relatively well, although triethylamine proved to be too volatile. A number of successful devices were manufactured with the amylamine using the ELV-400 vinyl films as the diffusion barrier. The longest delay obtained to date, 14 days, was achieved with amylamine. Amylamine unfortunately is fairly toxic and its odor is offensive.

Example 4: Testing Material for Layer 5.

A number of devices were made using heat-sealed Tevlar for both layers 1 and 5. A permeability study was started using heat-sealed pouches of Tevlar containing either ammonia or water. However, the Tevlar did not perform nearly as well as the polypropylene films previously tested. The Tevlar pouches lost all of their contents within the first 4-5 days, whereas the polypropylene pouches lasted closer to 2-3 weeks.

It is understood that the disclosed invention is not limited to the particular methodology, protocols, and reagents described as these may vary.

It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims.