Abstract:
Electrical monitoring devices may include alarm devices that are designed to assist parents or attendants in identifying a wet diaper condition shortly after the diaper has been soiled. The devices may produce a visual, an audible, or an electronic signal. These electrical monitoring devices have been powered by batteries, specifically small coin cell batteries. The power that is supplied by batteries dissipates over time requiring that the batteries be periodically replaced.

Description:
BACKGROUND 
     Almost all incontinence products sold today, including diapers, training pants, adult incontinence products, absorbent swimwear, and the like are manufactured to be disposed of after a single use. The absorbent articles typically contain a cover material, a liner, and an absorbent structure positioned between the cover material and the liner. The absorbent structure may include superabsorbent particles. Many absorbent articles are so efficient at absorbing liquids that it is sometimes difficult to ascertain whether or not the absorbent article has been insulted with a bodily fluid. 
     Accordingly, various types of electrical monitoring devices, such as moisture or wetness indicators, have been suggested for use in absorbent articles. The electrical monitoring devices may include alarm devices that are designed to assist parents or attendants in identifying a wet diaper condition shortly after the diaper has been soiled. The devices may produce a visual, an audible, or an electronic signal. These electrical monitoring devices have been powered by batteries, specifically small coin cell batteries. The power that is supplied by batteries dissipates over time requiring that the batteries be periodically replaced. A need therefore exists for an absorbent article having an electrical monitoring device that includes a source of electrical energy generated from ambient energy. 
     SUMMARY 
     In general, the present disclosure is directed to an absorbent article. For example, in one embodiment, the absorbent article includes an outer cover material, a liner, and an absorbent structure positioned between the outer cover material and the liner. Further, the absorbent article includes a monitoring system, where the monitoring system includes a current source that provides electrical energy from ambient energy. 
     Another version of the present invention includes an absorbent article having an outer cover material, a liner, and an absorbent structure positioned between the outer cover material and the liner. The absorbent article includes a monitoring system, where the monitoring system comprises a current source that provides electrical energy from ambient energy. The ambient energy being either a temperature gradient, motion, light, or vibration. The absorbent article also has an accumulator that accumulates an electric charge from the current source. 
     Finally, another version of the present invention includes an absorbent article having an outer cover material, a liner, and an absorbent structure positioned between the outer cover material and the liner. The absorbent article includes a monitoring system, wherein the monitoring system comprises a current source that provides electrical energy from ambient energy. The absorbent article also includes an accumulator that accumulates an electric charge from the current source. Further, the accumulator is a battery. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side perspective of an article shown in the form of a pair of training pants having a mechanical fastening system fastened on one side of the training pants and unfastened on the opposite side thereof; 
         FIG. 2  is a perspective view of the pants of  FIG. 1 ; 
         FIG. 3  is a perspective view of the pants similar to  FIG. 2  showing a housing of a monitoring system removed from the article; 
         FIG. 4  is a top plan view of the training pants of  FIG. 1  with the pants in an unfastened, unfolded, and laid flat condition, showing the surface of the training pants that faces the wearer when worn, with portions cut away to show underlying features; 
         FIG. 5  is a cross-sectional view of the pants taken along the plane including line  5 - 5  of  FIG. 4 ; 
         FIG. 6  is a schematic illustration of the pants and one embodiment of a monitoring system; 
         FIG. 7  is a block diagram for one embodiment illustrating an order of operation for components/devices, including a measuring device for measuring an electrical property of the pants and an analog-to-digital converter for converting an analog output from a measuring device into digital values to be read by a microprocessor. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the drawings. 
     DETAILED DESCRIPTION 
     Referring now to the drawings and in particular to  FIG. 1 , an absorbent article is representatively illustrated therein in the form of children&#39;s toilet training pants and is indicated in its entirety by the reference numeral  20 . The absorbent article  20  may or may not be disposable, which refers to articles that are intended to be discarded after a limited period of use instead of being laundered or otherwise conditioned for reuse. It is understood that the present invention is suitable for use with various other absorbent articles intended for personal wear, including but not limited to diapers, feminine hygiene products, incontinence products, medical garments, surgical pads and bandages, other personal care or health care garments, and the like without departing from the scope of the present invention. 
     By way of illustration only, various materials and methods for constructing training pants such as the pants  20 , are disclosed in PCT Patent Application WO 00/37009 published Jun. 29, 2000, by A. Fletcher et al; U.S. Pat. No. 4,940,464 issued Jul. 10, 1990, to Van Gompel et al.; U.S. Pat. No. 5,766,389 issued Jun. 16, 1998, to Brandon et al., and U.S. Pat. No. 6,645,190 issued Nov. 11, 2003, to Olson et al. which are incorporated herein by reference. 
     The pair of training pants  20  is illustrated in  FIG. 1  in a partially fastened condition. The pants  20  define a longitudinal direction  48  of the pants and a lateral direction  49  thereof perpendicular to the longitudinal direction as shown in  FIG. 4 . The pants  20  further define a pair of longitudinal end regions, otherwise referred to herein as a front waist region, generally indicated at  22 , and a back waist region, generally indicated at  24 , and a center region, otherwise referred to herein as a crotch region, generally indicated at  26 , extending longitudinally between and interconnecting the front and back waist regions  22 ,  24 . The front and back waist regions  22 ,  24  comprise those portions of the pants  20 , which when worn, wholly or partially cover or encircle the waist or mid-lower torso of the wearer. The crotch region  26  generally is that portion of the pants  20  which, when worn, is positioned between the legs of the wearer and covers the lower torso and crotch of the wearer. The pants  20  also define an inner surface  28  that faces toward the wearer when the pants are being worn, and an outer surface  30  opposite the inner surface. With additional reference to  FIG. 4 , the pair of training pants  20  has a pair of laterally opposite side edges  36  and a pair of longitudinally opposite waist edges (broadly, longitudinal ends), respectively designated front waist edge  38  and back waist edge  39 . 
     In the embodiment of  FIGS. 1-4 , the training pants  20  comprise a generally rectangular central absorbent assembly, generally indicated at  32 , and side panels  34 A,  34 B formed separately from and secured to the central absorbent assembly. The side panels  34 A,  34 B are permanently bonded along seams to the central absorbent assembly  32  in the respective front and back waist regions  22  and  24  of the pants  20 . More particularly, the front side panels  34 A can be permanently bonded to and extend transversely outward beyond side margins  47  of the absorbent assembly  32  at the front waist region  22 , and the back side panels  34 B can be permanently bonded to and extend transversely outward beyond the side margins of the absorbent assembly at the back waist region  24 . The side panels  34 A and  34 B may be bonded to the absorbent assembly  32  using attachment means known to those skilled in the art such as adhesive, thermal or ultrasonic bonding. 
     The front and back side panels  34 A and  34 B, upon wearing of the pants  20 , thus comprise the portions of the training pants  20  which are positioned on the hips of the wearer. The front and back side panels  34 A and  34 B can be permanently bonded together to form the three-dimensional configuration of the pants  20 , or be releasably connected with one another such as by a fastening system  59  of the illustrated aspects. As is known in the art, the side panels  34 A,  34 B may comprise elastic material or stretchable but inelastic materials. 
     The absorbent assembly  32  is illustrated in  FIGS. 1-3  as having a rectangular shape. However, it is contemplated that the absorbent assembly  32  may have other shapes (e.g., hourglass, T-shaped, I-shaped, and the like) without departing from the scope of this invention. It is also understood that the side panels  34 A,  34 B may instead be formed integrally with the absorbent assembly  32  without departing from the scope of this invention. 
     As shown best in  FIGS. 4 and 5 , the absorbent assembly  32  comprises an outer cover  40  and a bodyside liner  42  attached to the outer cover  40  in a superposed (opposed) relation therewith by adhesives, ultrasonic bonds, thermal bonds, pressure bonds, or other conventional techniques. The liner  42  is suitably joined to the outer cover  40  along at least a portion of the longitudinal ends of the pants  20 . In addition, the liner  42  is suitably joined to the outer cover  40  along at least a portion of the lateral side edges of the pant  20 . The liner  42  is suitably adapted, i.e., positioned relative to the other components of the pants  20 , for a contiguous relationship with the wearer&#39;s skin during wear of the pants. The absorbent assembly  32  also comprises an absorbent structure  44  disposed between the outer cover  40  and the bodyside liner  42  for absorbing liquid body exudates released by the wearer and a surge management layer  45  disposed between the absorbent structure and the bodyside liner. A pair of containment flaps  46  is secured to the bodyside liner  42  for inhibiting the lateral flow of body exudates. 
     With the training pants  20  in the fastened position as partially illustrated in  FIG. 1 , the front and back waist regions are connected together by the fastening system  48  to define the three-dimensional pants configuration having a waist opening  50  and a pair of leg openings  52 . The front and back waist edges  38  and  39  (e.g., longitudinal ends) of the training pants  20  are configured to encircle the waist of the wearer to define the waist opening  50  ( FIG. 1 ) of the pants. 
     As illustrated in  FIG. 4 , a flap elastic member  53  can be operatively joined with each containment flap  46  in any suitable manner as is well known in the art. Suitable constructions and arrangements for the containment flaps  46  are generally well known to those skilled in the art and are described in U.S. Pat. No. 4,704,116 issued Nov. 3, 1987, to Enloe, which is incorporated herein by reference. 
     To further enhance containment and/or absorption of body exudates, the training pants  20  may comprise a front waist elastic member  54  ( FIG. 1 ), a rear waist elastic member  56 , and leg elastic members  58  ( FIGS. 2-4 ), as are known to those skilled in the art. The flap elastic members  53 , the waist elastic members  54  and  56 , and the leg elastic members  58  can be formed of any suitable elastic material that is well known to those skilled in the art. 
     The fastening system  80  of the illustrated embodiment comprises laterally opposite first fastening components  60  adapted for refastenable engagement to corresponding laterally opposite second fastening components  62 . In one embodiment, a front or outer surface of each of the fastening components  60 ,  62  comprise a plurality of engaging elements. The engaging elements of the first fastening components  60  are adapted to repeatedly engage and disengage corresponding engaging elements of the second fastening components  62  to releasably secure the pants  20  in its three-dimensional configuration. The fastening components  60 ,  62  can comprise any refastenable fasteners suitable for absorbent articles such as adhesive fasteners, cohesive fasteners, mechanical fasteners, or the like. Suitable fastening systems are also disclosed in the previously incorporated PCT Patent Application WO 00/37009 published Jun. 29, 2000, by A. Fletcher et al. and the previously incorporated U.S. Pat. No. 6,645,190 issued Nov. 11, 2003, to Olson et al. 
     The outer cover  40  suitably comprises a material that is substantially liquid impermeable. The outer cover  40  may comprise a single layer of liquid impermeable material, or more suitably comprise a multi-layered laminate structure in which at least one of the layers is liquid impermeable. While it is not a necessity for the outer layer to be liquid permeable, it is suitable that it provides a relatively cloth-like texture to the wearer. Alternatively, the outer cover  40  may comprise a woven or non-woven fibrous web layer that has been totally or partially constructed or treated to impart the desired levels of liquid impermeability to selected regions that are adjacent or proximate to the absorbent structure. The outer cover  40  may also be stretchable, and in some embodiments it may be elastomeric. Reference is made to U.S. Pat. No. 5,883,028, issued to Morman et al., U.S. Pat. No. 5,116,662 issued to Morman and U.S. Pat. No. 5,114,781 issued to Morman, all of which are hereby incorporated herein by reference, for additional information regarding suitable outer cover materials. 
     The bodyside liner  42  is suitably compliant, soft-feeling, and non-irritating to the wearer&#39;s skin. The bodyside liner  42  is also sufficiently liquid permeable to permit liquid body exudates to readily penetrate through its thickness to the absorbent structure  44 . The bodyside liner  42  may also be stretchable, and in some embodiments it may be elastomeric. Reference is made to U.S. patent application Ser. No. 09/563,417 filed on May 3, 2000, by Roessler et al., U.S. patent application Ser. No. 09/698,512 filed on Oct. 27, 2000, by Vukos et al., both of which are incorporated by reference herein, for additional information regarding bodyside liner material. 
     The absorbent structure  44  is disposed between the outer cover  40  and the bodyside liner  42 , which can be joined together by any suitable means such as adhesives, ultrasonic bonds, thermal bonds, or the like. While the illustrated absorbent structure  44  is shown and described herein as extending from the crotch region  26  into both the front and back waist regions  22  and  24 , it is contemplated that the absorbent structure may extend from the crotch region into only the front waist region, or only the back waist region, without departing from the scope of this invention. 
     The absorbent structure  44  is suitably compressible, conformable, non-irritating to a wearer&#39;s skin, and capable of absorbing and retaining liquids and certain body wastes. For example, the absorbent structure  44  may comprise cellulosic fibers (e.g., wood pulp fibers), other natural fibers, synthetic fibers, woven or nonwoven sheets, scrim netting or other stabilizing structures, superabsorbent material, binder materials, surfactants, selected hydrophobic materials, pigments, lotions, odor control agents, or the like, as well as combinations thereof. 
     The materials may be formed into an absorbent web structure by employing various conventional methods and techniques known in the art. For example, the absorbent structure  44  may be formed by a dry-forming technique, an air forming technique, a wet-forming technique, a foam-forming technique, or the like, as well as combinations thereof. Methods and apparatus for carrying out such techniques are well known in the art. The absorbent structure  44  may alternatively comprise a coform material such as the material disclosed in U.S. Pat. No. 4,100,324 to Anderson, et al.; U.S. Pat. No. 5,284,703 to Everhart, et al.; and U.S. Pat. No. 5,350,624 to Georger, et al.; which are incorporated herein by reference. 
     Superabsorbent material is suitably present in the absorbent structure  44  in an amount of from about 0 to about 90 weight percent based on total weight of the absorbent structure. The absorbent structure  44  may suitably have a density within the range of about 0.10 to about 0.35 grams per cubic centimeter. Superabsorbent materials are well known in the art and can be selected from natural, synthetic, and modified natural polymers and materials. 
     In one embodiment, the absorbent structure  44  may be stretchable so as not to inhibit the stretchability of other components to which the absorbent structure may be adhered, such as the outer cover  40  and bodyside liner  42 . For example, the absorbent structure may comprise materials disclosed in U.S. Pat. Nos. 5,964,743; 5,645,542; 6,231,557; 6,362,389; and international patent application WO 03/051254, the disclosure of each of which is incorporated by reference herein. 
     The surge management layer  45  may be attached to various components of the article  20  such as the absorbent structure  44  and/or the bodyside liner  42  by methods known in the art, such as by adhesive, ultrasonic, or thermal bonding. The surge management layer  45  helps to decelerate and diffuse surges or gushes of liquid that may be rapidly introduced into the absorbent structure  44  of the article  20 . Desirably, the surge management layer  45  can rapidly accept and temporarily hold the liquid prior to releasing the liquid into the storage or retention portions of the absorbent structure  44 . Examples of suitable surge management layers  45  are described in U.S. Pat. Nos. 5,486,166 and 5,490,846. Other suitable surge management materials are described in U.S. Pat. No. 5,820,973. The entire disclosures of these patents are incorporated by reference herein. 
     Optionally, a substantially liquid permeable wrapsheet (not shown) may surround the absorbent structure  44  to help maintain the integrity of the absorbent structure  44 . 
     The training pants  20  include a monitoring system that includes one or more sensors. The monitoring system may include sensors to indicate the presence of moisture or a bowel movement. The monitoring system may include a biosensor. The biosensor may be activated when contacted with an analyte contained in a body fluid. The analyte may be, for instance, a protein, a glycoprotein, an antibody, an antigen, hemoglobin, an enzyme, a metal salt, a hormone, or the like. 
     Healthcare products and incontinence products in care-giving institutions may include a monitoring system adapted to monitor humidity, temperature or a host of bio-indicators. In incontinence articles, for example, biosensors for a variety of disease conditions (e.g., cancer, diabetes, etc.) may be present and associated with respective warning indicators that are activated when a positive reading for a target analyte occurs. In one particular embodiment, the biosensor may be configured to sense a particular protein that would indicate a kidney problem. The monitoring system may also monitor the hydration level with a sensor quantifying the ionic strength of urine. Alternatively, the system may monitor sugar in urine or indicators for yeast in feminine care products. 
     Although the monitoring system may take on other configurations, this representative configuration of the system monitors an electrical characteristic of the pants and determines whether the child has urinated in the pants using such electrical characteristic. After detection of urine, the system may inform a caregiver and/or a child of the presence of the urine by generating an insult alarm. The alarm may be, for example, either an auditory signal, such as a song, or a tactile signal, such as temperature change, or a visual signal, such as a blinking light. It is understood that the system may comprise a device for sending a wireless signal to a remote auditory, visual, tactile or other sensory alarm. 
     In one particularly suitable embodiment, shown best in  FIGS. 2-4 , one example of the monitoring system is generally indicated by reference numeral  70 . The monitoring system  70  includes a sensor for detecting the electrical property (e.g., resistance Ω) of the article. The sensor includes a pair of spaced-apart generally parallel conductors C 1 , C 2  disposed within the pants  20  that define a monitoring area  74  of the pants disposed between the conductors. The conductors C 1 , C 2  may be constructed of any material that is generally electrically conductive. For example, the conductors may be constructed of metal strips (e.g., aluminum strips), metal films, coated films, conductive polymers, conductive inks, or conductive threads. Other conductors are within the scope of this invention. The conductors C 1 , C 2  extend longitudinally from the front waist region  22 , through the crotch region  26 , to the back waist region  24  of the pants  20 . As shown best in  FIG. 5 , the conductors C 1 , C 2  are disposed within the absorbent assembly  32  between the absorbent structure  44  and the surge management layer  45 , although the conductors may be disposed at other locations without departing from the scope of this invention. 
     Current i from a current source B (illustrated schematically in  FIG. 6 ) runs through the conductors C 1 , C 2  of the sensor. The current source B may be a single current source, a plurality of current sources, or a combination of current sources and current accumulators as described below. The current source B may be a direct current source or an alternating current source. The current source B provides electrical energy for the monitoring system from ambient energy as described below. In the illustrated embodiment, the conductors C 1 , C 2  are electrically connected to the current source by way of electrically conductive snap fasteners  79 . Other ways of electrically connecting the conductors to the current source are within the scope of this invention. As illustrated in  FIG. 3 , each corresponding end of each conductor C 1 , C 2  is connected to a first snap fastener member  79 A located in the front waist region  22  of the pants  20 . Alternatively, the first snap fastener member may be located in the back waist region  24 , or other locations on the pants  20 . A housing  82  that houses the current source B has corresponding second snap fastener elements  79 B for engaging the first snap fasteners  79 A and securing the housing to the pants  20 . In addition to the current source B, the housing  82  of the present embodiment also houses the remaining components of the monitoring system  70  that will be described hereinafter, although it is contemplated that the housing may include only some or none of the remaining components. In the illustrated embodiment the housing  82  is releasably secured to the pants  20  by way of the snap fasteners  79 , although it is understood that the housing may be permanently secured to the pants without departing from the scope of this invention. 
     A measuring device  85  ( FIG. 6 ) of the sensor measures an electrical property of the monitoring area  74  of the pants  20 . In one embodiment, the resistance R of the monitoring area  74  of the pants  20  is measured. Because the conductors C 1 , C 2  are spaced apart, current from the current source B must pass through the monitoring area  74  to complete the circuit. As illustrated schematically in  FIG. 6 , the monitoring area  74  acts essentially as a resistor, as indicated by reference character R. When the monitoring area  74  is dry (e.g., before the presence of an insult), the resistance of the monitoring area is relatively high, for example, some resistance above 200 kΩ. When the monitoring area  74  is wetted, its resistance drops, to some resistance less than 200 kΩ because of the electrically conductive nature of urine. 
     In another embodiment, the conductance of the monitoring area  74  of the pants  20  is measured. As stated above, urine is electrically conductive and the article  20  generally is not electrically conductive. Therefore, when the monitoring area  74  of the pants  20  is wetted, its conductance is greater than when it is dry. Other electrical properties of the pants  20 , including impedance, may be measured without departing from the scope of this invention. 
     The measuring device  85  produces an analog output signal ( FIG. 6 ) indicative of the electrical property of the monitoring area  74  of the pants  20 . For example, the measuring device  85  can measure a resistance drop across the monitoring area  74 , and produce an analog output signal corresponding to the resultant voltage drop. The output voltage signal can be used to determine other electrical properties, such as resistance or current, by performing suitable calculations known in the art or by using a reference table. For example, as is well known in the art, the voltage drop is indicative of the resistance of the pants when the current is constant. Thus, as explained below in further detail, the resistance of the pants  20  may be determined using the analog output signal of the measuring device  85 . 
     In one embodiment, a percent difference test is conducted on the measured resistance of the pants  20  to determine the presence (or lack thereof) of an insult in the pants as the pants are being worn by the user. In this embodiment, a proportional difference (e.g., a percent difference) in the measured electrical property of the monitoring area of the pants over time is determined, and this proportional difference is compared with a difference threshold value to determine if an insult is present in the pants. 
     In one example of this embodiment, illustrated in  FIG. 7 , an analog-to-digital converter  89  receives the analog output signal from the measuring device  85  and converts the signal into a digital output signal. A microprocessor  93  receives the digital output signal, which is representative of the magnitude of the electrical property (e.g., resistance) of the pants  20 , and analyzes it to determine the presence of an insult. If the microprocessor  93  detects the presence of an insult, then it may activate the insult alarm  95 . The analog-to-digital converter  89  is a conventional device for converting analog signals into digital signals that can be read by a microprocessor. The analog-to-digital converter  89  of the present embodiment may be a separate device or it may be a component of the microprocessor  93 . For illustrative purposes, the electrical property will hereinafter be referred to as resistance although, as noted above, it may be any variable property of the garment which reflects wetness. 
     The sole current source B in traditional monitoring systems in absorbent articles has been batteries. The current that is supplied by batteries dissipates over time. As such, the traditional monitoring systems have had the disadvantage that either the batteries required changing, or in systems with batteries that couldn&#39;t be changed, the monitoring system had a limited life. 
     The monitoring systems of the present invention include a current source that provides electrical energy from ambient energy. Ambient energy is any energy that is generally present in the user&#39;s environment and is not directed to power electrical devices. Examples of ambient energy include motion, light, a temperature gradient, and vibration. The ambient energy may come from the user of the absorbent article. For example, the ambient energy may be motion from the user or a temperature gradient between the skin of the user and room temperature. The ambient energy may come from the environment that the user is in, for example the sun if the user is outdoors or electric lighting if the user is indoors. 
     A current source that provides electrical energy from ambient energy provides several benefits over a current source that dissipates over time. These benefits may include longer shelf life and longer usable life. These benefits are useful in the context of monitoring systems incorporated into absorbent articles. 
     A long shelf life may be particularly useful for absorbent articles used for toilet training. A caregiver may purchase a package of diapers or training pants having a monitoring system for the purpose of toilet training. If the user of the articles becomes toilet trained before the package of articles are depleted, there will be leftover articles. These articles may be disposed of, given to others, or perhaps saved for use on another child in the family. In this last instance, the articles may sit unused for months or, more likely, years. An absorbent article having a monitoring system including a current source that provides electrical energy from ambient energy provides a caregiver with confidence that the monitoring system will be useful for immediate use with a first child and for use in the future with a second child. 
     A long useable life is also useful in absorbent articles used for toilet training. The current source of the monitoring system may be included in a durable portion of the system that is designed to be moved from a first absorbent article to a second absorbent article. Some users in training may use this durable portion including the current source for many months, and perhaps more than a year. The life may be even longer if the durable portion of the system is then used by a subsequent user. A current source that provides electrical energy from ambient energy may theoretically power a monitoring system indefinitely, providing a consistent response. This consistent response may be critical in effective toilet training. A monitoring system that relies solely on battery power may provide an inconsistent response when the battery is depleted. 
     Many absorbent articles are designed to be fit near or around the waist and legs of a user. In addition, these articles may be designed to be as discrete as possible. A monitoring system incorporated into these articles would also be located near or around the waist and legs, and also be designed to be as discrete as possible. A monitoring system that provides electrical energy from ambient energy may be designed to provide additional functions beyond providing a current source. For example, in the case of electrostrictive polymers, the current source may also provide one or more elastic components to the absorbent article, for example waist elastic members  54 ,  56 , leg elastic members  58 , or flap elastic members  53 . This multi-functional aspect may provide for a smaller, more discrete monitoring system. 
     As stated above, the ambient energy may be a temperature gradient. In this case, a thermoelectric generator takes advantage of a thermal gradient to generate a current according to the Seebeck effect. The thermoelectric generator may comprise a bottom plate, a top plate, and an array of foil segments. The array of foil segments is interposed between the bottom plate and the top plate in a side-by-side arrangement. Each of the foil segments is perpendicularly disposed between and in thermal contact with the bottom and top plates. A series of alternating n-type and p-type thermoelectric legs is disposed on a substrate of each one of the foil segments. The thermoelectric legs are generally fabricated from a bismuth telluride-type thermoelectric material, although any suitable material may be used. The top plate is disposed in spaced relation above the bottom plate. 
     The bottom and top plates may have a generally orthogonal configuration and may be fabricated from any rigid material such as ceramic material. The bottom plate and top plate are configured to provide thermal contact between a heat sink and a heat source such that a temperature gradient may be developed across the alternating n-type and p-type thermoelectric legs. The bottom plate may be thermally connected to the air surrounding a user and the top plate may be thermally connected to the skin of a user. 
     Each one of the foil segments may have a front substrate surface and a back substrate surface opposing the front substrate surface. The foil segments are arranged such that the back substrate surface of a foil segment faces the front substrate surface of an adjacent foil segment. The spaced, alternating n-type and p-type thermoelectric legs may be disposed in parallel arrangement to each other on the front substrate surface. Each of the n-type and p-type thermoelectric legs may be formed of a thermoelectric material generally having a thickness in the range of from about 5 microns (μm) to about 100 μm, with a preferable thickness of about 7 μm. The front substrate surface may have a surface roughness that is smoother than that of the back substrate surface in order to enhance the repeatability of forming the n-type and p-type thermoelectric legs on the front substrate surface. 
     A p-type and n-type thermoelectric leg pair makes up a thermocouple of the thermoelectric generator. The width of the thermoelectric legs may be in the range of from about 10 μm to about 100 μm. The length of the thermoelectric legs may be in the range of from about 100 μm to about 500 μm. A preferred length of the n-type and p-type thermoelectric legs is about 500 μm. A preferred width of the n-type thermoelectric leg is about 60 μm, while a preferred width of the p-type thermoelectric leg is about 40 μm. The geometry of the respective n-type and p-type thermoelectric legs may be adjusted to a certain extent depending on differences in the electrical conductivities of each n-type and p-type thermoelectric leg. 
     Alternatively, as stated above, the ambient energy source may be motion or vibration. In this case, a piezo-electric generator or electrostrictive polymer may take advantage of the motion or vibration to produce a current. 
     In the case of vibration, a piezo-electric generator may take advantage of a vibration to produce a current. In a piezo-electric generator, a pair of electrodes are provided on a piezo-electric plate. The piezo-electric plate moves when vibrated such that the piezo-electric plate is expanded or contracted during vibration. This expansion and contraction generates an AC voltage. Also a combination of vibration plates, orthogonal to one another, may be used so that the vibration can be divided two-dimensionally or three-dimensionally. This vibration may be caused by large movements of the user, for example walking or crawling, or by smaller movements of the wearer, for example breathing. 
     In the case of motion, a piezo-electric generator or an electrostrictive polymer may take advantage of the motion to produce a current. Electrostrictive (or synonymously, electroactive) polymers have been known to be used as low-mass actuators (artificial muscles). In one such artificial muscle application, a voltage is applied across the electrostrictive polymer via electrodes, causing the polymer to bend, stretch, or otherwise move or deform. The electrostrictive polymers can be dimensionally altered to a much greater extent than piezoelectric materials. This property of electrostrictive polymers may be used in reverse to harvest or generate electrical power from the general movement of objects such as from a human walking or crawling. As stated above, the electrostrictive polymers may comprise elastic elements of the absorbent article. 
     The polymer may be arranged in a variety of ways. Some candidate polymers for this application are, for example, polyacrylic acid, often referred to as PAA, and polyvinyl chloride (PVC). In addition, poly (3,3′-phthalidylidene-4,4′-biphenylylene), abbreviated PPB, is also a candidate electrostrictive polymer. 
     A promising polymer-electrode configuration for power generation, for example, is essentially a sandwich structure where polymer material and electrodes are interleaved. This combination of polymers between conductive sheets may be called ion-exchange polymer-metal composites or IPMCs for short. 
     The electrodes may be wired (hooked-up) in a “series” configuration. In this configuration, adjacent positive electrodes are attached to nearest neighbor negative electrodes. This series hook-up configuration for the interleaved electrodes permits the voltages generated across each polymer to be added, so that a relatively high ultimate output voltage is generated by the system. Alternatively, a parallel hook-up may be provided. In yet another configuration, combinations of series and parallel hook-ups are possible. 
     As stated above, the ambient energy may be light. In this case, a solar cell may take advantage of the light to produce a current. Solar cells may be comprised of semiconductor materials, such as silicon. In solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current. 
     A photovoltaic module is a number of solar cells electrically connected to each other and mounted in a support structure or frame. Modules are designed to supply electricity at a certain voltage, such as a common 12-volt system. The current produced is directly dependent on how much light strikes the module. 
     An absorbent article having a monitoring system including a current source that provides electrical energy from ambient energy may utilize a single source of ambient energy. For example, the source may be a temperature gradient only utilizing a thermoelectric generator. Alternatively a plurality of sources of ambient energy may be utilized, for example a temperature gradient utilizing a thermoelectric generator and light utilizing a solar cell. This second configuration may be useful in situations when a single source may not provide a steady supply of current. In these situations, the multiple supplies of current may be chosen dependent upon the specific absorbent article and current demands of the monitoring system. 
     An absorbent article having a monitoring system including a current source that provides electrical energy from ambient energy may also include an accumulator that accumulates an electric charge from the current source. As stated above, the current sources that provide electrical energy from ambient energy may not provide a steady supply of electrical energy, therefore, an accumulator may be incorporated into the monitoring system. During periods when an excess amount of electrical energy is provided by ambient energy, the accumulator may store the excess electrical energy. The accumulator may then release the electrical energy during periods when a shortage of electrical energy is provided by ambient energy. 
     The accumulator may be any device adapted to accumulate, store, and release an electrical charge. The accumulator may store the electrical charge in any form, for example chemically, electrically, or mechanically. Suitable devices include batteries, capacitors, flywheels, and the like. A single accumulator may be used; alternatively, a plurality of similar or dissimilar accumulators may be used. 
     An absorbent article having a monitoring system including a current source that provides electrical energy from ambient energy may also include a second current source that provides electrical energy from non-ambient energy. This second source may be a battery. The second source may be an antenna that harvests tuned electromagnetic radio frequencies such as used in RFID devices. The second source may be a pair of electrodes that create a galvanic couple upon the addition of a conductive fluid, for example the addition of urine. 
     When introducing elements of the present invention or the embodiments thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     As various changes could be made in the above constructions, products, and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.