Device for sensing environmental changes

Abstract

A sensor system is provided that includes a communication element and a switch configured to enable or disable the communication element. The switch includes a switchable polymer element. The polymer element has at least a first electrical state and a second electrical state, and is switchable between the first electrical state and the second electrical state in response to a predetermined environmental change.

Description

TECHNICAL FIELD

[0001] The present invention relates to sensing devices that are sensitive to changes in the environment. The invention specifically relates to sensing devices that are sensitive to chemical and mechanical changes in the environment of the device. BACKGROUND

[0002] Sensing systems are now ubiquitous in the world. Feedback systems with dedicated sensors and processor loops provide indications of speed, acceleration, temperature, mechanical state, and a host of other pieces of information. These systems often require expensive hardware elements to achieve their performance. There is an unmet need for sensors that can be incorporated into systems at low cost to enable the daily situation-desired information to improve the consumer's daily life. One unique advantage of the current world in the availability of smart phones is that they can also act as sensor interrogation devices via capabilities built into the device such as near field communication, RFID, Bluetooth, WiFi, and other communication protocols that enable the device to find out the current state of a properly constructed sensor. There is a need for simple, low cost environmental sensors that can be interrogated remotely. SUMMARY

[0003] In one aspect, a sensing device includes a coating of material that is sensitive to an aspect of the environment that is subject to change. The coating of material forms part of a sensing circuit that can be interrogated by an external system. The state of the circuit can change as a result of the response of the coating of material to a particular change in the local environment. The change in the state of the circuit can be detected by the interrogation system.

[0004] The particular environmental aspect that is subject to detection includes the humidity level of the environment or the presence of liquid water in the environment, the presence of a particular chemical in the environment, the pH level of the environment, and mechanical stress and attendant strain as a result of mechanical changes in the environment. BRIEF DESCRIPTION OF DRAWINGS

[0005] Figure 1 A schematic diagram of an embodiment of the invention is provided.

[0006] Figure 2 A schematic diagram of an embodiment of the invention is provided. DETAILED DESCRIPTION

[0007] The following presents a broad overview of various embodiments of the application. This overview should not be considered as an exhaustive description of every possible embodiment, as describing every possible embodiment would be impractical, if not impossible, and is understood that any feature, characteristic, component, composition, ingredient, product, step, or method described herein can be deleted, added, or combined with any other feature, characteristic, component, composition, ingredient, product, step, or method described herein or in the alternative. Numerous alternative embodiments can be devised by those skilled in the art without departing from the scope of the present claims as recited in the following written description and attached drawings, and it is understood that such embodiments must fit within the scope of the claims.

[0008] It is also to be understood that, unless a term is expressly defined in the specification as used in the sentence "the term '______' is hereby defined to mean, unless the context clearly dictates otherwise, the term '______' is specifically intended to be defined as" or similar sentence, the use of a term in this patent does not limit its meaning over its plain or ordinary meaning and such a term should not be interpreted to be limited in scope based on any statement made in any portion of this patent other than the language of the claims. Unless indicated, no term is intended to be essential to the invention. When any of the terms recited in the concluding claims of this patent are referred to in this patent in a manner consistent with a single meaning, that reference is intended only for the clarity of the reader and is not intended to imply, either expressly or implicitly, that the claim term is limited to a single meaning. Finally, unless a claim element is defined by the description of the word "means" and function without the description of any structure, no claim element is intended to be construed as means-plus-function limiting.

[0009] As described herein, "chip" can be replaced by a chipless RFID element as is known in the art. LC resonant RF tags or multi-resonant elements can be used in place of the chip in the described embodiments.

[0010] In one aspect, a sensor system includes an analog-to-digital converter and a sensor. The sensor is adapted to provide an output that is analog to a change in pH of an environment of the sensor. The analog-to-digital converter is adapted to convert the analog output of the sensor to a digital value. The digital value is adapted to convert the analog output of the sensor to a digital value. The analog-to-digital converter includes an input terminal and an output terminal. The input terminal of the analog-to-digital converter is disposed in electrical communication with the output terminal of the sensor.

[0011] In one aspect, a sensor system includes a tag. The tag can include one or more layers of conductive and non-conductive inks printed on a substrate. Exemplary substrate materials include polymeric films, paper, high dielectric constant dielectric materials, and FR-4 materials. The multi-layer structure can also include a local layer of non-conductive material that separates at least a portion of the conductive layer. Exemplary conductive layers include copper and silver inks. The tag includes at least one radio frequency chip, a first antenna configured as a circuit on a card, coin, or inlay. Exemplary chip / first antenna combinations include the following models: RI-I03-112A-03 (13.56 MHz), and RI-INL-R9QM (134.2 kHz), or model TRF7970A, each available from Texas Instruments (Dallas, TX). The antenna can be in the physical form of a coil or dipole, or can include a conductive component of a product or package in electrical communication with the rest of the tag. The chip / first antenna combination can be integrated into a unit tag available from Kovio (San Jose, CA). The tag also includes a conductive polymer system in electrical communication with the chip and antenna.

[0012] The power source required for the tag can be provided by the harvested energy of the RFID circuit, as the current required is in the microamp range. The harvested power can then be stored using elements such as capacitors for use by the tag.

[0013] In one embodiment, a sensor system includes a communication element and a switch. The switch is configured to enable or disable the communication element. The switch includes a switchable polymer element. The polymer element has at least a first electrical state and a second electrical state, and is switchable between the first electrical state and the second electrical state according to a predetermined environmental change. The switch can enable or disable the functional capability of the communication element of the system upon or after the environmental change occurs. Exemplary environmental changes include wetness, humidity, pH, mechanical strain, solvent compatibility, and combinations thereof.

[0014] The corresponding sensor element generally functions by having an electrical state that changes in response to swelling of the sensor polymer component, which changes in response to a selectivity of the sensor environment.

[0015] The humidity sensor can include a high polymer electrolyte coating. When the high polymer electrolyte is dry, the smart coating has a resistance in the mega-ohm range (open circuit) and less than 3 kilo-ohms when exposed to the environment (closed circuit). When exposed to water (deionized) or humidity, the polymer swells with water, thus solubilizing the electrolyte. In the unexposed, unswollen state, the embedded electrolyte provides a path for radio frequency energy to open the antenna, thus enabling the RFID to transmit. In one embodiment, the smart coating formulation is capable of this transition in about 10 to 15 seconds after exposure. The embedded electrolyte enhances the hygroscopic properties of the smart coating, effectively making it humidity sensitive.

[0016] The humidity, pH, and mechanical strain sensors can include a conductive filler element immersed in a non-conductive polymer matrix. Upon exposure of the sensor to moisture or humidity, the polymer swells as it absorbs water from the environment. The swollen polymer matrix reduces the electrical conductivity of the sensor element by increasing the spacing between discrete conductive filler particles. As this spacing increases, the path for conductive current flow through the filler of the sensor is reduced and can become completely open when or after the swelling leaves no complete conductive path through the matrix via the filler.

[0017] The swollen continuum can be controlled by a predetermined level of chemical and / or physical cross-linking. For example, chemical cross-linking can be thermally initiated, initiated by an initiator, initiated by ultraviolet light, initiated by light. For example, physical cross-linking can be initiated by entanglement, freeze-thaw cycling, and crystallization. The predetermined level of cross-linking provides for balanced swelling within the conductive region of the swelling zone by water or humidity only. The cross-linking also acts as a means to amplify the effects of pH sensitivity. In the cross-linked system, changes in pH cause the sensor to swell or shrink within a predetermined dynamic range.

[0018] Prior to exposure, the sensor includes a conductive path, which is comprised of a series of discrete particles of conductive material in physical contact with one another. The conductive path provides a path for current flow either as part of the circuit to which the sensor has been incorporated, or in an alternative embodiment, the conductive path can provide a known resistance as part of the circuit. Upon exposure of the sensor to environmental insult, the electrical conductivity of the sensor will decrease as the swelling of the polymer matrix increases the distance between the discrete conductive particles, and can decrease to zero in the event that the swelling creates complete separation of the conductive particles at any cross-section of the aforementioned conductive path. The change in electrical conductivity can be correlated to the environmental pH.

[0019] The chemical resistor humidity sensitive smart coating has a resistance in the low ohm range when dry, enabling an electrical conductivity, and a resistance in the high mega ohm range when compromised by the environment to get a very low electrical conductivity. When the smart coating is compromised by a water based liquid, the polymer begins to swell. This swelling causes a percolation threshold where the volume of the polymer increases to 20-40% of its dry volume. In so doing, the conductive filler reaches a point where it can no longer conduct radio frequency energy between the anode side and the cathode side of an open circuit or between two IC leads. In one embodiment, the chemical resistor smart coating formulation is able to make this transition in about 5 seconds after being compromised. To better disperse the filler, a non-ionic surfactant Triton X-100 is used.

[0020] A chemically sensitive sensor can be formed that is sensitive to an exemplary target chemical having a Hildebrand solubility parameter in 2 times polyethylene co- ethylene acetate. Because it is not soluble in water, the system shows selective chemical testing in an aqueous environment. The chemical resistance in humidity sensing is comprised of a water soluble polymer: [poly(vinyl alcohol), M W = 89,000-98,000] and a conductive filler (silver coated copper). In the case of a chemical / biological sensor, the polymer of the chemical resistor can be replaced by another polymer having a similar solubility parameter, specifically the Hildebrand parameter, as the target.

[0021] When the selected polymer is contacted with the analyte of interest, the polymer swells behind the percolation threshold of the conductive filler, where the filler does not make sufficient contact to maintain electrical conductivity.

[0022] The chemical resistor can be further modified to respond only to an environment within a predetermined pH range. A model polymer system can be intended for enteric coating. Such a coating is designed to withstand the low pH in the stomach and when it passes through the higher pH environment in the intestines, the polymer swells / dissolves to release the drug. In the case herein, of a basic pH sensor, of interest is a system that swells beyond a certain pH threshold, causing the filler to exceed the percolation threshold for electrical conductivity. The polymer system is essentially an aqueous dispersion of a proprietary anionic polymer functionalized with methacrylic acid. The system can be tuned to dissolve at pH 5.5. In one embodiment, the sensor can be configured to provide an indication of the pH of the environment. In such an embodiment, the volume change of the polymer matrix as a function of the pH of the environment can be used to provide an indication of the pH. The matrix can be configured such that there is a known volume change through swelling due to exposure to an aqueous environment, where the matrix responds to the environment by absorbing water and swelling. By exposure to a pH aacidic or basic environment, the matrix can be induced to further change in volume. The polymer can be configured to respond to an increase in pH by swelling, which also results from deprotonation of the acidic matrix in response to a pH a above the pK of the acidic component of the matrix. The basic matrix can alternatively be configured to undergo protonation and experience a volume contraction in response to an elevated pH.

[0023] The polymer matrix can also be configured to respond to a range of pH values by undergoing a volume contraction in a first portion of the range and a volume increase in a second portion of the range. For example, a polymer matrix comprising both an acidic component and a basic component can be configured to contract in volume due to protonation of the acidic component when the environmental pH rises above the pK of the matrix component, and at a predetermined pH threshold, the basic second component undergoes deprotonation resulting in swelling of the matrix volume. a

[0024] The matrix can be formulated such that it will respond to a falling pH. In one embodiment, the matrix can swell due to deprotonation when the pH of the environment falls. In an alternative embodiment, the matrix can contract due to protonation of the matrix when the pH falls.

[0025] In one embodiment, the polymer matrix undergoes a volume hysteresis associated with a change in exposure to an environment of a particular pH value. In such an embodiment, the polymer matrix can undergo a volume change in response to a change in the pH of the environment, and subsequently undergo a volume change reversal in response to a reversal of the pH of the environment. The hysteresis can not be perfectly symmetrical, as the final matrix volume at a particular pH can not precisely reflect the initial state of the matrix volume and pH. This imperfect hysteresis symmetry can provide an indication that an environmental event of interest has occurred, as the change in the volume of the sensor's matrix during that event can produce a sensor with different electrical characteristics compared to a sensor that did not experience that insult.

[0026] In one embodiment, when insulted by a solution having a pH in a range of interest, the polymer matrix will transition from a first electrical state to a second electrical state. Following the insult, the matrix can be dried, resulting in a third electrical state. Depending on the predetermined environmental pH change, the third state after drying corresponds to the insulted state, but is not electrically equivalent to the second state. Without being bound by theory, the change in electrical resistance in the third state relative to the first or second state involves a combination of broken bonds from strain in the polymer network, reorganization of salt retention and filler orientation, depending on the pH and swelling.

[0027] ​In one embodiment, the polymeric matrix will transition from a first electrical state to a second electrical state when compromised by moisture or humidity. After compromise, the matrix can be dried, resulting in a third electrical state. Depending on the amount of water content, the third state after drying corresponds to the initial state, but is not electrically equivalent to the first state.

[0028] From a materials perspective, a polymeric strain sensor is very similar to a chemical resistor. The elastic polymer can be replaced by an environmentally sensitive polymer. As the polymer elongates due to strain, the crystalline structure and physical entanglements change orientation, thus changing the amount of contact of the conductive filler. As the strain increases, the conductive resistance increases. The mechanical properties, coating geometry (specifically, cross-sectional area), and filler loading content affect the conductive resistance change as well as hysteresis. Ideally, the polymeric system should be insoluble in any potential chemicals it will come into contact with. The polymeric sensor only works when the antenna construction and attachments are such that the coating detaches from the tag as a continuous film.

[0029] The strain sensor element can also be made directional, providing an indication of the magnitude and direction of strain on the sensor. In one embodiment, a laminate structure is formed, with a first layer having conductive filler particles dispersed within a polymeric matrix as described above. A second layer comprising only a polymeric matrix can be added to the laminate structure. Deformation of the laminate where the outer surface of the conductive layer is concave results in higher electrical conductivity, as the spacing between the conductive particles is reduced. Alternatively, deformation in the opposite direction, where the outer surface of the conductive layer is convex, results in greater spacing between the filler particles and lower electrical conductivity.

[0030] A sensor and communication element comprising a tag can be used to detect an environment by providing a product comprising an environmentally sensitive sensor system, the sensor system including: a communication element and a switch configured to enable or disable the communication element, the switch including a switchable polymeric element having at least a first electrical state and a second electrical state and switchable between the first electrical state and the second electrical state in response to a predetermined environmental change, providing an interrogator adapted to communicate with the sensor system to determine the state of the communication element, exposing the product to a potential environmental change, interrogating the state of the communication element of the sensor system. An exemplary interrogator and interrogation includes the use of an NFC-enabled smartphone and appropriate NFC application to interrogate the current state of a tag placed in an environment of interest.

[0031] The elements described herein can be configured to include a device comprising a sensor system. The sensor system in turn includes: a communication element and a switch configured to enable or disable the communication element. The switch includes a switchable polymeric element having at least a first electrical state and a second electrical state and switchable between the first electrical state and the second electrical state in response to a predetermined environmental change.

[0032] In one embodiment, the device can comprise a consumer product or packaging for a consumer product. The sensor element can contact the product within the packaging. The sensor can be positioned within the product in a manner and location intended to expose the sensor to a particular environmental change during use of the product by the consumer. An exemplary application in this manner would comprise a label with a sensor positioned within a diaper such that tampering with the diaper while it is being worn by a baby can create an environmental change that in turn can change the electrical state of the sensor element and the entire label.

[0033] Exemplary sensor element :

[0034] A humidity sensitive polymer electrolyte coating with high salinity was developed in the following manner: A vial was filled with 10 mL of ultrafiltered deionized water. 1.1688 grams of sodium chloride was added to the vial and mixed with a magnetic stir bar at room temperature until the salt dissolved, resulting in a 2 molar salt solution. When the system appeared clear, 0.3 grams of poly(vinyl alcohol) was added. The solution was heated to 90 °C to allow the polymer to enter the solution. When the system was clear, a 10 microliter pipette tip (approximately 1-2 mm of the tip was removed) was used to apply the solution to the surface. The pipette was set to 5 microliters and the hot polymer solution was applied to the area of interest on the RFID tag. The system was then placed in a desiccant chamber and allowed to dry overnight at room temperature.

[0035] A chemical resistor humidity sensitive polymer coating was developed in the following manner. A vial was filled with 9 mL of ultrafiltered deionized water. A separate vial was used to add 0.1 grams of triton X 100 to 10 milliliters of ultrafiltered deionized water to form a 1 wt% solution. One milliliter of the 1 wt% Triton X-100 was added to the 9 milliliters of ultrafiltered deionized water to form a 0.1 wt% Triton X-100 solution. 0.3 grams of poly(vinyl alcohol) was added to the 0.1 wt% Triton X-100 solution (lower molecular weight and higher % hydrolysis makes this system respond faster than a higher molecular weight and lower % hydrolysis system). The solution was heated to 90 °C allowing the polymer to go into solution. When the system was clear, 0.1 grams of the silver coated copper (AgCU550) conductive filler was added, the filler was purchased from Ferro Electronic Materials Systems (Mayfield Heights, OH). The solution was sonicated (degassing mode, level 5) for 5 minutes. The system was applied to the surface using a 10 microliter pipette tip (approximately 1-2 millimeters of the tip was removed). The pipette was set to 5 microliters and the hot polymer solution was applied to the area of interest on the RFID tag. The system was then placed in a desiccant chamber and allowed to dry overnight at room temperature.

[0036] A second chemical resistor polymer coating designed to respond to other environmental chemicals and not to water was developed in the following manner. A vial was filled with 10 mL of trichloroethylene. 0.6 grams of [poly(ethylene-co-vinyl acetate)] was added to the vial. The solution was mixed at room temperature until the polymer went into solution. When the system was clear, 0.2 grams of the silver coated copper (AgCU550) conductive filler was added. The system was applied to the surface using a 10 microliter pipette tip (approximately 1-2 millimeters of the tip was removed). The pipette was set to 5 microliters and the hot polymer solution was applied to the area of interest on the RFID tag. The system was then placed in a fume hood and allowed to dry overnight at room temperature.

[0037] A chemical resistor polymer system designed to respond only to an environment with a pH within a target range was formed as follows: The method can use talc as an anti-tack agent and triethyl citrate as a plasticizer or PlasACRYL HTP20 as an anti-tack agent / plasticizer. In a 200 mL beaker, 41.7 mL of Eudragit L30 D-55, available from Evonik Industries (Essen, Germany), was added to 57 mL of deionized water, 14.6 mL of PlasACRYL HTP20, available from Evonik Industries, and 4.3 grams of the silver-coated copper (AgCU550) conductive filler. The solution was stirred with a magnetic stir bar for 10 minutes. The solution was used to coat the desired area of an RF tag and cured in a circulating drying oven at 40 °C for 2 hours. The RFID tag was turned off when the polymer was exposed to an environment with a pH value greater than 5.5.

[0038] Additional chemical resistor sensor systems were designed to respond to environmental changes in pH. It should be understood that, without limitation, polymers, initiators, and / or cross-linking agents suitable for forming a pH sensitive matrix in combination with a conductive filler can include or be a combination of the following: poly(acrylic acid) (PAA), acrylic acid (AA), 2-hydroxyethyl methacrylate (HEMA), poly(hydroxyethyl methacrylate-co-methacrylic acid) (PHEMA-co-MAA), poly(acrylic acid-co-isooctyl acrylate) (poly(AA-co-IOA)), poly(acrylamide) (PAAm), poly(methacrylic acid) (PMAA), poly(diethylaminoethyl methacrylate) (PDEAEMA), poly(dimethylaminoethyl methacrylate) (PDMAEMA), poly( vinyl alcohol) (PVOH or PVA), poly(ethylene glycol) dimethacrylate (PEGDMA), acrylamide (AAm), N,N-dimethylaminoethyl methacrylate (DMAEMA), N-isopropylacrylamide (NIPAAm), 2-(dimethylmaleimide) acrylamide (DMIAAm), 2-(dimethylmaleimide) ethyl methacrylate (DMIMA), poly(2-vinylpyridine) (P2VP), poly(4-vinylpyridine) (P4VP), ethylene glycol dimethacrylate (EGDMA), glutaraldehyde, azobisdimethylpropyl nitrile (AIBN), glyoxal, glycerol, the cellulose family, any polymer or molecule with alcohol functionality, any polymer or molecule with carboxylic acid functionality.

[0039] A model conductive composite system contained conductive graphitized carbon as the conductive filler and the polymer matrix was composed of poly(vinyl alcohol) and poly(acrylic acid). It should be understood that the cross-linked water-sensitive polymer can be composed of any of the aforementioned polymers but is not necessarily pH sensitive.

[0040] Sensing materials can be prepared as follows :

[0041] PVOH / PAA / filler composite sensor element :

[0042] Fill two, 150 mL Pyrex glass beakers with 40 mL of deionized water. Add a magnetic stir bar and place the beakers on a hot / stir plate. Set the stirrer to 400 rpm. Weigh out 3 grams of A99 conductive graphitized carbon filler (44 micron diameter) from Asbury Carbon and add to each beaker. Allow the stirrer to mix the dry powder into the solution. Manual mixing with a spatula can help push any remaining powder into solution. Remove the beakers from the hot / stir plate and place the beakers in an ultrasonic bath and sonicate for 5 minutes to better disperse the filler. After sonication, place the beakers back on the hot / stir plate. Set the temperature of the polyvinyl alcohol (PVOH) and poly(acrylic acid) (PAA) hot / stir plate to 200 °C with the stirrer set to 400 rpm. Weigh 4 g of PVOH (89-98K MW, 99% hydrolyzed) and 4 g of PAA (450K MW) from Sigma Aldrich into a weighing boat. The PVOH can be added all at once to the beaker. The PAA needs to be added slowly to prevent clumping in the solution. After each spatula addition, allow the polymer powder on the surface to enter the solution for enough time before adding the next spatula. Once the polymers are well dispersed into the solution, add a JKEM thermocouple to monitor the temperature to ensure they remain between 70-80 °C. The system is covered with a paraffin film and allowed to dissolve and continue for three hours. After three hours, turn off the heat and allow the system to cool for 30 minutes while still stirring. When the temperature drops below 30 °C, mix the PVOH and PAA solutions into a 500 mL beaker. A overhead mechanical stirrer is used to handle the higher viscosity and prevent bubble formation. Mix the two solutions at 70 rpm for at least two hours but preferably up to 17 hours at room temperature to control the viscosity and prevent settling of the filler. After mixing, remove any surface bubbles with a disposable pipette. Pour the resulting solution into a 150 x 20 mm petri dish and allow it to dry overnight. Alternatively, pour the resulting solution into a syringe to be injected over a conductive wire to form a sensor. After air drying, use a razor blade to shave the edges of the petri dish or dried surface and carefully remove to prevent plastic strain of the polymer system. Place between two silicone sheets and cure at 130 °C for 1 hour. It should be understood that alternative curing times and temperatures can be used to effect esterification between the carboxylic acid groups on the PAA and the alcohol groups on the PVOH. Before separating the silicone sheets, remove and allow to cool to room temperature.

[0043] PAA / glycerol / filler composite sensor element :

[0044] A 150 mL Pyrex glass beaker was filled with 80 mL of deionized water. A magnetic stir bar was added and the beaker was placed on a hot / stir plate. The stirrer was set to 400 rpm. 2.4 grams of A99 conductive graphitized carbon filler (44 micron diameter) from Asbury Carbon was weighed out and added to the beaker. The stirrer was allowed to mix the dry powder into the solution. Manual mixing with a spatula can help push any remaining powder into the solution. The beaker was removed from the hot / stir plate and placed in an ultrasonic bath and sonicated for 5 minutes to better disperse the filler. After sonication, the beaker was placed back on the hot / stir plate. The temperature of the hot / stir plate was set to 200 °C and the stirrer was set to 400 rpm. 8 g of PAA (450 K MW) from Sigma Aldrich was weighed into a weighing boat. The PAA needs to be added slowly to prevent clumping in the solution. After each spatula addition, the polymer powder on the surface was allowed to enter the solution for enough time before the next spatula was added. Once the polymer was well dispersed into the solution, a JKEM thermocouple was added to monitor the temperature to ensure it remained between 50-60 °C and the system was allowed to dissolve while covered with a paraffin film and for three hours. After three hours, the heat was turned off and the plate was allowed to cool. After the temperature of the solution dropped below 30 °C, it was removed from the hot plate to an overhead mechanical stirrer. The overhead mechanical stirrer was used to handle the higher viscosity and prevent bubble formation. 0.8 g of glycerol from Sigma Aldrich was added slowly. The two solutions were mixed at 70 rpm for 1 hour at room temperature. After mixing, any surface bubbles were removed with a disposable pipette. The resulting solution was poured into a 150 x 20 mm petri dish and allowed to dry overnight. The polymer system can also be incorporated into a mold with conductive leads. After air drying, the edges of the petri dish were shaved with a razor blade and carefully removed to prevent plastic strain of the composite. It was placed between two silicone sheets and cured at 130 °C for 1 hour. It should be understood that alternative curing times and temperatures can be used to achieve esterification between the carboxylic acid groups on the PAA and the alcohol groups on the glycerol. Prior to separating the silicone sheets, they were removed and allowed to cool to room temperature.

[0045] PAA / filler composite sensor element :

[0046] A 150 mL Pyrex glass beaker was filled with 80 mL of deionized water. A magnetic stir bar was added and the beaker was placed on a hot / stir plate. The stirrer was set to 400 rpm. 2.4 grams of A99 conductive graphitized carbon filler (44 micron diameter) from Asbury Carbon was weighed out and added to the beaker. The stirrer was used to mix the dry powder into the solution. Manual mixing with a spatula can help push any remaining powder into the solution. The beaker was removed from the hot / stir plate and placed in an ultrasonic bath and sonicated for 5 minutes to better disperse the filler. After sonication, the beaker was placed back on the hot / stir plate. The temperature of the hot / stir plate was set to 200 °C and the stirrer was set to 400 rpm. 8 g of PAA (450K MW) from Sigma Aldrich was weighed into a weighing boat. The PAA needs to be added slowly to prevent clumping in the solution. After each spatula addition, the polymer powder on the surface was allowed to enter the solution for enough time before the next spatula was added. Once the polymer was well dispersed into the solution, a JKEM thermocouple was added to monitor the temperature to ensure it remained between 50-60 °C and allow the system to dissolve and continue for three hours and until covered with a paraffin film. The heat was turned off and the hot plate was allowed to cool for 30 minutes. After mixing, any surface air bubbles were removed with a disposable pipette. The resulting solution was poured into a 150 x 20 mm petri dish and allowed to dry overnight. The polymer system can also be incorporated into a mold with conductive leads. After air drying, the edges around the petri dish were shaved with a razor blade and carefully removed to prevent plastic strain of the composite. Placed between two silicone sheets and cured at 130 °C for 1 hour. It should be understood that alternative curing times and temperatures can be used to achieve self-crosslinking between the carboxylic acid groups on the PAA to form anhydrides. Before separating the silicone sheets, they were removed and allowed to cool to room temperature.

[0047] Material preparation :

[0048] To solubilize the polymers in the aqueous containing solution, heat was added to the system. The polymers were solubilized in separate beakers and mixed later to ensure that phase separation between the polymer systems did not occur during the drying process. Although hydrogen bonding is easy to perform between the carboxylic acid of PAA and the alcohol of either PVOH or glycerol, above 62 °C the free volume effect dominates. To circumvent this, the corresponding polymer solutions were cooled to room temperature while mixing in their corresponding beakers. Once at room temperature, the PAA was slowly added to the crosslinking system (PVOH or glycerol) and mixed for two hours to ensure that both systems were well dispersed for hydrogen bonding. Longer mixing was performed to remove water from the system to increase the viscosity to prevent settling of the filler during the drying process. In practice, phase separation was identified by anomalies in the ATR spectra as well as pH sensing data. A mechanical stirrer was used in the final step to avoid air bubble formation in the polymer systems.

[0049] The pH sensor crosslinking was verified by ATR spectra of ester formation using Thermo Nicolet Nexus 670 FTIR and days of exposure to aqueous systems to demonstrate that the system does not dissolve. To obtain dynamic resistance data from the sensor and to prevent electrolysis, a power source supplies 1.0 volts and the resulting current is measured by a 2831E Measurement (data logging multimeter). Initially, a crocodile clip was used to attach to the sensing material. The measured current was converted to resistance using Ohm's law. Later, an improvement was made where copper wire was cured into the sensing material to improve the measurement and scalability. The weight of the sensor was also recorded to continuously track changes as a function of pH. Dynamic readings were taken of the pH sensor when in solution. At pH 3 and 10, a swelling plateau was reached in about 2 minutes with corresponding resistance changes for the PAA / PVOH formulation. At pH 3 and 10, a swelling plateau was reached in about 1 minute 30 seconds with corresponding resistance changes for the PAA / glycerol formulation. Because PAA can deprotonate and protonate easily as a function of pH and time, a single sensor with the primary PAA / PVOH system was used for proof of concept hysteresis loop testing. The weight of the sensor was recorded before initial insult started at pH 4. An hour later the insult was followed and the weight change due to deprotonation was recorded for pH 5, 5.5, 6, 7, and 9. In an ideal system, reversal of the same pH insult can cause the new volume to shrink back to the corresponding volume. However, the volume shrinkage goes through a hysteresis due to the hysteresis formed by the protonation time constant, the distance of the pH value from the pKa value, and irreversible changes in the strained network of some broken anhydrides and PAA / PVOH ester bonds. This hysteresis can be correlated to the insult time and the ambient pH and ultimately to the resistance value. Once the pH drops to the pKa of the polymer, the protonation will reach a plateau.

[0050] A mechanically-strain sensitive polymer system was formed by replacing the elastomeric polymer with an environmentally sensitive polymer as follows: 8 grams of silicone RTV rubber was mixed with 8 grams of conductive filler in a beaker to obtain a 50 / 50 ratio of polymer. The mixture was extruded through a plastic 20 mL syringe. The strips were extruded onto a silicone surface for easy removal. In some embodiments, an additional layer of silicone was extruded onto the silicone conductive filler layer and allowed to cure. The room temperature vulcanization was allowed to proceed for 24 hours. The strain sensor strip was removed and tested for dynamic conductivity and mechanical properties (Young's modulus, elastic region, yield point). The Instron was set to elongate constantly at 1 mm / sec until breakage. The resistance was measured in parallel with the 2831E Measurement (data logging multimeter) and a small crocodile clip attached to the sample. The Young's modulus was calculated with the Instron software. An auxiliary test was performed without the use of a crocodile clip where the final strain of 150% elongation due to breakage occurred in the middle of the strain sensor.

[0051] The exemplary tag system exhibits the combination of a sensor element and a communication element. The sensor element can also be formed as a stand-alone device for use in any system that requires an electrically switchable sensor for the environmental change.

[0052] A polymer system is formed that is sensitive to directional strain by tailoring the viscosity of the polymer system such that the filler settles due to gravity to create a predetermined non-conductive to conductive continuum in the matrix. In the case of the filler loaded continuum, the directional strain can be identified by a drop in resistance as the system bends towards the conductive side or an increase in resistance as it bends towards the non-conductive side. The polymer system can be thermoset, thermoplastic, or elastomeric in nature. Suitable polymer families are ester, amide, polyurethane, silicone, epoxy, ether, ethylene, and vinyl, for example. The conductive filler can be metallic or non-metallic. In the case herein, the model system is designed with a non-metallic conductive graphitized carbon filler and a polymer matrix consisting of poly(vinyl alcohol) and poly(acrylic acid).

[0053] PAA / PVOH / filler oriented strain sensor composite :

[0054] Two 150 mL Pyrex glass beakers were filled with 40 mL of deionized water. A magnetic stir bar was added and the beakers were placed on a hot / stir plate. The stirrer was set to 400 rpm. 1.2 grams of A99 conductive graphitized carbon filler (44 micron diameter) from Asbury Carbon was weighed out and added to each beaker. The stirrer was used to mix the dry powder into the solution. Manual mixing with a spatula can help push any remaining powder into the solution. The beakers were removed from the hot / stir plate and placed in an ultrasonic bath and sonicated for 5 minutes to better disperse the filler. After sonication, the beakers were placed back on the hot / stir plate. The temperature of the polyvinyl alcohol (PVOH) and poly(acrylic acid) (PAA) hot / stir plate was set to 200 °C with the stirrer set to 400 rpm. 4 g of PVOH (89-98K MW, 99% hydrolyzed) and 4 g of PAA (450K MW) from Sigma Aldrich were weighed into a weighing boat. The PVOH can be added all at once to the beaker. The PAA needs to be added slowly to prevent clumping in the solution. After each spatula addition, allow the polymer powder on the surface to enter the solution for enough time before adding the next spatula. Once the polymers are well dispersed into the solution, a JKEM thermocouple was added to monitor the temperature to ensure they stay between 70-80 °C. The system was covered with a paraffin film and allowed to dissolve and continue for three hours. After three hours, the heat was turned off and the system was allowed to cool for 30 minutes while still stirring. When the temperature dropped below 30 °C, the PVOH and PAA solution was mixed into a 500 mL beaker. A overhead mechanical stirrer was used to handle the higher viscosity and prevent bubble formation. The two solutions were mixed at 70 rpm for at least two hours at room temperature to mix well but maintain a low viscosity water content to enable the filler to settle into a continuous unity. After mixing, any surface bubbles were removed with a disposable pipette. The resulting solution was poured into a 150 x 20 mm petri dish and allowed to dry overnight. After air drying, the edges or perimeter of the dried surface were shaved with a razor blade and carefully removed to prevent plastic strain of the polymer system. Placed between two silicone sheets and cured at 130 °C for 1 hour. It should be understood that alternative curing times and temperatures can be used to effect esterification between the carboxylic acid groups on the PAA and the alcohol groups on the PVOH. Prior to separating the silicone sheets, they were removed and allowed to cool to room temperature.

[0055] The material strip was cut into 1 cm by 4 cm strips and clamped at the ends with alligator clips. A fluke multimeter was used to take resistance changes. The balanced resistance was about 490 ohms. When the sensor was bent towards the conductive side, the resistance dropped to 336 ohms due to compression of the conductive filler. When the sensor was bent towards the non-conductive side, the resistance increased to 618 ohms due to slippage and separation of the conductive filler path. Upon release of the strain, the sensor returned to its balanced resistance of about 490 ohms.

[0056] As shown in FIG. 1, sensor element 1000 includes a polymer matrix 100 and a conductive filler element 200 embedded in the matrix. As shown in FIG. 2, sensor element 1000 includes a polymer matrix 100, a conductive filler element 200, and a layer of an unfilled matrix 300. Figure 1 As shown in FIG. 1, sensor element 1000 includes a polymer matrix 100 and a conductive filler element 200 embedded in the matrix. As shown in FIG. 2, sensor element 1000 includes a polymer matrix 100, a conductive filler element 200, and a layer of an unfilled matrix 300. Figure 2 As shown in FIG. 1, sensor element 1000 includes a polymer matrix 100 and a conductive filler element 200 embedded in the matrix. As shown in FIG. 2, sensor element 1000 includes a polymer matrix 100, a conductive filler element 200, and a layer of an unfilled matrix 300.

[0057] In one aspect, a sensor system includes a tag. The tag can include one or more layers of conductive and non-conductive inks printed on a substrate. Exemplary substrate materials include polymeric films, paper, high dielectric constant dielectric materials, and FR-4 materials. The multi-layer structure can also include a local layer of non-conductive material that separates at least a portion of the conductive layer. Exemplary conductive layers include copper and silver inks. The tag includes at least one sensor, a radio frequency chip, and a first antenna configured as a circuit on a card, coin, or inlay. The chip can be active or passive. Exemplary chip / first antenna combinations include the following models: RI-I03-112A-03 (13.56 MHz), and RI-INL-R9QM (134.2 kHz), or model TRF7970A, each available from Texas Instruments (Dallas, TX). The antenna can be in the physical form of a coil or dipole, or a conductive component of a product or package in electrical communication with the rest of the tag.

[0058] The power source required for the sensor can be provided by the harvested energy of the RFID circuit, as the current required is in the microamp range. The harvested power can then be stored using elements such as capacitors for use by the sensor.

[0059] The tag can be configured such that the output of the sensor changes the value of one or more bits of a word stored in the memory of the chip of the tag. In one embodiment, any non-zero sensor output changes the value of the specified bit from one to zero or from zero to one. Alternatively, the circuit of the tag can provide a bias voltage against which the sensor output is compared. In this embodiment, only sensor outputs above the bias threshold, or between a lower and upper threshold set, can change the value of the bit.

[0060] The tag can include more than a single sensor. In one configuration of a multi-sensor tag, the output of each sensor can be used to change the value of its own respective bit. In an alternative configuration, the set of sensors can be polled when the tag is powered, such that a single specific bit of the memory of the tag steps through a series of values depending on the output of each polled sensor. As before, the tag can be designed such that any non-zero sensor output will change the value of the associated bit, or such that only values above a lower threshold or between an upper and lower threshold will change the value of the respective bit.

[0061] The tag can be read using radio frequency protocols such as Near Field Communications (NFC). When the tag is interrogated or read, power is supplied to the tag circuitry, and the sensor output changes the tag's memory. The tag's memory is then read by the interrogator. The interrogator acquires digital values ​​of memory words indicating the sensed state of the tag's environment. The tag's associated communication frequency range can be HF, UHF, or other appropriately selected frequency ranges, determined by the specific requirements of the tag based on the intended environment and the tag's purpose.

[0062] The sensor system may also include an interrogator. The interrogator includes a power supply and a second antenna adapted to generate electromagnetic radiation including the resonant frequency of the first antenna; and a receiver adapted to detect the electromagnetic radiation and demodulate the detected radiation, thereby extracting embedded data from the detected radiation. A Bluetooth device, model 223012, purchased from GAO ​​RFID (Toronto Canada). ™ The RFID reader illustrates one form of interrogator. The interrogator, model 223012, is capable of interrogating an RFID tag and determining the state of the tag's memory, thus retrieving information associated with the outputs of one or more sensors relevant to the tag's environment. The 223012 also includes an auxiliary network communication link that utilizes Bluetooth to transmit the information retrieved from the tag to an auxiliary device or interrogator. ™ Bluetooth enabled on a computer or smartphone ™ Communication protocol. The auxiliary interrogator may also analyze information about the status of the label and / or the label environment and provide output associated with the specific label and / or label environment status. The interrogator may also include a display element, such as an LCD or LED screen for displaying output associated with the analyzed label information. The interrogator may also include one or more sensors for detecting information associated with the interrogator's environment. Sensors may include: temperature sensors, humidity sensors, acceleration sensors. The interrogator may also include one or more cameras that enable the capture of images associated with the product, label, or environment. The interrogator may include global positioning capabilities, enabling the interrogator to detect and share information about the interrogator's geographical location.

[0063] In one aspect, a smartphone can be used as the only interrogator. In this aspect, the smartphone can interrogate a tag, thereby ascertaining the information from the tag's memory. The interrogator can analyze or otherwise interpret the information and can generate an output. The output can be provided to a user of the system via an audible output, a visual output, a tactile output, or a combination thereof. In generating the output, the interrogator can utilize inputs from sensors or systems native to the smartphone, including information and analysis sourced from network resources such as cloud computing resources, in addition to the tag information. Exemplary smartphones suitably configured for use as a system interrogator include: Acer ™ E320 Liquid Express, Blackberry ™ Bold ™ 970, available from Research In Motion (Waterloo, Ontario, Canada); Casio IT-800; Google Nexus 7 ™ , available from Google, Inc. Mountain View Ca.; HTC Desire C ™ ; LG Optimus Elite; Motorola Droid ™ Razr ™ ; Nokia 700; Panasonic BizPad ™ ; and Samsung Galaxy S Advance ™ .

[0064] In one aspect, the sensor system can include a product. The term "one or more products" is used in its broadest sense and refers to any product, group of products, service, communication, entertainment, environment, organization, system, tool, and the like. For example, one example of a group of products is personal and home care products, such as products used by an individual, a family, or a household. Representative, non-limiting lists of product categories within the group of personal and home care products include antiperspirants, baby care, colognes, business products (including wholesale simulation of industrial and business markets targeting the consumer goods), cosmetics, deodorants, dish care, feminine care, hair care, hair colorants, health care, household cleaners, laundry detergents, oral care, paper products, personal cleansing, disposable absorbent articles, pet health and nutrition, prescription products, prestige fragrances, skin care, food, snack and beverage, specialty fabric care, shaving and other hair growth management products, small appliances, devices and batteries, services such as haircuts, beauty, spa, medical, dental, eye care services, entertainment sites such as theaters, stadiums, and entertainment services such as movies or theatrical productions, plays, and sporting events. A variety of product forms can fall within each of these product categories.

[0065] Example product forms and brands are described at The Procter & Gamble Company's website www.pg.com, and linked websites found thereon. It should be understood that the present application contemplates consumer goods that are part of product categories other than those listed above, and the present application also encompasses alternative product forms and brands that are not those disclosed on the above-identified website.

[0066] Other product groups include, but are not limited to, sporting equipment, entertainment categories (books, movies, music, etc.), visual categories, and home medical and first aid supplies, among others.

[0067] The tag can be attached to a package of a product, such as a primary package of a liquid product or a granular product. The tag can be immersed in a liquid or granular product of the package or float on a surface of the product. The tag can be incorporated within a product, such as incorporated within a disposable absorbent article, such as incorporated within a diaper, for the purpose of detecting tampering with an absorbent core of the diaper. The tag can be disposed on a surface of the product itself, such as disposed on a surface of a battery, for the purpose of sensing information about remaining power available in the battery.

[0068] It is believed that conforming the tag's antenna to the shape of the product's outer surface results in a system in which communication between the interrogator and the tag can be omnidirectional or can be achieved at a variety of angles between the interrogator and the tag.

[0069] One of these problems associated with creating a communication device for various products arises when the communication device is used on an electromagnetically conductive body. The principles of propagation of radio waves in free space do not apply near highly conductive bodies. In addition, when an antenna is placed in close proximity to metal, the antenna performance is severely degraded. Thus, simply placing an RFID tag on a battery or on an object with a conductive body can not achieve the desired effect, e.g., power harvesting and / or data transfer. Notably, this problem is not limited to rechargeable / disposable batteries. For example, a can of shaving gel, foam, etc., or a package that includes a metallized film can experience the same problem due to the conductive nature of the container. In general, an RFID tag in close proximity to a metal body reduces the signal coupling between the reader and the tag by a factor of 10.

[0070] One method of preventing this effect due to the proximity of metal to the antenna is to prevent the electromagnetic field from entering the metal. For example, by placing a material with the appropriate electromagnetic properties and size between the antenna and the metal surface to shield them, the electromagnetic field around the metal body / conductive body of the product can be diverted. The properties of the diverter material depend on the exact metal used and the RFID frequency. A magnetic diverter effectively isolates the tag from the can. An air-filled gap between these materials can also be used to achieve effective isolation.

[0071] In one aspect, a method of determining product information includes the step of providing a product including a tag as described above. The tag includes at least one sensor adapted to provide an output analog to an environmental change of the sensor. The sensor has at least one output terminal. The tag also includes a radio frequency chip and a first antenna, the radio frequency chip including a memory element, one or more input terminals and one or more output terminals, the one or more input terminals being disposed in electrical communication with the output terminal of the sensor and the first antenna being disposed in electrical communication with the output terminal of the chip.

[0072] The method can also include providing an interrogator adapted to detect radiation associated with the data of the tag. The interrogator can be an RF or NFC protocol reader coupled with Bluetooth ™ capabilities as described above, or a smart phone or other computing device that includes a reader with RF or NFC capabilities.

[0073] In one aspect, the method can minimize to provide a product including a tag and provide software compatible with devices available on the market or owned by a consumer. The consumer can choose to utilize application software that will enable their device to function as the interrogator.

[0074] The interrogator can determine the current status of the tag by utilizing an RF communication protocol such as the NFC protocol. The interrogator can use a software application written for that purpose to interpret the data received from the tag.

[0075] In one aspect, the interrogator can include a secondary network communication module to provide the means and ability to send and receive data through a cellular telephone or other network, including a local area network or WIFI network. In this aspect, the interrogator can transmit data received from the tag and / or analysis of the data originating from the tag. The software application of the interrogator can analyze the data from the tag to determine if a replenishment of the product associated with the tag is needed, or to predict when such a replenishment will be needed based on a history of product usage established via a series of interrogations of the tag. In this aspect, the application can be used to complete a purchase of more of the product via the network. The application can also be used to offer the user related products for purchase, or other products that are not directly related to the product.

[0076] In one embodiment, the system tag can be subdivided into portions. One portion can include the antenna and chip, and the other portion can include the sensor. The two portions of the tag can be arranged with the sensor exposed to the functional environment of the absorbent article, and the antenna and chip portion removed from exposure to the functional environment of the article. The antenna and chip portion can be made removable and thus reusable as well. In one embodiment, electrically conductive hook-and-loop fasteners, such as those available from APLIX Inc. (Charlotte, NC) can be used to form the interface between the functional environment of the article and the exterior of the article. The attachment mechanism between the electrically conductive article, the sensor, and the removable tag can be hook and loop, compression (e.g. elastic, stretch), adhesion (e.g. adhesive tape), magnetic, or combinations thereof. In this embodiment, the sensor can be made as an assembly that makes electrical contact with an electrically conductive hook-and-loop pad that in turn is arranged on the exterior surface of the article while the sensor can be arranged within the article in the functional environment. The mating pad can be incorporated as an assembly portion of the antenna and chip assembly and the two respective assemblies can be joined for operative use of the tag using a mating pair of hook-and-loop pads. In this way, the more expensive antenna and chip assembly can be reused to reduce the overall cost associated with using a system having a plurality of respective disposable articles. The respective assemblies of the tag can be formed using electrically conductive adhesives such as those available from MG Chemicals (Surrey, B.C., Canada) to secure the electrical leads of the respective portions of the tag to their respective hook-and-loop fastener pads.

[0077] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the exact value and a functional equivalent range surrounding that value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 mm."

[0078] Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or along with any other document or multiple documents, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall control.

[0079] While particular embodiments of the present application have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the application. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this application.

Claims

1. A sensor system comprising: A communication element, the communication element including a tag, wherein the tag includes an antenna and a chip; and A switch configured to change the value of one or more bits stored in a chip's memory, the switch comprising a switchable polymer element having a first electrical state and a second electrical state, and capable of switching between the first electrical state and the second electrical state according to a predetermined environmental change; wherein the predetermined environmental change is selected from: wetting, humidity, pH, mechanical stress, solvent compatibility, and combinations thereof; wherein the polymer element comprises a non-conductive polymer matrix and discrete conductive filler particles impregnated in the non-conductive polymer matrix; wherein the discrete conductive filler particles comprise particles selected from the group consisting of: graphitized carbon powder and silver-copper clad powder; and wherein the polymer element undergoes a volume change between the first electrical state and the second electrical state; Wherein the first electrical state corresponds to a first or more bits, and the second electrical state corresponds to a second or more bits, wherein the first or more bits of the first electrical state are different from the second or more bits of the second electrical state; The viscosity of the polymer system is tailored to allow conductive filler particles to settle due to gravity, creating a predetermined non-conductive to conductive continuum within the non-conductive polymer matrix, thus forming a polymer system sensitive to directional strain. This directional strain is identified by a decrease in resistance when the system bends toward the conductive side or an increase in resistance when it bends toward the non-conductive side. The tag is configured to be readable by an interrogator, wherein when the tag is powered, the interrogator reads the tag and one or more bits of the first electrical state or one or more bits of the second electrical state.

2. A method for monitoring the environment, the method comprising: Provide products, said products including an environmentally sensitive sensor system, said sensor system comprising: A communication element, the communication element including a tag, wherein the tag includes a radio frequency chip and a first antenna, and wherein the chip includes a memory; and A switch configured to change the value of one or more bits stored in a chip's memory, the switch comprising a switchable polymer element having a first electrical state and a second electrical state, and capable of switching between the first electrical state and the second electrical state according to a predetermined environmental change; wherein the predetermined environmental change is selected from: wetting, humidity, pH, mechanical stress, solvent compatibility, and combinations thereof; wherein the polymer element comprises a non-conductive polymer matrix and discrete conductive filler particles impregnated in the non-conductive polymer matrix; wherein the discrete conductive filler particles comprise particles selected from the group consisting of: graphitized carbon powder and silver-copper-clad powder; wherein the first electrical state corresponds to a first or more bits, and the second electrical state corresponds to a second or more bits; wherein the first or more bits of the first electrical state are different from the second or more bits of the second electrical state; wherein the viscosity of the polymer system is tailored such that the conductive filler particles settle due to gravity to form a predetermined non-conductive to conductive continuous body in the non-conductive polymer matrix to form a polymer system sensitive to directional strain, wherein the directional strain is identified by a decrease in resistance when the system bends toward the conductive side or an increase in resistance when it bends toward the non-conductive side. An interrogator is provided that is adapted to communicate with the sensor system to determine the state of the communication element, wherein the interrogator includes a second antenna; Expose the product to environmental changes; The volume of the polymer element changes between at least one of the first electrical state and the second electrical state; Based on the change from the first electrical state to the second electrical state, change one or more bits in the tag's memory; and The interrogator is used to interrogate the communication element of the sensor system, wherein the second antenna of the interrogator communicates with the first antenna of the tag, and wherein the interrogator determines the state of the tag's memory.

3. An apparatus including a sensor system, the sensor system comprising: A communication element, the communication element including a tag, wherein the tag includes a chip having a memory, wherein the memory is configured to store one or more bits; and A switch configured to change the value of one or more bits stored in a chip's memory, the switch comprising a switchable polymer element having at least a first electrical state and a second electrical state, and capable of switching between the first electrical state and the second electrical state in response to a predetermined environmental change; wherein the predetermined environmental change is selected from: wetting, humidity, pH, mechanical stress, solvent compatibility, and combinations thereof; wherein the polymer element comprises a non-conductive polymer matrix and discrete conductive filler particles impregnated in the non-conductive polymer matrix; wherein the discrete conductive filler particles comprise particles selected from: graphitized carbon powder and silver-copper-clad powder; and wherein the polymer element undergoes at least one volume change in response to the predetermined environmental change; wherein the viscosity of the polymer system is tailored such that the conductive filler particles settle due to gravity to form a predetermined non-conductive to conductive continuous uniformity in the non-conductive polymer matrix to form a polymer system sensitive to directional strain, wherein the directional strain is identified by a decrease in resistance when the system bends toward the conductive side or an increase in resistance when it bends toward the non-conductive side. One or more bits stored in the memory of the chip are changed based on a change between the first electrical state and the second electrical state; and The memory of the tag is configured to be read using a radio frequency protocol.

4. A sensor system comprising: A communication element, comprising a tag, wherein the tag includes a sensor, an radio frequency chip, and a first antenna, wherein the sensor is configured to generate a sensor output, and wherein the radio frequency chip includes a memory; and A switch configured to change the sensor output, the switch including a switchable polymer element having at least a first electrical state and a second electrical state, and capable of switching between the first electrical state and the second electrical state according to a predetermined environmental change; The polymer element has a laminated structure comprising: a first layer having discrete conductive filler particles dispersed within a polymer matrix, and a second layer comprising only the polymer matrix; wherein the viscosity of the polymer system is tailored such that the conductive filler particles settle due to gravity to form a predetermined non-conductive to conductive continuous uniformity in the polymer matrix to form a polymer system sensitive to directional strain, wherein the directional strain is identified by a decrease in resistance when the system bends toward the conductive side or an increase in resistance when it bends toward the non-conductive side. The switch alters the sensor output by switching from a first electrical state to a second electrical state, wherein the sensor output alters the memory of the chip, and wherein the memory of the chip is configured to be readable by an interrogator communicating with the first antenna of the tag.

5. The sensor system of claim 4, wherein the discrete conductive filler particles comprise particles selected from the group consisting of graphitized carbon powder and silver-copper clad powder.

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