Fabric with degradable sensor

Abstract

A fabric comprising at least one conductive element to define at least one portion of an electric circuit, and a sensor coupled to said conductive element, wherein the sensor comprises a degradable element configured to at least partially degrade in preset conditions to change an electric feature of said sensor. An article comprising the fabric and a process for monitoring the life-cycle of the fabric are also disclosed.

Claims

1. A fabric comprising at least one conductive element defining at least a portion of an electric circuit, and a sensor coupled to said conductive element, wherein the sensor comprises a degradable element configured to provide a plurality of degrees of degradation of the degradable element itself in preset conditions to change an electric feature of said sensor.

2. The fabric according to claim 1, wherein the fabric is a woven or knitted fabric.

3. The fabric according to claim 1, wherein the conductive element comprises conductive yarn.

4. The fabric according to claim 1, wherein said preset conditions comprise at least one of a cleaning cycle, a heat treatment and wearing conditions.

5. The fabric according to claim 1, wherein said degradable element is configured to reduce its mass or dimension when put in contact with a liquid, to vary said electric feature.

6. The fabric according to claim 5, wherein the change of said electric feature of said sensor upon said degradation in said preset condition comprises a change between 1% and 5%.

7. The fabric according to claim 1, wherein said degradable element comprises at least one of a resistor and a dielectric portion of a capacitor interposed between two conductive elements.

8. The fabric according to claim 1, wherein said degradable element comprises a core of an inductor that defines the inductance of said inductor or includes a conductive element wound around said degradable element.

9. The fabric according to claim 1, wherein said degradable element comprises a piezoelectric element.

10. The fabric according to claim 9, wherein the change of the electric feature upon said degradation comprises a change of 10% to 50%.

11. The fabric according to claim 4, wherein the degradable element is configured to provide a first degree of degradation when the fabric is worn by a user, and a second degree of degradation at said cleaning cycle or at said heat treatment.

12. The fabric according to claim 11, wherein the degradable element is further configured to provide a third degree of degradation due to an undesired event being different from said preset condition.

13. An article comprising a fabric according to claim 1.

14. The article according to claim 13, further comprising a controller coupled to said sensor to monitor the change of said electric feature.

15. The article according to claim 14, wherein said controller is disposed within a button of said article.

16. The article according to claim 13, wherein said article is a garment.

17. The article according to claim 16, wherein the garment comprises at least one seam, and the sensor is disposed within said at least one seams.

18. The article according to claim 17, wherein said garment is a pair of pants and said controller is disposed within a button of said garment.

19. The article according to claim 18, wherein said sensor is disposed within at least one of an outer lateral seam extending in a longitudinal direction along a wearer's leg and an inner medial seam extending in said longitudinal direction along said wearer's leg.

20. A process for monitoring life-cycle of a fabric, said process comprising: (a) providing a fabric with at least one conductive element defining at least one portion of an electric circuit, and a sensor coupled to said conductive element, said sensor having a degradable element configured to at least partially degrade in preset conditions, whereby degradation of said element changes an electric feature of said sensor; (b) monitoring said electric feature and storing said monitored electric feature; (c) evaluating at least one of a value of said degradation of said electric feature and a number of degradation events as a function of said monitored and stored data; (d) determining status of said fabric as a function of the evaluation.

21. The process according to claim 20, wherein said step (c) comprises the steps of: (c1) evaluating a function of the monitored electric feature as a function of time; (c2) evaluating a derivative of the function of the monitored electric feature of step (c1) (c3) counting peaks of the derivative function, wherein each said peak is associated with one occurrence of said degradation event.

22. The process according to claim 20, wherein said sensor comprises at least one of resistor, an inductor, a capacitor and a piezoelectric element.

23. An electric circuit comprising at least one conductive element defining at least one portion of said electric circuit and a sensor coupled to said conductive element, the sensor including a degradable element configured to provide a plurality of degrees of degradation of the degradable element itself in preset conditions to change an electric feature of said sensor, said circuit being suitable to be inserted into a fabric.

24. A fabric comprising at least one conductive element to define at least one portion of an electric circuit, and a sensor coupled to said conductive element, wherein the sensor comprises a degradable element configured to provide a plurality of degrees of degradation in preset conditions to change an electric feature of said sensor, wherein said preset conditions comprise at least one of a cleaning cycle, a heat treatment and wearing conditions and wherein the degradable element is configured to provide a first degree of degradation when the fabric is worn by a user, and a second degree of degradation at said cleaning cycle or heat treatment.

25. The fabric according to claim 24, wherein the degradable element is provided with a third degree of degradation at an undesired event, different from said preset condition.

Description

DESCRIPTION OF THE DRAWING

(1) Exemplary and non-limiting embodiments will be now discussed with reference to the enclosed figures, in which:

(2) FIGS. 1 and 2 are schematic views of a fabric of embodiments of the invention;

(3) FIGS. 2A, 2B, and 20 are different embodiment of water degradable elements, respectively a resistor, a capacitor and an inductor;

(4) FIG. 3 is a schematic view of an electric circuit comprising a water degradable resistor according to an embodiment of the invention;

(5) FIG. 3A is a schematic view of the progressive degradation of a water degradable resistor according to an embodiment of the invention;

(6) FIG. 4 is a schematic view of an electric circuit comprising a water degradable capacitor according to an embodiment of the invention;

(7) FIG. 5 is a schematic view of an electric circuit comprising a water degradable inductor according to an embodiment of the invention;

(8) FIG. 6 is a schematic view of a degradable element according to a further embodiment of the invention;

(9) FIG. 6A is a schematic view of an alternative embodiment of FIG. 6;

(10) FIG. 7 is a view of the electric resistance of a water degradable resistor as a function of time, when subject to different conditions, shown schematically in FIG. 8A;

(11) FIG. 8 is a view of the derivative of the resistance of FIG. 7 as a function of time;

(12) FIG. 8A is a schematic view of the different conditions of a test on a water degradable elements.

(13) FIG. 9 is a schematic view of an electric circuit comprising a piezoelectric degradable element according to an embodiment of the invention;

(14) FIG. 9A is a SEM image of a piezoelectric degradable element of the embodiment of FIG. 9;

(15) FIG. 9B is a schematic view of a further electric circuit with the sensor of FIG. 9;

(16) FIG. 10 is a schematic view of the progressive degradation of the piezoelectric degradable element of FIG. 9;

(17) FIGS. 11, 11A, 11B are schematic views of electric circuits of further embodiments of the invention;

(18) FIG. 12 is a view of the variation of the electric feature of different degradable elements;

(19) FIGS. 13A-13B show the results of a test carried out on a sensor placed on a fabric that was not subject to washing cycles;

(20) FIGS. 13C-13D show the results of a test carried out on a sensor placed on a fabric that was subject to washing cycles at 60 degrees Celsius;

(21) FIG. 14 shows a denim article with a sensor in the seams.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(22) With reference to the figures, an article 11 (shown schematically in FIGS. 1 and 2) comprises a fabric 1 which in turn comprises at least one conductive element 2 to define an electric circuit 3. A sensor 12 comprises a degradable element 4 coupled to the one or more conductive element 2. Degradation of the degradable element 4 causes a variation of one (or more) electric feature of the electric circuit 3.

(23) Preferably, a controller 10 can be coupled to the electric circuit 3 to evaluate the variation of such an electric feature.

(24) The fabric 1 is preferably a woven or knitted fabric. Conductive elements 2 can thus be conductive yarns 2a, 2b that are part of the woven or knitted fabric, i.e. they can be inserted in the fabric as yarns of the woven or knitted structure of the fabric itself.

(25) In a preferred embodiment, fabric 1 is a denim fabric for trousers. In any case, fabric 1 can be a generic fabric.

(26) In FIG. 1, two conductive yarns 2a, 2b in a woven structure of a fabric 1 are shown. In FIG. 2 a conductive yarn 2 in a knitted structure of a further fabric 1b is shown.

(27) Conductive yarns can comprise e.g. steel or copper or silver wires, and they can be e.g. monofilament, or they can be blends of multiple fibers forming the final yarn.

(28) Alternative conductive elements can be used. In the exemplary embodiment of FIG. 6, two metal elements 2c coupled to the fabric are used as a conductive element.

(29) According to a further embodiment, shown in FIG. 6B, snaps 2e (typically male snaps) may be crimped to conductive elements 2a, 2b (e.g. steel yarns)shown in dotted linesto provide ohmic contacts with the latter, so that they may be connected (e.g. via standard female snaps) to an external circuitry, e.g. to download data recorded by the controller to an external data processor.

(30) In general, conductive elements allow transmission of an electric signal along a portion of the fabric. In more detail, conductive elements are coupled to degradable elements, so as to form a portion of an electric closed path.

(31) In more detail, the conductive element(s) 2, 2a, 2b, 2c is/are disposed within/coupled to the fabric 1 so as to form a closed path, i.e. an electric circuit 3, preferably together with the controller 10. The controller 10 can be inserted within the fabric 1, or it can be an element external to the fabric 1.

(32) As an example, a controller 10 can be inserted within a button which is configured to be coupled to the fabric, as disclosed in pending application EP 15179147.2 in the name of the present applicant. The conductive elements(s) 2, 2a, 2b, 2c is/are disposed so as to close an electric path with the external controller 10, when the latter is coupled to the fabric 1 in the final garment. The electric controller 10 comprises known means to generate and/or evaluate an electric signal, and to monitor an electric feature of the electric circuit 3.

(33) As an example, in FIG. 3 an electric circuit 3 in a schematic and simplified view is shown.

(34) The electric circuit 3 comprises two conductive yarns 2a, 2b. The yarns 2a, 2b can be inserted within the fabric 1 as per above disclosed. The fabric 1 is not shown for clarity. A degradable element 4a is interposed between the yarns 2a, 2b. The electric circuit is closed by a controller 10.

(35) The electric circuit 3 may be more complex than what shown. As shown for example in FIG. 11, the circuit 3 can comprise an analog-to-digital converter (ADC) 5, to allow the controller 10 to manage a digital signal, as better discussed later.

(36) According to an embodiment, the electric circuit 3 can comprise a pull-up or pull-down resistance 7, to avoid short circuits and to limit external disturbances. In general, the sensor 12 is able to generate a signal towards and/or from the degradable element 4, for example a degradable resistor 4a as per FIG. 11. In particular, the electric circuit 3 is generally configured to allow transmission of a signal between the degradable element 4 and the controller 10.

(37) In the particular embodiment of FIG. 11, the sensor comprises a degradable resistor 4a, and a further resistor 7a arranged in series with respect to the resistor 4a, so as to form a voltage divider. According to an aspect, the resistance value of the resistor 7a may be chosen as follows.

(38) R_ini being the initial value of the resistance of the resistor 4a (i.e. before any degradation) and R_fin being the larger expected final resistance value of the resistor 4a at the end of its operative life time, the voltage divider resistor 7a has preferably a resistance value R_div defined by the geometric average of R_ini and R_fin. In other words the value of the resistance of the voltage divider resistor 7a can be chosen as per the following formula:
R.sub.div={square root over ((R.sub.ini*R.sub.fin))}

(39) The above mentioned preferred value of the voltage divider resistor 7a guarantees the maximum dynamic range at the input of the ADC 5. The above disclosed voltage divider is particularly useful during measurement the resistance value of the resistor 4a.

(40) A resistor 7a may be used to form a voltage divider also in combination with a degradable sensor having a degradable inductor 4c, as shown in FIG. 11A. In this case, the degradable inductor 4c (better discussed later) is preferably arranged in parallel with respect to a non-degradable capacitor 7b.

(41) Also, a voltage divider may be used without a (pull up/pull down) resistor, as shown in FIG. 11B, where a capacitive voltage divider is shown, wherein a degradable capacitor 4b is put in series with a reference capacitor 7c.

(42) A pull up/pull down resistor 7 is also shown in combination with a degradable piezoelectric sensor in an exemplary embodiment in FIG. 9B. In this case the value of the resistance of the pull up/pull down resistor 7 can be chosen with more freedom as it is not used in a voltage divide together with a degradable resistor as per FIG. 11.

(43) According to an embodiment, the sensor 12 can be placed within seams 11a, 11b of the article 11 (see FIG. 14), so that the sensors 12 are not visible when looking at the article, i.e. they are hidden within the seams. In other words, the sensors 12 may be surrounded by fabric and be placed inside a seam 11a. As used herein, a seam 11a, 11b is a portion of an article 11 in which two overlapping portions of fabric(s) are joined together. A close-up of a seam 11a is schematically shown in FIG. 14. Seam 11a shown in FIG. 14 represents one seam embodiment but various types of seams are used in other embodiments. Various stitching types and other methods may be used to form seams in other embodiments. In the shown embodiment, the article 11 is a pair of denim jeans but other materials as well as different articles can be used in other embodiments. As an example, article 11 may be an item of apparel worn by a wearer including but not limited to shorts, a shirt, a full body suit, sleeves for legs and arms and the like.

(44) FIG. 14 shows seam 11a formed of two fabric pieces 1a, 1b that are joined together to form seam 11a by stitchings 13. A sensor 12 is placed within the seam 11a, and it is connected to conductive elements 2a, 2b that at least partially run within the seam 4.

(45) In particular, FIG. 14 shows an article 11, namely a garment, which is a pair of denim pants. In other embodiments according to various aspects of the disclosure, the article may be a different garment, e.g. a piece of apparel such as may be worn by a user. In the illustrated embodiment, the article 11 includes seams 11a, 11b, at least at outer lateral locations (seam 11a) and medial internal locations (seam 11b) on each pant leg. Seams 11a, 11b generally extend along the longitudinal direction of a wearer's legs and are therefore generally parallel to the wearer's femur in the upper portion of the pant legs, and parallel to the wearer's tibia and fibula in the lower portion of the pants leg, when the article 11 is worn by a wearer.

(46) Furthermore, even if not shown in detail, further seams may be provided on the article 11, e.g. at the top portion of the pants, i.e. at the portion of the pants usually configured to house a belt. The sensor 12 may be placed within any of these seams, according to the needs. It is further noted that seams 11a, 11b are used to produce the article, so that the sensor can be placed within a pre-existing seam of the article. Such a seam may be provided with an area having greater dimension (e.g. greater width) with respect to the other areas of the seams, in order to house a sensor in the greater area. Also, in some embodiments, a sensor may be placed within a seam that is created ad hoc for the sensor. In other words, a seam that have no structural function can be provided on the article with the only purpose to house a sensor. A seam may be thus formed on an article in order to form a pocket where a sensor may be housed.

(47) Also, the controller 10 can be placed within a seam 11a, 11b of an article 11. The controller 10 can be connected to the sensor by means of conducting elements (e.g. conducting yarns such as steel yarns) that do not degrade.

(48) As before mentioned, various kinds of degradable elements can be used in different embodiments of the present invention. Embodiments with water degradable elements and piezoelectric elements will be now discussed in detail.

(49) With reference to FIG. 3, a water degradable resistor 4a is interposed between two conductive yarns.

(50) The water degradable resistor 4 is preferably made of polyether and/or polyester based polyurethanes.

(51) The water degradable resistor 4a partially reduces its mass/dimensions each time the fabric 1 is washed. This is schematically shown in FIG. 3A. In particular, degradation of the water degradable resistor is shown from bottom to top of FIG. 3A. In more detail, at the bottom of FIG. 3A a complete water degradable resistor is shown. At the top, the water degradable resistor 4a is completely degraded. Between the bottom and the top portion of FIG. 3A intermediate conditions are shown.

(52) Each time the water soluble resistor reduces its mass/dimension, i.e. each time the water soluble resistor loses part of its material, the relevant electric feature (i.e. the resistance) is changed.

(53) A water degradable resistor (and more in general a water degradable element, as the water degradable elements 42b and 41c subsequently discussed) is preferably configured to vary the relevant electric feature (e.g. resistance in the present case of a resistor) of about 1% to 5% at each washing cycle. As mentioned, in fact, the resistance of the resistor 4a is dependent on the mass/dimensions of the resistor 4a itself. In particular, the resistance increases with a decrease of the mass/dimensions of the resistor 4a. In fact, when the resistor loses mass (both by a reduction of the external dimension of the resistor, or by losing a filler of the resistor), the electric path that is traversed by the electric current narrows, thus raising the resistance of the resistor.

(54) As better discussed later, a change in the resistance of the resistor 4a in the sensor 12 can be sensed by the controller 10, in order to evaluate the life-cycle of the fabric 1, and in particular to evaluate the history of washing cycles on the fabric 1.

(55) Water degradable elements can be used not only as a resistor. As an example, in FIG. 4, an embodiment is shown wherein a water degradable element is used in a capacitor 4b. In particular, the capacitor 4b comprises a portion 40b, 41b of two conductive yarns 2a, 2b (i.e. one portion 40b of a first conductive yarn 2a and one portion 41b of a second conductive yarn 2b). A water-degradable dielectric portion 42b is interposed between the two portions 40b, 41b, so as to form a capacitor 4b. As before, during a washing cycle, the dielectric portion 42b partially reduces its mass/dimensions, and thus the capacitance of the capacitor 4b is changed, e.g. lowered.

(56) In a further embodiment, shown schematically in FIG. 5, a degradable element is used as the core 41c of an inductor 4c. In more detail, one portion 40c of a conductive yarn 2a is wound around a water degradable core 41c, so as to form an inductor 4c.

(57) During a washing cycle, the water degradable core 41c partially reduces its mass/dimensions, so that the inductance of the inductor 4c is changed, e.g. lowered.

(58) More in general, different water degradable elements can be used in different embodiments of the present invention, provided that the partial degradation (e.g. by erosion caused by hydrolysis) of the water degradable element causes a sensible variation within the electric circuit 3, i.e. it changes the value of an electric features of the electric circuit 3.

(59) In the above disclosed embodiments, the electric feature changed by the water degradable element are respectively the resistance (in FIG. 3), the capacitance (in FIG. 4) and the inductance (FIG. 5) of the electric circuit 3 at the relevant water degradable element 4a, 42b, 41c.

(60) As mentioned, the conductive elements are not limited to conductive yarns.

(61) With reference to the embodiment of FIG. 6, a water degradable element 4 is interposed between two metal elements 2c coupled to the garment, e.g. they can be parts of a metal button.

(62) In particular, the degradable element 4 connects the two metal elements 2c so as to allow transmission of an electric signal between the metal elements 2c.

(63) Such an electric signal can be generated by a controller 10 (not shown in FIG. 6), e.g. embedded in a further button (not shown).

(64) Water degradable elements were disclosed. However, different degradable elements can be configured to reduce their mass/dimensions when put in contact with different fluids (i.e. other than water), e.g. tetrachloroethylene, or other solvents used in dry cleaning. Moreover, in further embodiments of the present invention, degradable elements 4 that do not reduce their mass/dimensions when they are put in contact with a liquid can be used.

(65) As an example, in FIG. 9, a piezoelectric degradable element 4d is shown. In particular, in the shown embodiment, a piezoelectric degradable element 4d can be formed as a layer interposed between two conductive layers 20a, 20b (other conductive elements can be used as well together with a piezoelectric degradable element).

(66) The piezoelectric degradable element 4d of the embodiment is made of a polyvinylidene difluoride (PVDF), in particular, of a semi-crystalline poly(vinylidene fluoride) polymer. The piezoelectric degradable element 4d generates an electric signal when it is subjected to mechanical stimulation, e.g. when the fabric carrying the piezoelectric degradable element is bent, stretched, pressed, wrinkled, sheared, stressed, released/relaxed, etc.

(67) A SEM (scanning electron microscope) image of a PVDF family member is shown in FIG. 9A. In FIG. 9B a piezoelectric sensor 12 is shown in an electric circuit, wherein the sensor (in particular the conductive layers) is connected directly to an analog to digital converter 5 of the controller 10 with pull-up/down resistors 7.

(68) The strength of this signal is dependent on the polarization (i.e. the orientation of the electric dipoles 41d of FIG. 10) of the piezoelectric degradable element. Piezoelectric element can partially lose polarization (i.e. partially lose the alignment between the electric dipoles 41d) when subjected to heat. In an embodiment, the material of the piezoelectric degradable element 4d is thus chosen so as to lose polarization at temperatures reached during cleaning cycles.

(69) As a result, when the fabric 1 is heated during a cleaning cycle (e.g. due to contact with hot water), the piezoelectric degradable element 4d partially loses polarization, and thus the strength of the electric signal generated by the piezoelectric degradable element 4d is lowered.

(70) As before, the piezoelectric degradable element 4d can be made of a material that does not to completely lose polarization when heated during a single cleaning cycle.

(71) In other words, the signal generated by the piezoelectric degradable element is preferably varied after a heat treatment. This variation is preferably comprised between 5% and 95%, more preferably between 10 and 50%.

(72) In FIG. 10, the degradation of a piezoelectric element is shown, wherein a not degraded piezoelectric element is shown at the left (i.e. a completely polarized piezoelectric element), and a completely degraded piezoelectric element is shown at the right (i.e. a completely de-polarized piezoelectric element). An intermediate condition is shown in the middle.

(73) In other words, electric dipoles 41d of the piezoelectric degradable element 4d are completely aligned at the left, partially aligned in the middle, and not aligned at the right of FIG. 10.

(74) The material of the piezoelectric element 4d can be chosen to allow counting of the occurrence of heat treatments. Different piezoelectric elements can be used to count the occurrences of different events, in particular heat treatments.

(75) Different degradable elements can be used as well in other embodiments of the present invention.

(76) In general, as mentioned, a degradable element 4 is configured to partially degrade during a preset condition, i.e. at the occurrence of a predetermined event, so as to change an electric feature of the electric circuit 3 to which the degradable element 4 is coupled.

(77) According to further embodiments of the invention, the degradable element 4 can be configured to degrade not only during the predetermined events. As an example, the degradable element 4 can degrade also during normal use of the fabric 1, e.g. when the garment comprising fabric 1 is worn by a user.

(78) Preferably, the degradation rate (i.e. the speed of degradation) during normal use is different from degradation during the predetermined event. In particular, degradation during a preset event is greater (and preferably also faster) than degradation during normal use. In other words, the percentage of degradation during normal use is lower than the percentage of degradation during the predetermined event. Degradation is normally detected as a change in the signal generated by the sensor.

(79) An example of such an embodiment is shown in FIGS. 7 and 8A. In particular, in FIG. 7 the result of a test carried out on a fabric 1 provided with water degradable resistor 4a is shown, to evaluate the response of the water degradable resistor during different conditions (i.e. during normal use and during a washing cycle). The test is shown schematically in FIG. 8A.

(80) In particular, sweat simulations 6 (i.e. simulations of a normal use) and washing cycles simulations 8 were carried out on a fabric 1. Sweat simulation were carried out by immersion of the fabric into a pH 5.5 solution prepared with histidine monohydrochloride monohydrate, sodium phosphate and sodium chloride.

(81) Phases M of measuring the resistance of the water degradable resistor 4a were carried out before and after the sweat simulations 6 and the washing cycles simulations 8. As shown, two cycles of sweat simulations 6 and washing cycles simulations were carried out. After that, the fabric was placed at rest, i.e. it was not worn by a used nor subjected to particular treatment.

(82) In more detail, with reference also to FIG. 7, between times A and B, and between times C and D, a sweat simulation 6 was performed. Between times B and C, and between times D and E, a washing simulation 8 was performed. Between times E and F, the fabric was placed at rest.

(83) As mentioned, the result of the test of FIG. 8A is shown in FIG. 7. In particular, between times A and B, and between times C and D, a slow and little increase of the resistance of a water degradable resistor 4a (corresponding to a slow degradation of the water degradable resistor 4a) is shown. This slow degradation is due to a normal use of the fabric 1, e.g. to contact with the skin and sweat of a user.

(84) Between times B and C and D and E, a fast degradation is shown. This fast degradation is due to washing cycles. In particular, it can be noted that washing cycle between time B and time C was longer than washing cycle between time D and time E. After time E, the resistance of the water degradable water resistor 4a is substantially constant. This is due to non-use of the fabric.

(85) The behavior is not limited only to a water degradable resistor 4a. As an example, the water degradable capacitor 4b and inductor 4c can be configured to show similar behavior, e.g. a first degree of degradation during normal use, and a second degree of degradation during a heat treatment.

(86) Piezoelectric degradable element 4d can also show a similar behavior. As an example, the heat emitted by a user body can cause a slow degradation of the polarization of the piezoelectric degradable element 4d.

(87) Furthermore, in other embodiments, the degradable element can have a third degree of degradation, other than the degradation during normal use and the degradation during a heat treatment/washing cycle. In particular, the third degree of degradation is preferably configured to show the occurrence of an undesired event.

(88) The third degree of degradation is typically different from the degree of degradation during the preset condition. In other words, the percentage of degradation during an undesired event is different (typically greater and/or faster) than the percentage of degradation during the preset condition.

(89) As an example, a piezoelectric degradable element can lose a great amount of polarization if the fabric 1 is heated at a too high temperature. In an embodiment, the piezoelectric element undergoes a glass transition at a certain temperature (which is a temperature that should not be applied to the fabric 1), so as to totally lose polarization. In other words, a degradable element can be totally degraded during a single undesired event.

(90) With reference to the embodiments previously disclosed, a water degradable element can be highly degraded (e.g. greatly eroded or dissolved) if the fabric is placed in water for a too long period.

(91) In general, embodiments of the present invention can have a degradable element with only one degree of degradation, i.e. degradation at a preset event. Different embodiments can have a degradable element with two degrees of degradation (i.e. degradation at a predetermined event and degradation during normal use or during an undesired event).

(92) Further embodiments can have a degradable element with all the three degrees of degradation previously discussed.

(93) Embodiments with one degradable element 4 have been shown. It is however possible to have a greater number of degradable elements 4. Furthermore, degradable elements of different kinds can be used in the same embodiment, to monitor different events. As an example, a water degradable element can be used to count washing cycles, while a piezoelectric degradable element can be used to monitor heat treatments.

(94) With particular reference to FIGS. 7 and 8, testing of a degradable element 4 (with particular reference to a water degradable resistor 4a) will be now discussed. The controller 10 checks an electric feature of the electric circuit 3. In the present embodiment, the controller 10 checks the resistance of the electric circuit 3. This check can be continuous, or it can be carried out at discrete time intervals, e.g. with a number of consecutive measurements each time. The variation of the monitored electric feature can show the occurrence of a predetermined event.

(95) As before mentioned, an ADC 5 (FIG. 11) preferably transforms the monitored data into a digital signal, that can be handled by the controller 10. The variation of the monitored data are then stored in a memory of the controller 10. Thanks to this, it is possible to have the value of the monitored data as a function of time. Time information can be provided by the controller 10 itself, which can be provided with an internal clock. In the embodiment of FIG. 7, the trend of the values of the resistance of the circuit 3 over time is shown.

(96) The variation of the monitored data (i.e. the electric feature of the electric circuit 3) is then used to evaluate the number of occurrences of a predetermined event.

(97) Various analytic methods can be used for the purpose, e.g. real-time and on-line fast data analysis on the controller, or off-line data mining carried out e.g. by means of a PC.

(98) In the shown embodiment, with particular reference to FIG. 8, the derivative of the function between the electric feature (the resistance in this case) and time is calculated. As known, the derivative of a function shows the degree of variation of a function. Thus, the peaks p1 and p2 of the derivative function correspond to the moments of greater variation of the monitored data. As known this great variation occurs at a predetermined event.

(99) A threshold value can be established to evaluate the number of significant peaks p1 and p2. In other words, every time that the derivative function exceeds the threshold value, the controller counts one peak, i.e. it counts the occurrences of a predetermined event.

(100) In the shown embodiment, two washing cycles have been carried out, i.e. between times B and C, and D and E of FIG. 7. As a result, the derivative function of FIG. 8 shows two peaks p1 (between time B and time C) and p2 (between time D and time E). These peaks are greater than the predetermined threshold value TV, and so the controller counts two predetermined events.

(101) A further threshold value TV2, greater than threshold value TV, can be chosen in order to count the occurrences of undesired events. Thanks to this, if a peak p1 is between TV and TV2, the controller 10 will count an occurrence of a predetermined event. On the contrary if a peak is above both TV and TV2, an occurrence of an undesired event will be counted. In the shown embodiment, no undesired events were carried out on the fabric 1. As a result no peaks of the derivative function above TV2 are present.

(102) Other methods can be used to evaluate the number of occurrences of predetermined events. As an example, tests can be carried out on different sensors 12, to evaluate the change in the relevant electrical feature at the occurrence of one or more events (e.g. washing cycles) or in the whole life-cycle of the sensors 12.

(103) FIGS. 13A-13D show the results of a further test. Sensors on two fabric samples were tested for 2500 minutes. A first sensors was placed on a sample that did not undergo any washing (test results of FIGS. 11C and 11 D). The second sample underwent a series of washing at 60 C. The sensor of both samples was a resistor sensor.

(104) FIG. 13A shows that the resistance of the sensor on the sample that wasn't washed showed a slight fluctuation of the value of the resistance. In particular the value of the resistance ranged between 200 and 215 k. Such a fluctuation is due to the response to the humidity of the environment. The derivative value (whose trend is shown in FIG. 13B) shows a number of peaks that are very low, and that are not recognized as washing events by the controller 10.

(105) On the contrary, the sensor of the sample that was subjected to washings changed sensibly its resistance value, in fact a total variation of over 600 k is shown in FIG. 130. Each washing cycle caused the reduction in the degradable portion of the sensor, so as to rapidly (and sensibly) increase the value of the relevant resistance. As a result, the derivative value of FIG. 13D shows higher peaks with respect to the one of FIG. 13B (please note that the ratio of the scale on the y-axis is 1:10). As per before, these peaks are thus identified by the controller 10 as washing cycles.

(106) FIG. 12 shows the result of a simulation of the life-cycle of four different sensors 12, identified by references 12a, 12b, 12c and 12d.

(107) The sensors 12a, 12b, 12c and 12d where put in a strong chemical bath, to simulate the whole life of the sensors 12a, 12b, 12c and 12d.

(108) As can be seen, sensor 12a is a provided with a particularly high sensitivity to the event (i.e. it provides a sensibly great and fast variation of the electric feature), but it is provided with lower lifetime with respect to the other sensors 12b and 12d. In fact it can be seen that the curve of sensor 12a in FIG. 4 becomes substantially flat earlier than the other sensors 12b and 12d. Sensor 12c provides a behavior similar to sensor 12a but with lower sensitivity to the event (sensor 12c would thus cause smaller steps in a graph as the one of FIG. 7 or lower peaks in a graph as the one of FIG. 8). Sensors 12b and 12d are provided with a much longer lifetime than sensor 12a and 12c, wherein sensor 12b has greater sensitivity than sensor 12d (resembling the relationship between sensors 12a and 12c respectively).

(109) In general, from the results of these or similar tests, it is possible to configure the controller 10 to evaluate the response of each of the sensor 12a, 12b, 12c and 12d, e.g. to predict the variation of the electric feature (i.e. the height of the steps of FIG. 7), to predict the speed of variation of the electric feature (i.e. the pendency of the steps of FIG. 7 and thus the height of the peaks of FIG. 8).

(110) Furthermore, from these results, it is possible to predict the end of life of the sensors 12a, 12b, 12c and 12d, that is when there is substantially no variation in the electric feature of the sensor 12a, 12b, 12c and 12d in response to an event (washing cycle), i.e. when, at their end, the curves of FIG. 12 become substantially flat.

(111) In general, the controller 10 can be configured to recognize the variation of the value of the electric feature in response to certain events, e.g. a washing cycle. Further analytic methods can be carried out to evaluate the normal use carried out on the fabric. As an example, a small variation of the resistance that happens in a long time, e.g. the small variation between times C and D of FIG. 7, can be recognized by the controller 10 as normal use. In general, the controller 10 can be provided with algorithms to associate the amplitude of each jump to a certain event.

(112) In general, the evaluation of the monitored data (e.g. the resistance of FIG. 7) allows the controller 10 to estimate the life-cycle of a fabric 1 (and thus of garments having fabric 1), i.e. the events carried out on the fabric 1. In particular, the evaluation of the monitored data can be used to estimate the events carried out on the fabric 1, and possibly to monitor and distinguish between each other different kinds of events (e.g. washing cycle and/or heat treatments and/or normal use and/or undesired events, etc.), occurred on the fabric 1.