Patent Publication Number: US-2022226166-A1

Title: Sensor for urine and stool detection

Description:
FIELD OF THE INVENTION 
     The invention relates to sensors for urine and stool detection. 
     BACKGROUND 
     Various systems and devices for infant and adult incontinency monitoring have been previously proposed and implemented to monitor the condition of a diaper, bedding, adult incontinence brief and other similar articles. Today&#39;s parents also have an increased desire to instantly know when their infant&#39;s diaper is wet or soiled. 
     Common drawbacks of many existing detection systems arc their size, complexity and reliability. There is still an unmet need for devices, systems and methods for monitoring urine and stool secretion of a subject, and optionally alerting a caregiver as to the secretion. 
     U.S. Pat. No. 4,796,014 to Chia discloses a urine-detecting device adapted to be associated with a baby&#39;s diaper, detects and signals the presence of urine after a sufficient time delay from the initiation of urination so as not to interfere with the baby&#39;s act of urination. The signal is audio and optionally with visual. The device is aiming at safety, compactness and convenience. It combines sensing means and fastening means with signaling means attached to it. A fastening means such as a safety pin with spaced apart electrical conductors on it is used to engage the device to a diaper. When urine bridges the space between the conductive a detection circuit is completed which activates the signal. 
     U.S Patent Application Publication No. 2012/0310192 to Suzuki et al. discloses an excretion detection device that includes a power supply unit having an electrode and an electrode configured by using materials having different ionization tendencies; a solution retention unit configured to retain an electrolyte solution, a temperature sensor configured to detect the temperature information, and an active tag including a radio transmission unit configured to transmit the temperature information detected by the sensor to outside the excretion detection device. The electrode and the electrode are installed at a position where the electrodes can be in contact with the bodily waste and the electrolyte solution, and can also be in contact with the electrolyte solution before the excretion of the bodily waste. 
     The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the figures. 
     SUMMARY 
     The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. 
     There is provided, in accordance with an embodiment, a sensor for detecting urine and stool secretion mounted over two or more layers of garment, said sensor comprising: at least one light source configured to illuminate said garment; at least one photodetector configured to output an indication of the amount of light reflected from said garment; and an electronic circuit configured to detect said secretion by monitoring said output of said photodetector and identifying a temporal pattern being characteristic of said secretion event. 
     There is further provided, in accordance with an embodiment, a sensor for detecting urine and stool secretion mounted over two or more layers of garment, said sensor comprising: at least one capacitive detector, said detector configured to output an indication of the magnitude of the capacitance of said capacitive detector; and an electronic circuit configured to detect said secretion by monitoring said output of said capacitive detector and identifying a temporal pattern being characteristic of said secretion event. 
     In some embodiments, the sensor further comprises a curved bottom shape. 
     In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Exemplary embodiments are illustrated in referenced figures. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below. 
         FIG. 1  shows an illustration of a diaper equipped with a sensor; 
         FIG. 2A  shows an illustration of a close up perspective view of an exemplary sensor; 
         FIG. 2B  shows an illustration of a close up perspective side view of the sensor of  FIG. 2A ; 
         FIG. 3  shows an illustration of a distribution of detectors on the backside of a sensor; 
         FIG. 4A  shows a cross-sectional view of an exemplary capacitor; 
         FIG. 4B  shows an exploded view of an exemplary capacitive detector; 
         FIG. 4C  shows a cross-sectional view of a capacitive detector mounted on a diaper, while the diaper is soiled with a secretion; 
         FIG. 5  shows a schematic circuit of a capacitive or LDR detector connected to operational amplifier converter/conditioner; 
         FIG. 6  shows a schematic circuit of a capacitive or LDR detector connected to transistor converter/conditioner; 
         FIG. 7  shows a schematic circuit of a capacitive or LDR sensor connected to comparator converter/conditioner; 
         FIG. 8  shows a block diagram of an exemplary sensor; 
         FIG. 9  shows a schematic illustration of an exemplary acoustic communication interface between a sensing device and a receiving device; 
         FIG. 10  shows a schematic illustration of an acoustic interface of a sensor system; 
         FIG. 11A  shows graphs of output voltage vs. time of a sensor configuration including a control LDR and an LDR joint with an LPF positioned on an infant during a first period of time in which no secretion was found; 
         FIG. 11B  shows graphs of output voltage vs. time of the sensor configuration of  FIG. 11A  during a second period of time in which the infant defecated; 
         FIG. 11C  shows the output voltage of the LDR of the sensor configuration of  FIG. 11B  in a separate manner; 
         FIG. 12A to 12E  show graphs of a LDR output voltage vs. time as a result of a red LED illumination on red, white, black, green and blue garments correspondingly; 
         FIG. 13A to 13E  show graphs of a LDR output voltage vs. time as a result of a green LED illumination on blue, white, black, green and red garments correspondingly; 
         FIG. 14A to 14E  show graphs of a LDR output voltage vs. time as a result of a blue LED illumination on red, white, black, green and blue garments correspondingly; 
         FIG. 15A to 15E  show graphs of a LDR output voltage vs. time as a result of a white LED illumination on red, white, black, green and blue garments correspondingly; 
         FIG. 16A to 16E  show graphs of an IR photodetector output voltage vs. time as a result of a red LED illumination on red, white, black, green and blue garments correspondingly; 
         FIG. 17  shows a graph of an IR photodetector output voltage vs. time positioned on a doll dressed with a non-illuminated white garment; 
         FIG. 18A to 18E  show graphs of a photodiode output voltage vs. time positioned on a doll dressed with a non-illuminated white, black, green, red and blue garments correspondingly; 
         FIG. 19  shows a graph of a photodiode output voltage vs. time as a result of a white LED illumination on a white garment; and 
         FIGS. 20A and 20B  show graphs of an LDR output voltage vs. time as a result of a red LED illumination on white and black garments correspondingly. 
         FIG. 21  shows a graph of output voltage vs. time of a sensor configuration including a capacitive detector mounted to a diaper put on an infant during a period of time in which the infant defecated; 
         FIG. 22  shows a graph of output voltage vs. time of a sensor configuration including a capacitive detector mounted to a two layers of cloths, put on an infant during a period of time in which the infant defecated; 
         FIG. 23  shows a flowchart of an algorithm for detecting urine and stool secretions; and 
         FIG. 24  shows a graph of output capacitance vs. time of a capacitive sensor mounted on an infant diaper during a period of time in which the diaper was soiled with urine. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein are a device and a system for sensing and monitoring urine and stool secretion. One or multiple sensors may be attached to, worn on, embedded in or integrally formed with a wearable garment, such as a disposable infant diaper, pants, overall, baby strollers, baby cribs, baby swings, baby bouncers, adult incontinence product, etc. in order to sense urine and stool secretion of the wearer. Furthermore, in some embodiments, sensing of the urine and stool is performed through a plurality of garment layers, for example through a diaper and pants worn over the diaper. Advantageously, the present sensor(s) detect urine and stool secretion using optical and/or capacitive means. 
     The sensing of urine and stool secretion may be advantageous, in particular, for un-weaned infants as well as for certain individuals who suffer incontinence problems. For example, parents of an un-weaned infant may desire to be able to monitor such parameters and be alerted when a change occurs. 
     The sensor may output an alert, such as an audio, visual and/or tactile alert, when urine and stool secretion may be detected. In an embodiment, a photodetector (also “light sensor”) such as CCD, CMOS, LDR (Light Dependent Resistor), photovoltaic cell, photodiodes (operative in photovoltaic mode or photoconductive mode), phototransistor, etc may be used for detecting urine and stool secretion, based on the principle of a varying output signal dependant on reflected light, which varies due to urine and stool absorption in the diaper. In another embodiment, a capacitive detector such as implemented in humidity sensors may be used for detecting urine and stool secretion, based on the principle of a varying output signal dependant on capacitance which varies due to urine and stool absorption in the diaper. 
     The present disclosure may be better understood with reference to the accompanying figures. Reference is now made to  FIG. 1 , which shows an illustration of a diaper equipped with a urine and or stool sensor. The basic layers found in many modem diapers, such as diaper  100 , are commonly: (a) an outer shell  102 , commonly made of a breathable polyethylene film or a nonwoven and film composite, which prevents wetness and soil transfer to the outside environment; (b) an inner absorbent layer  104 , usually containing a mixture of air-laid paper and superabsorbent polymers; and (c) a layer  106  nearest the skin, oftentimes made of a nonwoven material with a distribution layer directly beneath, which transfers wetness to the absorbent layer. A pair of fasteners  108  is commonly used to close the diaper around the wearer&#39;s abdomen. In an embodiment, diaper  100  may embed on outer shell  102  a sensor  110 , which includes one or more detector, and an electronic circuit (not shown here). If optical detectors are used, then the sensor may further include one or more illuminators such as LEDs (Light Emitting Diode). Sensor  110  may be positioned on the front bottom of the diaper, which covers the infant&#39;s groin. Reference is now made to  FIGS. 2A and 2B , which show perspective views of an exemplary sensor  150 . A housing of sensor  150  have a curved bottom shape  152 , for better fitting to the curved groin shape, and for implying the infant caregiver where to locate sensor  150  on a diaper (not shown). With reference back to  FIG. 1 , components of sensor  110  may be distributed in different layers and/or in different positions. The detectors may be positioned such that their sensing surface is directed towards the inside of diaper  100 , and the LEDs (in case photodetectors are used) may be positioned such that their light emission is also directed towards the inside of diaper  100 . Also, the detectors may be variously located upon sensor  110 , enabling differential sensing upon diaper  100  and more enhanced calculation. Reference is now made to  FIG. 3  which shows an illustration of a distribution of detectors on the backside of sensor  110 . Sensor  110  may include a top detector  200 , a bottom detector  202 , a right detector  204 , and a left detector  206  with respect to the infant&#39;s body. The distribution of the detectors is such to allow a proper coverage of the relevant area of the diaper. Thus, the position and distribution of the detectors is also dependent on the specific characteristics of the detectors. For example, bottom detector  202  is better positioned for stool detection. 
     In some embodiments, a capacitive sensor is used as a sensor for detecting urine secretion and/or stool secretion. Reference is now made to  FIGS. 4A, 4B and 4C .  FIG. 4A  shows a cross-sectional view of an exemplary capacitor  2200 . Capacitor  2200  includes two metal conductive plates  2202   a  and  2202   b,  which are separated by a dielectric material  2204 . The capacitance C is given by: 
     
       
         
           
             
               C 
               = 
               
                 
                   
                     ɛ 
                     0 
                   
                   ⁢ 
                   
                     ɛ 
                     r 
                   
                   ⁢ 
                   A 
                 
                 d 
               
             
             , 
           
         
       
     
     where:
 
A is the area of overlap between the two plates;
 
ε r  is the relative static permittivity (also known as the dielectric constant) of the material between the plates (for a vacuum, ε r =1);
 
ε 0  is the electric constant (ε 0 ≈8.854×10 −12  F m −1 ); and
 
d is the distance between the plates.
 
       FIG. 4B  shows an exploded view of an exemplary capacitive detector  2210 . Capacitive detectors are typically built on a substrate of glass, ceramic, or silicon (substrate  2218 ). A dielectric layer  2214  made from a thin polymer film or a metal oxide is placed between two metal electrodes  2212  and  2216 . The surface electrode  2212  is porous. 
     Urine and stool may be considered as having the characteristics of an electrolyte solution. Hence, they may influence the electrical field in their surroundings. Reference is now made to  FIG. 4C , which shows a cross-sectional view of a capacitive detector  2304  mounted on a diaper  2302 , while the diaper is soiled with a secretion  2310 . Capacitive detector  2304  includes a porous electrode  2306  and capacitive element  2308 . Capacitive detector  2304  is coupled with the outer shell  2302  of diaper  2300 . Porous electrode  2306  and secretion  2310  serve here as the  2202   a  and  2202   b  plates of capacitor  2200  of  FIG. 4A  accordingly. Outer shell with internal diaper absorption material  2302  serves here as dielectric layer  2204  of capacitor  2200  of  FIG. 4A . Such configuration implements the physics of a capacitor and may be referred to as a “diaper capacitor”. Thus, the “diaper capacitor” is connected in series with capacitive element  2308  of detector  2304 . 
     In order to detect the capacitance in steady state and during change, detector  2304  is coupled with suitable electronics (not shown). The electronics are either embedded in the diaper during the manufacturing process, or externally coupled with the diaper, e.g. with the outer shell of the diaper. 
     Since secretion  2310  appears to be a part of the capacitor of the diaper, it may immediately influence the capacitance magnitude of capacitive detector  2304 . 
     In some embodiments, a photodetector is used as a sensor for detecting urine secretion and/or stool secretion. As urine and/or stool are secreted into the diaper, the amount of light reaching a photodetector decreases, since a greater portion of the light may now be blocked by the secretions. Generally, the amount of light reaching the photodetector changes as a function of the amount of urine and/or stool disposed inside the diaper. An LDR sensor may be based on the principle of a decreasing resistance when light incidence increases. 
     Reference is now made to  FIG. 5  which shows a schematic circuit of LDR detector  304  or a capacitor  301  connected to operational amplifier converter/conditioner. The operational amplifier  300  may have high input impedance and unity gain, and if LDR  304  is used, the principle may be based on a voltage divider between a fixed resistor  302 , referred also as R m , and LDR  304 , referred also as R photo . The output voltage V out  may be given by 
     
       
         
           
             
               
                 V 
                 out 
               
               = 
               
                 
                   V 
                   
                     c 
                     ⁢ 
                     c 
                   
                 
                 
                   ( 
                   
                     1 
                     + 
                     
                       
                         R 
                         m 
                       
                       / 
                       
                         R 
                         
                           p 
                           ⁢ 
                           h 
                           ⁢ 
                           oto 
                         
                       
                     
                   
                   ) 
                 
               
             
             , 
           
         
       
     
     i.e. output voltage is rather linear to LDR resistance. Alternatively, an integrator circuit including capacitive sensor  301 , resistor  303  and amplifier  305  may be used (instead of resistor  302  and LDR  304 ). The value of the output voltage (indicated Vout) depends on the value of capacitive sensor charge or discharge  301  as a function of time. 
     Reference is now made to  FIG. 6  which shows a schematic circuit of LDR detector  400  or capacitive sensor  401  connected to transistor converter/conditioner. An LDR  400  and a 2 MΩ resistor  402  may serve as a voltage divider. When light level is low (in our case, when pieces are interlocked), the resistance of LDR  400  may be high. This may prevent current from flowing to the base of the transistor  404 . Consequently, the output voltage may be low, commonly close to 0 volts. However, when light illuminates the LDR without much interference (in our case, when pieces are not interlocked) the resistance may fall and current may flow into the base of transistor  404 , increasing the output voltage to high level (about 5 volts). Alternatively, an integrator circuit including capacitive sensor  401 , resistor  403  and amplifier  405  may be used (instead of resistor  402  and LDR  400 ). 
     Reference is now made to  FIG. 7  which shows a schematic circuit of LDR detector  504  or capacitive sensor  501  connected to comparator converter/conditioner. Resistor  500 , referred also as R 1 , and Resistor  502 , referred also as R 2 , may serve as voltage divider with a known preset level. The LDR  504  and resistor  506 , also referred as R 3 , may also serve as voltage divider. When the voltage of the negative pole (−) of the operational amplifier  508  may be smaller than the positive pole input voltage (+), then V out  may be set to high level. When the voltage of the negative pole (−) may be greater than the positive pole input voltage (+), then V out  may be set to low level. Alternatively, an integrator circuit including capacitor  501 , resistor  503  and amplifier  505  may be used (instead of resistor  506  and LDR  504 ). 
     Reference is now made to  FIG. 8 , which shows a block diagram of a sensor based on exemplary LDR-based photodetectors and/or capacitive detectors. As described before, a sensor may include optical detectors  600  or capacitive detectors  601  which may be coupled with one of multiple components: an operational amplifier  602 , a transistor  604 , or a comparator  606 . The signal may be then transferred through an ADC (Analog to Digital) converter  608 , and may be fed to a microcontroller  610  (e.g., P/NPIC18F46J50 made by Microchip) for further processing. Alternatively, one of the multiple components may be directly coupled in simplicity with a notification element. Microcontroller  610  may collect the signals of two or more detectors  600  and  601  to compute existence of urine and/or stool secretion, and in case of detection, trigger an output. Microcontroller  610  may perform an exemplary algorithm for detecting urine and stool secretion. 
     For any implementation, the output may be in a form of a vibration alert, and/or visual alert, and/or vocal alert, and/or transmit alert indication to a distant receiver (not shown here). 
     The described photodetector and a capacitance detector in this paper are using analog output interface. There are many kinds of detector parameters as for example output signal topologies, like various analog and digital interfaces which can be use. Such as for example of digital interfaces are: I2C, SPI, 1-wire, etc. 
     The described photodetector and a capacitance detector in this paper are using analog output interface. There are many kinds of detector parameters as for example output signal topologies, like analog and digital interfaces which can be use. 
     According to some embodiments, the sensor disclosed herein may further interface and/or communicate with an external and/or remote device to convey a signal generated by the sensor(s) disclosed herein to the device (herein, a “receiver” or a “receiving device”). Conveying the signal from the sensor of the sensing device to the receiving device may be performed by various communication routes, such as radio frequency or acoustic communication. Acoustic communication makes use of sound and/or ultrasound, whereby a “transmitter” produces a sound that is detected by a “receiver”. Sound is produced by the transmitter when a physical object vibrates rapidly, disturbs nearby air molecules (or other surrounding medium) and generates compression waves that travel in all directions away from the source. Sound can be made to vary in frequency (high pitch vs. low pitch), amplitude (loudness), and periodicity (the temporal pattern of frequency and amplitude). Since acoustic waves move rapidly through the medium, acoustic signals can be quickly started, stopped, or modified to send a time-sensitive message. 
     Reference is now made to  FIG. 9 , which shows a schematic illustration of an exemplary acoustic communication interface between a sensing device and a receiving device. Sensing device  700  includes an audio encoder  702 , adapted to produce an acoustic signal based on the signal produced by the sensor. Audio encoder  702  may be incorporated in the microcontroller discussed earlier, or be coupled with it. The sensing device further includes a transducing element  704 , adapted to convert an electrical signal from audio encoder  702  into an acoustic signal transmitted towards the remote receiver. In some exemplary embodiments, the transducing element  704  is a speaker. The acoustic signal produced by the sensing device may then be detected by transducer unit  712  of receiving device  710 . In some exemplary embodiments, transducer  712  is a microphone. The acoustic signal may then be decoded by audio decoder  714  of the receiving device. Decoding the acoustic signal may be used to convert the acoustic signal to an electrical signal. The decoded signal may be processed and conveyed to a user. In some embodiments, the decoded signal may be converted to an alarm signal that may be a visual signal, a tactile signal, an audible signal, and the like, or any combination thereof. 
     According to some embodiments, the receiving device may be portable. In some embodiments, the receiving device may be placed in the vicinity of the sensing device. In some embodiments, the receiving device may be placed at a remote location, but still in acoustic communication range from the transmitting device. In some exemplary embodiments, the receiving device is a smart phone. In some exemplary embodiments, the receiving device is configured to communicate with a smart phone. 
     Reference is now made to  FIG. 10 , which shows a schematic illustration of an acoustic interface of a sensing system, according to some embodiments. In a system  800 , a sensing device  802  is placed on a subject (exemplary baby  804 ). When an event is detected by the sensor of the sensing device, an acoustic alert is produced by the sensing device. The acoustic alert is detected by a receiving device such as receiving device  806 , which is located in the proximity of the subject. The receiving device may then issue an alert (such as audible, tactile and/or visual alert) to a supervisor. Additionally or alternatively, the receiving device may serve as a relay station configured to communicate with a remote device (such as smart phone  808 ), which is, in turn, configured to generate an appropriate alarm to the supervisor. In another embodiment, remote device  808  may embed receiving device  806 , and no relaying device may be required. 
     In some embodiments, the receiving device is configured to communicate with the remote device via the Internet and/or via short-range radio, utilizing technologies such as WiFi, Bluetooth, SMS, cellular data communication, push notification protocol, and activate the alarm therein, in order to notify a supervisor which may be located in a remote location. The remote device may execute an application for communicating with the receiving device and to produce audible and/or visual alarm and/or tactile alarms. 
     A flowchart of an algorithm for detecting urine and stool secretions is shown in  FIG. 23 . Such an algorithm may be implemented as a software routine. In a first step  910 , variables are zeroed and the microcontroller is initialized. At least one measurement is performed for calibration purposes. This measurement is used as a baseline value for further measurements. In step  920 , an N-sized array for storing the last N consecutive sensor readings is generated. In step  930  the N-sized array is zeroed. The N-sized array may include a number of cells corresponding, for examples, to a few seconds or a few dozen seconds based on the sampling rate of the sensor. In step  940 , a difference between the N consecutive sensor readings is calculated. The calculation may include a process for noise filtering. In step  950 , it is checked if the difference exceeds a pre-set threshold T C , which is pre-programmed in the integrated circuit. If the threshold is exceeded, then the algorithm continues to step  960  and an alert is issued. If the threshold is not exceeded, then the routine returns to step  930  in which zeroing of the array is performed. 
     In addition for the optically methods of stool detection, before checking the T C , the DC time decay &amp; slope are measured for pre-set threshold. 
     T C  may be pre-set to match a specific type of diapers which have the same material characteristics, (e.g., in regard to their light reflection or capacitive behavior), when the diaper is dry and when urine and/or stool are present. The pre-setting may be performed during manufacturing, based on tests run on the pertinent type of diaper. 
     Alternatively, T C  may be set dynamically each time it is coupled with a new diaper. A calibration phase occurs in step  910  may be employed each time the sensor is turned on and/or coupled with a diaper. In such a calibration phase, the initial average value received from the detector is stored for later use as a baseline, namely—T C . 
     Experimental Results 
     Multiple experiments have been conducted in order to establish the efficacy of present embodiments, and show their supremacy over other configurations. 
     In a first experiment (also referred as experiment no. 1), a capacitive sensor (P/N:HCH-1000-001 made by Honeywell) was positioned on the outer side of an infant diaper on a lab table. The output leads of the sensor was connected to a capacitance measuring instrument. 
     Reference is now made to  FIG. 24  which shows graph of output capacitance vs. time of a the capacitive sensor. A 30 cc of urine was poured into the backside of the diaper. during a period of time in which the diaper was soiled the capacitance was increased from 0.47 nF to 0.60 nF, 
     Therefore an obvious change of capacitance was observed from t=0 to steady state, after poured the urine into the diaper. 
     In a second experiment (also referred as experiment no. 2), two LDRs (Light Dependent Resistor) (P/N:PDV5001 made by Advanced Photonix) and a 645 nm red LED (P/N:HT-191URO made by Harvatek) have been used. In a first configuration, both LDRs were positioned, on the bottom of the front part of a diaper put on an infant for better detection of stool. One LDR was equipped with a Low Pass Filter (LPF) including a capacitor of 1 μF and resistor of 10 KΩ (made by AVX Corporation) in order to diminish noise. As one can see, the graphs have fluctuations, probably due to the infant&#39;s movements but the first one the fluctuations is lower because of the LPF. Therefore a noise filter is desired. In this experiment no defecation was observed, accordingly, the output voltage of both LDRs is quite similar. In a second configuration, which was the same as the first configuration. At some point in time the infant defecated and stool was found in the diaper. The results can be seen in  FIGS. 11B to 11D , which show graphs of the LDRs output voltage vs. time. During a first period of time, shown in  FIG. 11B , no secretion was found. Accordingly, the output voltage of both LDRs is quite similar. During a second period of time, shown in  FIG. 11C , the infant defecated and stool was found in the diaper. Reference is now made to  FIG. 11D  which show the output voltage of the LDR without LPF as shown in  FIG. 11C . One can see that at the relevant time (i.e., time of defecation), a difference of 350 mV is shown in the output voltage of the LDR. Furthermore, since the difference of the output voltage of the LDR occurred during a period of time of several minutes, one should note that the identification of stool is not immediate. 
     In summary, the results show that detection of decay in the DC signal level and following that, stabilization in a steady state level, will indicate the presence of stool and/or urine secretion. 
     In a third experiment (also referred as experiment no. 3), a sensor was positioned on a doll of an infant dressed with an article of clothing (i.e., pants or shirt) put over a diaper. Thus, the sensor was positioned over two layers of garment. Different photodetectors (i.e., LDR, IR 940 nm and a photodiode 565 nm) joined with different colors of LEDs (i.e.: red, green, blue and white) were tested on different colors of garments (i.e., red, green, blue, black and white). The type and thickness of each garment is detailed in the table below: 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                 Garment Color 
                 Garment Type 
                 Garment thickness 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Red 
                 Cotton 
                 0.375 
                 mm 
               
               
                   
                 Green 
                 Cotton 
                 0.52 
                 mm 
               
               
                   
                 Blue 
                 Cotton 
                 0.325 
                 mm 
               
               
                   
                 Black 
                 Cotton 
                 0.45 
                 mm 
               
               
                   
                 White 
                 Cotton 
                 0.45 
                 mm 
               
               
                   
                   
               
            
           
         
       
     
     Water was injected into the diaper and the difference in the photodetectors output, while utilizing different colors of LED on different colors of garments was measured. 
       FIGS. 12A to 12E  show graphs of a LDR (P/N:PDV5001 made by Advanced Photonix) output voltage vs. time as a result of a 645 nm red LED (P/N:HT-191URO made by Harvatek) illumination on red, white, black, green and blue garments correspondingly. The received voltage outputs in millivolts from t=0 (time identified as the time of the occurrence) to t=steady state, was 16 during one minute, 20 during one minute, 3.5 during one minute, 5 during one minute and 10 during one minute correspondingly. 
       FIGS. 13A to 13E  show graphs of an LDR output voltage vs. time as a result of a 565 nm green LED (P/N:SML-LX0603GW made by Lumex) illumination on blue, white, black, green and red garments correspondingly. The received voltage outputs in millivolts from t=0 to t=steady state were: 0 during one minute, 5 during one minute, 4 during one minute. 4 during one minute, and 0 during three seconds correspondingly. 
       FIGS. 14A to 14E  show graphs of an LDR output voltage vs. time as a result of a 475 nm blue LED (P/N: QTLP6010EBTR made by Everlight) illumination on red, white, black, green and blue garments correspondingly. The received voltage outputs in millivolts from t=0 to t=steady state were: 1 during one minute, 6 during one minute, 3 during one minute. 3 during one minute, and 1 during three seconds correspondingly. 
       FIGS. 15A to 15E  show graphs of an LDR output voltage vs. time as a result of a white LED (P/N:HT-F199TW5 made by Harvatek) illumination on red, white, black, green and blue garments correspondingly. The received voltage outputs in millivolts from t=0 to t=steady state were: 7 during one minute, 2 during one minute, 1 during one minute, 1 during one minute and 4 during one minute correspondingly. 
       FIGS. 16A to 16E  show graphs of an IR photodetector (P/N: QRE1113GR made by Fairchild) output voltage vs. time as a result of a red LED illumination on red, white, black, green and blue garments correspondingly. The received voltage outputs in millivolts from t=0 to t=steady state were: 25 during one minute, 30 during one minute, 10 during one minute. 20 during one minute and 35 during one minute correspondingly. 
       FIG. 17  shows a graph of an IR photodetector output voltage vs. time positioned on a doll dressed with a non-illuminated white garment. The received voltage output in millivolts from t=0 to t=steady state was 13 during one minute. 
       FIGS. 18A to 18E  show graphs of a photodiode output voltage vs. time positioned on a doll dressed with a non-illuminated white, black, green, red and blue garments correspondingly. The received voltage outputs in millivolts from t=0 to t=steady state were: 20 during one minute, 5 during one minute, 10 during one minute. 50 during one minute and 45 during one minute correspondingly. 
       FIG. 19  shows a graph of a photodiode (P/N: TEMT6200FX01 made by Everlight) output voltage vs. time as a result of a white LED illumination on white garment. The received voltage output in millivolts from t=0 to t=steady state was 20 during one minute. 
       FIGS. 20A and 20B  show graphs of a LDR output voltage vs. time as a result of a red LED illumination on white and black garments correspondingly. The received voltage outputs in millivolts from t=0 to t=steady state were 20 during one minute and 15 during one minute. 
     A table summarizing all of the above results is presented below: 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                   
               
               
                   
                 Illumonation 
                 red 
                 white 
                 black 
                 green 
                 blue 
                 Total 
               
               
                 Photodetector 
                 Spectrum 
                 garment 
                 garment 
                 garment 
                 garment 
                 garment 
                 Output 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 LDR 
                 red 
                 16 
                 20 
                 3.5 
                 5 
                 10 
                 54.5 
               
               
                   
                 green 
                 0 
                 5 
                 4 
                 4 
                 0 
                 18 
               
               
                   
                 blue 
                 1 
                 6 
                 3 
                 3 
                 1 
                 14 
               
               
                   
                 white 
                 7 
                 2 
                 1 
                 1 
                 4 
                 15 
               
               
                 IR 
                 red 
                 25 
                 30 
                 10 
                 20 
                 35 
                 120 
               
               
                   
                 no led 
                 — 
                 13 
                 — 
                 — 
                 — 
                 * 
               
               
                 Photodiode 
                 white 
                 — 
                 20 
                 — 
                 — 
                 — 
                 * 
               
               
                   
                 red 
                 — 
                 20 
                 15 
                 — 
                 — 
                 * 
               
               
                   
                 no led 
                 50 
                 20 
                 5 
                 10 
                 45 
                 * 
               
               
                   
                 garment thickness 
                 0.375 
                 0.45 
                 0.45 
                 0.52 
                 0.325 
               
               
                   
               
            
           
         
       
     
     One can see that detection of urine secretion may be performed through two layers of garment: a diaper and an article of clothing such as pants or shirt. Furthermore, one can see that when using an LDR, a red LED provides the highest output with respect to different color garments. The highest output was received when an IR photodetector was used in conjoint with a red LED with respect to different color garments. When a photodiode was used, the highest output was received when there was no illumination. In addition, one can see that the thickness of the garment did not affect the output. 
     In a fourth experiment (also referred as experiment no. 4), a capacitive sensor (P/N:HIH-4030 made by Honeywell) was positioned on the bottom part of the diaper. During a period of time, shown in  FIG. 21 , the infant defecated and stool was found in the diaper. Reference is now made to  FIG. 21  which shows the output voltage of the capacitive sensor. One can see that at the relevant time (i.e., time of defecation), started at minute &#39;50, a difference of 350 mV is shown in the output voltage of the capacitive sensor. Furthermore, since the difference of the output voltage occurred during a period of time of less than a minute, one should note that the identification of stool is immediate. 
     In a fifth experiment (also referred as experiment no. 5) a capacitive sensor (P/N:HIH-4030 made by Honeywell) was positioned on the bottom part of a diaper. During a period of time, shown in  FIG. 22 , the infant defecated and stool was found in the diaper. Reference is now made to  FIG. 22  which shows the output voltage of the capacitive sensor. One can see that at the relevant time (i.e., time of defecation), started at minute &#39;00, a difference of 400 mV is shown in the output voltage of the capacitive sensor. Furthermore, since the difference is approx 100 mV of the output voltage occurred during a period of time of several minutes, one should note that the identification of stool is very fast. 
     In the description and claims of the application, each of the words “comprise” “include” and “have”, and forms thereof, are not necessarily limited to members in a list with which the words may be associated. In addition, where there are inconsistencies between this application and any document incorporated by reference, it is hereby intended that the present application controls.