NL2010569C2

NL2010569C2 - A moisture sensing module and a napkin.

Info

Publication number: NL2010569C2
Application number: NL2010569A
Authority: NL
Inventors: Irene Martine Beld; Benno Groosman
Original assignee: Salusion Ip B V
Priority date: 2013-04-04
Filing date: 2013-04-04
Publication date: 2014-10-07
Also published as: WO2014163503A1

Abstract

The invention relates to a moisture sensing module for monitoring an amount of moisture. The module comprises a tag layer including a passive electrical resonance circuit, a dielectric layer covering the tag layer, and an absorption layer on top of the dielectric layer for receiving the amount of moisture to be monitored. Preferably, the tag layer, the dielectric layer and the absorption form a sandwiched structure.

Description

Title: A moisture sensing module and a napkin

The invention relates to a moisture sensing module for monitoring an amount of moisture, comprising a tag layer including an electrical passive resonance circuit.

Such a moisture sensing module is e.g. known from the International patent publication WO 2011/005096, including a moisture sensitive sensor and a moisture non-permeable layer covering the sensor. The sensing module can e.g. be attached to a moisture absorbing section of a napkin.

The moisture sensitive sensor in WO Ό96 includes a passive electrical resonance circuit generating a resonance signal when the module is impinged by an external magnetic field. Then, the resonance signal is wirelessly read by a reading device. Electrical characteristics of the resonance circuit, such as the amplitude of the resonance signal, are highly influenced by the presence of any moisture in the sensor. Discrimination between a wet state and a dry state of the sensor is possible by checking whether resonance signal is received from the resonance circuit.

When moisture is detected in the napkin, the reading device may generate a warning signal so that a nursing or caring professional is made aware that the napkin of the person has to be replaced. Applying such moisture sensing modules enables a more efficient treatment of people that wear a napkin due to incontinence problems, e.g. elderly people, especially if said people can not actively indicate that a current napkin has to be replaced, either because they do not realize that the napkin is wet or are less able to warn a nurse.

Although the moisture sensing module disclosed in WO Ό96 has proven that a significant improvement can be reached, in a reduction of unnecessary napkin replacements as well as in a reduction of leaking napkins, it appears that a further efficiency improvement could be reached if both the dry state and the wet state of the sensor are determined more reliably. The design of the sensor disclosed in WO ‘096 is such that no differentiation is possible between a wet state of the sensor and a situation wherein no sensor at all is detected, e.g. when the reading device is not close enough to the moisture sensitive sensor. Differentiation between theses two situations can be relevant in practice to avoid unnecessary napkin replacements.

It is an object of the invention to provide a moisture sensing module according to the preamble enabling differentiating between a dry state, a wet state and a state wherein no module is detected by a reading device. Thereto, the moisture detecting module also comprises a dielectric layer covering the tag layer, and an absorption layer on top of the dielectric layer for receiving the amount of moisture to be monitored.

By providing an absorption layer-dielectric layer-tag layer structure, a variable capacitive element is connected to the resonance circuit. The actual capacitive value of the variable capacitive element is directly related to a degree of moisture in the absorption layer. Then, the amplitude variation in the resonance signal due to moisture in the module is only moderate so that a resonance signal can be read both in the dry state and in the wet state of the module. The electrical properties of the resonance circuit components in the tag layer are not modified by the presence of any moisture in the module. Due to the variable capacitance of the structure, also the resonance frequency of the entire electrical system including the resonance circuit and the variable capacitive element varies, thus enabling that a reader can distinguish between the dry state and the wet state. Further, no resonance signal is read when no module is detected. Advantageously, the dry state, the wet state and the situation wherein no module is detected can reliably be distinguished by an external reading device, so that a further improvement in efficiency can be obtained.

The invention is also directed to a napkin comprising a moisture absorbing section and a moisture sensing module as above described.

Advantageous embodiments according to the invention are described in the following claims.

By way of example only, embodiments of the present invention will now be described with reference to the accompanying figures in which

Fig. 1 shows a schematic cross sectional side view of a first embodiment of a moisture detecting module according to the invention attached to a napkin;

Fig. 2 shows an electrical equivalent of the moisture detecting module of Fig. 1;

Fig. 3 shows a schematic cross sectional side view of a second embodiment of a moisture detecting module according to the invention attached to a napkin; and

Fig. 4 shows a diagram of the resonance frequency of a moisture detecting module as a function of moisture.

It is noted that the figures show merely a preferred embodiment according to the invention. In the figures, the same reference numbers refer to equal or corresponding parts.

Figure 1 shows schematic cross sectional side view of a first embodiment of a moisture detecting module according to the invention. The module 1 is arranged for monitoring an amount of moisture, and comprises a tag layer 2 including a passive electrical resonance circuit, a dielectric layer 3 covering the tag layer 2, and an absorption layer 4 on top of the dielectric layer 3 for receiving the amount of moisture to be monitored.

The tag layer 2, the dielectric layer 3 and the absorption layer 4 form a sandwich structure. Further, the top surface 8 and the bottom surface 9 of the tag layer 2 are shielded against moisture particles, so that the electrical properties of the passive electrical resonance circuit components on the tag layer 2 remain unaffected when moisture particles are received by the module 1. However, the electric behavior of the resonance circuit is influenced by the actual state of the absorption layer 4.

In the shown embodiment, the dielectric layer 3 forms a barrier shielding the tag layer 2 against moisture particles. Further, the dielectric layer 3 serves as an electric isolator forming a dielectric element of a capacitor, as described in more detail below. Alternatively, however, a separate barrier layer is applied, e.g. as an intermediate layer between the tag layer 2 and the dielectric layer 3.

Further, the module 1 comprises an additional dielectric layer 10 arranged below the tag layer 2 such that the tag layer 2 is sandwiched between the dielectric layer 3 and the additional dielectric layer 10. The additional dielectric layer 10 forms a barrier shielding the tag layer 2 against moisture particles. Similar to the dielectric layer 3 covering the tag layer 2, the additional dielectric layer 10 further serves as an electric isolator forming a dielectric element of a capacitor, as described below. It is noted that a separate barrier layer can be applied, e.g. as an intermediate layer between the tag layer 2 and the additional dielectric layer 10. The electrical properties of the dielectric layers 3, 10 are designed such that the electrical influence of any moisture in the absorbing layer 4 is dominant compared with the electrical influence of moisture in the moisture absorbing section 7 of the napkin 6.

In particular, the capacitance formed by the structure including the absorption layer 4, the dielectric layer 3 and the tag layer 2 is significantly larger than the capacitance formed via the additional dielectric layer 10, e.g. by selecting material such that the electrical permittivity of the dielectric layer 3 is larger than the electrical permittivity of the additional dielectric layer 10 and/or by choosing the thickness of the dielectric layer 3 significantly smaller than the thickness of the additional dielectric layer 10. As an example, the dielectric layer 3 is made from a plastic and/or the additional dielectric layer 10 is made from a foam.

The bottom surface of the module 1 is arranged for attachment to the skin facing surface 11 of a napkin 6 including a moisture absorbing section 7. Therefore, the bottom surface of the module 1 is provided with an adhesive layer 5 attaching the module 1 to the skin facing surface moisture absorbing section 7 of the napkin 6.

Alternatively, the top surface of the module 1 is attached to the moisture absorbing section 7 of the napkin 6.

Figure 2 shows an electrical equivalent of the moisture detecting module 1 of Fig. 1. The resonance circuit R includes an inductance L and a resonance capacitance Cres, thus forming a resonance LC-loop. Preferably, the resonance circuit R includes thin film technology components. More preferably, the resonance circuit R is integrally formed using thin film technology. The resonance circuit R is tuned to a specific RF resonance frequency, e.g. circa 8.2 MHz. However, the sensor can also be set to another RF resonance frequency, e.g. 8.0 MHz. Apparently, the resonance frequency can be tuned to other frequencies as well. The resonance circuit R can be implemented as a so-called EAS tag type. The dielectric layer 3 in combination with the absorption layer 4 represents a parasitic circuit PC including a variable electric capacitance Cvar.

During use of the moisture sensing module 1 according to the invention, the passive resonance circuit interacts with an electromagnetic interrogation field so as to transmit local moisture information in a noncontacting way to an external reading device.

The reading device generates an interrogating electromagnetic field, e.g. a signal having fixed RF frequency of e.g. circa 8.2 MHz, or a signal having a sweeping frequency ranging between circa 7.7 MHz and circa 8.7 MHz, or between circa 7.45 MHz and circa 8.55 MHz. When the resonance circuit R, having a resonance characteristic, is activated, the circuit acts as a RF transmission element, also called RF tag, transmitting an electromagnetic response signal that is received by the reading device, thereby obtaining a wireless RF moisture detecting system for monitoring a moisture state of the sensor.

Figure 3 shows a schematic cross sectional side view of a second embodiment of a moisture detecting module 1 according to the invention.

Here, the electrical properties of the dielectric layers 3, 10 have been interchanged compared with the embodiment shown in Fig. 1, so that moisture in the moisture absorbing section 7 of the napkin is now dominant with respect to moisture in the absorbtion layer 4. The capacitance resulting via the dielectric layer 3, arranged between the tag layer 2 and the absorption layer 4, is now significantly smaller than the capacitance resulting via the additional dielectric layer 10, e.g. by selecting material such that the electrical permittivity of the dielectric layer 3 is smaller than the electrical permittivity of the additional dielectric layer 10 and/or by choosing the thickness of the dielectric layer 3 significantly larger than the thickness of the additional dielectric layer 10.

Again, the module 1 can be attached upside-down to the napkin 6 such that the additional dielectric layer 10 is facing away from the napkin 6. Optionally, the surface of the module 1 facing away from the napkin 6 can be provided with a comfort layer to enhance comfort of wearing a napkin with a moisture sensing module 1, and to counteract undesired physiological reactions on the skin, such as irritation reactions.

Figure 4 shows a diagram of the resonance frequency of a moisture detecting module as a function of moisture. The diagram D indicates the actual resonance frequency Res [MHz] as a function of moisture [%] in the absorption layer 4 of the module 1. When no moisture is present in the absorption layer 4, the resonance frequency Res has a maximum at circa 8.2 MHz. When moisture has been received in the absorption layer 4, the variable capacitance Cvar increases, thus lowering the resonance frequency Res. The permittivity of the dielectric layer 3 and the thickness of said layer 3 are chosen such that, on the one hand, variation in the resonance frequency is easily detectable by a reading device, while, on the other hand, the resonance frequency is still in a range that is detectable by the reading device, e.g. higher than circa 7.65 MHz. In this context it is noted that the mentioned resonance frequencies are not limiting as other frequencies can be applied as well. It is further noted that the permittivity and the thickness of the dielectric layer 3 are chosen such that the amplitude of the resonance signal is in a range that is detectable by the reader.

It is noted that the moisture sensing module can not only be used in combination with a napkin, but also with other nursing articles wherein a moisture state has to be monitored, e.g. a banding or dressing. In addition, the moisture sensing module can also be used in industrial processes, e.g. for monitoring a sealing, such as a seam or joint of pipe segments, or seals between moisture impermeable plates. Especially, the moisture sensing module can be used in water impermeable plates, underground pipes, sewer draines, pipelines, etc. Advantageously, the moisture sensing module is mounted at a side of a structure that is shielded against ground water, thus measuring the effectiveness of the sealing can be tested. As an example, a moisture sensing module is installed at the inner side of watertight pipes to monitore the water permeability of the pipes. Similarly, a moisture sensing module can be located at the side of a water impermeable plate that should be dry.

The invention is not restricted to the embodiments described herein. It will be understood that many variants are possible.

Optionally, also the additional dielectric layer can be provided with a covering moisture absorbing layer, thereby influencing the actual resonance frequency by a moisture content at both surfaces of the tag layer 2.

Further, an identification can be added to the moisture sensing module rendering a so-called RF-ID tag, enabling identification of the module upon reading it.

Instead of applying a passive resonance circuit, the moisture detecting module can also be provided with an active resonance circuit.

Further, the module can be arranged with another transmission element type, such as an active strip antenna.

Further, if it is desired to switch off the resonance circuit externally, a local electromagnetic field may be applied having a relatively high field strength, thereby irreversibly damaging the circuit structure of the coil.

Preferably, the moisture sensing module is reversible, i.e. the resonance characteristics of the sensor are not influenced by an earlier state of the sensor. In particular, when a wet absorption layer becomes dry, the resonance signal is identical or similar to the situation before the absorption layer became wet.

Optionally, the components of the moisture sensing module are stable, so that the module is durable, meaning that its function is reliable during a relatively long period, e.g. more than circa a year or more than circa 10 years.

Other such variants will be apparent for the person skilled in the art and are considered to fall within the scope of the invention as defined in the following claims.

Claims

A module for measuring moisture for monitoring a quantity of moisture, comprising a tag layer with a passive electrical resonance circuit, a dielectric layer covering the tag layer, and an absorption layer on top of the dielectric layer for receiving the amount of moisture that must be followed.

A moisture measurement module according to claim 1, wherein the tag layer, the dielectric layer and the absorption layer form a stacked structure.

A moisture measuring module according to claim 1 or 2, wherein the top layer and the bottom layer of the tag layer are protected against moisture particles.

A moisture measuring module according to any one of the preceding claims, further comprising an additional dielectric layer arranged below the tag layer so that the tag layer is located between the dielectric layer and the additional dielectric layer.

A moisture measuring module according to any one of the preceding claims, wherein the dielectric layer and / or the additional dielectric layer forms a barrier that shields the tag layer against moisture particles.

A moisture measuring module according to claim 4 or 5, wherein the capacity via the dielectric layer is significantly smaller than the capacity via the additional dielectric layer.

A moisture measuring module according to claim 4, 5 or 6, wherein the electrical permitivity of the dielectric layer is smaller than the electrical permitivity of the additional dielectric layer.

A moisture measurement module according to any one of the preceding claims, wherein the dielectric layer is made of a plastic and / or wherein the additional dielectric layer is made of foam.

A moisture measurement module according to any of the preceding claims, wherein a bottom surface or a top surface of the module is adapted to be applied to a moisture-absorbing section of a diaper.

The moisture measuring module according to claim 9, wherein the bottom surface or the top surface of the module is provided with an adhesive layer for applying to the moisture-absorbing section of the diaper surface.

A moisture measurement module according to claim 9 or 10, further comprising a comfort layer that forms a top layer or a bottom layer of the module.

A module for measuring moisture according to any one of the preceding claims, wherein the resonance circuit comprises a resonance LC magnifier.

A moisture measurement module according to any one of the preceding claims, wherein the resonance circuit comprises thin film technology components.

A diaper comprising a moisture-absorbing section and a moisture-measuring module according to any one of the preceding claims 1-13.